diff options
| -rw-r--r-- | include/linux/lsm_hook_defs.h | 1 | ||||
| -rw-r--r-- | security/security.c | 70 | ||||
| -rw-r--r-- | security/selinux/hooks.c | 28 | ||||
| -rw-r--r-- | security/smack/smack_lsm.c | 31 |
4 files changed, 98 insertions, 32 deletions
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index f804b76cde44..8fd87f823d3a 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -144,6 +144,7 @@ LSM_HOOK(int, 0, inode_setattr, struct mnt_idmap *idmap, struct dentry *dentry, LSM_HOOK(void, LSM_RET_VOID, inode_post_setattr, struct mnt_idmap *idmap, struct dentry *dentry, int ia_valid) LSM_HOOK(int, 0, inode_getattr, const struct path *path) +LSM_HOOK(int, 0, inode_xattr_skipcap, const char *name) LSM_HOOK(int, 0, inode_setxattr, struct mnt_idmap *idmap, struct dentry *dentry, const char *name, const void *value, size_t size, int flags) diff --git a/security/security.c b/security/security.c index e5da848c50b9..b52e81ac5526 100644 --- a/security/security.c +++ b/security/security.c @@ -2278,7 +2278,20 @@ int security_inode_getattr(const struct path *path) * @size: size of xattr value * @flags: flags * - * Check permission before setting the extended attributes. + * This hook performs the desired permission checks before setting the extended + * attributes (xattrs) on @dentry. It is important to note that we have some + * additional logic before the main LSM implementation calls to detect if we + * need to perform an additional capability check at the LSM layer. + * + * Normally we enforce a capability check prior to executing the various LSM + * hook implementations, but if a LSM wants to avoid this capability check, + * it can register a 'inode_xattr_skipcap' hook and return a value of 1 for + * xattrs that it wants to avoid the capability check, leaving the LSM fully + * responsible for enforcing the access control for the specific xattr. If all + * of the enabled LSMs refrain from registering a 'inode_xattr_skipcap' hook, + * or return a 0 (the default return value), the capability check is still + * performed. If no 'inode_xattr_skipcap' hooks are registered the capability + * check is performed. * * Return: Returns 0 if permission is granted. */ @@ -2286,20 +2299,20 @@ int security_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, const char *name, const void *value, size_t size, int flags) { - int ret; + int rc; if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) return 0; - /* - * SELinux and Smack integrate the cap call, - * so assume that all LSMs supplying this call do so. - */ - ret = call_int_hook(inode_setxattr, idmap, dentry, name, value, size, - flags); - if (ret == 1) - ret = cap_inode_setxattr(dentry, name, value, size, flags); - return ret; + /* enforce the capability checks at the lsm layer, if needed */ + if (!call_int_hook(inode_xattr_skipcap, name)) { + rc = cap_inode_setxattr(dentry, name, value, size, flags); + if (rc) + return rc; + } + + return call_int_hook(inode_setxattr, idmap, dentry, name, value, size, + flags); } /** @@ -2452,26 +2465,39 @@ int security_inode_listxattr(struct dentry *dentry) * @dentry: file * @name: xattr name * - * Check permission before removing the extended attribute identified by @name - * for @dentry. + * This hook performs the desired permission checks before setting the extended + * attributes (xattrs) on @dentry. It is important to note that we have some + * additional logic before the main LSM implementation calls to detect if we + * need to perform an additional capability check at the LSM layer. + * + * Normally we enforce a capability check prior to executing the various LSM + * hook implementations, but if a LSM wants to avoid this capability check, + * it can register a 'inode_xattr_skipcap' hook and return a value of 1 for + * xattrs that it wants to avoid the capability check, leaving the LSM fully + * responsible for enforcing the access control for the specific xattr. If all + * of the enabled LSMs refrain from registering a 'inode_xattr_skipcap' hook, + * or return a 0 (the default return value), the capability check is still + * performed. If no 'inode_xattr_skipcap' hooks are registered the capability + * check is performed. * * Return: Returns 0 if permission is granted. */ int security_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry, const char *name) { - int ret; + int rc; if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) return 0; - /* - * SELinux and Smack integrate the cap call, - * so assume that all LSMs supplying this call do so. - */ - ret = call_int_hook(inode_removexattr, idmap, dentry, name); - if (ret == 1) - ret = cap_inode_removexattr(idmap, dentry, name); - return ret; + + /* enforce the capability checks at the lsm layer, if needed */ + if (!call_int_hook(inode_xattr_skipcap, name)) { + rc = cap_inode_removexattr(idmap, dentry, name); + if (rc) + return rc; + } + + return call_int_hook(inode_removexattr, idmap, dentry, name); } /** diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 7eed331e90f0..17e6640bbf5b 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3177,6 +3177,23 @@ static bool has_cap_mac_admin(bool audit) return true; } +/** + * selinux_inode_xattr_skipcap - Skip the xattr capability checks? + * @name: name of the xattr + * + * Returns 1 to indicate that SELinux "owns" the access control rights to xattrs + * named @name; the LSM layer should avoid enforcing any traditional + * capability based access controls on this xattr. Returns 0 to indicate that + * SELinux does not "own" the access control rights to xattrs named @name and is + * deferring to the LSM layer for further access controls, including capability + * based controls. + */ +static int selinux_inode_xattr_skipcap(const char *name) +{ + /* require capability check if not a selinux xattr */ + return !strcmp(name, XATTR_NAME_SELINUX); +} + static int selinux_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, const char *name, const void *value, size_t size, int flags) @@ -3188,15 +3205,9 @@ static int selinux_inode_setxattr(struct mnt_idmap *idmap, u32 newsid, sid = current_sid(); int rc = 0; - if (strcmp(name, XATTR_NAME_SELINUX)) { - rc = cap_inode_setxattr(dentry, name, value, size, flags); - if (rc) - return rc; - - /* Not an attribute we recognize, so just check the - ordinary setattr permission. */ + /* if not a selinux xattr, only check the ordinary setattr perm */ + if (strcmp(name, XATTR_NAME_SELINUX)) return dentry_has_perm(current_cred(), dentry, FILE__SETATTR); - } if (!selinux_initialized()) return (inode_owner_or_capable(idmap, inode) ? 0 : -EPERM); @@ -7175,6 +7186,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = { LSM_HOOK_INIT(inode_permission, selinux_inode_permission), LSM_HOOK_INIT(inode_setattr, selinux_inode_setattr), LSM_HOOK_INIT(inode_getattr, selinux_inode_getattr), + LSM_HOOK_INIT(inode_xattr_skipcap, selinux_inode_xattr_skipcap), LSM_HOOK_INIT(inode_setxattr, selinux_inode_setxattr), LSM_HOOK_INIT(inode_post_setxattr, selinux_inode_post_setxattr), LSM_HOOK_INIT(inode_getxattr, selinux_inode_getxattr), diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 70ba2841e181..1833bd50d97a 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -1283,6 +1283,33 @@ static int smack_inode_getattr(const struct path *path) } /** + * smack_inode_xattr_skipcap - Skip the xattr capability checks? + * @name: name of the xattr + * + * Returns 1 to indicate that Smack "owns" the access control rights to xattrs + * named @name; the LSM layer should avoid enforcing any traditional + * capability based access controls on this xattr. Returns 0 to indicate that + * Smack does not "own" the access control rights to xattrs named @name and is + * deferring to the LSM layer for further access controls, including capability + * based controls. + */ +static int smack_inode_xattr_skipcap(const char *name) +{ + if (strncmp(name, XATTR_SMACK_SUFFIX, strlen(XATTR_SMACK_SUFFIX))) + return 0; + + if (strcmp(name, XATTR_NAME_SMACK) == 0 || + strcmp(name, XATTR_NAME_SMACKIPIN) == 0 || + strcmp(name, XATTR_NAME_SMACKIPOUT) == 0 || + strcmp(name, XATTR_NAME_SMACKEXEC) == 0 || + strcmp(name, XATTR_NAME_SMACKMMAP) == 0 || + strcmp(name, XATTR_NAME_SMACKTRANSMUTE) == 0) + return 1; + + return 0; +} + +/** * smack_inode_setxattr - Smack check for setting xattrs * @idmap: idmap of the mount * @dentry: the object @@ -1325,8 +1352,7 @@ static int smack_inode_setxattr(struct mnt_idmap *idmap, size != TRANS_TRUE_SIZE || strncmp(value, TRANS_TRUE, TRANS_TRUE_SIZE) != 0) rc = -EINVAL; - } else - rc = cap_inode_setxattr(dentry, name, value, size, flags); + } if (check_priv && !smack_privileged(CAP_MAC_ADMIN)) rc = -EPERM; @@ -5051,6 +5077,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = { LSM_HOOK_INIT(inode_permission, smack_inode_permission), LSM_HOOK_INIT(inode_setattr, smack_inode_setattr), LSM_HOOK_INIT(inode_getattr, smack_inode_getattr), + LSM_HOOK_INIT(inode_xattr_skipcap, smack_inode_xattr_skipcap), LSM_HOOK_INIT(inode_setxattr, smack_inode_setxattr), LSM_HOOK_INIT(inode_post_setxattr, smack_inode_post_setxattr), LSM_HOOK_INIT(inode_getxattr, smack_inode_getxattr), |