Re: [PATCH] Undo some of the pseudo-security madness
* Samium Gromoff: >> > Lisp environments can produce standalone executables >> >> If you've got a stand-alone executable, you don't need MAP_FIXED. The >> ELF loader maps the program at a fixed address anyway (at least on >> i386 and x86_64, I haven't checked others). > > Not so. > > The thing is that the picture is of two pieces: > > - the executable > - the unrelocatable lisp core (which is unrelocatable by the virtue >of non-PIC code) which is mapped into the AS of the executable. > > It is the latter which breaks, as its map can overlap with randomized > pieces of the executable (along with its libraries). I think it boils down to the question if you can use ELF relocations to create a relocatable (but not necessarily position-independent) object that ld can link with the SBCL run-time system to produce an executable. This executable would truly be stand-alone because no separate core file is required anymore. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sat, 24 Feb 2007 10:51:20 +0100, Florian Weimer wrote: > > > Randomisation has nothing to do with C. In fact from a C perspective the > > compiler and linker do a lot of work to deal with ELF and loading code at > > arbitary addresses for dynamic linking and the like, not the user and > > not as language constructs. Perhaps the Lisp universe should wake up and > > meet the 1980s 8) > > Uhm, C++ folks and others have run into loader performance issues due > to the way DSOs are handled. The problem is more severe in the lisp > context because a typical image contains hundreds of thousands of > small objects on startup. Well: [EMAIL PROTECTED]:/mnt/shared/video1 # cat /proc/`pgrep sbcl | head -n1`/maps | wc -l 1378 regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sat, 24 Feb 2007 10:40:51 +0100, Florian Weimer wrote: > > * Samium Gromoff: > > > Lisp environments can produce standalone executables > > If you've got a stand-alone executable, you don't need MAP_FIXED. The > ELF loader maps the program at a fixed address anyway (at least on > i386 and x86_64, I haven't checked others). Not so. The thing is that the picture is of two pieces: - the executable - the unrelocatable lisp core (which is unrelocatable by the virtue of non-PIC code) which is mapped into the AS of the executable. It is the latter which breaks, as its map can overlap with randomized pieces of the executable (along with its libraries). > AFAIK, PolyML has recently made the switch to stand-alone executables > for this reason. regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
> Randomisation has nothing to do with C. In fact from a C perspective the > compiler and linker do a lot of work to deal with ELF and loading code at > arbitary addresses for dynamic linking and the like, not the user and > not as language constructs. Perhaps the Lisp universe should wake up and > meet the 1980s 8) Uhm, C++ folks and others have run into loader performance issues due to the way DSOs are handled. The problem is more severe in the lisp context because a typical image contains hundreds of thousands of small objects on startup. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
* Samium Gromoff: > Lisp environments can produce standalone executables If you've got a stand-alone executable, you don't need MAP_FIXED. The ELF loader maps the program at a fixed address anyway (at least on i386 and x86_64, I haven't checked others). AFAIK, PolyML has recently made the switch to stand-alone executables for this reason. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
* Samium Gromoff: Lisp environments can produce standalone executables If you've got a stand-alone executable, you don't need MAP_FIXED. The ELF loader maps the program at a fixed address anyway (at least on i386 and x86_64, I haven't checked others). AFAIK, PolyML has recently made the switch to stand-alone executables for this reason. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Randomisation has nothing to do with C. In fact from a C perspective the compiler and linker do a lot of work to deal with ELF and loading code at arbitary addresses for dynamic linking and the like, not the user and not as language constructs. Perhaps the Lisp universe should wake up and meet the 1980s 8) Uhm, C++ folks and others have run into loader performance issues due to the way DSOs are handled. The problem is more severe in the lisp context because a typical image contains hundreds of thousands of small objects on startup. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sat, 24 Feb 2007 10:40:51 +0100, Florian Weimer wrote: * Samium Gromoff: Lisp environments can produce standalone executables If you've got a stand-alone executable, you don't need MAP_FIXED. The ELF loader maps the program at a fixed address anyway (at least on i386 and x86_64, I haven't checked others). Not so. The thing is that the picture is of two pieces: - the executable - the unrelocatable lisp core (which is unrelocatable by the virtue of non-PIC code) which is mapped into the AS of the executable. It is the latter which breaks, as its map can overlap with randomized pieces of the executable (along with its libraries). AFAIK, PolyML has recently made the switch to stand-alone executables for this reason. regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sat, 24 Feb 2007 10:51:20 +0100, Florian Weimer wrote: Randomisation has nothing to do with C. In fact from a C perspective the compiler and linker do a lot of work to deal with ELF and loading code at arbitary addresses for dynamic linking and the like, not the user and not as language constructs. Perhaps the Lisp universe should wake up and meet the 1980s 8) Uhm, C++ folks and others have run into loader performance issues due to the way DSOs are handled. The problem is more severe in the lisp context because a typical image contains hundreds of thousands of small objects on startup. Well: [EMAIL PROTECTED]:/mnt/shared/video1 # cat /proc/`pgrep sbcl | head -n1`/maps | wc -l 1378 regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
* Samium Gromoff: Lisp environments can produce standalone executables If you've got a stand-alone executable, you don't need MAP_FIXED. The ELF loader maps the program at a fixed address anyway (at least on i386 and x86_64, I haven't checked others). Not so. The thing is that the picture is of two pieces: - the executable - the unrelocatable lisp core (which is unrelocatable by the virtue of non-PIC code) which is mapped into the AS of the executable. It is the latter which breaks, as its map can overlap with randomized pieces of the executable (along with its libraries). I think it boils down to the question if you can use ELF relocations to create a relocatable (but not necessarily position-independent) object that ld can link with the SBCL run-time system to produce an executable. This executable would truly be stand-alone because no separate core file is required anymore. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
* Arjan van de Ven: >> No amount of carefulness will prevent vendors stick arbitrarily >> damaging values of stack and mmap base randomisation, severely reducing >> the usefullness of MAP_FIXED. > > MAP_FIXED is useful still. The only safe way is to use addresses you got > from mmap(), eg you overmap something. > Anything else is madness, with or without randomization. The C library > for example is free, and does, allocate memory and stacks etc etc. This reminds me of a different matter: What is the recommended way to reserve address space (so that libc etc. won't use it) *without* increasing the VM committed memory counter? In other words, without allocating backing store for it? IIRC, mmap(PROT_NONE) followed by mprotect(PROT_READ | PROT_WRITE) seems to work, but I wonder if this is just an accident, or if this is part of the API. This is an interesting topic because such functionality is required to make many virtual machines work with address space randomization and (especially) vm.overcommit_memory=2. They don't need the backing store from the beginning, but they really like (if not need, even) huge regions of continuous address space. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
* Arjan van de Ven: No amount of carefulness will prevent vendors stick arbitrarily damaging values of stack and mmap base randomisation, severely reducing the usefullness of MAP_FIXED. MAP_FIXED is useful still. The only safe way is to use addresses you got from mmap(), eg you overmap something. Anything else is madness, with or without randomization. The C library for example is free, and does, allocate memory and stacks etc etc. This reminds me of a different matter: What is the recommended way to reserve address space (so that libc etc. won't use it) *without* increasing the VM committed memory counter? In other words, without allocating backing store for it? IIRC, mmap(PROT_NONE) followed by mprotect(PROT_READ | PROT_WRITE) seems to work, but I wonder if this is just an accident, or if this is part of the API. This is an interesting topic because such functionality is required to make many virtual machines work with address space randomization and (especially) vm.overcommit_memory=2. They don't need the backing store from the beginning, but they really like (if not need, even) huge regions of continuous address space. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
> No amount of carefulness will prevent vendors stick arbitrarily > damaging values of stack and mmap base randomisation, severely reducing > the usefullness of MAP_FIXED. MAP_FIXED is useful still. The only safe way is to use addresses you got from mmap(), eg you overmap something. Anything else is madness, with or without randomization. The C library for example is free, and does, allocate memory and stacks etc etc. Same for many other libraries; in addition libraries change in size all the time... MAP_FIXED of an address you don't KNOW is free is a bug. Period. (using an address previously obtained from mmap() is safest, but you could in theory also parse /proc/self/maps, although that is racey, since nothing guarantees that the C library didn't spawn a background thread that allocates memory) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
No amount of carefulness will prevent vendors stick arbitrarily damaging values of stack and mmap base randomisation, severely reducing the usefullness of MAP_FIXED. MAP_FIXED is useful still. The only safe way is to use addresses you got from mmap(), eg you overmap something. Anything else is madness, with or without randomization. The C library for example is free, and does, allocate memory and stacks etc etc. Same for many other libraries; in addition libraries change in size all the time... MAP_FIXED of an address you don't KNOW is free is a bug. Period. (using an address previously obtained from mmap() is safest, but you could in theory also parse /proc/self/maps, although that is racey, since nothing guarantees that the C library didn't spawn a background thread that allocates memory) - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
> SBCL is the most actively developed open source Common Lisp implementation, > which has an optimising native compiler built in, so it is not an interpreter, > and is, most certainly, not crappy. If it requires MAP_FIXED I would beg to disagree. > 1. cannot serve as a vehicle for exploitation for binaries unmarked > with this flag > 2. serve the application deployment cause -- abolish the need for > application-specific system tweaks > 3. remove the need for the ugly self-reexecution tweak people > needing an absolutely unadulterated memory map have to resort to /now/, > even in a non-setuid case Seems sensible to me. If you specifically need that mapping behaviour and ask for it then it wouldn't be hard to provide. > Please, shrug off that C-esque center-of-the-world attitude, > the fact there are thousand times as many C programmers does not Randomisation has nothing to do with C. In fact from a C perspective the compiler and linker do a lot of work to deal with ELF and loading code at arbitary addresses for dynamic linking and the like, not the user and not as language constructs. Perhaps the Lisp universe should wake up and meet the 1980s 8) Alan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Tue, 23 Jan 2007 08:48:07 +, Pavel Machek wrote: > > Are you saying that the usefulness of AS randomisation is > > overall exceeding that of MAP_FIXED, and the latter should be > > abolished? > > MAP_FIXED still works. You just have to be more careful where you map. No amount of carefulness will prevent vendors stick arbitrarily damaging values of stack and mmap base randomisation, severely reducing the usefullness of MAP_FIXED. And they actively take this freedom -- Arjan must know this first-hand. > > > > the only way to achieve this i see, is to directly setuid root > > > > the lisp system executable itself -- because the lisp code > > > > is read, compiled and executed in the process of the lisp > > > > system executable. > > > > > > If that's the only way you can see to do it, maybe you should think a > > > bit harder before making kernel hacks to do something. > > > > I want equal grounds for platforms, that`s all. > > Well, noone ever said all languages are equal. You have crappy lisp > interpreters, and you want to break kernel because you are too lazy to > fix them, and insist they must do suid in any way you choose. We won't > break kernel because lisp is misdesigned. SBCL is the most actively developed open source Common Lisp implementation, which has an optimising native compiler built in, so it is not an interpreter, and is, most certainly, not crappy. Speaking on the matter, how would you regard a patch which enhances the ELF loader with interpretation of an x86-specific e_flags bit which would mean a mandatory AS randomisation disable? this has the following properties: 1. cannot serve as a vehicle for exploitation for binaries unmarked with this flag 2. serve the application deployment cause -- abolish the need for application-specific system tweaks 3. remove the need for the ugly self-reexecution tweak people needing an absolutely unadulterated memory map have to resort to /now/, even in a non-setuid case > Pavel P.S.: Please, shrug off that C-esque center-of-the-world attitude, the fact there are thousand times as many C programmers does not automatically mean there is a free-for-all no-questions-asked licence to raise the implementation complexity bar for other languages. regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Hi! > > > not "core-dumps" but "core files", in the lispspeak, but anyway. > > > > > > the reason is trivial -- if i can write programs enjoying setuid > > > privileges in C, i want to be able to do the same in Lisp. > > > > Go read up on how the XEmacs crew designed their "portable dumper", > > specifically to get around a lot of these sorts of problems because the > > old Emacs 'unexec' code was incredibly fragile. > > I should take the freedom to respond in your manner :-) > > Are you saying that the usefulness of AS randomisation is > overall exceeding that of MAP_FIXED, and the latter should be > abolished? MAP_FIXED still works. You just have to be more careful where you map. > > > the only way to achieve this i see, is to directly setuid root > > > the lisp system executable itself -- because the lisp code > > > is read, compiled and executed in the process of the lisp > > > system executable. > > > > If that's the only way you can see to do it, maybe you should think a > > bit harder before making kernel hacks to do something. > > I want equal grounds for platforms, that`s all. Well, noone ever said all languages are equal. You have crappy lisp interpreters, and you want to break kernel because you are too lazy to fix them, and insist they must do suid in any way you choose. We won't break kernel because lisp is misdesigned. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Hi! > > nor will they work if the sysadmin applies a security update and glibc > > or another library changes one page in size. Or changes the stack rlimit > > or .. or .. > > Now, i figured out, there is a certain reasonable safety gap which works > for people, because the libraries depended on are well known. > > What happens with AS randomisation, is that the variance is simply too > large. But what is more important, is that vendors do modifications > which change the amount of randomisation, which means that potentially Complain to vendors, not here. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Hi! nor will they work if the sysadmin applies a security update and glibc or another library changes one page in size. Or changes the stack rlimit or .. or .. Now, i figured out, there is a certain reasonable safety gap which works for people, because the libraries depended on are well known. What happens with AS randomisation, is that the variance is simply too large. But what is more important, is that vendors do modifications which change the amount of randomisation, which means that potentially Complain to vendors, not here. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Hi! not core-dumps but core files, in the lispspeak, but anyway. the reason is trivial -- if i can write programs enjoying setuid privileges in C, i want to be able to do the same in Lisp. Go read up on how the XEmacs crew designed their portable dumper, specifically to get around a lot of these sorts of problems because the old Emacs 'unexec' code was incredibly fragile. I should take the freedom to respond in your manner :-) Are you saying that the usefulness of AS randomisation is overall exceeding that of MAP_FIXED, and the latter should be abolished? MAP_FIXED still works. You just have to be more careful where you map. the only way to achieve this i see, is to directly setuid root the lisp system executable itself -- because the lisp code is read, compiled and executed in the process of the lisp system executable. If that's the only way you can see to do it, maybe you should think a bit harder before making kernel hacks to do something. I want equal grounds for platforms, that`s all. Well, noone ever said all languages are equal. You have crappy lisp interpreters, and you want to break kernel because you are too lazy to fix them, and insist they must do suid in any way you choose. We won't break kernel because lisp is misdesigned. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Tue, 23 Jan 2007 08:48:07 +, Pavel Machek wrote: Are you saying that the usefulness of AS randomisation is overall exceeding that of MAP_FIXED, and the latter should be abolished? MAP_FIXED still works. You just have to be more careful where you map. No amount of carefulness will prevent vendors stick arbitrarily damaging values of stack and mmap base randomisation, severely reducing the usefullness of MAP_FIXED. And they actively take this freedom -- Arjan must know this first-hand. the only way to achieve this i see, is to directly setuid root the lisp system executable itself -- because the lisp code is read, compiled and executed in the process of the lisp system executable. If that's the only way you can see to do it, maybe you should think a bit harder before making kernel hacks to do something. I want equal grounds for platforms, that`s all. Well, noone ever said all languages are equal. You have crappy lisp interpreters, and you want to break kernel because you are too lazy to fix them, and insist they must do suid in any way you choose. We won't break kernel because lisp is misdesigned. SBCL is the most actively developed open source Common Lisp implementation, which has an optimising native compiler built in, so it is not an interpreter, and is, most certainly, not crappy. Speaking on the matter, how would you regard a patch which enhances the ELF loader with interpretation of an x86-specific e_flags bit which would mean a mandatory AS randomisation disable? this has the following properties: 1. cannot serve as a vehicle for exploitation for binaries unmarked with this flag 2. serve the application deployment cause -- abolish the need for application-specific system tweaks 3. remove the need for the ugly self-reexecution tweak people needing an absolutely unadulterated memory map have to resort to /now/, even in a non-setuid case Pavel P.S.: Please, shrug off that C-esque center-of-the-world attitude, the fact there are thousand times as many C programmers does not automatically mean there is a free-for-all no-questions-asked licence to raise the implementation complexity bar for other languages. regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
SBCL is the most actively developed open source Common Lisp implementation, which has an optimising native compiler built in, so it is not an interpreter, and is, most certainly, not crappy. If it requires MAP_FIXED I would beg to disagree. 1. cannot serve as a vehicle for exploitation for binaries unmarked with this flag 2. serve the application deployment cause -- abolish the need for application-specific system tweaks 3. remove the need for the ugly self-reexecution tweak people needing an absolutely unadulterated memory map have to resort to /now/, even in a non-setuid case Seems sensible to me. If you specifically need that mapping behaviour and ask for it then it wouldn't be hard to provide. Please, shrug off that C-esque center-of-the-world attitude, the fact there are thousand times as many C programmers does not Randomisation has nothing to do with C. In fact from a C perspective the compiler and linker do a lot of work to deal with ELF and loading code at arbitary addresses for dynamic linking and the like, not the user and not as language constructs. Perhaps the Lisp universe should wake up and meet the 1980s 8) Alan - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Mon, 22 Jan 2007 01:35:46 +0100, Arjan van de Ven wrote: > > > > the core of the problem are the cores which are customarily > > dumped by lisps during the environment generation (or modification) stage, > > and then mapped back, every time the environment is invoked. > > > > > at the current step of evolution, those core files are not relocatable > > in certain natively compiling lisp systems. > > nor will they work if the sysadmin applies a security update and glibc > or another library changes one page in size. Or changes the stack rlimit > or .. or .. Now, i figured out, there is a certain reasonable safety gap which works for people, because the libraries depended on are well known. What happens with AS randomisation, is that the variance is simply too large. But what is more important, is that vendors do modifications which change the amount of randomisation, which means that potentially no MAP_FIXED is safe, generally. Yes, there is uncertainty in both cases -- library variance or AS randomisation, but the latter arguably crosses a practical manageability boundary. > -- > if you want to mail me at work (you don't), use arjan (at) linux.intel.com > Test the interaction between Linux and your BIOS via > http://www.linuxfirmwarekit.org regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Mon, 22 Jan 2007 10:20:21 -0500, [EMAIL PROTECTED] wrote: > On Mon, 22 Jan 2007 02:23:30 +0300, Samium Gromoff said: > > > > not "core-dumps" but "core files", in the lispspeak, but anyway. > > > > the reason is trivial -- if i can write programs enjoying setuid > > privileges in C, i want to be able to do the same in Lisp. > > Go read up on how the XEmacs crew designed their "portable dumper", > specifically to get around a lot of these sorts of problems because the > old Emacs 'unexec' code was incredibly fragile. I should take the freedom to respond in your manner :-) Are you saying that the usefulness of AS randomisation is overall exceeding that of MAP_FIXED, and the latter should be abolished? Did we silently enter an era where support for buggy software is more important than a basic mmap feature? > > the only way to achieve this i see, is to directly setuid root > > the lisp system executable itself -- because the lisp code > > is read, compiled and executed in the process of the lisp > > system executable. > > If that's the only way you can see to do it, maybe you should think a > bit harder before making kernel hacks to do something. I want equal grounds for platforms, that`s all. regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
On Mon, 22 Jan 2007 02:23:30 +0300, Samium Gromoff said: > > not "core-dumps" but "core files", in the lispspeak, but anyway. > > the reason is trivial -- if i can write programs enjoying setuid > privileges in C, i want to be able to do the same in Lisp. Go read up on how the XEmacs crew designed their "portable dumper", specifically to get around a lot of these sorts of problems because the old Emacs 'unexec' code was incredibly fragile. > the only way to achieve this i see, is to directly setuid root > the lisp system executable itself -- because the lisp code > is read, compiled and executed in the process of the lisp > system executable. If that's the only way you can see to do it, maybe you should think a bit harder before making kernel hacks to do something. pgpCDea0NdYeg.pgp Description: PGP signature
Re: [PATCH] Undo some of the pseudo-security madness
On Mon, 22 Jan 2007 02:23:30 +0300, Samium Gromoff said: not core-dumps but core files, in the lispspeak, but anyway. the reason is trivial -- if i can write programs enjoying setuid privileges in C, i want to be able to do the same in Lisp. Go read up on how the XEmacs crew designed their portable dumper, specifically to get around a lot of these sorts of problems because the old Emacs 'unexec' code was incredibly fragile. the only way to achieve this i see, is to directly setuid root the lisp system executable itself -- because the lisp code is read, compiled and executed in the process of the lisp system executable. If that's the only way you can see to do it, maybe you should think a bit harder before making kernel hacks to do something. pgpCDea0NdYeg.pgp Description: PGP signature
Re: [PATCH] Undo some of the pseudo-security madness
At Mon, 22 Jan 2007 10:20:21 -0500, [EMAIL PROTECTED] wrote: On Mon, 22 Jan 2007 02:23:30 +0300, Samium Gromoff said: not core-dumps but core files, in the lispspeak, but anyway. the reason is trivial -- if i can write programs enjoying setuid privileges in C, i want to be able to do the same in Lisp. Go read up on how the XEmacs crew designed their portable dumper, specifically to get around a lot of these sorts of problems because the old Emacs 'unexec' code was incredibly fragile. I should take the freedom to respond in your manner :-) Are you saying that the usefulness of AS randomisation is overall exceeding that of MAP_FIXED, and the latter should be abolished? Did we silently enter an era where support for buggy software is more important than a basic mmap feature? the only way to achieve this i see, is to directly setuid root the lisp system executable itself -- because the lisp code is read, compiled and executed in the process of the lisp system executable. If that's the only way you can see to do it, maybe you should think a bit harder before making kernel hacks to do something. I want equal grounds for platforms, that`s all. regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Mon, 22 Jan 2007 01:35:46 +0100, Arjan van de Ven wrote: the core of the problem are the cores which are customarily dumped by lisps during the environment generation (or modification) stage, and then mapped back, every time the environment is invoked. at the current step of evolution, those core files are not relocatable in certain natively compiling lisp systems. nor will they work if the sysadmin applies a security update and glibc or another library changes one page in size. Or changes the stack rlimit or .. or .. Now, i figured out, there is a certain reasonable safety gap which works for people, because the libraries depended on are well known. What happens with AS randomisation, is that the variance is simply too large. But what is more important, is that vendors do modifications which change the amount of randomisation, which means that potentially no MAP_FIXED is safe, generally. Yes, there is uncertainty in both cases -- library variance or AS randomisation, but the latter arguably crosses a practical manageability boundary. -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sun, 21 Jan 2007 19:36:27 -0500, Kyle Moffett wrote: > > On Jan 21, 2007, at 18:34:56, David Wagner wrote: > > [1] In comparison, suidperl was designed to be installed setuid- > > root, and it takes special precautions to be safe in this usage. > > (And even it has had some security vulnerabilities, despite its > > best efforts, which illustrates how tricky this business can be.) > > Setting the setuid-root bit on a large complex interpreter that > > wasn't designed to be setuid-root seems like a pretty dubious > > proposition to me. > > Well, there's also the fact that Linux does *NOT* need suidperl, as > it has proper secure support for suid pound-bang scripts anyways. > The only reason for suidperl in the first place was broken operating > systems which had a race condition between the operating system > checking the suid bits and reading the '#! /usr/bin/perl' line in the > file, and the interpreter getting executed and opening a different > file (think symlink redirection attacks). I believe Linux jumps > through some special hoops to ensure that can't happen. Uh, this does not work, unfortunately in the Lisp case. Lisp environments can produce standalone executables, which are 1. supposed to be runnable like a usual binary, without any additions 2. will suffer from the very same problem, as it merely is a runtime bundled with the core file (and the core file is unrelocatable) > Kyle Moffett regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Mon, 22 Jan 2007 01:35:46 +0100, Arjan van de Ven wrote: > > the core of the problem are the cores which are customarily > > dumped by lisps during the environment generation (or modification) stage, > > and then mapped back, every time the environment is invoked. > > > > > at the current step of evolution, those core files are not relocatable > > in certain natively compiling lisp systems. > > nor will they work if the sysadmin applies a security update and glibc > or another library changes one page in size. Or changes the stack rlimit > or .. or .. At this point i should just step down and declare incompetence -- SBCL works around shlib size variance, somehow, and /yet/ the whole turn-off-AS-randomisation-and-reexec-self thing is still present in the source, for some reason. I should let more competent people (read, the actual SBCL developers) take the way from now... (I could have digged the source myself, but it is way too late today. However, if nobody from the development team answers by tomorrow`s evening (gmt+3), i should see into the thing for myself). > -- > if you want to mail me at work (you don't), use arjan (at) linux.intel.com > Test the interaction between Linux and your BIOS via > http://www.linuxfirmwarekit.org regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
David Wagner wrote: > Samium Gromoff wrote: > >[...] directly setuid root the lisp system executable itself [...] > > Like I said, that sounds like a bad idea to me. Sounds like a recipe for > privilege escalation vulnerabilities. Was the lisp system executable > really implemented to be secure even when you make it setuid root? > Setting the setuid-root bit on programs that didn't expect to be > setuid-root is generally not a very safe thing to do. [1] 1. Unsafe setuid programs have been written, and they doubtlessly will continue to be written. 2. Lisp systems are written by extremely competent people. (who make mistakes nonetheless, but still..) 3. I think that the ability to choose whether or not to shoot oneself in the foot is an important freedom. 4. The whole issue is a little bit unfair, because the UNIX world is inherently C-centric -- everything outside the C niche does not, indeed, fit flawlessly in the picture.. This is where the "if you want to write system software, do it in C" model comes from. 5. If a killer use-case is needed, an X server might do -- these need root privileges for a certain period. What if i decide that i want to write one in Lisp? > The more I hear, the more unconvinced I am by this use case. > > If you don't care about the security issues created by (mis)using the lisp > interpreter in this way, then like I suggested before, you can always ^^^ make that a compiler -- these days, probably, there are more native-bytecode-generating lisp compilers than interpreters. > write a tiny setuid-root wrapper program that turns off address space > randomization and exec()s the lisp system executable, and leave the lisp > system executable non-setuid and don't touch the code in the Linux kernel. > That strikes me as a better solution: those who don't mind the security > risks can take all the risks they want, without forcing others to take > unwanted and unnecessary risks. This might sound as a reasonable solution. Although it places a certain burden, which has to be considered... I should see what the SBCL people will say about that. > It's not that I'm wedded to address space randomization of setuid > programs, or that I think it would be a disaster if this patch were > accepted. Local privilege escalation attacks aren't the end of the world; > in all honesty, they're pretty much irrelevant to many or most users. > It's just that the arguments I'm hearing advanced in support of this > change seem dubious, and the change does eliminate one of the defenses > against a certain (narrow) class of attacks. > > > [1] In comparison, suidperl was designed to be installed setuid-root, > and it takes special precautions to be safe in this usage. (And even it > has had some security vulnerabilities, despite its best efforts, which > illustrates how tricky this business can be.) Setting the setuid-root > bit on a large complex interpreter that wasn't designed to be setuid-root > seems like a pretty dubious proposition to me. Compiler, not interpreter, careful with the insults :-) regards, Samium Gromoff P.S. please cc me, as i am not subscribed to the list... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
On Jan 21, 2007, at 18:34:56, David Wagner wrote: [1] In comparison, suidperl was designed to be installed setuid- root, and it takes special precautions to be safe in this usage. (And even it has had some security vulnerabilities, despite its best efforts, which illustrates how tricky this business can be.) Setting the setuid-root bit on a large complex interpreter that wasn't designed to be setuid-root seems like a pretty dubious proposition to me. Well, there's also the fact that Linux does *NOT* need suidperl, as it has proper secure support for suid pound-bang scripts anyways. The only reason for suidperl in the first place was broken operating systems which had a race condition between the operating system checking the suid bits and reading the '#! /usr/bin/perl' line in the file, and the interpreter getting executed and opening a different file (think symlink redirection attacks). I believe Linux jumps through some special hoops to ensure that can't happen. Cheers, Kyle Moffett - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
> the core of the problem are the cores which are customarily > dumped by lisps during the environment generation (or modification) stage, > and then mapped back, every time the environment is invoked. > > at the current step of evolution, those core files are not relocatable > in certain natively compiling lisp systems. nor will they work if the sysadmin applies a security update and glibc or another library changes one page in size. Or changes the stack rlimit or .. or .. -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Samium Gromoff wrote: >[...] directly setuid root the lisp system executable itself [...] Like I said, that sounds like a bad idea to me. Sounds like a recipe for privilege escalation vulnerabilities. Was the lisp system executable really implemented to be secure even when you make it setuid root? Setting the setuid-root bit on programs that didn't expect to be setuid-root is generally not a very safe thing to do. [1] The more I hear, the more unconvinced I am by this use case. If you don't care about the security issues created by (mis)using the lisp interpreter in this way, then like I suggested before, you can always write a tiny setuid-root wrapper program that turns off address space randomization and exec()s the lisp system executable, and leave the lisp system executable non-setuid and don't touch the code in the Linux kernel. That strikes me as a better solution: those who don't mind the security risks can take all the risks they want, without forcing others to take unwanted and unnecessary risks. It's not that I'm wedded to address space randomization of setuid programs, or that I think it would be a disaster if this patch were accepted. Local privilege escalation attacks aren't the end of the world; in all honesty, they're pretty much irrelevant to many or most users. It's just that the arguments I'm hearing advanced in support of this change seem dubious, and the change does eliminate one of the defenses against a certain (narrow) class of attacks. [1] In comparison, suidperl was designed to be installed setuid-root, and it takes special precautions to be safe in this usage. (And even it has had some security vulnerabilities, despite its best efforts, which illustrates how tricky this business can be.) Setting the setuid-root bit on a large complex interpreter that wasn't designed to be setuid-root seems like a pretty dubious proposition to me. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
David Wagner wrote: > Samium Gromoff wrote: > >the core of the problem are the cores which are customarily > >dumped by lisps during the environment generation (or modification) stage, > >and then mapped back, every time the environment is invoked. > > > >at the current step of evolution, those core files are not relocatable > >in certain natively compiling lisp systems. > > > >in an even smaller subset of them, these cores are placed after > >the shared libraries and the executable. > > > >which obviously breaks when the latter are placed unpredictably. > >(yes, i know, currently mmap_base() varies over a 1MB range, but who > >says it will last indefinitely -- probably one day these people > >from full-disclosure will prevail and it will become, like, 256MB ;-) > > > >so, what do you propose? > > The obvious solution is: Don't make them setuid root. > Then this issue disappears. > > If there is some strong reason why they need to be setuid root, then > you'll need to explain that reason and your requirements in more detail. > But, based on your explanation so far, I have serious doubts about > whether it is a good idea to make such core-dumps setuid root in the > first place. not "core-dumps" but "core files", in the lispspeak, but anyway. the reason is trivial -- if i can write programs enjoying setuid privileges in C, i want to be able to do the same in Lisp. the only way to achieve this i see, is to directly setuid root the lisp system executable itself -- because the lisp code is read, compiled and executed in the process of the lisp system executable. there is such a thing as suid-perl -- for precise same reasons. regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Samium Gromoff wrote: >the core of the problem are the cores which are customarily >dumped by lisps during the environment generation (or modification) stage, >and then mapped back, every time the environment is invoked. > >at the current step of evolution, those core files are not relocatable >in certain natively compiling lisp systems. > >in an even smaller subset of them, these cores are placed after >the shared libraries and the executable. > >which obviously breaks when the latter are placed unpredictably. >(yes, i know, currently mmap_base() varies over a 1MB range, but who >says it will last indefinitely -- probably one day these people >from full-disclosure will prevail and it will become, like, 256MB ;-) > >so, what do you propose? The obvious solution is: Don't make them setuid root. Then this issue disappears. If there is some strong reason why they need to be setuid root, then you'll need to explain that reason and your requirements in more detail. But, based on your explanation so far, I have serious doubts about whether it is a good idea to make such core-dumps setuid root in the first place. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sun, 21 Jan 2007 03:16:04 +0100, Arjan van de Ven wrote: > > On Sat, 2007-01-20 at 17:37 +0300, Samium Gromoff wrote: > > This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of > > setuid > > binaries. > > > > Why? The answer consists of two parts: > > > > Firstly, there are valid applications which need an unadulterated memory > > map. > > Some of those which do their memory management, like lisp systems (like > > SBCL). > > They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting > > themselves. > > this is a ... funny way of achieving this > > if an application for some reason wants some fixed address for a piece > of memory there are other ways to do that (but to some degree all > apps that can't take randomization broken; for example a glibc upgrade > on a system will also move the address space around by virtue of being > bigger or smaller etc etc) the core of the problem are the cores which are customarily dumped by lisps during the environment generation (or modification) stage, and then mapped back, every time the environment is invoked. at the current step of evolution, those core files are not relocatable in certain natively compiling lisp systems. in an even smaller subset of them, these cores are placed after the shared libraries and the executable. which obviously breaks when the latter are placed unpredictably. (yes, i know, currently mmap_base() varies over a 1MB range, but who says it will last indefinitely -- probably one day these people from full-disclosure will prevail and it will become, like, 256MB ;-) so, what do you propose? regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sun, 21 Jan 2007 03:16:04 +0100, Arjan van de Ven wrote: > On Sat, 2007-01-20 at 17:37 +0300, Samium Gromoff wrote: > > This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of > > setuid > > binaries. > > > > Why? The answer consists of two parts: > > > > Firstly, there are valid applications which need an unadulterated memory > > map. > > Some of those which do their memory management, like lisp systems (like > > SBCL). > > They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting > > themselves. > > this is a ... funny way of achieving this > > if an application for some reason wants some fixed address for a piece > of memory there are other ways to do that (but to some degree all > apps that can't take randomization broken; for example a glibc upgrade > on a system will also move the address space around by virtue of being > bigger or smaller etc etc) > > [1]. See the excellent, 'Hackers Hut' by Andries Brouwer, which describes > > how AS randomisation can be got around by the means of linux-gate.so.1 > > got a URL to this? If this is exploiting the fact that the vdso is at a > fixed spot... it's no longer the case since quite a while. hmm, it seems to rely on that, yes: http://www.win.tue.nl/~aeb/linux/hhh/hh-9.html#ss9.6 > -- > if you want to mail me at work (you don't), use arjan (at) linux.intel.com > Test the interaction between Linux and your BIOS via > http://www.linuxfirmwarekit.org regards, Samium Gromoff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sun, 21 Jan 2007 03:16:04 +0100, Arjan van de Ven wrote: On Sat, 2007-01-20 at 17:37 +0300, Samium Gromoff wrote: This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of setuid binaries. Why? The answer consists of two parts: Firstly, there are valid applications which need an unadulterated memory map. Some of those which do their memory management, like lisp systems (like SBCL). They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting themselves. this is a ... funny way of achieving this if an application for some reason wants some fixed address for a piece of memory there are other ways to do that (but to some degree all apps that can't take randomization broken; for example a glibc upgrade on a system will also move the address space around by virtue of being bigger or smaller etc etc) [1]. See the excellent, 'Hackers Hut' by Andries Brouwer, which describes how AS randomisation can be got around by the means of linux-gate.so.1 got a URL to this? If this is exploiting the fact that the vdso is at a fixed spot... it's no longer the case since quite a while. hmm, it seems to rely on that, yes: http://www.win.tue.nl/~aeb/linux/hhh/hh-9.html#ss9.6 -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sun, 21 Jan 2007 03:16:04 +0100, Arjan van de Ven wrote: On Sat, 2007-01-20 at 17:37 +0300, Samium Gromoff wrote: This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of setuid binaries. Why? The answer consists of two parts: Firstly, there are valid applications which need an unadulterated memory map. Some of those which do their memory management, like lisp systems (like SBCL). They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting themselves. this is a ... funny way of achieving this if an application for some reason wants some fixed address for a piece of memory there are other ways to do that (but to some degree all apps that can't take randomization broken; for example a glibc upgrade on a system will also move the address space around by virtue of being bigger or smaller etc etc) the core of the problem are the cores which are customarily dumped by lisps during the environment generation (or modification) stage, and then mapped back, every time the environment is invoked. at the current step of evolution, those core files are not relocatable in certain natively compiling lisp systems. in an even smaller subset of them, these cores are placed after the shared libraries and the executable. which obviously breaks when the latter are placed unpredictably. (yes, i know, currently mmap_base() varies over a 1MB range, but who says it will last indefinitely -- probably one day these people from full-disclosure will prevail and it will become, like, 256MB ;-) so, what do you propose? regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Samium Gromoff wrote: the core of the problem are the cores which are customarily dumped by lisps during the environment generation (or modification) stage, and then mapped back, every time the environment is invoked. at the current step of evolution, those core files are not relocatable in certain natively compiling lisp systems. in an even smaller subset of them, these cores are placed after the shared libraries and the executable. which obviously breaks when the latter are placed unpredictably. (yes, i know, currently mmap_base() varies over a 1MB range, but who says it will last indefinitely -- probably one day these people from full-disclosure will prevail and it will become, like, 256MB ;-) so, what do you propose? The obvious solution is: Don't make them setuid root. Then this issue disappears. If there is some strong reason why they need to be setuid root, then you'll need to explain that reason and your requirements in more detail. But, based on your explanation so far, I have serious doubts about whether it is a good idea to make such core-dumps setuid root in the first place. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
David Wagner wrote: Samium Gromoff wrote: the core of the problem are the cores which are customarily dumped by lisps during the environment generation (or modification) stage, and then mapped back, every time the environment is invoked. at the current step of evolution, those core files are not relocatable in certain natively compiling lisp systems. in an even smaller subset of them, these cores are placed after the shared libraries and the executable. which obviously breaks when the latter are placed unpredictably. (yes, i know, currently mmap_base() varies over a 1MB range, but who says it will last indefinitely -- probably one day these people from full-disclosure will prevail and it will become, like, 256MB ;-) so, what do you propose? The obvious solution is: Don't make them setuid root. Then this issue disappears. If there is some strong reason why they need to be setuid root, then you'll need to explain that reason and your requirements in more detail. But, based on your explanation so far, I have serious doubts about whether it is a good idea to make such core-dumps setuid root in the first place. not core-dumps but core files, in the lispspeak, but anyway. the reason is trivial -- if i can write programs enjoying setuid privileges in C, i want to be able to do the same in Lisp. the only way to achieve this i see, is to directly setuid root the lisp system executable itself -- because the lisp code is read, compiled and executed in the process of the lisp system executable. there is such a thing as suid-perl -- for precise same reasons. regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Samium Gromoff wrote: [...] directly setuid root the lisp system executable itself [...] Like I said, that sounds like a bad idea to me. Sounds like a recipe for privilege escalation vulnerabilities. Was the lisp system executable really implemented to be secure even when you make it setuid root? Setting the setuid-root bit on programs that didn't expect to be setuid-root is generally not a very safe thing to do. [1] The more I hear, the more unconvinced I am by this use case. If you don't care about the security issues created by (mis)using the lisp interpreter in this way, then like I suggested before, you can always write a tiny setuid-root wrapper program that turns off address space randomization and exec()s the lisp system executable, and leave the lisp system executable non-setuid and don't touch the code in the Linux kernel. That strikes me as a better solution: those who don't mind the security risks can take all the risks they want, without forcing others to take unwanted and unnecessary risks. It's not that I'm wedded to address space randomization of setuid programs, or that I think it would be a disaster if this patch were accepted. Local privilege escalation attacks aren't the end of the world; in all honesty, they're pretty much irrelevant to many or most users. It's just that the arguments I'm hearing advanced in support of this change seem dubious, and the change does eliminate one of the defenses against a certain (narrow) class of attacks. [1] In comparison, suidperl was designed to be installed setuid-root, and it takes special precautions to be safe in this usage. (And even it has had some security vulnerabilities, despite its best efforts, which illustrates how tricky this business can be.) Setting the setuid-root bit on a large complex interpreter that wasn't designed to be setuid-root seems like a pretty dubious proposition to me. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
the core of the problem are the cores which are customarily dumped by lisps during the environment generation (or modification) stage, and then mapped back, every time the environment is invoked. at the current step of evolution, those core files are not relocatable in certain natively compiling lisp systems. nor will they work if the sysadmin applies a security update and glibc or another library changes one page in size. Or changes the stack rlimit or .. or .. -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
On Jan 21, 2007, at 18:34:56, David Wagner wrote: [1] In comparison, suidperl was designed to be installed setuid- root, and it takes special precautions to be safe in this usage. (And even it has had some security vulnerabilities, despite its best efforts, which illustrates how tricky this business can be.) Setting the setuid-root bit on a large complex interpreter that wasn't designed to be setuid-root seems like a pretty dubious proposition to me. Well, there's also the fact that Linux does *NOT* need suidperl, as it has proper secure support for suid pound-bang scripts anyways. The only reason for suidperl in the first place was broken operating systems which had a race condition between the operating system checking the suid bits and reading the '#! /usr/bin/perl' line in the file, and the interpreter getting executed and opening a different file (think symlink redirection attacks). I believe Linux jumps through some special hoops to ensure that can't happen. Cheers, Kyle Moffett - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
David Wagner wrote: Samium Gromoff wrote: [...] directly setuid root the lisp system executable itself [...] Like I said, that sounds like a bad idea to me. Sounds like a recipe for privilege escalation vulnerabilities. Was the lisp system executable really implemented to be secure even when you make it setuid root? Setting the setuid-root bit on programs that didn't expect to be setuid-root is generally not a very safe thing to do. [1] 1. Unsafe setuid programs have been written, and they doubtlessly will continue to be written. 2. Lisp systems are written by extremely competent people. (who make mistakes nonetheless, but still..) 3. I think that the ability to choose whether or not to shoot oneself in the foot is an important freedom. 4. The whole issue is a little bit unfair, because the UNIX world is inherently C-centric -- everything outside the C niche does not, indeed, fit flawlessly in the picture.. This is where the if you want to write system software, do it in C model comes from. 5. If a killer use-case is needed, an X server might do -- these need root privileges for a certain period. What if i decide that i want to write one in Lisp? The more I hear, the more unconvinced I am by this use case. If you don't care about the security issues created by (mis)using the lisp interpreter in this way, then like I suggested before, you can always ^^^ make that a compiler -- these days, probably, there are more native-bytecode-generating lisp compilers than interpreters. write a tiny setuid-root wrapper program that turns off address space randomization and exec()s the lisp system executable, and leave the lisp system executable non-setuid and don't touch the code in the Linux kernel. That strikes me as a better solution: those who don't mind the security risks can take all the risks they want, without forcing others to take unwanted and unnecessary risks. This might sound as a reasonable solution. Although it places a certain burden, which has to be considered... I should see what the SBCL people will say about that. It's not that I'm wedded to address space randomization of setuid programs, or that I think it would be a disaster if this patch were accepted. Local privilege escalation attacks aren't the end of the world; in all honesty, they're pretty much irrelevant to many or most users. It's just that the arguments I'm hearing advanced in support of this change seem dubious, and the change does eliminate one of the defenses against a certain (narrow) class of attacks. [1] In comparison, suidperl was designed to be installed setuid-root, and it takes special precautions to be safe in this usage. (And even it has had some security vulnerabilities, despite its best efforts, which illustrates how tricky this business can be.) Setting the setuid-root bit on a large complex interpreter that wasn't designed to be setuid-root seems like a pretty dubious proposition to me. Compiler, not interpreter, careful with the insults :-) regards, Samium Gromoff P.S. please cc me, as i am not subscribed to the list... - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Mon, 22 Jan 2007 01:35:46 +0100, Arjan van de Ven wrote: the core of the problem are the cores which are customarily dumped by lisps during the environment generation (or modification) stage, and then mapped back, every time the environment is invoked. at the current step of evolution, those core files are not relocatable in certain natively compiling lisp systems. nor will they work if the sysadmin applies a security update and glibc or another library changes one page in size. Or changes the stack rlimit or .. or .. At this point i should just step down and declare incompetence -- SBCL works around shlib size variance, somehow, and /yet/ the whole turn-off-AS-randomisation-and-reexec-self thing is still present in the source, for some reason. I should let more competent people (read, the actual SBCL developers) take the way from now... (I could have digged the source myself, but it is way too late today. However, if nobody from the development team answers by tomorrow`s evening (gmt+3), i should see into the thing for myself). -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sun, 21 Jan 2007 19:36:27 -0500, Kyle Moffett wrote: On Jan 21, 2007, at 18:34:56, David Wagner wrote: [1] In comparison, suidperl was designed to be installed setuid- root, and it takes special precautions to be safe in this usage. (And even it has had some security vulnerabilities, despite its best efforts, which illustrates how tricky this business can be.) Setting the setuid-root bit on a large complex interpreter that wasn't designed to be setuid-root seems like a pretty dubious proposition to me. Well, there's also the fact that Linux does *NOT* need suidperl, as it has proper secure support for suid pound-bang scripts anyways. The only reason for suidperl in the first place was broken operating systems which had a race condition between the operating system checking the suid bits and reading the '#! /usr/bin/perl' line in the file, and the interpreter getting executed and opening a different file (think symlink redirection attacks). I believe Linux jumps through some special hoops to ensure that can't happen. Uh, this does not work, unfortunately in the Lisp case. Lisp environments can produce standalone executables, which are 1. supposed to be runnable like a usual binary, without any additions 2. will suffer from the very same problem, as it merely is a runtime bundled with the core file (and the core file is unrelocatable) Kyle Moffett regards, Samium Gromoff - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
On Sat, 2007-01-20 at 17:37 +0300, Samium Gromoff wrote: > This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of setuid > binaries. > > Why? The answer consists of two parts: > > Firstly, there are valid applications which need an unadulterated memory map. > Some of those which do their memory management, like lisp systems (like SBCL). > They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting > themselves. this is a ... funny way of achieving this if an application for some reason wants some fixed address for a piece of memory there are other ways to do that (but to some degree all apps that can't take randomization broken; for example a glibc upgrade on a system will also move the address space around by virtue of being bigger or smaller etc etc) > [1]. See the excellent, 'Hackers Hut' by Andries Brouwer, which describes > how AS randomisation can be got around by the means of linux-gate.so.1 got a URL to this? If this is exploiting the fact that the vdso is at a fixed spot... it's no longer the case since quite a while. -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Samium Gromoff wrote: >This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of setuid >binaries. > >Why? The answer consists of two parts: > >Firstly, there are valid applications which need an unadulterated memory map. >Some of those which do their memory management, like lisp systems (like SBCL). >They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting >themselves. > >Secondly, there also are valid reasons to want those applications to be setuid >root. Like poking hardware. This has the unfortunate side-effect of making it easier for local attackers to mount privilege escalation attacks against setuid binaries -- even those setuid binaries that don't need unadulterated memory maps. There's a cleaner solution to the problem case you mentioned. Rather than re-exec()ing itself, the application could be split into two executables: the first is a tiny setuid-root wrapper which sets ADDR_NO_RANDOMIZE and then executes the second program; the second is not setuid-anything and does all the real work. Such a decomposition is often better for security for other reasons, too (such as the fact that the wrapper can drop all unneeded privileges before exec()ing the second executable). Why would you need an entire lisp system to be setuid root? That sounds like a really bad idea. I fail to see why that is a relevant example. Perhaps the fact that such a lisp system breaks if you have security features enabled should tell you something. It may be possible to defeat address space randomization in some cases, but that doesn't mean address space randomization is worthless. It sounds like there is a tradeoff between security and backwards compatibility. I don't claim to know how to choose between those tradeoffs, but I think one ought to at least be aware of the pros and cons on both sides. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sat, 20 Jan 2007 17:37:22 +0300, Samium Gromoff wrote: [snip] > So, here we have a buffer-overflow protection technique, which does not > actually protect against buffer overflows[1], breaking valid applications. > > I suggest getting rid of it. i botched it slightly: --- linux/include/linux/personality.h 2007-01-20 17:31:01.0 +0300 +++ linux-sane/include/linux/personality.h 2007-01-20 17:32:50.0 +0300 @@ -40,7 +40,7 @@ * Security-relevant compatibility flags that must be * cleared upon setuid or setgid exec: */ -#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE) +#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC) Signed-off-by: Samium Gromoff <[EMAIL PROTECTED]> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] Undo some of the pseudo-security madness
This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of setuid binaries. Why? The answer consists of two parts: Firstly, there are valid applications which need an unadulterated memory map. Some of those which do their memory management, like lisp systems (like SBCL). They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting themselves. Secondly, there also are valid reasons to want those applications to be setuid root. Like poking hardware. So, here we have a buffer-overflow protection technique, which does not actually protect against buffer overflows[1], breaking valid applications. I suggest getting rid of it. --- include/linux/personality.h 2007-01-20 17:31:01.0 +0300 +++ include/linux-sane/personality.h2007-01-20 17:32:50.0 +0300 @@ -40,7 +40,7 @@ * Security-relevant compatibility flags that must be * cleared upon setuid or setgid exec: */ -#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE) +#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC) /* * Personality types. Signed-off-by: Samium Gromoff <[EMAIL PROTECTED]> [1]. See the excellent, 'Hackers Hut' by Andries Brouwer, which describes how AS randomisation can be got around by the means of linux-gate.so.1 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] Undo some of the pseudo-security madness
This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of setuid binaries. Why? The answer consists of two parts: Firstly, there are valid applications which need an unadulterated memory map. Some of those which do their memory management, like lisp systems (like SBCL). They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting themselves. Secondly, there also are valid reasons to want those applications to be setuid root. Like poking hardware. So, here we have a buffer-overflow protection technique, which does not actually protect against buffer overflows[1], breaking valid applications. I suggest getting rid of it. --- include/linux/personality.h 2007-01-20 17:31:01.0 +0300 +++ include/linux-sane/personality.h2007-01-20 17:32:50.0 +0300 @@ -40,7 +40,7 @@ * Security-relevant compatibility flags that must be * cleared upon setuid or setgid exec: */ -#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE) +#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC) /* * Personality types. Signed-off-by: Samium Gromoff [EMAIL PROTECTED] [1]. See the excellent, 'Hackers Hut' by Andries Brouwer, which describes how AS randomisation can be got around by the means of linux-gate.so.1 - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
At Sat, 20 Jan 2007 17:37:22 +0300, Samium Gromoff wrote: [snip] So, here we have a buffer-overflow protection technique, which does not actually protect against buffer overflows[1], breaking valid applications. I suggest getting rid of it. i botched it slightly: --- linux/include/linux/personality.h 2007-01-20 17:31:01.0 +0300 +++ linux-sane/include/linux/personality.h 2007-01-20 17:32:50.0 +0300 @@ -40,7 +40,7 @@ * Security-relevant compatibility flags that must be * cleared upon setuid or setgid exec: */ -#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE) +#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC) Signed-off-by: Samium Gromoff [EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
Samium Gromoff wrote: This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of setuid binaries. Why? The answer consists of two parts: Firstly, there are valid applications which need an unadulterated memory map. Some of those which do their memory management, like lisp systems (like SBCL). They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting themselves. Secondly, there also are valid reasons to want those applications to be setuid root. Like poking hardware. This has the unfortunate side-effect of making it easier for local attackers to mount privilege escalation attacks against setuid binaries -- even those setuid binaries that don't need unadulterated memory maps. There's a cleaner solution to the problem case you mentioned. Rather than re-exec()ing itself, the application could be split into two executables: the first is a tiny setuid-root wrapper which sets ADDR_NO_RANDOMIZE and then executes the second program; the second is not setuid-anything and does all the real work. Such a decomposition is often better for security for other reasons, too (such as the fact that the wrapper can drop all unneeded privileges before exec()ing the second executable). Why would you need an entire lisp system to be setuid root? That sounds like a really bad idea. I fail to see why that is a relevant example. Perhaps the fact that such a lisp system breaks if you have security features enabled should tell you something. It may be possible to defeat address space randomization in some cases, but that doesn't mean address space randomization is worthless. It sounds like there is a tradeoff between security and backwards compatibility. I don't claim to know how to choose between those tradeoffs, but I think one ought to at least be aware of the pros and cons on both sides. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Undo some of the pseudo-security madness
On Sat, 2007-01-20 at 17:37 +0300, Samium Gromoff wrote: This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of setuid binaries. Why? The answer consists of two parts: Firstly, there are valid applications which need an unadulterated memory map. Some of those which do their memory management, like lisp systems (like SBCL). They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting themselves. this is a ... funny way of achieving this if an application for some reason wants some fixed address for a piece of memory there are other ways to do that (but to some degree all apps that can't take randomization broken; for example a glibc upgrade on a system will also move the address space around by virtue of being bigger or smaller etc etc) [1]. See the excellent, 'Hackers Hut' by Andries Brouwer, which describes how AS randomisation can be got around by the means of linux-gate.so.1 got a URL to this? If this is exploiting the fact that the vdso is at a fixed spot... it's no longer the case since quite a while. -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
