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-rw-r--r--lib/canonicalize.c249
1 files changed, 249 insertions, 0 deletions
diff --git a/lib/canonicalize.c b/lib/canonicalize.c
new file mode 100644
index 0000000..6f85b47
--- /dev/null
+++ b/lib/canonicalize.c
@@ -0,0 +1,249 @@
+/*
+ * canonicalize.c -- canonicalize pathname by removing symlinks
+ *
+ * This file may be distributed under the terms of the
+ * GNU Lesser General Public License.
+ *
+ * Copyright (C) 2009-2013 Karel Zak <kzak@redhat.com>
+ */
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+
+#include "canonicalize.h"
+#include "pathnames.h"
+#include "all-io.h"
+
+/*
+ * Converts private "dm-N" names to "/dev/mapper/<name>"
+ *
+ * Since 2.6.29 (patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128) kernel sysfs
+ * provides the real DM device names in /sys/block/<ptname>/dm/name
+ */
+char *__canonicalize_dm_name(const char *prefix, const char *ptname)
+{
+ FILE *f;
+ size_t sz;
+ char path[256], name[sizeof(path) - sizeof(_PATH_DEV_MAPPER)], *res = NULL;
+
+ if (!ptname || !*ptname)
+ return NULL;
+
+ if (!prefix)
+ prefix = "";
+
+ snprintf(path, sizeof(path), "%s/sys/block/%s/dm/name", prefix, ptname);
+ if (!(f = fopen(path, "r" UL_CLOEXECSTR)))
+ return NULL;
+
+ /* read "<name>\n" from sysfs */
+ if (fgets(name, sizeof(name), f) && (sz = strlen(name)) > 1) {
+ name[sz - 1] = '\0';
+ snprintf(path, sizeof(path), _PATH_DEV_MAPPER "/%s", name);
+
+ if ((prefix && *prefix) || access(path, F_OK) == 0)
+ res = strdup(path);
+ }
+ fclose(f);
+ return res;
+}
+
+char *canonicalize_dm_name(const char *ptname)
+{
+ return __canonicalize_dm_name(NULL, ptname);
+}
+
+static int is_dm_devname(char *canonical, char **name)
+{
+ struct stat sb;
+ char *p = strrchr(canonical, '/');
+
+ *name = NULL;
+
+ if (!p
+ || strncmp(p, "/dm-", 4) != 0
+ || !isdigit(*(p + 4))
+ || stat(canonical, &sb) != 0
+ || !S_ISBLK(sb.st_mode))
+ return 0;
+
+ *name = p + 1;
+ return 1;
+}
+
+/*
+ * This function does not canonicalize the path! It just prepends CWD before a
+ * relative path. If the path is no relative than returns NULL. The path does
+ * not have to exist.
+ */
+char *absolute_path(const char *path)
+{
+ char cwd[PATH_MAX], *res, *p;
+ size_t psz, csz;
+
+ if (!is_relative_path(path)) {
+ errno = EINVAL;
+ return NULL;
+ }
+ if (!getcwd(cwd, sizeof(cwd)))
+ return NULL;
+
+ /* simple clean up */
+ if (startswith(path, "./"))
+ path += 2;
+ else if (strcmp(path, ".") == 0)
+ path = NULL;
+
+ if (!path || !*path)
+ return strdup(cwd);
+
+ csz = strlen(cwd);
+ psz = strlen(path);
+
+ p = res = malloc(csz + 1 + psz + 1);
+ if (!res)
+ return NULL;
+
+ memcpy(p, cwd, csz);
+ p += csz;
+ *p++ = '/';
+ memcpy(p, path, psz + 1);
+
+ return res;
+}
+
+char *canonicalize_path(const char *path)
+{
+ char *canonical, *dmname;
+
+ if (!path || !*path)
+ return NULL;
+
+ canonical = realpath(path, NULL);
+ if (!canonical)
+ return strdup(path);
+
+ if (is_dm_devname(canonical, &dmname)) {
+ char *dm = canonicalize_dm_name(dmname);
+ if (dm) {
+ free(canonical);
+ return dm;
+ }
+ }
+
+ return canonical;
+}
+
+char *canonicalize_path_restricted(const char *path)
+{
+ char *canonical = NULL;
+ int errsv = 0;
+ int pipes[2];
+ ssize_t len;
+ pid_t pid;
+
+ if (!path || !*path)
+ return NULL;
+
+ if (pipe(pipes) != 0)
+ return NULL;
+
+ /*
+ * To accurately assume identity of getuid() we must use setuid()
+ * but if we do that, we lose ability to reassume euid of 0, so
+ * we fork to do the check to keep euid intact.
+ */
+ pid = fork();
+ switch (pid) {
+ case -1:
+ close(pipes[0]);
+ close(pipes[1]);
+ return NULL; /* fork error */
+ case 0:
+ close(pipes[0]); /* close unused end */
+ pipes[0] = -1;
+ errno = 0;
+
+ if (drop_permissions() != 0)
+ canonical = NULL; /* failed */
+ else {
+ char *dmname = NULL;
+
+ canonical = realpath(path, NULL);
+ if (canonical && is_dm_devname(canonical, &dmname)) {
+ char *dm = canonicalize_dm_name(dmname);
+ if (dm) {
+ free(canonical);
+ canonical = dm;
+ }
+ }
+ }
+
+ len = canonical ? (ssize_t) strlen(canonical) :
+ errno ? -errno : -EINVAL;
+
+ /* send length or errno */
+ write_all(pipes[1], (char *) &len, sizeof(len));
+ if (canonical)
+ write_all(pipes[1], canonical, len);
+ exit(0);
+ default:
+ break;
+ }
+
+ close(pipes[1]); /* close unused end */
+ pipes[1] = -1;
+
+ /* read size or -errno */
+ if (read_all(pipes[0], (char *) &len, sizeof(len)) != sizeof(len))
+ goto done;
+ if (len < 0) {
+ errsv = -len;
+ goto done;
+ }
+
+ canonical = malloc(len + 1);
+ if (!canonical) {
+ errsv = ENOMEM;
+ goto done;
+ }
+ /* read path */
+ if (read_all(pipes[0], canonical, len) != len) {
+ errsv = errno;
+ goto done;
+ }
+ canonical[len] = '\0';
+done:
+ if (errsv) {
+ free(canonical);
+ canonical = NULL;
+ }
+ close(pipes[0]);
+
+ /* We make a best effort to reap child */
+ waitpid(pid, NULL, 0);
+
+ errno = errsv;
+ return canonical;
+}
+
+
+#ifdef TEST_PROGRAM_CANONICALIZE
+int main(int argc, char **argv)
+{
+ if (argc < 2) {
+ fprintf(stderr, "usage: %s <device>\n", argv[0]);
+ exit(EXIT_FAILURE);
+ }
+
+ fprintf(stdout, "orig: %s\n", argv[1]);
+ fprintf(stdout, "real: %s\n", canonicalize_path(argv[1]));
+ exit(EXIT_SUCCESS);
+}
+#endif