From 39030e1351aa1aa7443bb2da24426573077c83da Mon Sep 17 00:00:00 2001 From: Thomas Cedeno Date: Tue, 9 Jun 2020 10:22:13 -0700 Subject: security: Add LSM hooks to set*gid syscalls 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. Signed-off-by: Thomas Cedeno Signed-off-by: Micah Morton --- 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 5616b2567aa7..2a5a53a83ecb 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -190,6 +190,8 @@ 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 988ca0df7824..b20132bcea2d 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -651,6 +651,15 @@ * @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 a8d9310472df..88749bf0d1d7 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -389,6 +389,8 @@ 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); @@ -1027,6 +1029,13 @@ 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 d325f3ab624a..f5c06c48d585 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 51de970fbb1e..5d4ad6f3fc55 100644 --- a/security/security.c +++ b/security/security.c @@ -1685,6 +1685,12 @@ 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); -- cgit