libsemanage: Preserve file context and ownership in policy store

Make sure that file context (all parts) and ownership of
files/directories in policy store does not change no matter which user
and under which context executes policy rebuild.

Fixes:
  # semodule -B
  # ls -lZ  /etc/selinux/targeted/contexts/files

-rw-r--r--. 1 root root unconfined_u:object_r:file_context_t:s0 421397 Jul 11 09:57 file_contexts
-rw-r--r--. 1 root root unconfined_u:object_r:file_context_t:s0 593470 Jul 11 09:57 file_contexts.bin
-rw-r--r--. 1 root root unconfined_u:object_r:file_context_t:s0  14704 Jul 11 09:57 file_contexts.homedirs
-rw-r--r--. 1 root root unconfined_u:object_r:file_context_t:s0  20289 Jul 11 09:57 file_contexts.homedirs.bin

  SELinux user changed from system_u to the user used to execute semodule

  # capsh --user=testuser --caps="cap_dac_override,cap_chown+eip" --addamb=cap_dac_override,cap_chown -- -c "semodule -B"
  # ls -lZ  /etc/selinux/targeted/contexts/files

-rw-r--r--. 1 testuser testuser unconfined_u:object_r:file_context_t:s0 421397 Jul 19 09:10 file_contexts
-rw-r--r--. 1 testuser testuser unconfined_u:object_r:file_context_t:s0 593470 Jul 19 09:10 file_contexts.bin
-rw-r--r--. 1 testuser testuser unconfined_u:object_r:file_context_t:s0  14704 Jul 19 09:10 file_contexts.homedirs
-rw-r--r--. 1 testuser testuser unconfined_u:object_r:file_context_t:s0  20289 Jul 19 09:10 file_contexts.homedirs.bin

  Both file context and ownership changed -- causes remote login
  failures and other issues in some scenarios.

Signed-off-by: Vit Mojzis <[email protected]>
Acked-by: Stephen Smalley <[email protected]>

Author: vmojzis

libsemanage/src/semanage_store.c

@@ -36,6 +36,7 @@ typedef struct dbase_policydb dbase_t;
 #include "database_policydb.h"
 #include "handle.h"
 
+#include <selinux/restorecon.h>
 #include <selinux/selinux.h>
 #include <sepol/policydb.h>
 #include <sepol/module.h>
@@ -767,6 +768,7 @@ int semanage_copy_file(const char *src, const char *dst, mode_t mode,
 	if (!retval && rename(tmp, dst) == -1)
 		return -1;
 
+	semanage_setfiles(dst);
 out:
 	errno = errsv;
 	return retval;
@@ -819,6 +821,8 @@ static int semanage_copy_dir_flags(const char *src, const char *dst, int flag)
 			goto cleanup;
 		}
 		umask(mask);
+
+		semanage_setfiles(dst);
 	}
 
 	for (i = 0; i < len; i++) {
@@ -837,6 +841,7 @@ static int semanage_copy_dir_flags(const char *src, const char *dst, int flag)
 				goto cleanup;
 			}
 			umask(mask);
+			semanage_setfiles(path2);
 		} else if (S_ISREG(sb.st_mode) && flag == 1) {
 			mask = umask(0077);
 			if (semanage_copy_file(path, path2, sb.st_mode,
@@ -938,6 +943,7 @@ int semanage_mkdir(semanage_handle_t *sh, const char *path)
 
 		}
 		umask(mask);
+		semanage_setfiles(path);
 	}
 	else {
 		/* check that it really is a directory */
@@ -1614,16 +1620,19 @@ static int semanage_validate_and_compile_fcontexts(semanage_handle_t * sh)
 		    semanage_final_path(SEMANAGE_FINAL_TMP, SEMANAGE_FC)) != 0) {
 		goto cleanup;
 	}
+	semanage_setfiles(semanage_final_path(SEMANAGE_FINAL_TMP, SEMANAGE_FC_BIN));
 
 	if (sefcontext_compile(sh,
 		    semanage_final_path(SEMANAGE_FINAL_TMP, SEMANAGE_FC_LOCAL)) != 0) {
 		goto cleanup;
 	}
+	semanage_setfiles(semanage_final_path(SEMANAGE_FINAL_TMP, SEMANAGE_FC_LOCAL_BIN));
 
 	if (sefcontext_compile(sh,
 		    semanage_final_path(SEMANAGE_FINAL_TMP, SEMANAGE_FC_HOMEDIRS)) != 0) {
 		goto cleanup;
 	}
+	semanage_setfiles(semanage_final_path(SEMANAGE_FINAL_TMP, SEMANAGE_FC_HOMEDIRS_BIN));
 
 	status = 0;
 cleanup:
@@ -3018,3 +3027,26 @@ int semanage_nc_sort(semanage_handle_t * sh, const char *buf, size_t buf_len,
 
 	return 0;
 }
+
+/* Make sure the file context and ownership of files in the policy
+ * store does not change */
+void semanage_setfiles(const char *path){
+	struct stat sb;
+	int fd;
+	/* Fix the user and role portions of the context, ignore errors
+	 * since this is not a critical operation */
+	selinux_restorecon(path, SELINUX_RESTORECON_SET_SPECFILE_CTX | SELINUX_RESTORECON_IGNORE_NOENTRY);
+
+	/* Make sure "path" is owned by root */
+	if ((geteuid() != 0 || getegid() != 0) &&
+	    ((fd = open(path, O_RDONLY)) != -1)){
+		/* Skip files with the SUID or SGID bit set -- abuse protection */
+		if ((fstat(fd, &sb) != -1) &&
+		    !(S_ISREG(sb.st_mode) &&
+		      (sb.st_mode & (S_ISUID | S_ISGID))) &&
+		    (fchown(fd, 0, 0) == -1))
+			fprintf(stderr, "Warning! Could not set ownership of %s to root\n", path);
+
+		close(fd);
+	}
+}

libsemanage/src/semanage_store.h

@@ -124,6 +124,7 @@ int semanage_get_cil_paths(semanage_handle_t * sh, semanage_module_info_t *modin
 int semanage_get_active_modules(semanage_handle_t *sh,
 			       semanage_module_info_t **modinfo, int *num_modules);
 
+void semanage_setfiles(const char *path);
 
 /* lock file routines */
 int semanage_get_trans_lock(semanage_handle_t * sh);