1 files changed, 247 insertions, 0 deletions

diff --git a/libblkid/canonicalize.c b/libblkid/canonicalize.c
new file mode 100644
index 000000000..1e8aff4f2
--- /dev/null
+++ b/libblkid/canonicalize.c
@@ -0,0 +1,247 @@
+/*
+ * canonicalize.c -- canonicalize pathname by removing symlinks
+ * Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library Public License for more details.
+ *
+ */
+
+/*
+ * This routine is part of libc.  We include it nevertheless,
+ * since the libc version has some security flaws.
+ *
+ * TODO: use canonicalize_file_name() when exist in glibc
+ */
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdlib.h>
+
+#include "canonicalize.h"
+
+#ifndef MAXSYMLINKS
+# define MAXSYMLINKS 256
+#endif
+
+static char *
+myrealpath(const char *path, char *resolved_path, int maxreslth) {
+	int readlinks = 0;
+	char *npath;
+	char link_path[PATH_MAX+1];
+	int n;
+	char *buf = NULL;
+
+	npath = resolved_path;
+
+	/* If it's a relative pathname use getcwd for starters. */
+	if (*path != '/') {
+		if (!getcwd(npath, maxreslth-2))
+			return NULL;
+		npath += strlen(npath);
+		if (npath[-1] != '/')
+			*npath++ = '/';
+	} else {
+		*npath++ = '/';
+		path++;
+	}
+
+	/* Expand each slash-separated pathname component. */
+	while (*path != '\0') {
+		/* Ignore stray "/" */
+		if (*path == '/') {
+			path++;
+			continue;
+		}
+		if (*path == '.' && (path[1] == '\0' || path[1] == '/')) {
+			/* Ignore "." */
+			path++;
+			continue;
+		}
+		if (*path == '.' && path[1] == '.' &&
+		    (path[2] == '\0' || path[2] == '/')) {
+			/* Backup for ".." */
+			path += 2;
+			while (npath > resolved_path+1 &&
+			       (--npath)[-1] != '/')
+				;
+			continue;
+		}
+		/* Safely copy the next pathname component. */
+		while (*path != '\0' && *path != '/') {
+			if (npath-resolved_path > maxreslth-2) {
+				errno = ENAMETOOLONG;
+				goto err;
+			}
+			*npath++ = *path++;
+		}
+
+		/* Protect against infinite loops. */
+		if (readlinks++ > MAXSYMLINKS) {
+			errno = ELOOP;
+			goto err;
+		}
+
+		/* See if last pathname component is a symlink. */
+		*npath = '\0';
+		n = readlink(resolved_path, link_path, PATH_MAX);
+		if (n < 0) {
+			/* EINVAL means the file exists but isn't a symlink. */
+			if (errno != EINVAL)
+				goto err;
+		} else {
+			int m;
+			char *newbuf;
+
+			/* Note: readlink doesn't add the null byte. */
+			link_path[n] = '\0';
+			if (*link_path == '/')
+				/* Start over for an absolute symlink. */
+				npath = resolved_path;
+			else
+				/* Otherwise back up over this component. */
+				while (*(--npath) != '/')
+					;
+
+			/* Insert symlink contents into path. */
+			m = strlen(path);
+			newbuf = malloc(m + n + 1);
+			if (!newbuf)
+				goto err;
+			memcpy(newbuf, link_path, n);
+			memcpy(newbuf + n, path, m + 1);
+			free(buf);
+			path = buf = newbuf;
+		}
+		*npath++ = '/';
+	}
+	/* Delete trailing slash but don't whomp a lone slash. */
+	if (npath != resolved_path+1 && npath[-1] == '/')
+		npath--;
+	/* Make sure it's null terminated. */
+	*npath = '\0';
+
+	free(buf);
+	return resolved_path;
+
+ err:
+	free(buf);
+	return NULL;
+}
+
+/*
+ * 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 *ptname)
+{
+	FILE	*f;
+	size_t	sz;
+	char	path[256], name[256], *res = NULL;
+
+	snprintf(path, sizeof(path), "/sys/block/%s/dm/name", ptname);
+	if (!(f = fopen(path, "r")))
+		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), "/dev/mapper/%s", name);
+		res = strdup(path);
+	}
+	fclose(f);
+	return res;
+}
+
+char *
+canonicalize_path(const char *path)
+{
+	char canonical[PATH_MAX+2];
+	char *p;
+
+	if (path == NULL)
+		return NULL;
+
+	if (!myrealpath(path, canonical, PATH_MAX+1))
+		return strdup(path);
+
+
+	p = strrchr(canonical, '/');
+	if (p && strncmp(p, "/dm-", 4) == 0 && isdigit(*(p + 4))) {
+		p = canonicalize_dm_name(p+1);
+		if (p)
+			return p;
+	}
+
+	return strdup(canonical);
+}
+
+char *
+canonicalize_path_restricted(const char *path)
+{
+	char canonical[PATH_MAX+2];
+	char *p = NULL;
+	int errsv;
+	uid_t euid;
+	gid_t egid;
+
+	if (path == NULL)
+		return NULL;
+
+	euid = geteuid();
+	egid = getegid();
+
+	/* drop permissions */
+	if (setegid(getgid()) < 0 || seteuid(getuid()) < 0)
+		return NULL;
+
+	errsv = errno = 0;
+
+	if (myrealpath(path, canonical, PATH_MAX+1)) {
+		p = strrchr(canonical, '/');
+		if (p && strncmp(p, "/dm-", 4) == 0 && isdigit(*(p + 4)))
+			p = canonicalize_dm_name(p+1);
+		else
+			p = NULL;
+		if (!p)
+			p = strdup(canonical);
+	} else
+		errsv = errno;
+
+	/* restore */
+	if (setegid(egid) < 0 || seteuid(euid) < 0) {
+		free(p);
+		return NULL;
+	}
+
+	errno = errsv;
+	return p;
+}
+
+
+#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