Revamp srp_host_secret_nif()

* Add error checking on all OpenSSL calls.
* Change dlen to int.
* Consolidate all of the freeing of resources into a common path.

1 files changed, 69 insertions, 47 deletions

diff --git a/lib/crypto/c_src/srp.c b/lib/crypto/c_src/srp.c
index e5ef72af08..5a49a1c1b4 100644
--- a/lib/crypto/c_src/srp.c
+++ b/lib/crypto/c_src/srp.c
@@ -224,63 +224,85 @@ ERL_NIF_TERM srp_host_secret_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM ar
         <premaster secret> = (A * v^u) ^ b % N
 */
     BIGNUM *bn_b = NULL, *bn_verifier = NULL;
-    BIGNUM *bn_prime = NULL, *bn_A = NULL, *bn_u = NULL, *bn_base, *bn_result;
-    BN_CTX *bn_ctx;
-    unsigned char* ptr;
-    unsigned dlen;
+    BIGNUM *bn_prime = NULL, *bn_A = NULL, *bn_u = NULL, *bn_base = NULL, *bn_result = NULL;
+    BN_CTX *bn_ctx = NULL;
+    unsigned char *ptr;
+    int dlen;
     ERL_NIF_TERM ret;
 
     CHECK_NO_FIPS_MODE();
 
-    if (!get_bn_from_bin(env, argv[0], &bn_verifier)
-	|| !get_bn_from_bin(env, argv[1], &bn_b)
-	|| !get_bn_from_bin(env, argv[2], &bn_u)
-	|| !get_bn_from_bin(env, argv[3], &bn_A)
-	|| !get_bn_from_bin(env, argv[4], &bn_prime))
-    {
-	if (bn_verifier) BN_free(bn_verifier);
-	if (bn_b) BN_free(bn_b);
-	if (bn_u) BN_free(bn_u);
-	if (bn_A) BN_free(bn_A);
-	if (bn_prime) BN_free(bn_prime);
-	return enif_make_badarg(env);
-    }
-
-    bn_ctx = BN_CTX_new();
-    bn_result = BN_new();
+    if (argc != 5)
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[0], &bn_verifier))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[1], &bn_b))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[2], &bn_u))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[3], &bn_A))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[4], &bn_prime))
+        goto bad_arg;
 
-    /* check that A % N != 0 */
-    BN_nnmod(bn_result, bn_A, bn_prime, bn_ctx);
-    if (BN_is_zero(bn_result)) {
-	BN_free(bn_b);
-	BN_free(bn_verifier);
-	BN_free(bn_prime);
-	BN_free(bn_A);
-	BN_CTX_free(bn_ctx);
+    if ((bn_ctx = BN_CTX_new()) == NULL)
+        goto err;
+    if ((bn_result = BN_new()) == NULL)
+        goto err;
 
-	return atom_error;
-    }
+    /* check that A % N != 0 */
+    if (!BN_nnmod(bn_result, bn_A, bn_prime, bn_ctx))
+        goto err;
+    if (BN_is_zero(bn_result))
+        goto err;
 
     /* (A * v^u) */
-    bn_base = BN_new();
-    BN_mod_exp(bn_base, bn_verifier, bn_u, bn_prime, bn_ctx);
-    BN_mod_mul(bn_base, bn_A, bn_base, bn_prime, bn_ctx);
+    if ((bn_base = BN_new()) == NULL)
+        goto err;
+    if (!BN_mod_exp(bn_base, bn_verifier, bn_u, bn_prime, bn_ctx))
+        goto err;
+    if (!BN_mod_mul(bn_base, bn_A, bn_base, bn_prime, bn_ctx))
+        goto err;
 
     /* (A * v^u) ^ b % N */
-    BN_mod_exp(bn_result, bn_base, bn_b, bn_prime, bn_ctx);
-
-    dlen = BN_num_bytes(bn_result);
-    ptr = enif_make_new_binary(env, dlen, &ret);
-    BN_bn2bin(bn_result, ptr);
-    BN_free(bn_result);
-    BN_CTX_free(bn_ctx);
-
-    BN_free(bn_u);
-    BN_free(bn_base);
-    BN_free(bn_verifier);
-    BN_free(bn_prime);
-    BN_free(bn_A);
-    BN_free(bn_b);
+    if (!BN_mod_exp(bn_result, bn_base, bn_b, bn_prime, bn_ctx))
+        goto err;
+
+    if ((dlen = BN_num_bytes(bn_result)) < 0)
+        goto err;
+    if ((ptr = enif_make_new_binary(env, (size_t)dlen, &ret)) == NULL)
+        goto err;
+
+    if (BN_bn2bin(bn_result, ptr) < 0)
+        goto err;
+
+    goto done;
+
+ bad_arg:
+    ret = enif_make_badarg(env);
+    goto done;
+
+ err:
+    ret = atom_error;
+
+ done:
+    if (bn_verifier)
+        BN_free(bn_verifier);
+    if (bn_b)
+        BN_free(bn_b);
+    if (bn_u)
+        BN_free(bn_u);
+    if (bn_A)
+        BN_free(bn_A);
+    if (bn_prime)
+        BN_free(bn_prime);
+    if (bn_ctx)
+        BN_CTX_free(bn_ctx);
+    if (bn_result)
+        BN_free(bn_result);
+    if (bn_base)
+        BN_free(bn_base);
+
     return ret;
 }