guard against hard links to non-ordinary-files when reading tcb shadow

diff --git a/src/passwd/getspnam_r.c b/src/passwd/getspnam_r.c
index 1dd39ce01d973e5f8268cf6775fab909ce12fb49..d21ca810eb68c481c37b9b98f134d02cf70a41a5 100644 (file)
--- a/src/passwd/getspnam_r.c
+++ b/src/passwd/getspnam_r.c
@@ -1,5 +1,6 @@
 #include <fcntl.h>
 #include <unistd.h>
+#include <sys/stat.h>
 #include "pwf.h"
 
 /* This implementation support Openwall-style TCB passwords in place of
@@ -34,8 +35,9 @@ int getspnam_r(const char *name, struct spwd *sp, char *buf, size_t size, struct
 
        fd = open(path, O_RDONLY|O_NOFOLLOW|O_NONBLOCK);
        if (fd >= 0) {
-               f = fdopen(fd, "rb");
-               if (!f) {
+               struct stat st = { 0 };
+               errno = EINVAL;
+               if (fstat(fd, &st) || !S_ISREG(st.st_mode) || !(f = fdopen(fd, "rb"))) {
                        close(fd);
                        return errno;
                }