Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
On Thu, 2017-11-02 at 22:01 +, David Howells wrote:
> Mimi Zohar wrote:
>
> > Right, it would never get here if the IMA signature verification
> > fails. If sig_enforce is not enabled, then it will also work. So the
> > only case is if sig_enforced is enabled and there is no key.
> >
> > eg.
> > else if (can_do_ima_check && is_ima_appraise_enabled())
> > err = 0;
>
> I'm not sure where you want to put that, but I can't just do this:
>
> /* Not having a signature is only an error if we're strict. */
> if (err == -ENOKEY && !sig_enforce &&
> (!can_do_ima_check || !is_ima_appraise_enabled()) &&
The above IMA checks aren't needed here.
> !kernel_is_locked_down("Loading of unsigned modules"))
> err = 0;
> else if (can_do_ima_check && is_ima_appraise_enabled())
> err = 0;
>
> because that'll print out a message in lockdown mode saying that you're not
> allowed to do that and then maybe do it anyway.
Then at least for now, document that even though kernel modules might
be signed and verified by IMA-appraisal, that in lockdown mode they
also require an appended signature.
Mimi
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Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
Mimi Zohar wrote:
> Right, it would never get here if the IMA signature verification
> fails. If sig_enforce is not enabled, then it will also work. So the
> only case is if sig_enforced is enabled and there is no key.
>
> eg.
> else if (can_do_ima_check && is_ima_appraise_enabled())
> err = 0;
I'm not sure where you want to put that, but I can't just do this:
/* Not having a signature is only an error if we're strict. */
if (err == -ENOKEY && !sig_enforce &&
(!can_do_ima_check || !is_ima_appraise_enabled()) &&
!kernel_is_locked_down("Loading of unsigned modules"))
err = 0;
else if (can_do_ima_check && is_ima_appraise_enabled())
err = 0;
because that'll print out a message in lockdown mode saying that you're not
allowed to do that and then maybe do it anyway.
David
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Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
On Thu, 2017-11-02 at 21:30 +, David Howells wrote: > Mimi Zohar wrote: > > > By this point, IMA-appraisal has already verified the kernel module > > signature back in kernel_read_file_from_fd(), if it was required. > > Having a key with which to verify the appended signature or requiring > > an appended signature, should not be required as well. > > I guess I don't need to put in any support for IMA here, then, and you've > taken care of it in your patchset such that it won't actually go into > module_sig_check() in that case (or will at least return immediately). Right, it would never get here if the IMA signature verification fails. If sig_enforce is not enabled, then it will also work. So the only case is if sig_enforced is enabled and there is no key. eg. else if (can_do_ima_check && is_ima_appraise_enabled()) err = 0; Mimi -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
Mimi Zohar wrote: > By this point, IMA-appraisal has already verified the kernel module > signature back in kernel_read_file_from_fd(), if it was required. > Having a key with which to verify the appended signature or requiring > an appended signature, should not be required as well. I guess I don't need to put in any support for IMA here, then, and you've taken care of it in your patchset such that it won't actually go into module_sig_check() in that case (or will at least return immediately). David -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
On Thu, 2017-11-02 at 17:22 +, David Howells wrote:
> #ifdef CONFIG_MODULE_SIG
> -static int module_sig_check(struct load_info *info, int flags)
> +static int module_sig_check(struct load_info *info, int flags,
> + bool can_do_ima_check)
> {
> int err = -ENOKEY;
> const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
> @@ -2781,13 +2783,16 @@ static int module_sig_check(struct load_info *info,
> int flags)
> }
>
> /* Not having a signature is only an error if we're strict. */
> - if (err == -ENOKEY && !sig_enforce)
> + if (err == -ENOKEY && !sig_enforce &&
> + (!can_do_ima_check || !is_ima_appraise_enabled()) &&
> + !kernel_is_locked_down("Loading of unsigned modules"))
By this point, IMA-appraisal has already verified the kernel module
signature back in kernel_read_file_from_fd(), if it was required.
Having a key with which to verify the appended signature or requiring
an appended signature, should not be required as well.
Mimi
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Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
Hi Mimi,
I've altered this patch to allow for IMA appraisal on finit_module(). See the
attached.
David
---
commit c0d5336356004e7543314e388755a00e725521da
Author: David Howells
Date: Wed May 24 14:56:01 2017 +0100
Enforce module signatures if the kernel is locked down
If the kernel is locked down, require that all modules have valid
signatures that we can verify or that IMA can validate the file.
Signed-off-by: David Howells
Reviewed-by: "Lee, Chun-Yi"
Reviewed-by: James Morris
diff --git a/kernel/module.c b/kernel/module.c
index de66ec825992..0ce29c8aa75a 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -64,6 +64,7 @@
#include
#include
#include
+#include
#include
#include "module-internal.h"
@@ -2757,7 +2758,8 @@ static inline void kmemleak_load_module(const struct
module *mod,
#endif
#ifdef CONFIG_MODULE_SIG
-static int module_sig_check(struct load_info *info, int flags)
+static int module_sig_check(struct load_info *info, int flags,
+ bool can_do_ima_check)
{
int err = -ENOKEY;
const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
@@ -2781,13 +2783,16 @@ static int module_sig_check(struct load_info *info, int
flags)
}
/* Not having a signature is only an error if we're strict. */
- if (err == -ENOKEY && !sig_enforce)
+ if (err == -ENOKEY && !sig_enforce &&
+ (!can_do_ima_check || !is_ima_appraise_enabled()) &&
+ !kernel_is_locked_down("Loading of unsigned modules"))
err = 0;
return err;
}
#else /* !CONFIG_MODULE_SIG */
-static int module_sig_check(struct load_info *info, int flags)
+static int module_sig_check(struct load_info *info, int flags,
+ bool can_do_ima_check)
{
return 0;
}
@@ -3630,13 +3635,13 @@ static int unknown_module_param_cb(char *param, char
*val, const char *modname,
/* Allocate and load the module: note that size of section 0 is always
zero, and we rely on this for optional sections. */
static int load_module(struct load_info *info, const char __user *uargs,
- int flags)
+ int flags, bool can_do_ima_check)
{
struct module *mod;
long err;
char *after_dashes;
- err = module_sig_check(info, flags);
+ err = module_sig_check(info, flags, can_do_ima_check);
if (err)
goto free_copy;
@@ -3830,7 +3835,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
if (err)
return err;
- return load_module(&info, uargs, 0);
+ return load_module(&info, uargs, 0, false);
}
SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
@@ -3857,7 +3862,7 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user
*, uargs, int, flags)
info.hdr = hdr;
info.len = size;
- return load_module(&info, uargs, flags);
+ return load_module(&info, uargs, flags, true);
}
static inline int within(unsigned long addr, void *start, unsigned long size)
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Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
[Corrected Matthew Garrett's email address. Cc'ed Bruno Meneguele] On Mon, 2017-10-30 at 17:00 +, David Howells wrote: > Mimi Zohar wrote: > > > This kernel_is_locked_down() check is being called for both the > > original and new module_load syscalls. We need to be able > > differentiate them. This is fine for the original syscall, but for > > the new syscall we would need an additional IMA check - > > !is_ima_appraise_enabled(). > > IMA can only be used with finit_module()? Yes, without the file descriptor, IMA-appraisal can't access the xattrs. You should really look at Bruno's patches, which are in my next branch: 8168913c50d5 "ima: check signature enforcement against cmdline param instead of CONFIG" 404090509894 module: export module signature enforcement status Can we get an Ack on the module one? Mimi -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
Mimi Zohar wrote: > This kernel_is_locked_down() check is being called for both the > original and new module_load syscalls. We need to be able > differentiate them. This is fine for the original syscall, but for > the new syscall we would need an additional IMA check - > !is_ima_appraise_enabled(). IMA can only be used with finit_module()? David -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
On Thu, 2017-10-19 at 15:50 +0100, David Howells wrote:
> If the kernel is locked down, require that all modules have valid
> signatures that we can verify.
>
> Signed-off-by: David Howells
> ---
>
> kernel/module.c |3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index de66ec825992..3d9a3270c179 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2781,7 +2781,8 @@ static int module_sig_check(struct load_info *info, int
> flags)
> }
>
> /* Not having a signature is only an error if we're strict. */
> - if (err == -ENOKEY && !sig_enforce)
> + if (err == -ENOKEY && !sig_enforce &&
> + !kernel_is_locked_down("Loading of unsigned modules"))
This kernel_is_locked_down() check is being called for both the
original and new module_load syscalls. We need to be able
differentiate them. This is fine for the original syscall, but for
the new syscall we would need an additional IMA check -
!is_ima_appraise_enabled().
Mimi
> err = 0;
>
> return err;
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Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
On Thu, 19 Oct 2017, David Howells wrote: > If the kernel is locked down, require that all modules have valid > signatures that we can verify. > > Signed-off-by: David Howells Reviewed-by: James Morris -- James Morris -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down
Hi David,
Thanks for you send our this series.
On Thu, Oct 19, 2017 at 03:50:55PM +0100, David Howells wrote:
> If the kernel is locked down, require that all modules have valid
> signatures that we can verify.
>
> Signed-off-by: David Howells
I have reviewed and tested this patch. Please feel free to add:
Reviewed-by: "Lee, Chun-Yi"
Thanks a lot!
Joey Lee
> ---
>
> kernel/module.c |3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index de66ec825992..3d9a3270c179 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2781,7 +2781,8 @@ static int module_sig_check(struct load_info *info, int
> flags)
> }
>
> /* Not having a signature is only an error if we're strict. */
> - if (err == -ENOKEY && !sig_enforce)
> + if (err == -ENOKEY && !sig_enforce &&
> + !kernel_is_locked_down("Loading of unsigned modules"))
> err = 0;
>
> return err;
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-efi" in
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[PATCH 03/27] Enforce module signatures if the kernel is locked down
If the kernel is locked down, require that all modules have valid
signatures that we can verify.
Signed-off-by: David Howells
---
kernel/module.c |3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/module.c b/kernel/module.c
index de66ec825992..3d9a3270c179 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2781,7 +2781,8 @@ static int module_sig_check(struct load_info *info, int
flags)
}
/* Not having a signature is only an error if we're strict. */
- if (err == -ENOKEY && !sig_enforce)
+ if (err == -ENOKEY && !sig_enforce &&
+ !kernel_is_locked_down("Loading of unsigned modules"))
err = 0;
return err;
--
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