Curl_rand: fixed and moved to rand.c

Now Curl_rand() is made to fail if it cannot get the necessary random
level.

Changed the proto of Curl_rand() slightly to provide a number of ints at
once.

Moved out from vtls, since it isn't a TLS function and vtls provides
Curl_ssl_random() for this to use.

Discussion: https://curl.haxx.se/mail/lib-2016-11/0119.html

1 files changed, 129 insertions, 0 deletions

diff --git a/lib/rand.c b/lib/rand.c
new file mode 100644
index 000000000..107a1dd4a
--- /dev/null
+++ b/lib/rand.c
@@ -0,0 +1,129 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+
+#include <fcntl.h>
+
+#include <curl/curl.h>
+#include "vtls/vtls.h"
+#include "sendf.h"
+#include "rand.h"
+
+/* The last 3 #include files should be in this order */
+#include "curl_printf.h"
+#include "curl_memory.h"
+#include "memdebug.h"
+
+static CURLcode randit(struct Curl_easy *data, unsigned int *rnd)
+{
+  unsigned int r;
+  CURLcode result = CURLE_OK;
+  static unsigned int randseed;
+  static bool seeded = FALSE;
+
+#ifdef CURLDEBUG
+  char *force_entropy = getenv("CURL_ENTROPY");
+  if(force_entropy) {
+    if(!seeded) {
+      size_t elen = strlen(force_entropy);
+      size_t clen = sizeof(randseed);
+      size_t min = elen < clen ? elen : clen;
+      memcpy((char *)&randseed, force_entropy, min);
+      seeded = TRUE;
+    }
+    else
+      randseed++;
+    *rnd = randseed;
+    return CURLE_OK;
+  }
+#endif
+
+  /* data may be NULL! */
+  result = Curl_ssl_random(data, (unsigned char *)&rnd, sizeof(rnd));
+  if(result != CURLE_NOT_BUILT_IN)
+    /* only if there is no random funtion in the TLS backend do the non crypto
+       version, otherwise return result */
+    return result;
+
+  /* ---- non-cryptographic version following ---- */
+
+#ifdef RANDOM_FILE
+  if(!seeded) {
+    /* if there's a random file to read a seed from, use it */
+    int fd = open(RANDOM_FILE, O_RDONLY);
+    if(fd > -1) {
+      /* read random data into the randseed variable */
+      ssize_t nread = read(fd, &randseed, sizeof(randseed));
+      if(nread == sizeof(randseed))
+        seeded = TRUE;
+      close(fd);
+    }
+  }
+#endif
+
+  if(!seeded) {
+    struct timeval now = curlx_tvnow();
+    infof(data, "WARNING: Using weak random seed\n");
+    randseed += (unsigned int)now.tv_usec + (unsigned int)now.tv_sec;
+    randseed = randseed * 1103515245 + 12345;
+    randseed = randseed * 1103515245 + 12345;
+    randseed = randseed * 1103515245 + 12345;
+    seeded = TRUE;
+  }
+
+  /* Return an unsigned 32-bit pseudo-random number. */
+  r = randseed = randseed * 1103515245 + 12345;
+  *rnd = (r << 16) | ((r >> 16) & 0xFFFF);
+  return CURLE_OK;
+}
+
+/*
+ * Curl_rand() stores 'num' number of random unsigned integers in the buffer
+ * 'rndptr' points to.
+ *
+ * If libcurl is built without TLS support or with a TLS backend that lacks a
+ * proper random API (Gskit, PolarSSL or mbedTLS), this function will use
+ * "weak" random.
+ *
+ * When built *with* TLS support and a backend that offers strong random, it
+ * will return error if it cannot provide strong random values.
+ *
+ * NOTE: 'data' may be passed in as NULL when coming from external API without
+ * easy handle!
+ *
+ */
+
+CURLcode Curl_rand(struct Curl_easy *data, unsigned int *rndptr, int num)
+{
+  CURLcode result;
+  int i;
+
+  assert(num > 0);
+
+  for(i = 0; i < num; i++) {
+    result = randit(data, rndptr++);
+    if(result)
+      return result;
+  }
+  return result;
+}