Fix seeding from random device w/o getrandom syscall
[openssl.git] / crypto / rand / rand_unix.c
index e63d7789000d354f961510b4bfe60eaecae620fb..39c4e7e7417a627640cdc0fae68cd682d5de6541 100644 (file)
@@ -1,7 +1,7 @@
 /*
  * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
  *
- * Licensed under the OpenSSL license (the "License").  You may not use
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
  * in the file LICENSE in the source distribution or at
  * https://www.openssl.org/source/license.html
@@ -19,7 +19,7 @@
 #include <stdio.h>
 #include "internal/dso.h"
 #if defined(__linux)
-# include <sys/syscall.h>
+# include <asm/unistd.h>
 #endif
 #if defined(__FreeBSD__)
 # include <sys/types.h>
@@ -77,17 +77,47 @@ static uint64_t get_timer_bits(void);
 # endif
 #endif /* defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__) */
 
+#if defined(OPENSSL_RAND_SEED_NONE)
+/* none means none. this simplifies the following logic */
+# undef OPENSSL_RAND_SEED_OS
+# undef OPENSSL_RAND_SEED_GETRANDOM
+# undef OPENSSL_RAND_SEED_LIBRANDOM
+# undef OPENSSL_RAND_SEED_DEVRANDOM
+# undef OPENSSL_RAND_SEED_RDTSC
+# undef OPENSSL_RAND_SEED_RDCPU
+# undef OPENSSL_RAND_SEED_EGD
+#endif
+
 #if (defined(OPENSSL_SYS_VXWORKS) || defined(OPENSSL_SYS_UEFI)) && \
         !defined(OPENSSL_RAND_SEED_NONE)
 # error "UEFI and VXWorks only support seeding NONE"
 #endif
 
+#if defined(OPENSSL_SYS_VXWORKS)
+/* empty implementation */
+int rand_pool_init(void)
+{
+    return 1;
+}
+
+void rand_pool_cleanup(void)
+{
+}
+
+void rand_pool_keep_random_devices_open(int keep)
+{
+}
+
+size_t rand_pool_acquire_entropy(RAND_POOL *pool)
+{
+    return rand_pool_entropy_available(pool);
+}
+#endif
+
 #if !(defined(OPENSSL_SYS_WINDOWS) || defined(OPENSSL_SYS_WIN32) \
     || defined(OPENSSL_SYS_VMS) || defined(OPENSSL_SYS_VXWORKS) \
     || defined(OPENSSL_SYS_UEFI))
 
-static ssize_t syscall_random(void *buf, size_t buflen);
-
 # if defined(OPENSSL_SYS_VOS)
 
 #  ifndef OPENSSL_RAND_SEED_OS
@@ -244,6 +274,7 @@ static ssize_t sysctl_random(char *buf, size_t buflen)
 }
 #  endif
 
+#  if defined(OPENSSL_RAND_SEED_GETRANDOM)
 /*
  * syscall_random(): Try to get random data using a system call
  * returns the number of bytes returned in buf, or < 0 on error.
@@ -254,7 +285,7 @@ static ssize_t syscall_random(void *buf, size_t buflen)
      * Note: 'buflen' equals the size of the buffer which is used by the
      * get_entropy() callback of the RAND_DRBG. It is roughly bounded by
      *
-     *   2 * DRBG_MINMAX_FACTOR * (RAND_DRBG_STRENGTH / 8) = 2^13
+     *   2 * RAND_POOL_FACTOR * (RAND_DRBG_STRENGTH / 8) = 2^14
      *
      * which is way below the OSSL_SSIZE_MAX limit. Therefore sign conversion
      * between size_t and ssize_t is safe even without a range check.
@@ -293,8 +324,8 @@ static ssize_t syscall_random(void *buf, size_t buflen)
 #  endif
 
     /* Linux supports this since version 3.17 */
-#  if defined(__linux) && defined(SYS_getrandom)
-    return syscall(SYS_getrandom, buf, buflen, 0);
+#  if defined(__linux) && defined(__NR_getrandom)
+    return syscall(__NR_getrandom, buf, buflen, 0);
 #  elif (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
     return sysctl_random(buf, buflen);
 #  else
@@ -302,8 +333,9 @@ static ssize_t syscall_random(void *buf, size_t buflen)
     return -1;
 #  endif
 }
+#  endif    /* defined(OPENSSL_RAND_SEED_GETRANDOM) */
 
-#if  !defined(OPENSSL_RAND_SEED_NONE) && defined(OPENSSL_RAND_SEED_DEVRANDOM)
+#  if defined(OPENSSL_RAND_SEED_DEVRANDOM)
 static const char *random_device_paths[] = { DEVRANDOM };
 static struct random_device {
     int fd;
@@ -375,21 +407,13 @@ static void close_random_device(size_t n)
     rd->fd = -1;
 }
 
-static void open_random_devices(void)
-{
-    size_t i;
-
-    for (i = 0; i < OSSL_NELEM(random_devices); i++)
-        (void)get_random_device(i);
-}
-
 int rand_pool_init(void)
 {
     size_t i;
 
     for (i = 0; i < OSSL_NELEM(random_devices); i++)
         random_devices[i].fd = -1;
-    open_random_devices();
+
     return 1;
 }
 
@@ -403,16 +427,13 @@ void rand_pool_cleanup(void)
 
 void rand_pool_keep_random_devices_open(int keep)
 {
-    if (keep)
-        open_random_devices();
-    else
+    if (!keep)
         rand_pool_cleanup();
+
     keep_random_devices_open = keep;
 }
 
-#  else     /* defined(OPENSSL_RAND_SEED_NONE)
-             * || !defined(OPENSSL_RAND_SEED_DEVRANDOM)
-             */
+#  else     /* !defined(OPENSSL_RAND_SEED_DEVRANDOM) */
 
 int rand_pool_init(void)
 {
@@ -427,9 +448,7 @@ void rand_pool_keep_random_devices_open(int keep)
 {
 }
 
-#  endif    /* !defined(OPENSSL_RAND_SEED_NONE)
-             * && defined(OPENSSL_RAND_SEED_DEVRANDOM)
-             */
+#  endif    /* defined(OPENSSL_RAND_SEED_DEVRANDOM) */
 
 /*
  * Try the various seeding methods in turn, exit when successful.
@@ -450,14 +469,14 @@ void rand_pool_keep_random_devices_open(int keep)
  */
 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
 {
-#  ifdef OPENSSL_RAND_SEED_NONE
+#  if defined(OPENSSL_RAND_SEED_NONE)
     return rand_pool_entropy_available(pool);
 #  else
     size_t bytes_needed;
     size_t entropy_available = 0;
     unsigned char *buffer;
 
-#   ifdef OPENSSL_RAND_SEED_GETRANDOM
+#   if defined(OPENSSL_RAND_SEED_GETRANDOM)
     {
         ssize_t bytes;
         /* Maximum allowed number of consecutive unsuccessful attempts */
@@ -487,28 +506,56 @@ size_t rand_pool_acquire_entropy(RAND_POOL *pool)
     }
 #   endif
 
-#   ifdef OPENSSL_RAND_SEED_DEVRANDOM
+#   if defined(OPENSSL_RAND_SEED_DEVRANDOM)
     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
     {
         size_t i;
+#ifdef DEVRANDOM_WAIT
+        static int wait_done = 0;
+
+        /*
+         * On some implementations reading from /dev/urandom is possible
+         * before it is initialized. Therefore we wait for /dev/random
+         * to be readable to make sure /dev/urandom is initialized.
+         */
+        if (!wait_done && bytes_needed > 0) {
+             int f = open(DEVRANDOM_WAIT, O_RDONLY);
+
+             if (f >= 0) {
+                 fd_set fds;
+
+                 FD_ZERO(&fds);
+                 FD_SET(f, &fds);
+                 while (select(f+1, &fds, NULL, NULL, NULL) < 0
+                        && errno == EINTR);
+                 close(f);
+             }
+             wait_done = 1;
+        }
+#endif
 
         for (i = 0; bytes_needed > 0 && i < OSSL_NELEM(random_device_paths); i++) {
+            ssize_t bytes = 0;
+            /* Maximum allowed number of consecutive unsuccessful attempts */
+            int attempts = 3;
             const int fd = get_random_device(i);
 
             if (fd == -1)
                 continue;
-            buffer = rand_pool_add_begin(pool, bytes_needed);
-            if (buffer != NULL) {
-                const ssize_t n = read(fd, buffer, bytes_needed);
 
-                if (n <= 0) {
-                    close_random_device(i);
-                    continue;
-                }
+            while (bytes_needed != 0 && attempts-- > 0) {
+                buffer = rand_pool_add_begin(pool, bytes_needed);
+                bytes = read(fd, buffer, bytes_needed);
 
-                rand_pool_add_end(pool, n, 8 * n);
+                if (bytes > 0) {
+                    rand_pool_add_end(pool, bytes, 8 * bytes);
+                    bytes_needed -= bytes;
+                    attempts = 3; /* reset counter after successful attempt */
+                } else if (bytes < 0 && errno != EINTR) {
+                    break;
+                }
             }
-            if (!keep_random_devices_open)
+            if (bytes < 0 || !keep_random_devices_open)
                 close_random_device(i);
 
             bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
@@ -519,19 +566,19 @@ size_t rand_pool_acquire_entropy(RAND_POOL *pool)
     }
 #   endif
 
-#   ifdef OPENSSL_RAND_SEED_RDTSC
+#   if defined(OPENSSL_RAND_SEED_RDTSC)
     entropy_available = rand_acquire_entropy_from_tsc(pool);
     if (entropy_available > 0)
         return entropy_available;
 #   endif
 
-#   ifdef OPENSSL_RAND_SEED_RDCPU
+#   if defined(OPENSSL_RAND_SEED_RDCPU)
     entropy_available = rand_acquire_entropy_from_cpu(pool);
     if (entropy_available > 0)
         return entropy_available;
 #   endif
 
-#   ifdef OPENSSL_RAND_SEED_EGD
+#   if defined(OPENSSL_RAND_SEED_EGD)
     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
     if (bytes_needed > 0) {
         static const char *paths[] = { DEVRANDOM_EGD, NULL };
@@ -572,7 +619,7 @@ int rand_pool_add_nonce_data(RAND_POOL *pool)
 
     /*
      * Add process id, thread id, and a high resolution timestamp to
-     * ensure that the nonce is unique whith high probability for
+     * ensure that the nonce is unique with high probability for
      * different process instances.
      */
     data.pid = getpid();