rand_lib.c: fix null pointer dereferences after RAND_get_rand_method(…

…) failure RAND_get_rand_method() can return a NULL method pointer in the case of a malloc failure, so don't dereference it without a check. Reported-by: Zu-Ming Jiang (detected by FIFUZZ) Fixes #10480 Reviewed-by: Paul Dale <paul.dale@oracle.com> (Merged from #10483)
openssl · Dec 11, 2019 · 0402c90 · 0402c90
1 parent f5e77bb
commit 0402c90
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Showing 3 changed files with 25 additions and 17 deletions.
diff --git a/crypto/err/openssl.txt b/crypto/err/openssl.txt
@@ -1150,6 +1150,8 @@ RAND_F_RAND_POOL_ATTACH:124:rand_pool_attach
 RAND_F_RAND_POOL_BYTES_NEEDED:115:rand_pool_bytes_needed
 RAND_F_RAND_POOL_GROW:127:
 RAND_F_RAND_POOL_NEW:116:rand_pool_new
+RAND_F_RAND_PRIV_BYTES_EX:128:
+RAND_F_RAND_PSEUDO_BYTES:129:
 RAND_F_RAND_WRITE_FILE:112:RAND_write_file
 RSA_F_CHECK_PADDING_MD:140:check_padding_md
 RSA_F_ENCODE_PKCS1:146:encode_pkcs1

diff --git a/crypto/rand/rand_lib.c b/crypto/rand/rand_lib.c
@@ -311,6 +311,9 @@ int RAND_poll(void)
 
     const RAND_METHOD *meth = RAND_get_rand_method();
 
+    if (meth == NULL)
+        return 0;
+
     if (meth == RAND_OpenSSL()) {
         /* fill random pool and seed the master DRBG */
         RAND_DRBG *drbg = RAND_DRBG_get0_master();
@@ -831,15 +834,15 @@ void RAND_seed(const void *buf, int num)
 {
     const RAND_METHOD *meth = RAND_get_rand_method();
 
-    if (meth->seed != NULL)
+    if (meth != NULL && meth->seed != NULL)
         meth->seed(buf, num);
 }
 
 void RAND_add(const void *buf, int num, double randomness)
 {
     const RAND_METHOD *meth = RAND_get_rand_method();
 
-    if (meth->add != NULL)
+    if (meth != NULL && meth->add != NULL)
         meth->add(buf, num, randomness);
 }
 
@@ -851,18 +854,20 @@ void RAND_add(const void *buf, int num, double randomness)
 int rand_priv_bytes_ex(OPENSSL_CTX *ctx, unsigned char *buf, int num)
 {
     RAND_DRBG *drbg;
-    int ret;
     const RAND_METHOD *meth = RAND_get_rand_method();
 
-    if (meth != RAND_OpenSSL())
-        return meth->bytes(buf, num);
+    if (meth != NULL && meth != RAND_OpenSSL()) {
+        if (meth->bytes != NULL)
+            return meth->bytes(buf, num);
+        RANDerr(RAND_F_RAND_PRIV_BYTES_EX, RAND_R_FUNC_NOT_IMPLEMENTED);
+        return -1;
+    }
 
     drbg = OPENSSL_CTX_get0_private_drbg(ctx);
-    if (drbg == NULL)
-        return 0;
+    if (drbg != NULL)
+        return RAND_DRBG_bytes(drbg, buf, num);
 
-    ret = RAND_DRBG_bytes(drbg, buf, num);
-    return ret;
+    return 0;
 }
 
 int RAND_priv_bytes(unsigned char *buf, int num)
@@ -873,22 +878,20 @@ int RAND_priv_bytes(unsigned char *buf, int num)
 int rand_bytes_ex(OPENSSL_CTX *ctx, unsigned char *buf, int num)
 {
     RAND_DRBG *drbg;
-    int ret;
     const RAND_METHOD *meth = RAND_get_rand_method();
 
-    if (meth != RAND_OpenSSL()) {
+    if (meth != NULL && meth != RAND_OpenSSL()) {
         if (meth->bytes != NULL)
             return meth->bytes(buf, num);
         RANDerr(RAND_F_RAND_BYTES_EX, RAND_R_FUNC_NOT_IMPLEMENTED);
         return -1;
     }
 
     drbg = OPENSSL_CTX_get0_public_drbg(ctx);
-    if (drbg == NULL)
-        return 0;
+    if (drbg != NULL)
+        return RAND_DRBG_bytes(drbg, buf, num);
 
-    ret = RAND_DRBG_bytes(drbg, buf, num);
-    return ret;
+    return 0;
 }
 
 int RAND_bytes(unsigned char *buf, int num)
@@ -901,8 +904,9 @@ int RAND_pseudo_bytes(unsigned char *buf, int num)
 {
     const RAND_METHOD *meth = RAND_get_rand_method();
 
-    if (meth->pseudorand != NULL)
+    if (meth != NULL && meth->pseudorand != NULL)
         return meth->pseudorand(buf, num);
+    RANDerr(RAND_F_RAND_PSEUDO_BYTES, RAND_R_FUNC_NOT_IMPLEMENTED);
     return -1;
 }
 #endif
@@ -911,7 +915,7 @@ int RAND_status(void)
 {
     const RAND_METHOD *meth = RAND_get_rand_method();
 
-    if (meth->status != NULL)
+    if (meth != NULL && meth->status != NULL)
         return meth->status();
     return 0;
 }
diff --git a/include/openssl/randerr.h b/include/openssl/randerr.h
@@ -57,6 +57,8 @@ int ERR_load_RAND_strings(void);
 #  define RAND_F_RAND_POOL_BYTES_NEEDED                    0
 #  define RAND_F_RAND_POOL_GROW                            0
 #  define RAND_F_RAND_POOL_NEW                             0
+#  define RAND_F_RAND_PRIV_BYTES_EX                        0
+#  define RAND_F_RAND_PSEUDO_BYTES                         0
 #  define RAND_F_RAND_WRITE_FILE                           0
 # endif