Revamp srp_user_secret_nif()

* Add error handling for all OpenSSL calls.
* Consolidate freeing resources in both success and failure path.

1 files changed, 86 insertions, 59 deletions

diff --git a/lib/crypto/c_src/srp.c b/lib/crypto/c_src/srp.c
index 18b03206e0..e5ef72af08 100644
--- a/lib/crypto/c_src/srp.c
+++ b/lib/crypto/c_src/srp.c
@@ -114,80 +114,107 @@ ERL_NIF_TERM srp_user_secret_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM ar
         <premaster secret> = (B - (k * g^x)) ^ (a + (u * x)) % N
 */
     BIGNUM *bn_exponent = NULL, *bn_a = NULL;
-    BIGNUM *bn_u = NULL, *bn_multiplier = NULL, *bn_exp2,
-        *bn_base, *bn_prime = NULL, *bn_generator = NULL,
-        *bn_B = NULL, *bn_result;
-    BN_CTX *bn_ctx;
-    unsigned char* ptr;
-    unsigned dlen;
+    BIGNUM *bn_u = NULL, *bn_multiplier = NULL, *bn_exp2 = NULL;
+    BIGNUM *bn_base = NULL, *bn_prime = NULL, *bn_generator = NULL;
+    BIGNUM *bn_B = 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_a)
-	|| !get_bn_from_bin(env, argv[1], &bn_u)
-	|| !get_bn_from_bin(env, argv[2], &bn_B)
-	|| !get_bn_from_bin(env, argv[3], &bn_multiplier)
-	|| !get_bn_from_bin(env, argv[4], &bn_generator)
-	|| !get_bn_from_bin(env, argv[5], &bn_exponent)
-	|| !get_bn_from_bin(env, argv[6], &bn_prime))
-    {
-	if (bn_exponent) BN_free(bn_exponent);
-	if (bn_a) BN_free(bn_a);
-	if (bn_u) BN_free(bn_u);
-	if (bn_B) BN_free(bn_B);
-	if (bn_multiplier) BN_free(bn_multiplier);
-	if (bn_generator) BN_free(bn_generator);
-	if (bn_prime) BN_free(bn_prime);
-	return enif_make_badarg(env);
-    }
+    if (argc != 7)
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[0], &bn_a))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[1], &bn_u))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[2], &bn_B))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[3], &bn_multiplier))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[4], &bn_generator))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[5], &bn_exponent))
+        goto bad_arg;
+    if (!get_bn_from_bin(env, argv[6], &bn_prime))
+        goto bad_arg;
 
-    bn_ctx = BN_CTX_new();
-    bn_result = BN_new();
+    if ((bn_ctx = BN_CTX_new()) == NULL)
+        goto err;
+    if ((bn_result = BN_new()) == NULL)
+        goto err;
 
     /* check that B % N != 0 */
-    BN_nnmod(bn_result, bn_B, bn_prime, bn_ctx);
-    if (BN_is_zero(bn_result)) {
-	BN_free(bn_exponent);
-	BN_free(bn_a);
-	BN_free(bn_generator);
-	BN_free(bn_prime);
-	BN_free(bn_u);
-	BN_free(bn_B);
-	BN_CTX_free(bn_ctx);
-
-	return atom_error;
-    }
+    if (!BN_nnmod(bn_result, bn_B, bn_prime, bn_ctx))
+        goto err;
+    if (BN_is_zero(bn_result))
+        goto err;
 
     /* (B - (k * g^x)) */
-    bn_base = BN_new();
-    BN_mod_exp(bn_result, bn_generator, bn_exponent, bn_prime, bn_ctx);
-    BN_mod_mul(bn_result, bn_multiplier, bn_result, bn_prime, bn_ctx);
-    BN_mod_sub(bn_base, bn_B, bn_result, bn_prime, bn_ctx);
+    if ((bn_base = BN_new()) == NULL)
+        goto err;
+    if (!BN_mod_exp(bn_result, bn_generator, bn_exponent, bn_prime, bn_ctx))
+        goto err;
+    if (!BN_mod_mul(bn_result, bn_multiplier, bn_result, bn_prime, bn_ctx))
+        goto err;
+    if (!BN_mod_sub(bn_base, bn_B, bn_result, bn_prime, bn_ctx))
+        goto err;
 
     /* a + (u * x) */
-    bn_exp2 = BN_new();
-    BN_mul(bn_result, bn_u, bn_exponent, bn_ctx);
-    BN_add(bn_exp2, bn_a, bn_result);
+    if ((bn_exp2 = BN_new()) == NULL)
+        goto err;
+    if (!BN_mul(bn_result, bn_u, bn_exponent, bn_ctx))
+        goto err;
+    if (!BN_add(bn_exp2, bn_a, bn_result))
+        goto err;
 
     /* (B - (k * g^x)) ^ (a + (u * x)) % N */
-    BN_mod_exp(bn_result, bn_base, bn_exp2, bn_prime, bn_ctx);
+    if (!BN_mod_exp(bn_result, bn_base, bn_exp2, bn_prime, bn_ctx))
+        goto err;
 
-    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);
+    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_a)
+        BN_free(bn_a);
+    if (bn_u)
+        BN_free(bn_u);
+    if (bn_B)
+        BN_free(bn_B);
+    if (bn_multiplier)
+        BN_free(bn_multiplier);
+    if (bn_generator)
+        BN_free(bn_generator);
+    if (bn_exponent)
+        BN_free(bn_exponent);
+    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);
+    if (bn_exp2)
+        BN_free(bn_exp2);
 
-    BN_free(bn_multiplier);
-    BN_free(bn_exp2);
-    BN_free(bn_u);
-    BN_free(bn_exponent);
-    BN_free(bn_a);
-    BN_free(bn_B);
-    BN_free(bn_base);
-    BN_free(bn_generator);
-    BN_free(bn_prime);
     return ret;
 }