diff mbox series

[1/3] security: Add LSM hook to setgroups() syscall

Message ID 20220616171809.783277-1-mortonm@chromium.org (mailing list archive)
State New
Headers show
Series [1/3] security: Add LSM hook to setgroups() syscall | expand

Commit Message

Micah Morton June 16, 2022, 5:18 p.m. UTC
Give the LSM framework the ability to filter setgroups() syscalls. There
are already analagous hooks for the set*uid() and set*gid() syscalls.
The SafeSetID LSM will use this new hook to ensure setgroups() calls are
allowed by the installed security policy. Tested by putting print
statement in security_task_fix_setgroups() hook and confirming that it
gets hit when userspace does a setgroups() syscall.

Signed-off-by: Micah Morton <mortonm@chromium.org>
---
 include/linux/lsm_hook_defs.h |  1 +
 include/linux/lsm_hooks.h     |  7 +++++++
 include/linux/security.h      |  7 +++++++
 kernel/groups.c               | 13 +++++++++++++
 security/security.c           |  5 +++++
 5 files changed, 33 insertions(+)

Comments

Casey Schaufler June 20, 2022, 6:15 p.m. UTC | #1
On 6/16/2022 10:18 AM, Micah Morton wrote:
> Give the LSM framework the ability to filter setgroups() syscalls. There
> are already analagous hooks for the set*uid() and set*gid() syscalls.
> The SafeSetID LSM will use this new hook to ensure setgroups() calls are
> allowed by the installed security policy. Tested by putting print
> statement in security_task_fix_setgroups() hook and confirming that it
> gets hit when userspace does a setgroups() syscall.
>
> Signed-off-by: Micah Morton <mortonm@chromium.org>

I don't see any problems with this.
Acked-by: Casey Schaufler <casey@schaufler-ca.com>

> ---
>   include/linux/lsm_hook_defs.h |  1 +
>   include/linux/lsm_hooks.h     |  7 +++++++
>   include/linux/security.h      |  7 +++++++
>   kernel/groups.c               | 13 +++++++++++++
>   security/security.c           |  5 +++++
>   5 files changed, 33 insertions(+)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index eafa1d2489fd..806448173033 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -201,6 +201,7 @@ 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_fix_setgroups, struct cred *new, const struct cred * old)
>   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 91c8146649f5..84a0d7e02176 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -702,6 +702,13 @@
>    *	@old is the set of credentials that are being replaced.
>    *	@flags contains one of the LSM_SETID_* values.
>    *	Return 0 on success.
> + * @task_fix_setgroups:
> + *	Update the module's state after setting the supplementary group
> + *	identity attributes of the current process.
> + *	@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.
> + *	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 7fc4e9f49f54..1dfd32c49fa3 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -415,6 +415,7 @@ 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_fix_setgroups(struct cred *new, const struct cred *old);
>   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);
> @@ -1098,6 +1099,12 @@ static inline int security_task_fix_setgid(struct cred *new,
>   	return 0;
>   }
>   
> +static inline int security_task_fix_setgroups(struct cred *new,
> +					   const struct cred *old)
> +{
> +	return 0;
> +}
> +
>   static inline int security_task_setpgid(struct task_struct *p, pid_t pgid)
>   {
>   	return 0;
> diff --git a/kernel/groups.c b/kernel/groups.c
> index 787b381c7c00..9aaed2a31073 100644
> --- a/kernel/groups.c
> +++ b/kernel/groups.c
> @@ -134,13 +134,26 @@ EXPORT_SYMBOL(set_groups);
>   int set_current_groups(struct group_info *group_info)
>   {
>   	struct cred *new;
> +	const struct cred *old;
> +	int retval;
>   
>   	new = prepare_creds();
>   	if (!new)
>   		return -ENOMEM;
>   
> +	old = current_cred();
> +
>   	set_groups(new, group_info);
> +
> +	retval = security_task_fix_setgroups(new, old);
> +	if (retval < 0)
> +		goto error;
> +
>   	return commit_creds(new);
> +
> +error:
> +	abort_creds(new);
> +	return retval;
>   }
>   
>   EXPORT_SYMBOL(set_current_groups);
> diff --git a/security/security.c b/security/security.c
> index 188b8f782220..15c686145ad6 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1803,6 +1803,11 @@ int security_task_fix_setgid(struct cred *new, const struct cred *old,
>   	return call_int_hook(task_fix_setgid, 0, new, old, flags);
>   }
>   
> +int security_task_fix_setgroups(struct cred *new, const struct cred *old)
> +{
> +	return call_int_hook(task_fix_setgroups, 0, new, old);
> +}
> +
>   int security_task_setpgid(struct task_struct *p, pid_t pgid)
>   {
>   	return call_int_hook(task_setpgid, 0, p, pgid);
Serge E. Hallyn June 26, 2022, 11:33 p.m. UTC | #2
On Mon, Jun 20, 2022 at 11:15:05AM -0700, Casey Schaufler wrote:
> On 6/16/2022 10:18 AM, Micah Morton wrote:
> > Give the LSM framework the ability to filter setgroups() syscalls. There
> > are already analagous hooks for the set*uid() and set*gid() syscalls.
> > The SafeSetID LSM will use this new hook to ensure setgroups() calls are
> > allowed by the installed security policy. Tested by putting print
> > statement in security_task_fix_setgroups() hook and confirming that it
> > gets hit when userspace does a setgroups() syscall.
> > 
> > Signed-off-by: Micah Morton <mortonm@chromium.org>
> 
> I don't see any problems with this.
> Acked-by: Casey Schaufler <casey@schaufler-ca.com>
> 

Ditto.  Thanks.

Reviewed-by: Serge Hallyn <serge@hallyn.com>

> > ---
> >   include/linux/lsm_hook_defs.h |  1 +
> >   include/linux/lsm_hooks.h     |  7 +++++++
> >   include/linux/security.h      |  7 +++++++
> >   kernel/groups.c               | 13 +++++++++++++
> >   security/security.c           |  5 +++++
> >   5 files changed, 33 insertions(+)
> > 
> > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> > index eafa1d2489fd..806448173033 100644
> > --- a/include/linux/lsm_hook_defs.h
> > +++ b/include/linux/lsm_hook_defs.h
> > @@ -201,6 +201,7 @@ 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_fix_setgroups, struct cred *new, const struct cred * old)
> >   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 91c8146649f5..84a0d7e02176 100644
> > --- a/include/linux/lsm_hooks.h
> > +++ b/include/linux/lsm_hooks.h
> > @@ -702,6 +702,13 @@
> >    *	@old is the set of credentials that are being replaced.
> >    *	@flags contains one of the LSM_SETID_* values.
> >    *	Return 0 on success.
> > + * @task_fix_setgroups:
> > + *	Update the module's state after setting the supplementary group
> > + *	identity attributes of the current process.
> > + *	@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.
> > + *	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 7fc4e9f49f54..1dfd32c49fa3 100644
> > --- a/include/linux/security.h
> > +++ b/include/linux/security.h
> > @@ -415,6 +415,7 @@ 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_fix_setgroups(struct cred *new, const struct cred *old);
> >   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);
> > @@ -1098,6 +1099,12 @@ static inline int security_task_fix_setgid(struct cred *new,
> >   	return 0;
> >   }
> > +static inline int security_task_fix_setgroups(struct cred *new,
> > +					   const struct cred *old)
> > +{
> > +	return 0;
> > +}
> > +
> >   static inline int security_task_setpgid(struct task_struct *p, pid_t pgid)
> >   {
> >   	return 0;
> > diff --git a/kernel/groups.c b/kernel/groups.c
> > index 787b381c7c00..9aaed2a31073 100644
> > --- a/kernel/groups.c
> > +++ b/kernel/groups.c
> > @@ -134,13 +134,26 @@ EXPORT_SYMBOL(set_groups);
> >   int set_current_groups(struct group_info *group_info)
> >   {
> >   	struct cred *new;
> > +	const struct cred *old;
> > +	int retval;
> >   	new = prepare_creds();
> >   	if (!new)
> >   		return -ENOMEM;
> > +	old = current_cred();
> > +
> >   	set_groups(new, group_info);
> > +
> > +	retval = security_task_fix_setgroups(new, old);
> > +	if (retval < 0)
> > +		goto error;
> > +
> >   	return commit_creds(new);
> > +
> > +error:
> > +	abort_creds(new);
> > +	return retval;
> >   }
> >   EXPORT_SYMBOL(set_current_groups);
> > diff --git a/security/security.c b/security/security.c
> > index 188b8f782220..15c686145ad6 100644
> > --- a/security/security.c
> > +++ b/security/security.c
> > @@ -1803,6 +1803,11 @@ int security_task_fix_setgid(struct cred *new, const struct cred *old,
> >   	return call_int_hook(task_fix_setgid, 0, new, old, flags);
> >   }
> > +int security_task_fix_setgroups(struct cred *new, const struct cred *old)
> > +{
> > +	return call_int_hook(task_fix_setgroups, 0, new, old);
> > +}
> > +
> >   int security_task_setpgid(struct task_struct *p, pid_t pgid)
> >   {
> >   	return call_int_hook(task_setpgid, 0, p, pgid);
diff mbox series

Patch

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index eafa1d2489fd..806448173033 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -201,6 +201,7 @@  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_fix_setgroups, struct cred *new, const struct cred * old)
 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 91c8146649f5..84a0d7e02176 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -702,6 +702,13 @@ 
  *	@old is the set of credentials that are being replaced.
  *	@flags contains one of the LSM_SETID_* values.
  *	Return 0 on success.
+ * @task_fix_setgroups:
+ *	Update the module's state after setting the supplementary group
+ *	identity attributes of the current process.
+ *	@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.
+ *	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 7fc4e9f49f54..1dfd32c49fa3 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -415,6 +415,7 @@  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_fix_setgroups(struct cred *new, const struct cred *old);
 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);
@@ -1098,6 +1099,12 @@  static inline int security_task_fix_setgid(struct cred *new,
 	return 0;
 }
 
+static inline int security_task_fix_setgroups(struct cred *new,
+					   const struct cred *old)
+{
+	return 0;
+}
+
 static inline int security_task_setpgid(struct task_struct *p, pid_t pgid)
 {
 	return 0;
diff --git a/kernel/groups.c b/kernel/groups.c
index 787b381c7c00..9aaed2a31073 100644
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -134,13 +134,26 @@  EXPORT_SYMBOL(set_groups);
 int set_current_groups(struct group_info *group_info)
 {
 	struct cred *new;
+	const struct cred *old;
+	int retval;
 
 	new = prepare_creds();
 	if (!new)
 		return -ENOMEM;
 
+	old = current_cred();
+
 	set_groups(new, group_info);
+
+	retval = security_task_fix_setgroups(new, old);
+	if (retval < 0)
+		goto error;
+
 	return commit_creds(new);
+
+error:
+	abort_creds(new);
+	return retval;
 }
 
 EXPORT_SYMBOL(set_current_groups);
diff --git a/security/security.c b/security/security.c
index 188b8f782220..15c686145ad6 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1803,6 +1803,11 @@  int security_task_fix_setgid(struct cred *new, const struct cred *old,
 	return call_int_hook(task_fix_setgid, 0, new, old, flags);
 }
 
+int security_task_fix_setgroups(struct cred *new, const struct cred *old)
+{
+	return call_int_hook(task_fix_setgroups, 0, new, old);
+}
+
 int security_task_setpgid(struct task_struct *p, pid_t pgid)
 {
 	return call_int_hook(task_setpgid, 0, p, pgid);