util: simplify mkostemp_safe()

[elogind.git] / src / shared / util.c

diff --git a/src/shared/util.c b/src/shared/util.c
index 945f1525a266d73e70b4b188d3aac2da0bf27792..0e7d5c5fb3388e39236af01d73f73503b9ddafec 100644 (file)
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -2255,25 +2255,37 @@ char* dirname_malloc(const char *path) {
         return dir;
 }
 
-void random_bytes(void *p, size_t n) {
-        static bool srand_called = false;
+int dev_urandom(void *p, size_t n) {
         _cleanup_close_ int fd;
         ssize_t k;
-        uint8_t *q;
 
         fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
         if (fd < 0)
-                goto fallback;
+                return errno == ENOENT ? -ENOSYS : -errno;
 
         k = loop_read(fd, p, n, true);
-        if (k < 0 || (size_t) k != n)
-                goto fallback;
+        if (k < 0)
+                return (int) k;
+        if ((size_t) k != n)
+                return -EIO;
 
-        return;
+        return 0;
+}
 
-fallback:
+void random_bytes(void *p, size_t n) {
+        static bool srand_called = false;
+        uint8_t *q;
+        int r;
+
+        r = dev_urandom(p, n);
+        if (r >= 0)
+                return;
+
+        /* If some idiot made /dev/urandom unavailable to us, he'll
+         * get a PRNG instead. */
 
         if (!srand_called) {
+                unsigned x = 0;
 
 #ifdef HAVE_SYS_AUXV_H
                 /* The kernel provides us with a bit of entropy in
@@ -2285,16 +2297,16 @@ fallback:
 
                 auxv = (void*) getauxval(AT_RANDOM);
                 if (auxv)
-                        srand(*(unsigned*) auxv);
-                else
+                        x ^= *(unsigned*) auxv;
 #endif
-                        srand(time(NULL) + gettid());
 
+                x ^= (unsigned) now(CLOCK_REALTIME);
+                x ^= (unsigned) gettid();
+
+                srand(x);
                 srand_called = true;
         }
 
-        /* If some idiot made /dev/urandom unavailable to us, he'll
-         * get a PRNG instead. */
         for (q = p; q < (uint8_t*) p + n; q ++)
                 *q = rand();
 }
@@ -3823,12 +3835,13 @@ char* hostname_cleanup(char *s, bool lowercase) {
 }
 
 int pipe_eof(int fd) {
-        int r;
         struct pollfd pollfd = {
                 .fd = fd,
                 .events = POLLIN|POLLHUP,
         };
 
+        int r;
+
         r = poll(&pollfd, 1, 0);
         if (r < 0)
                 return -errno;
@@ -6099,23 +6112,29 @@ int writev_safe(int fd, const struct iovec *w, int j) {
 }
 
 int mkostemp_safe(char *pattern, int flags) {
-        char *s = pattern + strlen(pattern) - 6;
-        uint64_t tries = TMP_MAX;
-        int randfd, fd, i;
+        unsigned long tries = TMP_MAX;
+        char *s;
+        int r;
 
-        assert(streq(s, "XXXXXX"));
+        assert(pattern);
 
-        randfd = open("/dev/urandom", O_RDONLY);
-        if (randfd < 0)
-                return -ENOSYS;
+        /* This is much like like mkostemp() but avoids using any
+         * static variables, thus is async signal safe */
+
+        s = endswith(pattern, "XXXXXX");
+        if (!s)
+                return -EINVAL;
 
         while (tries--) {
-                fd = read(randfd, s, 6);
-                if (fd == 0)
-                        return -ENOSYS;
+                unsigned i;
+                int fd;
+
+                r = dev_urandom(s, 6);
+                if (r < 0)
+                        return r;
 
                 for (i = 0; i < 6; i++)
-                        s[i] = ALPHANUMERICAL[(unsigned) s[i] % strlen(ALPHANUMERICAL)];
+                        s[i] = ALPHANUMERICAL[(unsigned) s[i] % (sizeof(ALPHANUMERICAL)-1)];
 
                 fd = open(pattern, flags|O_EXCL|O_CREAT, S_IRUSR|S_IWUSR);
                 if (fd >= 0)