In case a setuid or setgid binary is mislabeled with a generic context,
either via a policy mistake or a move by the distribution package,
executing it will be checked by the file permission execute_no_trans on
the generic file context (e.g. bin_t). The setuid(2)/setgid(2) syscall
within will then be checked against the unchanged caller process
context, which might have been granted the capability permission setuid/
setgid to initially drop privileges. To avoid that scenario split the
execute_no_trans permission in case of a setuid/setgid binary into a new
permission execute_sxid_no_trans.
For backward compatibility this behavior is contained in a new policy
capability.
Signed-off-by: Christian Göttsche <[email protected]>
---
security/selinux/hooks.c | 9 ++++++++-
security/selinux/include/classmap.h | 2 +-
security/selinux/include/policycap.h | 1 +
security/selinux/include/policycap_names.h | 3 ++-
security/selinux/include/security.h | 8 ++++++++
5 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 5b6895e4fc29..b825fee39a70 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2348,9 +2348,16 @@ static int selinux_bprm_creds_for_exec(struct linux_binprm *bprm)
ad.u.file = bprm->file;
if (new_tsec->sid == old_tsec->sid) {
+ u32 perm;
+
+ if (selinux_policycap_execute_sxid_no_trans() && is_sxid(inode->i_mode))
+ perm = FILE__EXECUTE_SXID_NO_TRANS;
+ else
+ perm = FILE__EXECUTE_NO_TRANS;
+
rc = avc_has_perm(&selinux_state,
old_tsec->sid, isec->sid,
- SECCLASS_FILE, FILE__EXECUTE_NO_TRANS, &ad);
+ SECCLASS_FILE, perm, &ad);
if (rc)
return rc;
} else {
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 35aac62a662e..53a1eeeb86fb 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -65,7 +65,7 @@ struct security_class_mapping secclass_map[] = {
"quotaget", "watch", NULL } },
{ "file",
{ COMMON_FILE_PERMS,
- "execute_no_trans", "entrypoint", NULL } },
+ "execute_no_trans", "entrypoint", "execute_sxid_no_trans", NULL } },
{ "dir",
{ COMMON_FILE_PERMS, "add_name", "remove_name",
"reparent", "search", "rmdir", NULL } },
diff --git a/security/selinux/include/policycap.h b/security/selinux/include/policycap.h
index 2ec038efbb03..23929dc3e1db 100644
--- a/security/selinux/include/policycap.h
+++ b/security/selinux/include/policycap.h
@@ -11,6 +11,7 @@ enum {
POLICYDB_CAPABILITY_CGROUPSECLABEL,
POLICYDB_CAPABILITY_NNP_NOSUID_TRANSITION,
POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS,
+ POLICYDB_CAPABILITY_EXECUTE_SXID_NO_TRANS,
__POLICYDB_CAPABILITY_MAX
};
#define POLICYDB_CAPABILITY_MAX (__POLICYDB_CAPABILITY_MAX - 1)
diff --git a/security/selinux/include/policycap_names.h b/security/selinux/include/policycap_names.h
index b89289f092c9..4c014c2cf352 100644
--- a/security/selinux/include/policycap_names.h
+++ b/security/selinux/include/policycap_names.h
@@ -12,7 +12,8 @@ const char *selinux_policycap_names[__POLICYDB_CAPABILITY_MAX] = {
"always_check_network",
"cgroup_seclabel",
"nnp_nosuid_transition",
- "genfs_seclabel_symlinks"
+ "genfs_seclabel_symlinks",
+ "execute_sxid_no_trans",
};
#endif /* _SELINUX_POLICYCAP_NAMES_H_ */
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index ac0ece01305a..ab95241b6b7b 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -219,6 +219,14 @@ static inline bool selinux_policycap_genfs_seclabel_symlinks(void)
return READ_ONCE(state->policycap[POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS]);
}
+static inline bool selinux_policycap_execute_sxid_no_trans(void)
+{
+ struct selinux_state *state = &selinux_state;
+
+ return READ_ONCE(state->policycap[POLICYDB_CAPABILITY_EXECUTE_SXID_NO_TRANS]);
+}
+
+
struct selinux_policy_convert_data;
struct selinux_load_state {
--
2.34.1