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