Make the random number generator predictable when fuzzing.

Reviewed-by: Rich Salz <rsalz@openssl.org>
GH: #2023

diff --git a/crypto/rand/md_rand.c b/crypto/rand/md_rand.c
index 85ce4e6f982ed299cf1695a9f2b6a8cd4cce4eb2..0cf6e90834820f129ec29b7f6806e17df09b5c53 100644 (file)
--- a/crypto/rand/md_rand.c
+++ b/crypto/rand/md_rand.c
@@ -33,7 +33,7 @@
 # include <openssl/fips.h>
 #endif
 
-#ifdef BN_DEBUG
+#if defined(BN_DEBUG) || defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION)
 # define PREDICT
 #endif
 
@@ -307,7 +307,7 @@ static int rand_bytes(unsigned char *buf, int num, int pseudo)
 
 #ifdef PREDICT
     if (rand_predictable) {
-        static unsigned char val = 0;
+        unsigned char val = 0;
 
         for (i = 0; i < num; i++)
             buf[i] = val++;

diff --git a/fuzz/README.md b/fuzz/README.md
index c5a1ba9c9ae205cbde117cb70c9b6a02fcceb44d..d0c30f4461c8190b313e3f88565ed685d26027c9 100644 (file)
--- a/fuzz/README.md
+++ b/fuzz/README.md
@@ -38,7 +38,8 @@ Configure for fuzzing:
     $ CC=clang ./config enable-fuzz-libfuzzer \
             --with-fuzzer-include=../../svn-work/Fuzzer \
             --with-fuzzer-lib=../../svn-work/Fuzzer/libFuzzer \
-            -DPEDANTIC enable-asan enable-ubsan no-shared
+            -DPEDANTIC enable-asan enable-ubsan no-shared \
+            -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
     $ sudo apt-get install make
     $ LDCMD=clang++ make -j
     $ fuzz/helper.py $FUZZER

diff --git a/fuzz/server.c b/fuzz/server.c
index b8a3ac44e382a11b2d5fe88b1b1caaaa1087f5af..4f2c794a4ca513779a7001396f28037b47c8863b 100644 (file)
--- a/fuzz/server.c
+++ b/fuzz/server.c
@@ -191,6 +191,10 @@ static const uint8_t kRSAPrivateKeyDER[] = {
 
 static SSL_CTX *ctx;
 
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+extern int rand_predictable;
+#endif
+
 int FuzzerInitialize(int *argc, char ***argv)
 {
     const uint8_t *bufp = kRSAPrivateKeyDER;
@@ -214,6 +218,10 @@ int FuzzerInitialize(int *argc, char ***argv)
     OPENSSL_assert(ret == 1);
     X509_free(cert);
 
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+    rand_predictable = 1;
+#endif
+
     return 1;
 }