* [PATCH] security: Add LSM hooks to set*gid syscalls
@ 2020-06-05 19:38 Micah Morton
2020-06-05 21:25 ` Kees Cook
0 siblings, 1 reply; 3+ messages in thread
From: Micah Morton @ 2020-06-05 19:38 UTC (permalink / raw)
To: linux-security-module; +Cc: keescook, thomascedeno, Micah Morton
The SafeSetID LSM uses the security_task_fix_setuid hook to filter
set*uid() syscalls according to its configured security policy. In
preparation for adding analagous support in the LSM for set*gid()
syscalls, we add the requisite hook here. Tested by putting print
statements in the security_task_fix_setgid hook and seeing them get hit
during kernel boot.
From: Thomas Cedeno <thomascedeno@google.com>
Signed-off-by: Thomas Cedeno <thomascedeno@google.com>
Reviewed-by: Micah Morton <mortonm@chromium.org>
---
NOTE: I (Micah) will send this patch as a pull request to Linus through
my SafeSetID tree if there are no objections.
include/linux/lsm_hook_defs.h | 2 ++
include/linux/lsm_hooks.h | 9 +++++++++
include/linux/security.h | 9 +++++++++
kernel/sys.c | 15 ++++++++++++++-
security/security.c | 6 ++++++
5 files changed, 40 insertions(+), 1 deletion(-)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index fb3ce6cec997..d5401c09f2d3 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -191,6 +191,8 @@ LSM_HOOK(int, 0, kernel_post_read_file, struct file *file, char *buf,
loff_t size, enum kernel_read_file_id id)
LSM_HOOK(int, 0, task_fix_setuid, struct cred *new, const struct cred *old,
int flags)
+LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old,
+ int flags)
LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid)
LSM_HOOK(int, 0, task_getpgid, struct task_struct *p)
LSM_HOOK(int, 0, task_getsid, struct task_struct *p)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 3e62dab77699..8012b610fe53 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -659,6 +659,15 @@
* @old is the set of credentials that are being replaces
* @flags contains one of the LSM_SETID_* values.
* Return 0 on success.
+ * @task_fix_setgid:
+ * Update the module's state after setting one or more of the group
+ * identity attributes of the current process. The @flags parameter
+ * indicates which of the set*gid system calls invoked this hook.
+ * @new is the set of credentials that will be installed. Modifications
+ * should be made to this rather than to @current->cred.
+ * @old is the set of credentials that are being replaced.
+ * @flags contains one of the LSM_SETID_* values.
+ * Return 0 on success.
* @task_setpgid:
* Check permission before setting the process group identifier of the
* process @p to @pgid.
diff --git a/include/linux/security.h b/include/linux/security.h
index b3f2cb21b4f2..2b08a2e49ba6 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -390,6 +390,8 @@ int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
enum kernel_read_file_id id);
int security_task_fix_setuid(struct cred *new, const struct cred *old,
int flags);
+int security_task_fix_setgid(struct cred *new, const struct cred *old,
+ int flags);
int security_task_setpgid(struct task_struct *p, pid_t pgid);
int security_task_getpgid(struct task_struct *p);
int security_task_getsid(struct task_struct *p);
@@ -1034,6 +1036,13 @@ static inline int security_task_fix_setuid(struct cred *new,
return cap_task_fix_setuid(new, old, flags);
}
+static inline int security_task_fix_setgid(struct cred *new,
+ const struct cred *old,
+ int flags)
+{
+ return 0;
+}
+
static inline int security_task_setpgid(struct task_struct *p, pid_t pgid)
{
return 0;
diff --git a/kernel/sys.c b/kernel/sys.c
index 891667a49bb7..e65ec850bfae 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -393,6 +393,10 @@ long __sys_setregid(gid_t rgid, gid_t egid)
new->sgid = new->egid;
new->fsgid = new->egid;
+ retval = security_task_fix_setgid(new, old, LSM_SETID_RE);
+ if (retval < 0)
+ goto error;
+
return commit_creds(new);
error:
@@ -435,6 +439,10 @@ long __sys_setgid(gid_t gid)
else
goto error;
+ retval = security_task_fix_setgid(new, old, LSM_SETID_ID);
+ if (retval < 0)
+ goto error;
+
return commit_creds(new);
error:
@@ -756,6 +764,10 @@ long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid)
new->sgid = ksgid;
new->fsgid = new->egid;
+ retval = security_task_fix_setgid(new, old, LSM_SETID_RES);
+ if (retval < 0)
+ goto error;
+
return commit_creds(new);
error:
@@ -862,7 +874,8 @@ long __sys_setfsgid(gid_t gid)
ns_capable(old->user_ns, CAP_SETGID)) {
if (!gid_eq(kgid, old->fsgid)) {
new->fsgid = kgid;
- goto change_okay;
+ if (security_task_fix_setgid(new,old,LSM_SETID_FS) == 0)
+ goto change_okay;
}
}
diff --git a/security/security.c b/security/security.c
index 11c1a7da4fd1..639324c68dd0 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1690,6 +1690,12 @@ int security_task_fix_setuid(struct cred *new, const struct cred *old,
return call_int_hook(task_fix_setuid, 0, new, old, flags);
}
+int security_task_fix_setgid(struct cred *new, const struct cred *old,
+ int flags)
+{
+ return call_int_hook(task_fix_setgid, 0, new, old, flags);
+}
+
int security_task_setpgid(struct task_struct *p, pid_t pgid)
{
return call_int_hook(task_setpgid, 0, p, pgid);
--
2.27.0.278.ge193c7cf3a9-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] security: Add LSM hooks to set*gid syscalls
2020-06-05 19:38 [PATCH] security: Add LSM hooks to set*gid syscalls Micah Morton
@ 2020-06-05 21:25 ` Kees Cook
2020-06-05 22:51 ` Micah Morton
0 siblings, 1 reply; 3+ messages in thread
From: Kees Cook @ 2020-06-05 21:25 UTC (permalink / raw)
To: Micah Morton; +Cc: linux-security-module, thomascedeno
On Fri, Jun 05, 2020 at 12:38:05PM -0700, Micah Morton wrote:
> The SafeSetID LSM uses the security_task_fix_setuid hook to filter
> set*uid() syscalls according to its configured security policy. In
> preparation for adding analagous support in the LSM for set*gid()
> syscalls, we add the requisite hook here. Tested by putting print
> statements in the security_task_fix_setgid hook and seeing them get hit
> during kernel boot.
>
> From: Thomas Cedeno <thomascedeno@google.com>
^^^ this line should be before the commit log body (many tools won't
find it here).
> Signed-off-by: Thomas Cedeno <thomascedeno@google.com>
> Reviewed-by: Micah Morton <mortonm@chromium.org>
> ---
> NOTE: I (Micah) will send this patch as a pull request to Linus through
> my SafeSetID tree if there are no objections.
> include/linux/lsm_hook_defs.h | 2 ++
> include/linux/lsm_hooks.h | 9 +++++++++
> include/linux/security.h | 9 +++++++++
> kernel/sys.c | 15 ++++++++++++++-
> security/security.c | 6 ++++++
> 5 files changed, 40 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index fb3ce6cec997..d5401c09f2d3 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -191,6 +191,8 @@ LSM_HOOK(int, 0, kernel_post_read_file, struct file *file, char *buf,
> loff_t size, enum kernel_read_file_id id)
> LSM_HOOK(int, 0, task_fix_setuid, struct cred *new, const struct cred *old,
> int flags)
> +LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old,
> + int flags)
> LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid)
> LSM_HOOK(int, 0, task_getpgid, struct task_struct *p)
> LSM_HOOK(int, 0, task_getsid, struct task_struct *p)
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 3e62dab77699..8012b610fe53 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -659,6 +659,15 @@
> * @old is the set of credentials that are being replaces
> * @flags contains one of the LSM_SETID_* values.
> * Return 0 on success.
> + * @task_fix_setgid:
> + * Update the module's state after setting one or more of the group
> + * identity attributes of the current process. The @flags parameter
> + * indicates which of the set*gid system calls invoked this hook.
> + * @new is the set of credentials that will be installed. Modifications
> + * should be made to this rather than to @current->cred.
> + * @old is the set of credentials that are being replaced.
> + * @flags contains one of the LSM_SETID_* values.
> + * Return 0 on success.
The indenting here appears to be using spaces instead of a tab.
Everything else looks okay. (There are a surprising number of gid
changing places...)
--
Kees Cook
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] security: Add LSM hooks to set*gid syscalls
2020-06-05 21:25 ` Kees Cook
@ 2020-06-05 22:51 ` Micah Morton
0 siblings, 0 replies; 3+ messages in thread
From: Micah Morton @ 2020-06-05 22:51 UTC (permalink / raw)
To: Kees Cook; +Cc: linux-security-module, thomascedeno
On Fri, Jun 5, 2020 at 2:25 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Fri, Jun 05, 2020 at 12:38:05PM -0700, Micah Morton wrote:
> > The SafeSetID LSM uses the security_task_fix_setuid hook to filter
> > set*uid() syscalls according to its configured security policy. In
> > preparation for adding analagous support in the LSM for set*gid()
> > syscalls, we add the requisite hook here. Tested by putting print
> > statements in the security_task_fix_setgid hook and seeing them get hit
> > during kernel boot.
> >
> > From: Thomas Cedeno <thomascedeno@google.com>
>
> ^^^ this line should be before the commit log body (many tools won't
> find it here).
>
> > Signed-off-by: Thomas Cedeno <thomascedeno@google.com>
> > Reviewed-by: Micah Morton <mortonm@chromium.org>
> > ---
> > NOTE: I (Micah) will send this patch as a pull request to Linus through
> > my SafeSetID tree if there are no objections.
> > include/linux/lsm_hook_defs.h | 2 ++
> > include/linux/lsm_hooks.h | 9 +++++++++
> > include/linux/security.h | 9 +++++++++
> > kernel/sys.c | 15 ++++++++++++++-
> > security/security.c | 6 ++++++
> > 5 files changed, 40 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> > index fb3ce6cec997..d5401c09f2d3 100644
> > --- a/include/linux/lsm_hook_defs.h
> > +++ b/include/linux/lsm_hook_defs.h
> > @@ -191,6 +191,8 @@ LSM_HOOK(int, 0, kernel_post_read_file, struct file *file, char *buf,
> > loff_t size, enum kernel_read_file_id id)
> > LSM_HOOK(int, 0, task_fix_setuid, struct cred *new, const struct cred *old,
> > int flags)
> > +LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old,
> > + int flags)
> > LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid)
> > LSM_HOOK(int, 0, task_getpgid, struct task_struct *p)
> > LSM_HOOK(int, 0, task_getsid, struct task_struct *p)
> > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> > index 3e62dab77699..8012b610fe53 100644
> > --- a/include/linux/lsm_hooks.h
> > +++ b/include/linux/lsm_hooks.h
> > @@ -659,6 +659,15 @@
> > * @old is the set of credentials that are being replaces
> > * @flags contains one of the LSM_SETID_* values.
> > * Return 0 on success.
> > + * @task_fix_setgid:
> > + * Update the module's state after setting one or more of the group
> > + * identity attributes of the current process. The @flags parameter
> > + * indicates which of the set*gid system calls invoked this hook.
> > + * @new is the set of credentials that will be installed. Modifications
> > + * should be made to this rather than to @current->cred.
> > + * @old is the set of credentials that are being replaced.
> > + * @flags contains one of the LSM_SETID_* values.
> > + * Return 0 on success.
>
> The indenting here appears to be using spaces instead of a tab.
>
> Everything else looks okay. (There are a surprising number of gid
> changing places...)
Ah thanks! I'll fix those 2 things before doing the pull request.
Probably not worth doing a patch resend.
Will still give it some time to see if anyone else wants to comment.
>
> --
> Kees Cook
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-06-05 19:38 [PATCH] security: Add LSM hooks to set*gid syscalls Micah Morton
2020-06-05 21:25 ` Kees Cook
2020-06-05 22:51 ` Micah Morton
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