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Diffstat (limited to 'lib/canonicalize.c')
| -rw-r--r-- | lib/canonicalize.c | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/lib/canonicalize.c b/lib/canonicalize.c new file mode 100644 index 0000000..d181a14 --- /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" +#include "strutils.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; + + p = mempcpy(p, cwd, 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 */ + ignore_result( 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 |