protect against/handle cancellation reading shadow passwords

diff --git a/src/passwd/getspnam_r.c b/src/passwd/getspnam_r.c
index 9e29aa9..9f3378e 100644 (file)
--- a/src/passwd/getspnam_r.c
+++ b/src/passwd/getspnam_r.c
@@ -2,6 +2,7 @@
 #include <unistd.h>
 #include <sys/stat.h>
 #include <ctype.h>
+#include <pthread.h>
 #include "pwf.h"
 
 /* This implementation support Openwall-style TCB passwords in place of
@@ -16,6 +17,11 @@ static long xatol(const char *s)
        return isdigit(*s) ? atol(s) : -1;
 }
 
+static void cleanup(void *p)
+{
+       fclose(p);
+}
+
 int getspnam_r(const char *name, struct spwd *sp, char *buf, size_t size, struct spwd **res)
 {
        char path[20+NAME_MAX];
@@ -25,6 +31,7 @@ int getspnam_r(const char *name, struct spwd *sp, char *buf, size_t size, struct
        size_t k, l = strlen(name);
        char *s;
        int skip = 0;
+       int cs;
 
        *res = 0;
 
@@ -44,7 +51,9 @@ int getspnam_r(const char *name, struct spwd *sp, char *buf, size_t size, struct
                struct stat st = { 0 };
                errno = EINVAL;
                if (fstat(fd, &st) || !S_ISREG(st.st_mode) || !(f = fdopen(fd, "rb"))) {
+                       pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
                        close(fd);
+                       pthread_setcancelstate(cs, 0);
                        return errno;
                }
        } else {
@@ -52,6 +61,7 @@ int getspnam_r(const char *name, struct spwd *sp, char *buf, size_t size, struct
                if (!f) return errno;
        }
 
+       pthread_cleanup_push(cleanup, f);
        while (fgets(buf, size, f) && (k=strlen(buf))>0) {
                if (skip || strncmp(name, buf, l)) {
                        skip = buf[k-1] != '\n';
@@ -92,6 +102,6 @@ int getspnam_r(const char *name, struct spwd *sp, char *buf, size_t size, struct
                *res = sp;
                break;
        }
-       fclose(f);
+       pthread_cleanup_pop(1);
        return rv;
 }