Use *at functions for directory creation

Perform path traversal manually and do not follow symlinks.

sbin/create_dirs_from_rpmdb.c

@@ -21,10 +21,12 @@
 #include <config.h>
 #endif
 
+#include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <getopt.h>
 #include <grp.h>
+#include <libgen.h>
 #include <malloc.h>
 #include <pwd.h>
 #include <rpm/rpmcli.h>
@@ -270,19 +272,69 @@ int create_dirs(struct node *node, size_t size) {
         if (verbose_flag)
             printf("Create %s\n", node->dirname);
 
-        if (mkdir(node->dirname, node->fmode) < 0) {
+        const char *component = "/";
+        int dirfd = -1;
+        int saved_errno = 0;
+
+        {
+            // strdup for use with strtok
+            char *local_path = strdup(node->dirname);
+            if (!local_path) {
+                perror("strdup");
+                rc = 1;
+                continue;
+            }
+
+            char *saveptr = NULL;
+            while (1) {
+                const char *next_component = strtok_r(local_path, "/", &saveptr);
+                if (next_component == NULL) {
+                    // component is the last part
+                    break;
+                }
+
+                int nextdirfd = openat(dirfd, component, O_RDONLY | O_DIRECTORY | O_NOFOLLOW);
+                saved_errno = errno;
+                close(dirfd);
+
+                dirfd = nextdirfd;
+                component = next_component;
+
+                if (dirfd < 0) {
+                    break;
+                }
+
+                dirfd = nextdirfd;
+            }
+
+            free(local_path);
+
+            if (dirfd < 0) {
+                errno = saved_errno;
+                fprintf(stderr, "Failed to traverse path for '%s': %m\n", node->dirname);
+                rc = 1;
+                continue;
+            }
+        }
+
+        const char *node_basename = component;
+
+        // Ok to assign mode before chown?
+        if (mkdirat(dirfd, node_basename, node->fmode) < 0) {
             fprintf(stderr, "Failed to create directory '%s': %m\n", node->dirname);
             rc = 1;
             continue;
         }
 
-        if (chown(node->dirname, node->user_id, node->group_id) < 0) {
+        // Ok to assign ownership before se labels?
+        if (fchownat(dirfd, node_basename, node->user_id, node->group_id, AT_SYMLINK_NOFOLLOW) < 0) {
             fprintf(stderr, "Failed to set owner/group for '%s': %m\n", node->dirname);
             /* wrong permissions are bad, remove dir and continue */
-            rmdir(node->dirname);
+            unlinkat(dirfd, node_basename, AT_REMOVEDIR);
             rc = 1;
             continue;
         }
+
         /* ignore errors here, time stamps are not critical */
         utimes(node->dirname, stamps);
 
@@ -295,7 +347,7 @@ int create_dirs(struct node *node, size_t size) {
                 }
 
                 fprintf(stderr, "Failed to get default context for directory '%s': %m\n", node->dirname);
-                rmdir(node->dirname);
+                unlinkat(dirfd, node_basename, AT_REMOVEDIR);
                 rc = 1;
                 continue;
             }
@@ -307,7 +359,7 @@ int create_dirs(struct node *node, size_t size) {
                 if (errno != ENODATA) {
                     fprintf(stderr, "Failed to get old context for '%s': %m\n", node->dirname);
                     freecon(newcon);
-                    rmdir(node->dirname);
+                    unlinkat(dirfd, node_basename, AT_REMOVEDIR);
                     rc = 1;
                     continue;
                 }
@@ -319,7 +371,7 @@ int create_dirs(struct node *node, size_t size) {
                     printf("Set SELinux file context to %s\n", newcon);
                 if (setfilecon_raw(node->dirname, newcon) < 0) {
                     fprintf(stderr, "Failed to set new context for '%s': %m\n", node->dirname);
-                    rmdir(node->dirname);
+                    unlinkat(dirfd, node_basename, AT_REMOVEDIR);
                     rc = 1;
                 }
             }