rand: avoid using the derivation function for the public and private DRBGs

There is no point using it becuase they are getting full quality entropy from
the primary DRBG (which remains using the d.f.).

Also cleaned up the parameter passing to the DRBGs to not pass parameters that
are unknown.

Fixes #16117

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16156)

diff --git a/crypto/rand/rand_lib.c b/crypto/rand/rand_lib.c
index 8f76c8a5f024ec0c4abf5ef35ad334a38cec40d9..30b6cb817f446c09af7068923c6410c1728447e9 100644 (file)
--- a/crypto/rand/rand_lib.c
+++ b/crypto/rand/rand_lib.c
@@ -552,12 +552,13 @@ static EVP_RAND_CTX *rand_new_seed(OSSL_LIB_CTX *libctx)
 
 static EVP_RAND_CTX *rand_new_drbg(OSSL_LIB_CTX *libctx, EVP_RAND_CTX *parent,
                                    unsigned int reseed_interval,
-                                   time_t reseed_time_interval)
+                                   time_t reseed_time_interval, int use_df)
 {
     EVP_RAND *rand;
     RAND_GLOBAL *dgbl = rand_get_global(libctx);
     EVP_RAND_CTX *ctx;
-    OSSL_PARAM params[7], *p = params;
+    OSSL_PARAM params[8], *p = params;
+    const OSSL_PARAM *settables;
     char *name, *cipher;
 
     name = dgbl->rng_name != NULL ? dgbl->rng_name : "CTR-DRBG";
@@ -573,20 +574,23 @@ static EVP_RAND_CTX *rand_new_drbg(OSSL_LIB_CTX *libctx, EVP_RAND_CTX *parent,
         return NULL;
     }
 
-    /*
-     * Rather than trying to decode the DRBG settings, just pass them through
-     * and rely on the other end to ignore those it doesn't care about.
-     */
-    cipher = dgbl->rng_cipher != NULL ? dgbl->rng_cipher : "AES-256-CTR";
-    *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER,
-                                            cipher, 0);
-    if (dgbl->rng_digest != NULL)
+    settables = EVP_RAND_CTX_settable_params(ctx);
+    if (OSSL_PARAM_locate_const(settables, OSSL_DRBG_PARAM_CIPHER)) {
+        cipher = dgbl->rng_cipher != NULL ? dgbl->rng_cipher : "AES-256-CTR";
+        *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER,
+                                                cipher, 0);
+    }
+    if (dgbl->rng_digest != NULL
+            && OSSL_PARAM_locate_const(settables, OSSL_DRBG_PARAM_DIGEST))
         *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_DIGEST,
                                                 dgbl->rng_digest, 0);
     if (dgbl->rng_propq != NULL)
         *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_PROPERTIES,
                                                 dgbl->rng_propq, 0);
-    *p++ = OSSL_PARAM_construct_utf8_string(OSSL_ALG_PARAM_MAC, "HMAC", 0);
+    if (OSSL_PARAM_locate_const(settables, OSSL_ALG_PARAM_MAC))
+        *p++ = OSSL_PARAM_construct_utf8_string(OSSL_ALG_PARAM_MAC, "HMAC", 0);
+    if (OSSL_PARAM_locate_const(settables, OSSL_DRBG_PARAM_USE_DF))
+        *p++ = OSSL_PARAM_construct_int(OSSL_DRBG_PARAM_USE_DF, &use_df);
     *p++ = OSSL_PARAM_construct_uint(OSSL_DRBG_PARAM_RESEED_REQUESTS,
                                      &reseed_interval);
     *p++ = OSSL_PARAM_construct_time_t(OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL,
@@ -641,7 +645,7 @@ EVP_RAND_CTX *RAND_get0_primary(OSSL_LIB_CTX *ctx)
 
     ret = dgbl->primary = rand_new_drbg(ctx, dgbl->seed,
                                         PRIMARY_RESEED_INTERVAL,
-                                        PRIMARY_RESEED_TIME_INTERVAL);
+                                        PRIMARY_RESEED_TIME_INTERVAL, 1);
     /*
     * The primary DRBG may be shared between multiple threads so we must
     * enable locking.
@@ -683,7 +687,7 @@ EVP_RAND_CTX *RAND_get0_public(OSSL_LIB_CTX *ctx)
                 && !ossl_init_thread_start(NULL, ctx, rand_delete_thread_state))
             return NULL;
         rand = rand_new_drbg(ctx, primary, SECONDARY_RESEED_INTERVAL,
-                             SECONDARY_RESEED_TIME_INTERVAL);
+                             SECONDARY_RESEED_TIME_INTERVAL, 0);
         CRYPTO_THREAD_set_local(&dgbl->public, rand);
     }
     return rand;
@@ -716,7 +720,7 @@ EVP_RAND_CTX *RAND_get0_private(OSSL_LIB_CTX *ctx)
                 && !ossl_init_thread_start(NULL, ctx, rand_delete_thread_state))
             return NULL;
         rand = rand_new_drbg(ctx, primary, SECONDARY_RESEED_INTERVAL,
-                             SECONDARY_RESEED_TIME_INTERVAL);
+                             SECONDARY_RESEED_TIME_INTERVAL, 0);
         CRYPTO_THREAD_set_local(&dgbl->private, rand);
     }
     return rand;