rand: add a provider side seed source.

This allows the operating system sources that OpenSSL supports to be
used directly as RNGs.  It also allows DRBG seeding to be explicitly
specified rather than being left to a fall back case.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/13455)

1 files changed, 51 insertions, 2 deletions

diff --git a/crypto/rand/rand_lib.c b/crypto/rand/rand_lib.c
index 73d509a8dc..2ad3cf776f 100644
--- a/crypto/rand/rand_lib.c
+++ b/crypto/rand/rand_lib.c
@@ -325,6 +325,8 @@ typedef struct rand_global_st {
      */
     CRYPTO_RWLOCK *lock;
 
+    EVP_RAND_CTX *seed;
+
     /*
      * The <primary> DRBG
      *
@@ -363,6 +365,10 @@ typedef struct rand_global_st {
     char *rng_cipher;
     char *rng_digest;
     char *rng_propq;
+
+    /* Allow the randomness source to be changed */
+    char *seed_name;
+    char *seed_propq;
 } RAND_GLOBAL;
 
 /*
@@ -412,13 +418,16 @@ static void rand_ossl_ctx_free(void *vdgbl)
         return;
 
     CRYPTO_THREAD_lock_free(dgbl->lock);
-    EVP_RAND_CTX_free(dgbl->primary);
     CRYPTO_THREAD_cleanup_local(&dgbl->private);
     CRYPTO_THREAD_cleanup_local(&dgbl->public);
+    EVP_RAND_CTX_free(dgbl->primary);
+    EVP_RAND_CTX_free(dgbl->seed);
     OPENSSL_free(dgbl->rng_name);
     OPENSSL_free(dgbl->rng_cipher);
     OPENSSL_free(dgbl->rng_digest);
     OPENSSL_free(dgbl->rng_propq);
+    OPENSSL_free(dgbl->seed_name);
+    OPENSSL_free(dgbl->seed_propq);
 
     OPENSSL_free(dgbl);
 }
@@ -452,6 +461,35 @@ static void rand_delete_thread_state(void *arg)
     EVP_RAND_CTX_free(rand);
 }
 
+#ifndef FIPS_MODULE
+static EVP_RAND_CTX *rand_new_seed(OSSL_LIB_CTX *libctx)
+{
+    EVP_RAND *rand;
+    RAND_GLOBAL *dgbl = rand_get_global(libctx);
+    EVP_RAND_CTX *ctx;
+    char *name;
+
+    name = dgbl->seed_name != NULL ? dgbl->seed_name : "SEED-SRC";
+    rand = EVP_RAND_fetch(libctx, name, dgbl->seed_propq);
+    if (rand == NULL) {
+        ERR_raise(ERR_LIB_RAND, RAND_R_UNABLE_TO_FETCH_DRBG);
+        return NULL;
+    }
+    ctx = EVP_RAND_CTX_new(rand, NULL);
+    EVP_RAND_free(rand);
+    if (ctx == NULL) {
+        ERR_raise(ERR_LIB_RAND, RAND_R_UNABLE_TO_CREATE_DRBG);
+        return NULL;
+    }
+    if (!EVP_RAND_instantiate(ctx, 0, 0, NULL, 0)) {
+        ERR_raise(ERR_LIB_RAND, RAND_R_ERROR_INSTANTIATING_DRBG);
+        EVP_RAND_CTX_free(ctx);
+        return NULL;
+    }
+    return ctx;
+}
+#endif
+
 static EVP_RAND_CTX *rand_new_drbg(OSSL_LIB_CTX *libctx, EVP_RAND_CTX *parent,
                                    unsigned int reseed_interval,
                                    time_t reseed_time_interval)
@@ -522,8 +560,13 @@ EVP_RAND_CTX *RAND_get0_primary(OSSL_LIB_CTX *ctx)
     if (dgbl->primary == NULL) {
         if (!CRYPTO_THREAD_write_lock(dgbl->lock))
             return NULL;
+#ifndef FIPS_MODULE
+        if (dgbl->seed == NULL)
+            dgbl->seed = rand_new_seed(ctx);
+#endif
         if (dgbl->primary == NULL)
-            dgbl->primary = rand_new_drbg(ctx, NULL, PRIMARY_RESEED_INTERVAL,
+            dgbl->primary = rand_new_drbg(ctx, dgbl->seed,
+                                          PRIMARY_RESEED_INTERVAL,
                                           PRIMARY_RESEED_TIME_INTERVAL);
         CRYPTO_THREAD_unlock(dgbl->lock);
     }
@@ -644,6 +687,12 @@ static int random_conf_init(CONF_IMODULE *md, const CONF *cnf)
         } else if (strcasecmp(cval->name, "properties") == 0) {
             if (!random_set_string(&dgbl->rng_propq, cval->value))
                 return 0;
+        } else if (strcasecmp(cval->name, "seed") == 0) {
+            if (!random_set_string(&dgbl->seed_name, cval->value))
+                return 0;
+        } else if (strcasecmp(cval->name, "seed_properties") == 0) {
+            if (!random_set_string(&dgbl->seed_propq, cval->value))
+                return 0;
         } else {
             ERR_raise_data(ERR_LIB_CRYPTO,
                            CRYPTO_R_UNKNOWN_NAME_IN_RANDOM_SECTION,