Enable locking on the primary DRBG when we create it

The primary DRBG may be shared across multiple threads and therefore
we must use locking to access it. Previously we were enabling that locking
lazily when we attempted to obtain one of the child DRBGs. Part of the
process of enabling the lock, is to create the lock. But if we create the
lock lazily then it is too late - we may race with other threads where each
thread is independently attempting to enable the locking. This results
in multiple locks being created - only one of which "sticks" and the rest
are leaked.

Instead we enable locking on the primary when we first create it. This is
already locked and therefore we cannot race.
Reviewed-by: NTomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/13660)

crypto/err/openssl.txt

@@ -2609,7 +2609,7 @@ EVP_R_PRIVATE_KEY_ENCODE_ERROR:146:private key encode error
 EVP_R_PUBLIC_KEY_NOT_RSA:106:public key not rsa
 EVP_R_SET_DEFAULT_PROPERTY_FAILURE:209:set default property failure
 EVP_R_TOO_MANY_RECORDS:183:too many records
-EVP_R_UNABLE_TO_ENABLE_PARENT_LOCKING:212:unable to enable parent locking
+EVP_R_UNABLE_TO_ENABLE_LOCKING:212:unable to enable locking
 EVP_R_UNABLE_TO_GET_MAXIMUM_REQUEST_SIZE:215:unable to get maximum request size
 EVP_R_UNABLE_TO_GET_RANDOM_STRENGTH:216:unable to get random strength
 EVP_R_UNABLE_TO_LOCK_CONTEXT:211:unable to lock context

crypto/evp/evp_err.c

@@ -152,7 +152,7 @@ static const ERR_STRING_DATA EVP_str_reasons[] = {
     {ERR_PACK(ERR_LIB_EVP, 0, EVP_R_SET_DEFAULT_PROPERTY_FAILURE),
     "set default property failure"},
     {ERR_PACK(ERR_LIB_EVP, 0, EVP_R_TOO_MANY_RECORDS), "too many records"},
-    {ERR_PACK(ERR_LIB_EVP, 0, EVP_R_UNABLE_TO_ENABLE_PARENT_LOCKING),
+    {ERR_PACK(ERR_LIB_EVP, 0, EVP_R_UNABLE_TO_ENABLE_LOCKING),
     "unable to enable parent locking"},
     {ERR_PACK(ERR_LIB_EVP, 0, EVP_R_UNABLE_TO_GET_MAXIMUM_REQUEST_SIZE),
     "unable to get maximum request size"},

crypto/evp/evp_rand.c

@@ -333,12 +333,6 @@ EVP_RAND_CTX *EVP_RAND_CTX_new(EVP_RAND *rand, EVP_RAND_CTX *parent)
         return NULL;
     }
     if (parent != NULL) {
-        if (!EVP_RAND_enable_locking(parent)) {
-            ERR_raise(ERR_LIB_EVP, EVP_R_UNABLE_TO_ENABLE_PARENT_LOCKING);
-            CRYPTO_THREAD_lock_free(ctx->refcnt_lock);
-            OPENSSL_free(ctx);
-            return NULL;
-        }
         if (!evp_rand_ctx_up_ref(parent)) {
             ERR_raise(ERR_LIB_EVP, ERR_R_INTERNAL_ERROR);
             CRYPTO_THREAD_lock_free(ctx->refcnt_lock);

crypto/rand/rand_lib.c

@@ -571,6 +571,17 @@ EVP_RAND_CTX *RAND_get0_primary(OSSL_LIB_CTX *ctx)
             dgbl->primary = rand_new_drbg(ctx, dgbl->seed,
                                           PRIMARY_RESEED_INTERVAL,
                                           PRIMARY_RESEED_TIME_INTERVAL);
+        /*
+         * The primary DRBG may be shared between multiple threads so we must
+         * enable locking.
+         */
+        if (dgbl->primary != NULL && !EVP_RAND_enable_locking(dgbl->primary)) {
+            ERR_raise(ERR_LIB_EVP, EVP_R_UNABLE_TO_ENABLE_LOCKING);
+            EVP_RAND_CTX_free(dgbl->primary);
+            dgbl->primary = NULL;
+            CRYPTO_THREAD_lock_free(dgbl->lock);
+            return NULL;
+        }
         CRYPTO_THREAD_unlock(dgbl->lock);
     }
     return dgbl->primary;

doc/man3/EVP_RAND.pod

@@ -152,7 +152,9 @@ appropriate size.
 
 EVP_RAND_enable_locking() enables locking for the RAND I<ctx> and all of
 its parents.  After this I<ctx> will operate in a thread safe manner, albeit
-more slowly.
+more slowly. This function is not itself thread safe if called with the same
+I<ctx> from multiple threads. Typically locking should be enabled before a
+I<ctx> is shared across multiple threads.
 
 EVP_RAND_get_params() retrieves details about the implementation
 I<rand>.

include/openssl/evperr.h

@@ -243,7 +243,7 @@
 # define EVP_R_PUBLIC_KEY_NOT_RSA                         106
 # define EVP_R_SET_DEFAULT_PROPERTY_FAILURE               209
 # define EVP_R_TOO_MANY_RECORDS                           183
-# define EVP_R_UNABLE_TO_ENABLE_PARENT_LOCKING            212
+# define EVP_R_UNABLE_TO_ENABLE_LOCKING                   212
 # define EVP_R_UNABLE_TO_GET_MAXIMUM_REQUEST_SIZE         215
 # define EVP_R_UNABLE_TO_GET_RANDOM_STRENGTH              216
 # define EVP_R_UNABLE_TO_LOCK_CONTEXT                     211