1 files changed, 203 insertions, 0 deletions
diff --git a/lib/util/secure_path.c b/lib/util/secure_path.c
new file mode 100644
index 0000000..aaceb57
--- /dev/null
+++ b/lib/util/secure_path.c
@@ -0,0 +1,203 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2012, 2014-2022 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#include <sys/stat.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sudo_compat.h>
+#include <sudo_util.h>
+#include <sudo_debug.h>
+
+/*
+ * Verify that path is the right type and not writable by other users.
+ */
+static int
+sudo_check_secure(struct stat *sb, unsigned int type, uid_t uid, gid_t gid)
+{
+    int ret = SUDO_PATH_SECURE;
+    debug_decl(sudo_check_secure, SUDO_DEBUG_UTIL);
+
+    if ((sb->st_mode & S_IFMT) != type) {
+	ret = SUDO_PATH_BAD_TYPE;
+    } else if (uid != (uid_t)-1 && sb->st_uid != uid) {
+	ret = SUDO_PATH_WRONG_OWNER;
+    } else if (sb->st_mode & S_IWOTH) {
+	ret = SUDO_PATH_WORLD_WRITABLE;
+    } else if (ISSET(sb->st_mode, S_IWGRP) &&
+	(gid == (gid_t)-1 || sb->st_gid != gid)) {
+	ret = SUDO_PATH_GROUP_WRITABLE;
+    }
+
+    debug_return_int(ret);
+}
+
+/*
+ * Verify that path is the right type and not writable by other users.
+ */
+static int
+sudo_secure_path(const char *path, unsigned int type, uid_t uid, gid_t gid,
+     struct stat *sb)
+{
+    int ret = SUDO_PATH_MISSING;
+    struct stat stat_buf;
+    debug_decl(sudo_secure_path, SUDO_DEBUG_UTIL);
+
+    if (sb == NULL)
+	sb = &stat_buf;
+
+    if (path != NULL && stat(path, sb) == 0)
+	ret = sudo_check_secure(sb, type, uid, gid);
+
+    debug_return_int(ret);
+}
+
+/*
+ * Verify that path is a regular file and not writable by other users.
+ * Not currently used.
+ */
+int
+sudo_secure_file_v1(const char *path, uid_t uid, gid_t gid, struct stat *sb)
+{
+    return sudo_secure_path(path, S_IFREG, uid, gid, sb);
+}
+
+/*
+ * Verify that path is a directory and not writable by other users.
+ */
+int
+sudo_secure_dir_v1(const char *path, uid_t uid, gid_t gid, struct stat *sb)
+{
+    return sudo_secure_path(path, S_IFDIR, uid, gid, sb);
+}
+
+/*
+ * Verify that fd matches type and not writable by other users.
+ */
+int
+sudo_secure_fd_v1(int fd, unsigned int type, uid_t uid, gid_t gid,
+    struct stat *sb)
+{
+    int ret = SUDO_PATH_MISSING;
+    debug_decl(sudo_secure_fd, SUDO_DEBUG_UTIL);
+
+    if (fd != -1 && fstat(fd, sb) == 0)
+	ret = sudo_check_secure(sb, type, uid, gid);
+    debug_return_int(ret);
+}
+
+/*
+ * Open path read-only as long as it is not writable by other users.
+ * Returns an open file descriptor on success, else -1.
+ * Sets error to SUDO_PATH_SECURE on success, and a value < 0 on failure.
+ */
+static int
+sudo_secure_open(const char *path, unsigned int type, uid_t uid, gid_t gid,
+    struct stat *sb, int *error)
+{
+    struct stat stat_buf;
+    int fd;
+    debug_decl(sudo_secure_open, SUDO_DEBUG_UTIL);
+
+    if (sb == NULL)
+	sb = &stat_buf;
+
+    fd = open(path, O_RDONLY|O_NONBLOCK);
+    if (fd == -1 || fstat(fd, sb) != 0) {
+	if (fd != -1)
+	    close(fd);
+	*error = SUDO_PATH_MISSING;
+	debug_return_int(-1);
+    }
+
+    *error = sudo_check_secure(sb, type, uid, gid);
+    if (*error == SUDO_PATH_SECURE) {
+	(void)fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) & ~O_NONBLOCK);
+    } else {
+	/* Not secure, caller can check error flag. */
+	close(fd);
+	fd = -1;
+    }
+
+    debug_return_int(fd);
+}
+
+int
+sudo_secure_open_file_v1(const char *path, uid_t uid, gid_t gid,
+    struct stat *sb, int *error)
+{
+    return sudo_secure_open(path, S_IFREG, uid, gid, sb, error);
+}
+
+int
+sudo_secure_open_dir_v1(const char *path, uid_t uid, gid_t gid,
+    struct stat *sb, int *error)
+{
+    return sudo_secure_open(path, S_IFDIR, uid, gid, sb, error);
+}
+
+/*
+ * Open the first file found in a colon-separated list of paths.
+ * Subsequent files in the path are only attempted if the
+ * previous file does not exist.  Errors other than ENOENT are
+ * considered fatal and will stop processing the path.
+ * Sets name based on the last file it tried to open, even on error.
+ */
+int
+sudo_open_conf_path_v1(const char *path, char *name, size_t namesize,
+    int (*fn)(const char *, int))
+{
+    const char *cp, *ep, *path_end;
+    int fd = -1;
+    debug_decl(sudo_open_conf_path, SUDO_DEBUG_UTIL);
+
+    path_end = path + strlen(path);
+    for (cp = sudo_strsplit(path, path_end, ":", &ep);
+	cp != NULL; cp = sudo_strsplit(NULL, path_end, ":", &ep)) {
+
+	const size_t len = (size_t)(ep - cp);
+	if (len >= namesize) {
+	    /* We always set name, even on error. */
+	    memcpy(name, cp, namesize - 1);
+	    name[namesize - 1] = '\0';
+	    errno = ENAMETOOLONG;
+	    break;
+	}
+	memcpy(name, cp, len);
+	name[len] = '\0';
+
+	fd = fn ?
+	    fn(name, O_RDONLY|O_NONBLOCK) : open(name, O_RDONLY|O_NONBLOCK);
+	if (fd != -1) {
+	    (void)fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) & ~O_NONBLOCK);
+	    break;
+	}
+	if (errno != ENOENT)
+	    break;
+    }
+    debug_return_int(fd);
+}