Re: Cleaning up the users and locking down the shells in /etc/passwd
On Tue, Sep 27, 2011 at 11:03:55AM -0700, Matt Alexander wrote: > On Tue, Sep 27, 2011 at 8:06 AM, Colin Watson wrote: > > On Tue, Sep 27, 2011 at 06:12:24AM -0700, Matt Alexander wrote: > > > On Tue, Sep 27, 2011 at 1:28 AM, Colin Watson > > wrote: > > > > I'm afraid this is backwards. If you want to go and hunt down packages > > > > that rely on those global static users and get their maintainers > > > > (preferably in Debian) to work on a migration to dynamically-allocated > > > > system users, perhaps after that it would be worth removing the global > > > > static users. Until then, they need to stay where they are. > > > > > > Seems like detecting broken packages from system changes would already be > > > part of the Ubuntu qual. process. > > > > It's always better to not break things in the first place. > > Sometimes breaking things is necessary for forward progress. Certainly, in general. This isn't one of those times. -- Colin Watson [cjwat...@ubuntu.com] -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
Re: Cleaning up the users and locking down the shells in /etc/passwd
On Tue, Sep 27, 2011 at 8:06 AM, Colin Watson wrote: > On Tue, Sep 27, 2011 at 06:12:24AM -0700, Matt Alexander wrote: > > On Tue, Sep 27, 2011 at 1:28 AM, Colin Watson > wrote: > > > I'm afraid this is backwards. If you want to go and hunt down packages > > > that rely on those global static users and get their maintainers > > > (preferably in Debian) to work on a migration to dynamically-allocated > > > system users, perhaps after that it would be worth removing the global > > > static users. Until then, they need to stay where they are. > > > > Seems like detecting broken packages from system changes would already be > > part of the Ubuntu qual. process. > > It's always better to not break things in the first place. > Sometimes breaking things is necessary for forward progress. > > > But, OK, I'll setup a box, remove users, and run a script that > > installs/uninstalls everything one by one from the default repos and > > makes note of any packages that break. I'll then open bugs with the > > Debian maintainers of those packages to modify their install/uninstall > > script. > > Sounds great, thanks! > > Note that I will not remove these users in any event: > > root (obviously) > daemon (required by LSB) > bin (required by LSB) > sync (specialised, described in users-and-groups documentation) > games (shared among many packages, likely to be too disruptive) > man (man-db is widely installed anyway so any gain is not worth it) > mail (often has many non-system-owned files, too disruptive) > www-data (often has many non-system-owned files, too disruptive) > nobody (obviously) > > You can refer to /usr/share/doc/base-passwd/users-and-groups.txt.gz for > what's known about various system users. > > Great info. Thanks! -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
Re: Cleaning up the users and locking down the shells in /etc/passwd
On Tue, Sep 27, 2011 at 06:12:24AM -0700, Matt Alexander wrote: > On Tue, Sep 27, 2011 at 1:28 AM, Colin Watson wrote: > > I'm afraid this is backwards. If you want to go and hunt down packages > > that rely on those global static users and get their maintainers > > (preferably in Debian) to work on a migration to dynamically-allocated > > system users, perhaps after that it would be worth removing the global > > static users. Until then, they need to stay where they are. > > Seems like detecting broken packages from system changes would already be > part of the Ubuntu qual. process. It's always better to not break things in the first place. > But, OK, I'll setup a box, remove users, and run a script that > installs/uninstalls everything one by one from the default repos and > makes note of any packages that break. I'll then open bugs with the > Debian maintainers of those packages to modify their install/uninstall > script. Sounds great, thanks! Note that I will not remove these users in any event: root (obviously) daemon (required by LSB) bin (required by LSB) sync (specialised, described in users-and-groups documentation) games (shared among many packages, likely to be too disruptive) man (man-db is widely installed anyway so any gain is not worth it) mail (often has many non-system-owned files, too disruptive) www-data (often has many non-system-owned files, too disruptive) nobody (obviously) You can refer to /usr/share/doc/base-passwd/users-and-groups.txt.gz for what's known about various system users. -- Colin Watson [cjwat...@ubuntu.com] -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
Re: Cleaning up the users and locking down the shells in /etc/passwd
On Tue, Sep 27, 2011 at 1:28 AM, Colin Watson wrote: > On Mon, Sep 26, 2011 at 03:05:58PM -0700, Matt Alexander wrote: > > On Sat, Sep 24, 2011 at 9:48 AM, Colin Watson > wrote: > > > For almost everything, and certainly for the overwhelming majority of > > > new entries, we do exactly as you say. However, I (as base-passwd > > > maintainer) will not remove entries from the global static list unless > > > there is a very compelling reason to do so beyond cleaning up cruft; > > > packages are entitled to assume that they are present without declaring > > > any particular dependency and there's no reasonable way to know what > > > removing such entries would break. > > > > I end up modifying the passwd/group files on my computers for auditing > > purposes and to ensure that the only accounts on the system are required > > accounts. Removing cruft seems like a perfectly valid reason. In 10 > years > > will Ubuntu still have a uucp user and a news user and an irc user? > Seems > > silly. Let's clean things up and keep it to just the accounts that must > be > > there. We can then easily fix packages that wrongly assumed that their > > particular user would be always be there. > > I'm afraid this is backwards. If you want to go and hunt down packages > that rely on those global static users and get their maintainers > (preferably in Debian) to work on a migration to dynamically-allocated > system users, perhaps after that it would be worth removing the global > static users. Until then, they need to stay where they are. > Seems like detecting broken packages from system changes would already be part of the Ubuntu qual. process. But, OK, I'll setup a box, remove users, and run a script that installs/uninstalls everything one by one from the default repos and makes note of any packages that break. I'll then open bugs with the Debian maintainers of those packages to modify their install/uninstall script. -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
Re: Cleaning up the users and locking down the shells in /etc/passwd
On Mon, Sep 26, 2011 at 3:28 PM, Bear Giles wrote: > Matt, why not create a hardening package? Just write a script that scrubs > /etc/passwd and /etc/group and then create a small package that runs it once > (in postinst). I would also install it in, e.g., /etc/cron.daily so it's > rerun periodically. I haven't kept track of existing hardening packages > but I wouldn't be surprised if somebody else has already done this. I've used Bastille in the past, for example, but I think most users would prefer that Ubuntu is already hardened by default. > > P.S., if you want to have fun with package installation failing try > mounting /tmp as noexec. It's easy to fix - if you know how to do it. If not > you'll bang your head against the wall for hours while you're trying to > figure out why installations are failing. > > bear > > > On Mon, Sep 26, 2011 at 4:05 PM, Matt Alexander < > ubuntu@mattalexander.com> wrote: > >> On Sat, Sep 24, 2011 at 9:48 AM, Colin Watson wrote: >> >>> On Thu, Sep 22, 2011 at 04:33:00PM -0700, Matt Alexander wrote: >>> > Would it be possible to remove the vast majority of users from >>> /etc/passwd >>> > and instead rely on the application being installed to create the >>> specific >>> > user if needed? Most of the users appear to be historical remnants >>> that >>> > have been carried over from release to release. >>> >>> For almost everything, and certainly for the overwhelming majority of >>> new entries, we do exactly as you say. However, I (as base-passwd >>> maintainer) will not remove entries from the global static list unless >>> there is a very compelling reason to do so beyond cleaning up cruft; >>> packages are entitled to assume that they are present without declaring >>> any particular dependency and there's no reasonable way to know what >>> removing such entries would break. >>> >> >> I end up modifying the passwd/group files on my computers for auditing >> purposes and to ensure that the only accounts on the system are required >> accounts. Removing cruft seems like a perfectly valid reason. In 10 years >> will Ubuntu still have a uucp user and a news user and an irc user? Seems >> silly. Let's clean things up and keep it to just the accounts that must be >> there. We can then easily fix packages that wrongly assumed that their >> particular user would be always be there. >> >> >> >>> >>> In any case, there are only 18 entries in the global static list >>> (/usr/share/base-passwd/passwd.master), and even without thinking about >>> it too hard I know that at least four or five are still in use and >>> probably more, so there's not that much to be gained. All other system >>> entries in the passwd file are created dynamically by applications. >>> >>> Since I took over base-passwd in 2002, I have added no new global static >>> users and only two new global static groups, the last of which was in >>> 2004. >>> >>> > In addition, for users in the passwd file that must be there, could you >>> > please set their shell to /usr/sbin/nologin? >>> >>> Yes, I would like to do this eventually >>> (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=274229). However, >>> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=184979 has to be fixed >>> first, otherwise everyone will have their upgrades interrupted by a >>> non-debconf prompt. I haven't had time to work on #184979 in quite a >>> number of years, and to the best of my knowledge nobody has ever >>> contributed a patch for it; I'd be happy to review one if somebody did >>> so. >>> >>> The one wart here is that using /usr/sbin/nologin will break anything >>> that runs commands as one of those users using the 'su' command. This >>> isn't theoretical; one of my packages used to do so some years ago, >>> although it now uses start-stop-daemon instead. The breakage is >>> probably worthwhile, I'll admit, but I can't say that there would be no >>> problems with changing those users' shell since there's been such a long >>> time for packages to get used to it being /bin/sh. >>> >>> Cheers, >>> >>> -- >>> Colin Watson [cjwat...@ubuntu.com] >>> >>> -- >>> Ubuntu-devel-discuss mailing list >>> Ubuntu-devel-discuss@lists.ubuntu.com >>> Modify settings or unsubscribe at: >>> https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss >>> >> >> >> -- >> Ubuntu-devel-discuss mailing list >> Ubuntu-devel-discuss@lists.ubuntu.com >> Modify settings or unsubscribe at: >> https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss >> >> > -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
Re: Cleaning up the users and locking down the shells in /etc/passwd
On Mon, Sep 26, 2011 at 03:05:58PM -0700, Matt Alexander wrote: > On Sat, Sep 24, 2011 at 9:48 AM, Colin Watson wrote: > > For almost everything, and certainly for the overwhelming majority of > > new entries, we do exactly as you say. However, I (as base-passwd > > maintainer) will not remove entries from the global static list unless > > there is a very compelling reason to do so beyond cleaning up cruft; > > packages are entitled to assume that they are present without declaring > > any particular dependency and there's no reasonable way to know what > > removing such entries would break. > > I end up modifying the passwd/group files on my computers for auditing > purposes and to ensure that the only accounts on the system are required > accounts. Removing cruft seems like a perfectly valid reason. In 10 years > will Ubuntu still have a uucp user and a news user and an irc user? Seems > silly. Let's clean things up and keep it to just the accounts that must be > there. We can then easily fix packages that wrongly assumed that their > particular user would be always be there. I'm afraid this is backwards. If you want to go and hunt down packages that rely on those global static users and get their maintainers (preferably in Debian) to work on a migration to dynamically-allocated system users, perhaps after that it would be worth removing the global static users. Until then, they need to stay where they are. Regards, -- Colin Watson [cjwat...@ubuntu.com] -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
Re: Cleaning up the users and locking down the shells in /etc/passwd
Matt, why not create a hardening package? Just write a script that scrubs /etc/passwd and /etc/group and then create a small package that runs it once (in postinst). I would also install it in, e.g., /etc/cron.daily so it's rerun periodically. I haven't kept track of existing hardening packages but I wouldn't be surprised if somebody else has already done this. P.S., if you want to have fun with package installation failing try mounting /tmp as noexec. It's easy to fix - if you know how to do it. If not you'll bang your head against the wall for hours while you're trying to figure out why installations are failing. bear On Mon, Sep 26, 2011 at 4:05 PM, Matt Alexander < ubuntu@mattalexander.com> wrote: > On Sat, Sep 24, 2011 at 9:48 AM, Colin Watson wrote: > >> On Thu, Sep 22, 2011 at 04:33:00PM -0700, Matt Alexander wrote: >> > Would it be possible to remove the vast majority of users from >> /etc/passwd >> > and instead rely on the application being installed to create the >> specific >> > user if needed? Most of the users appear to be historical remnants that >> > have been carried over from release to release. >> >> For almost everything, and certainly for the overwhelming majority of >> new entries, we do exactly as you say. However, I (as base-passwd >> maintainer) will not remove entries from the global static list unless >> there is a very compelling reason to do so beyond cleaning up cruft; >> packages are entitled to assume that they are present without declaring >> any particular dependency and there's no reasonable way to know what >> removing such entries would break. >> > > I end up modifying the passwd/group files on my computers for auditing > purposes and to ensure that the only accounts on the system are required > accounts. Removing cruft seems like a perfectly valid reason. In 10 years > will Ubuntu still have a uucp user and a news user and an irc user? Seems > silly. Let's clean things up and keep it to just the accounts that must be > there. We can then easily fix packages that wrongly assumed that their > particular user would be always be there. > > > >> >> In any case, there are only 18 entries in the global static list >> (/usr/share/base-passwd/passwd.master), and even without thinking about >> it too hard I know that at least four or five are still in use and >> probably more, so there's not that much to be gained. All other system >> entries in the passwd file are created dynamically by applications. >> >> Since I took over base-passwd in 2002, I have added no new global static >> users and only two new global static groups, the last of which was in >> 2004. >> >> > In addition, for users in the passwd file that must be there, could you >> > please set their shell to /usr/sbin/nologin? >> >> Yes, I would like to do this eventually >> (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=274229). However, >> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=184979 has to be fixed >> first, otherwise everyone will have their upgrades interrupted by a >> non-debconf prompt. I haven't had time to work on #184979 in quite a >> number of years, and to the best of my knowledge nobody has ever >> contributed a patch for it; I'd be happy to review one if somebody did >> so. >> >> The one wart here is that using /usr/sbin/nologin will break anything >> that runs commands as one of those users using the 'su' command. This >> isn't theoretical; one of my packages used to do so some years ago, >> although it now uses start-stop-daemon instead. The breakage is >> probably worthwhile, I'll admit, but I can't say that there would be no >> problems with changing those users' shell since there's been such a long >> time for packages to get used to it being /bin/sh. >> >> Cheers, >> >> -- >> Colin Watson [cjwat...@ubuntu.com] >> >> -- >> Ubuntu-devel-discuss mailing list >> Ubuntu-devel-discuss@lists.ubuntu.com >> Modify settings or unsubscribe at: >> https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss >> > > > -- > Ubuntu-devel-discuss mailing list > Ubuntu-devel-discuss@lists.ubuntu.com > Modify settings or unsubscribe at: > https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss > > -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
Re: Cleaning up the users and locking down the shells in /etc/passwd
On Sat, Sep 24, 2011 at 9:48 AM, Colin Watson wrote: > On Thu, Sep 22, 2011 at 04:33:00PM -0700, Matt Alexander wrote: > > Would it be possible to remove the vast majority of users from > /etc/passwd > > and instead rely on the application being installed to create the > specific > > user if needed? Most of the users appear to be historical remnants that > > have been carried over from release to release. > > For almost everything, and certainly for the overwhelming majority of > new entries, we do exactly as you say. However, I (as base-passwd > maintainer) will not remove entries from the global static list unless > there is a very compelling reason to do so beyond cleaning up cruft; > packages are entitled to assume that they are present without declaring > any particular dependency and there's no reasonable way to know what > removing such entries would break. > I end up modifying the passwd/group files on my computers for auditing purposes and to ensure that the only accounts on the system are required accounts. Removing cruft seems like a perfectly valid reason. In 10 years will Ubuntu still have a uucp user and a news user and an irc user? Seems silly. Let's clean things up and keep it to just the accounts that must be there. We can then easily fix packages that wrongly assumed that their particular user would be always be there. > > In any case, there are only 18 entries in the global static list > (/usr/share/base-passwd/passwd.master), and even without thinking about > it too hard I know that at least four or five are still in use and > probably more, so there's not that much to be gained. All other system > entries in the passwd file are created dynamically by applications. > > Since I took over base-passwd in 2002, I have added no new global static > users and only two new global static groups, the last of which was in > 2004. > > > In addition, for users in the passwd file that must be there, could you > > please set their shell to /usr/sbin/nologin? > > Yes, I would like to do this eventually > (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=274229). However, > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=184979 has to be fixed > first, otherwise everyone will have their upgrades interrupted by a > non-debconf prompt. I haven't had time to work on #184979 in quite a > number of years, and to the best of my knowledge nobody has ever > contributed a patch for it; I'd be happy to review one if somebody did > so. > > The one wart here is that using /usr/sbin/nologin will break anything > that runs commands as one of those users using the 'su' command. This > isn't theoretical; one of my packages used to do so some years ago, > although it now uses start-stop-daemon instead. The breakage is > probably worthwhile, I'll admit, but I can't say that there would be no > problems with changing those users' shell since there's been such a long > time for packages to get used to it being /bin/sh. > > Cheers, > > -- > Colin Watson [cjwat...@ubuntu.com] > > -- > Ubuntu-devel-discuss mailing list > Ubuntu-devel-discuss@lists.ubuntu.com > Modify settings or unsubscribe at: > https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss > -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
Re: Cleaning up the users and locking down the shells in /etc/passwd
On Thu, Sep 22, 2011 at 04:33:00PM -0700, Matt Alexander wrote: > Would it be possible to remove the vast majority of users from /etc/passwd > and instead rely on the application being installed to create the specific > user if needed? Most of the users appear to be historical remnants that > have been carried over from release to release. For almost everything, and certainly for the overwhelming majority of new entries, we do exactly as you say. However, I (as base-passwd maintainer) will not remove entries from the global static list unless there is a very compelling reason to do so beyond cleaning up cruft; packages are entitled to assume that they are present without declaring any particular dependency and there's no reasonable way to know what removing such entries would break. In any case, there are only 18 entries in the global static list (/usr/share/base-passwd/passwd.master), and even without thinking about it too hard I know that at least four or five are still in use and probably more, so there's not that much to be gained. All other system entries in the passwd file are created dynamically by applications. Since I took over base-passwd in 2002, I have added no new global static users and only two new global static groups, the last of which was in 2004. > In addition, for users in the passwd file that must be there, could you > please set their shell to /usr/sbin/nologin? Yes, I would like to do this eventually (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=274229). However, http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=184979 has to be fixed first, otherwise everyone will have their upgrades interrupted by a non-debconf prompt. I haven't had time to work on #184979 in quite a number of years, and to the best of my knowledge nobody has ever contributed a patch for it; I'd be happy to review one if somebody did so. The one wart here is that using /usr/sbin/nologin will break anything that runs commands as one of those users using the 'su' command. This isn't theoretical; one of my packages used to do so some years ago, although it now uses start-stop-daemon instead. The breakage is probably worthwhile, I'll admit, but I can't say that there would be no problems with changing those users' shell since there's been such a long time for packages to get used to it being /bin/sh. Cheers, -- Colin Watson [cjwat...@ubuntu.com] -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
Cleaning up the users and locking down the shells in /etc/passwd
Hi! Would it be possible to remove the vast majority of users from /etc/passwd and instead rely on the application being installed to create the specific user if needed? Most of the users appear to be historical remnants that have been carried over from release to release. In addition, for users in the passwd file that must be there, could you please set their shell to /usr/sbin/nologin? Thanks for considering this! ~Matt -- Ubuntu-devel-discuss mailing list Ubuntu-devel-discuss@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
