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-rw-r--r--src/tests/check_and_open-tests.c4
-rw-r--r--src/util/check_and_open.c76
-rw-r--r--src/util/util.h29
3 files changed, 79 insertions, 30 deletions
diff --git a/src/tests/check_and_open-tests.c b/src/tests/check_and_open-tests.c
index 7ec8f3b..e3d9886 100644
--- a/src/tests/check_and_open-tests.c
+++ b/src/tests/check_and_open-tests.c
@@ -100,11 +100,11 @@ START_TEST(test_symlink)
ret = symlink(filename, newpath);
fail_unless(ret == 0, "symlink failed [%d][%s]", ret, strerror(ret));
- ret = check_and_open_readonly(newpath, &fd, uid, gid, mode, CHECK_REG);
+ ret = check_file(newpath, uid, gid, mode, CHECK_REG, NULL);
unlink(newpath);
+
fail_unless(ret == EINVAL,
"check_and_open_readonly succeeded on symlink");
- fail_unless(fd == -1, "check_and_open_readonly file descriptor not -1");
}
END_TEST
diff --git a/src/util/check_and_open.c b/src/util/check_and_open.c
index d010670..db926f1 100644
--- a/src/util/check_and_open.c
+++ b/src/util/check_and_open.c
@@ -29,6 +29,10 @@
#include "util/util.h"
+static errno_t perform_checks(struct stat *stat_buf,
+ const int uid, const int gid,
+ const int mode, enum check_file_type type);
+
errno_t check_file(const char *filename, const int uid, const int gid,
const int mode, enum check_file_type type,
struct stat *caller_stat_buf)
@@ -36,7 +40,6 @@ errno_t check_file(const char *filename, const int uid, const int gid,
int ret;
struct stat local_stat_buf;
struct stat *stat_buf;
- bool type_check;
if (caller_stat_buf == NULL) {
stat_buf = &local_stat_buf;
@@ -51,6 +54,39 @@ errno_t check_file(const char *filename, const int uid, const int gid,
return errno;
}
+ return perform_checks(stat_buf, uid, gid, mode, type);
+}
+
+errno_t check_fd(int fd, const int uid, const int gid,
+ const int mode, enum check_file_type type,
+ struct stat *caller_stat_buf)
+{
+ int ret;
+ struct stat local_stat_buf;
+ struct stat *stat_buf;
+
+ if (caller_stat_buf == NULL) {
+ stat_buf = &local_stat_buf;
+ } else {
+ stat_buf = caller_stat_buf;
+ }
+
+ ret = fstat(fd, stat_buf);
+ if (ret == -1) {
+ DEBUG(1, ("fstat for [%d] failed: [%d][%s].\n", fd, errno,
+ strerror(errno)));
+ return errno;
+ }
+
+ return perform_checks(stat_buf, uid, gid, mode, type);
+}
+
+static errno_t perform_checks(struct stat *stat_buf,
+ const int uid, const int gid,
+ const int mode, enum check_file_type type)
+{
+ bool type_check;
+
switch (type) {
case CHECK_DONT_CHECK_FILE_TYPE:
type_check = true;
@@ -77,28 +113,28 @@ errno_t check_file(const char *filename, const int uid, const int gid,
type_check = S_ISSOCK(stat_buf->st_mode);
break;
default:
- DEBUG(1, ("Unsupprted file type.\n"));
+ DEBUG(1, ("Unsupported file type.\n"));
return EINVAL;
}
if (!type_check) {
- DEBUG(1, ("File [%s] is not the right type.\n", filename));
+ DEBUG(1, ("File is not the right type.\n"));
return EINVAL;
}
if (mode >= 0 && (stat_buf->st_mode & ~S_IFMT) != mode) {
- DEBUG(1, ("File [%s] has the wrong mode [%.7o], expected [%.7o].\n",
- filename, (stat_buf->st_mode & ~S_IFMT), mode));
+ DEBUG(1, ("File has the wrong mode [%.7o], expected [%.7o].\n",
+ (stat_buf->st_mode & ~S_IFMT), mode));
return EINVAL;
}
if (uid >= 0 && stat_buf->st_uid != uid) {
- DEBUG(1, ("File [%s] must be owned by uid [%d].\n", filename, uid));
+ DEBUG(1, ("File must be owned by uid [%d].\n", uid));
return EINVAL;
}
if (gid >= 0 && stat_buf->st_gid != gid) {
- DEBUG(1, ("File [%s] must be owned by gid [%d].\n", filename, gid));
+ DEBUG(1, ("File must be owned by gid [%d].\n", gid));
return EINVAL;
}
@@ -111,36 +147,20 @@ errno_t check_and_open_readonly(const char *filename, int *fd, const uid_t uid,
{
int ret;
struct stat stat_buf;
- struct stat fd_stat_buf;
-
- *fd = -1;
-
- ret = check_file(filename, uid, gid, mode, type, &stat_buf);
- if (ret != EOK) {
- DEBUG(1, ("check_file failed.\n"));
- return ret;
- }
*fd = open(filename, O_RDONLY);
if (*fd == -1) {
DEBUG(1, ("open [%s] failed: [%d][%s].\n", filename, errno,
- strerror(errno)));
+ strerror(errno)));
return errno;
}
- ret = fstat(*fd, &fd_stat_buf);
- if (ret == -1) {
- DEBUG(1, ("fstat for [%s] failed: [%d][%s].\n", filename, errno,
- strerror(errno)));
- return errno;
- }
-
- if (stat_buf.st_dev != fd_stat_buf.st_dev ||
- stat_buf.st_ino != fd_stat_buf.st_ino) {
- DEBUG(1, ("File [%s] was modified between lstat and open.\n", filename));
+ ret = check_fd(*fd, uid, gid, mode, type, &stat_buf);
+ if (ret != EOK) {
close(*fd);
*fd = -1;
- return EIO;
+ DEBUG(1, ("check_fd failed.\n"));
+ return ret;
}
return EOK;
diff --git a/src/util/util.h b/src/util/util.h
index db8e1ac..fae8096 100644
--- a/src/util/util.h
+++ b/src/util/util.h
@@ -268,9 +268,38 @@ enum check_file_type {
CHECK_LNK,
CHECK_SOCK
};
+
+/* check_file()
+ * Verify that a file has certain permissions and/or is of a certain
+ * file type. This function can be used to determine if a file is a
+ * symlink.
+ * Warning: use of this function implies a potential race condition
+ * Opening a file before or after checking it does NOT guarantee that
+ * it is still the same file. Additional checks should be performed
+ * on the caller_stat_buf to ensure that it has the same device and
+ * inode to minimize impact. Permission changes may have occurred,
+ * however.
+ */
errno_t check_file(const char *filename, const int uid, const int gid,
const int mode, enum check_file_type type,
struct stat *caller_stat_buf);
+
+/* check_fd()
+ * Verify that an open file descriptor has certain permissions and/or
+ * is of a certain file type. This function CANNOT detect symlinks,
+ * as the file is already open and symlinks have been traversed. This
+ * is the safer way to perform file checks and should be preferred
+ * over check_file for nearly all situations.
+ */
+errno_t check_fd(int fd, const int uid, const int gid,
+ const int mode, enum check_file_type type,
+ struct stat *caller_stat_buf);
+
+/* check_and_open_readonly()
+ * Utility function to open a file and verify that it has certain
+ * permissions and is of a certain file type. This function wraps
+ * check_fd(), and is considered race-condition safe.
+ */
errno_t check_and_open_readonly(const char *filename, int *fd, const uid_t uid,
const gid_t gid, const mode_t mode,
enum check_file_type type);
generated by cgit (git 2.34.1) at 2024-11-01 00:06:04 +0000