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

10 files changed, 211 insertions, 98 deletions

diff --git a/lib/Makefile.inc b/lib/Makefile.inc
index 1328cadb0..19f58000a 100644
--- a/lib/Makefile.inc
+++ b/lib/Makefile.inc
@@ -51,7 +51,7 @@ LIB_CFILES = file.c timeval.c base64.c hostip.c progress.c formdata.c   \
   pingpong.c rtsp.c curl_threads.c warnless.c hmac.c curl_rtmp.c        \
   openldap.c curl_gethostname.c gopher.c idn_win32.c                    \
   http_proxy.c non-ascii.c asyn-ares.c asyn-thread.c curl_gssapi.c      \
-  http_ntlm.c curl_ntlm_wb.c curl_ntlm_core.c curl_sasl.c               \
+  http_ntlm.c curl_ntlm_wb.c curl_ntlm_core.c curl_sasl.c rand.c        \
   curl_multibyte.c hostcheck.c conncache.c pipeline.c dotdot.c          \
   x509asn1.c http2.c smb.c curl_endian.c curl_des.c system_win32.c
 
@@ -72,7 +72,7 @@ LIB_HFILES = arpa_telnet.h netrc.h file.h timeval.h hostip.h progress.h \
   curl_sasl.h curl_multibyte.h hostcheck.h conncache.h                  \
   curl_setup_once.h multihandle.h setup-vms.h pipeline.h dotdot.h       \
   x509asn1.h http2.h sigpipe.h smb.h curl_endian.h curl_des.h           \
-  curl_printf.h system_win32.h
+  curl_printf.h system_win32.h rand.h
 
 LIB_RCFILES = libcurl.rc
 
diff --git a/lib/Makefile.vc6 b/lib/Makefile.vc6
index 697993915..d028428a6 100644
--- a/lib/Makefile.vc6
+++ b/lib/Makefile.vc6
@@ -602,6 +602,7 @@ X_OBJS= \
 	$(DIROBJ)\pop3.obj \

 	$(DIROBJ)\progress.obj \

 	$(DIROBJ)\strcase.obj \

+	$(DIROBJ)\rand.obj \

 	$(DIROBJ)\rtsp.obj \

 	$(DIROBJ)\schannel.obj \

 	$(DIROBJ)\security.obj \

diff --git a/lib/formdata.c b/lib/formdata.c
index 785f1a678..1001bc191 100644
--- a/lib/formdata.c
+++ b/lib/formdata.c
@@ -36,6 +36,7 @@
 #include "strcase.h"
 #include "sendf.h"
 #include "strdup.h"
+#include "rand.h"
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
 #include "curl_memory.h"
@@ -1569,8 +1570,12 @@ static char *formboundary(struct Curl_easy *data)
 {
   /* 24 dashes and 16 hexadecimal digits makes 64 bit (18446744073709551615)
      combinations */
-  return aprintf("------------------------%08x%08x",
-                 Curl_rand(data), Curl_rand(data));
+  unsigned int rnd[2];
+  CURLcode result = Curl_rand(data, &rnd[0], 2);
+  if(result)
+    return NULL;
+
+  return aprintf("------------------------%08x%08x", rnd[0], rnd[1]);
 }
 
 #else  /* CURL_DISABLE_HTTP */
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;
+}
diff --git a/lib/rand.h b/lib/rand.h
new file mode 100644
index 000000000..36f89b526
--- /dev/null
+++ b/lib/rand.h
@@ -0,0 +1,42 @@
+#ifndef HEADER_CURL_RAND_H
+#define HEADER_CURL_RAND_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  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.
+ *
+ ***************************************************************************/
+
+/*
+ * Curl_rand() stores 'num' number of random unsigned integers in the buffer
+ * 'rnd' 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 *rnd, int num);
+
+#endif /* HEADER_CURL_RAND_H */
diff --git a/lib/vauth/digest.c b/lib/vauth/digest.c
index 0a11a308d..ca1d0c24a 100644
--- a/lib/vauth/digest.c
+++ b/lib/vauth/digest.c
@@ -40,6 +40,7 @@
 #include "strcase.h"
 #include "non-ascii.h" /* included for Curl_convert_... prototypes */
 #include "curl_printf.h"
+#include "rand.h"
 
 /* The last #include files should be: */
 #include "curl_memory.h"
@@ -387,10 +388,9 @@ CURLcode Curl_auth_create_digest_md5_message(struct Curl_easy *data,
     return CURLE_BAD_CONTENT_ENCODING;
 
   /* Generate 16 bytes of random data */
-  entropy[0] = Curl_rand(data);
-  entropy[1] = Curl_rand(data);
-  entropy[2] = Curl_rand(data);
-  entropy[3] = Curl_rand(data);
+  result = Curl_rand(data, &entropy[0], 4);
+  if(result)
+    return result;
 
   /* Convert the random data into a 32 byte hex string */
   snprintf(cnonce, sizeof(cnonce), "%08x%08x%08x%08x",
@@ -684,9 +684,12 @@ CURLcode Curl_auth_create_digest_http_message(struct Curl_easy *data,
     digest->nc = 1;
 
   if(!digest->cnonce) {
+    unsigned int rnd[4];
+    result = Curl_rand(data, &rnd[0], 4);
+    if(result)
+      return result;
     snprintf(cnoncebuf, sizeof(cnoncebuf), "%08x%08x%08x%08x",
-             Curl_rand(data), Curl_rand(data),
-             Curl_rand(data), Curl_rand(data));
+             rnd[0], rnd[1], rnd[2], rnd[3]);
 
     result = Curl_base64_encode(data, cnoncebuf, strlen(cnoncebuf),
                                 &cnonce, &cnonce_sz);
diff --git a/lib/vauth/ntlm.c b/lib/vauth/ntlm.c
index b484a011a..b4d345d63 100644
--- a/lib/vauth/ntlm.c
+++ b/lib/vauth/ntlm.c
@@ -41,7 +41,7 @@
 #include "curl_gethostname.h"
 #include "curl_multibyte.h"
 #include "warnless.h"
-
+#include "rand.h"
 #include "vtls/vtls.h"
 
 #ifdef USE_NSS
@@ -558,8 +558,9 @@ CURLcode Curl_auth_create_ntlm_type3_message(struct Curl_easy *data,
     unsigned int entropy[2];
     unsigned char ntlmv2hash[0x18];
 
-    entropy[0] = Curl_rand(data);
-    entropy[1] = Curl_rand(data);
+    result = Curl_rand(data, &entropy[0], 2);
+    if(result)
+      return result;
 
     result = Curl_ntlm_core_mk_nt_hash(data, passwdp, ntbuffer);
     if(result)
@@ -598,8 +599,9 @@ CURLcode Curl_auth_create_ntlm_type3_message(struct Curl_easy *data,
     unsigned int entropy[2];
 
     /* Need to create 8 bytes random data */
-    entropy[0] = Curl_rand(data);
-    entropy[1] = Curl_rand(data);
+    result = Curl_rand(data, &entropy[0], 2);
+    if(result)
+      return result;
 
     /* 8 bytes random data as challenge in lmresp */
     memcpy(lmresp, entropy, 8);
diff --git a/lib/vtls/gskit.h b/lib/vtls/gskit.h
index 41483cba6..e258a29f1 100644
--- a/lib/vtls/gskit.h
+++ b/lib/vtls/gskit.h
@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * 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
@@ -64,7 +64,7 @@ int Curl_gskit_check_cxn(struct connectdata *cxn);
 #define curlssl_version Curl_gskit_version
 #define curlssl_check_cxn(x) Curl_gskit_check_cxn(x)
 #define curlssl_data_pending(x,y) 0
-#define curlssl_random(x,y,z) -1
+#define curlssl_random(x,y,z) (x=x, y=y, z=z, CURLE_NOT_BUILT_IN)
 
 #endif /* USE_GSKIT */
 
diff --git a/lib/vtls/vtls.c b/lib/vtls/vtls.c
index 56a882341..ed65b46b9 100644
--- a/lib/vtls/vtls.c
+++ b/lib/vtls/vtls.c
@@ -177,77 +177,6 @@ void Curl_free_ssl_config(struct ssl_config_data* sslc)
   Curl_safefree(sslc->clientcert);
 }
 
-
-/*
- * Curl_rand() returns a random unsigned integer, 32bit.
- *
- * This non-SSL function is put here only because this file is the only one
- * with knowledge of what the underlying SSL libraries provide in terms of
- * randomizers.
- *
- * NOTE: 'data' may be passed in as NULL when coming from external API without
- * easy handle!
- *
- */
-
-unsigned int Curl_rand(struct Curl_easy *data)
-{
-  unsigned int r = 0;
-  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++;
-    return randseed;
-  }
-#endif
-
-  /* data may be NULL! */
-  if(!Curl_ssl_random(data, (unsigned char *)&r, sizeof(r)))
-    return r;
-
-  /* If Curl_ssl_random() returns non-zero it couldn't offer randomness and we
-     instead perform a "best effort" */
-
-#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;
-  return (r << 16) | ((r >> 16) & 0xFFFF);
-}
-
 int Curl_ssl_backend(void)
 {
   return (int)CURL_SSL_BACKEND;
@@ -736,11 +665,16 @@ CURLcode Curl_ssl_push_certinfo(struct Curl_easy *data,
   return Curl_ssl_push_certinfo_len(data, certnum, label, value, valuelen);
 }
 
-int Curl_ssl_random(struct Curl_easy *data,
-                     unsigned char *entropy,
-                     size_t length)
+CURLcode Curl_ssl_random(struct Curl_easy *data,
+                         unsigned char *entropy,
+                         size_t length)
 {
-  return curlssl_random(data, entropy, length);
+  int rc = curlssl_random(data, entropy, length);
+  if(rc) {
+    failf(data, "PRNG seeding failed");
+    return CURLE_FAILED_INIT; /* possibly weird return code */
+  }
+  return CURLE_OK;
 }
 
 /*
diff --git a/lib/vtls/vtls.h b/lib/vtls/vtls.h
index a41ecc325..69d206f52 100644
--- a/lib/vtls/vtls.h
+++ b/lib/vtls/vtls.h
@@ -56,8 +56,6 @@ bool Curl_clone_ssl_config(struct ssl_config_data* source,
                            struct ssl_config_data* dest);
 void Curl_free_ssl_config(struct ssl_config_data* sslc);
 
-unsigned int Curl_rand(struct Curl_easy *);
-
 int Curl_ssl_backend(void);
 
 #ifdef USE_SSL
@@ -140,10 +138,9 @@ void Curl_ssl_kill_session(struct curl_ssl_session *session);
  */
 void Curl_ssl_delsessionid(struct connectdata *conn, void *ssl_sessionid);
 
-/* get N random bytes into the buffer, return 0 if a find random is filled
-   in */
-int Curl_ssl_random(struct Curl_easy *data, unsigned char *buffer,
-                    size_t length);
+/* get N random bytes into the buffer */
+CURLcode Curl_ssl_random(struct Curl_easy *data, unsigned char *buffer,
+                         size_t length);
 CURLcode Curl_ssl_md5sum(unsigned char *tmp, /* input */
                          size_t tmplen,
                          unsigned char *md5sum, /* output */