lib/canonical: use realpath() from libc

.. after many many years it seems that we can follow libc code rather
than duplicate realpath(3) implementation.

Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 29 insertions, 151 deletions

diff --git a/lib/canonicalize.c b/lib/canonicalize.c
index 548e29b75..cac60d7a4 100644
--- a/lib/canonicalize.c
+++ b/lib/canonicalize.c
@@ -1,24 +1,10 @@
 /*
  * 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 file may be distributed under the terms of the
+ * GNU Lesser General Public License.
  *
- */
-
-/*
- * 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
+ * Copyright (C) 2009-2013 Karel Zak <kzak@redhat.com>
  */
 #include <stdio.h>
 #include <string.h>
@@ -26,126 +12,18 @@
 #include <unistd.h>
 #include <errno.h>
 #include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.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)
+char *canonicalize_dm_name(const char *ptname)
 {
 	FILE	*f;
 	size_t	sz;
@@ -170,34 +48,32 @@ canonicalize_dm_name(const char *ptname)
 	return res;
 }
 
-char *
-canonicalize_path(const char *path)
+char *canonicalize_path(const char *path)
 {
-	char canonical[PATH_MAX+2];
-	char *p;
+	char *canonical, *p;
 
 	if (!path || !*path)
 		return NULL;
 
-	if (!myrealpath(path, canonical, PATH_MAX+1))
+	canonical = realpath(path, NULL);
+	if (!canonical)
 		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;
+		char *dm = canonicalize_dm_name(p + 1);
+		if (dm) {
+			free(canonical);
+			return dm;
+		}
 	}
 
-	return strdup(canonical);
+	return canonical;
 }
 
-char *
-canonicalize_path_restricted(const char *path)
+char *canonicalize_path_restricted(const char *path)
 {
-	char canonical[PATH_MAX+2];
-	char *p = NULL;
+	char *canonical, *p = NULL;
 	int errsv;
 	uid_t euid;
 	gid_t egid;
@@ -214,25 +90,27 @@ canonicalize_path_restricted(const char *path)
 
 	errsv = errno = 0;
 
-	if (myrealpath(path, canonical, PATH_MAX+1)) {
+	canonical = realpath(path, NULL);
+	if (canonical) {
 		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);
+		if (p && strncmp(p, "/dm-", 4) == 0 && isdigit(*(p + 4))) {
+			char *dm = canonicalize_dm_name(p + 1);
+			if (dm) {
+				free(canonical);
+				canonical = dm;
+			}
+		}
 	} else
 		errsv = errno;
 
 	/* restore */
 	if (setegid(egid) < 0 || seteuid(euid) < 0) {
-		free(p);
+		free(canonical);
 		return NULL;
 	}
 
 	errno = errsv;
-	return p;
+	return canonical;
 }