1 files changed, 130 insertions, 0 deletions
diff --git a/crypto/ffc/ffc_key_validate.c b/crypto/ffc/ffc_key_validate.c
new file mode 100644
index 000000000000..342789621d6d
--- /dev/null
+++ b/crypto/ffc/ffc_key_validate.c
@@ -0,0 +1,130 @@
+/*
+ * Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include "internal/ffc.h"
+
+/*
+ * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Partial public key validation.
+ * To only be used with ephemeral FFC public keys generated using the approved
+ * safe-prime groups. (Checks that the public key is in the range [2, p - 1]
+ *
+ * ret contains 0 on success, or error flags (see FFC_ERROR_PUBKEY_TOO_SMALL)
+ */
+int ossl_ffc_validate_public_key_partial(const FFC_PARAMS *params,
+                                         const BIGNUM *pub_key, int *ret)
+{
+    int ok = 0;
+    BIGNUM *tmp = NULL;
+    BN_CTX *ctx = NULL;
+
+    *ret = 0;
+    if (params == NULL || pub_key == NULL || params->p == NULL) {
+        *ret = FFC_ERROR_PASSED_NULL_PARAM;
+        return 0;
+    }
+
+    ctx = BN_CTX_new_ex(NULL);
+    if (ctx == NULL)
+        goto err;
+
+    BN_CTX_start(ctx);
+    tmp = BN_CTX_get(ctx);
+    /* Step(1): Verify pub_key >= 2 */
+    if (tmp == NULL
+        || !BN_set_word(tmp, 1))
+        goto err;
+    if (BN_cmp(pub_key, tmp) <= 0) {
+        *ret |= FFC_ERROR_PUBKEY_TOO_SMALL;
+        goto err;
+    }
+    /* Step(1): Verify pub_key <=  p-2 */
+    if (BN_copy(tmp, params->p) == NULL
+        || !BN_sub_word(tmp, 1))
+        goto err;
+    if (BN_cmp(pub_key, tmp) >= 0) {
+        *ret |= FFC_ERROR_PUBKEY_TOO_LARGE;
+        goto err;
+    }
+    ok = 1;
+ err:
+    if (ctx != NULL) {
+        BN_CTX_end(ctx);
+        BN_CTX_free(ctx);
+    }
+    return ok;
+}
+
+/*
+ * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation.
+ */
+int ossl_ffc_validate_public_key(const FFC_PARAMS *params,
+                                 const BIGNUM *pub_key, int *ret)
+{
+    int ok = 0;
+    BIGNUM *tmp = NULL;
+    BN_CTX *ctx = NULL;
+
+    if (!ossl_ffc_validate_public_key_partial(params, pub_key, ret))
+        return 0;
+
+    if (params->q != NULL) {
+        ctx = BN_CTX_new_ex(NULL);
+        if (ctx == NULL)
+            goto err;
+        BN_CTX_start(ctx);
+        tmp = BN_CTX_get(ctx);
+
+        /* Check pub_key^q == 1 mod p */
+        if (tmp == NULL
+            || !BN_mod_exp(tmp, pub_key, params->q, params->p, ctx))
+            goto err;
+        if (!BN_is_one(tmp)) {
+            *ret |= FFC_ERROR_PUBKEY_INVALID;
+            goto err;
+        }
+    }
+
+    ok = 1;
+ err:
+    if (ctx != NULL) {
+        BN_CTX_end(ctx);
+        BN_CTX_free(ctx);
+    }
+    return ok;
+}
+
+/*
+ * See SP800-56Ar3 Section 5.6.2.1.2: Owner assurance of Private key validity.
+ * Verifies priv_key is in the range [1..upper-1]. The passed in value of upper
+ * is normally params->q but can be 2^N for approved safe prime groups.
+ * Note: This assumes that the domain parameters are valid.
+ */
+int ossl_ffc_validate_private_key(const BIGNUM *upper, const BIGNUM *priv,
+                                  int *ret)
+{
+    int ok = 0;
+
+    *ret = 0;
+
+    if (priv == NULL || upper == NULL) {
+        *ret = FFC_ERROR_PASSED_NULL_PARAM;
+        goto err;
+    }
+    if (BN_cmp(priv, BN_value_one()) < 0) {
+        *ret |= FFC_ERROR_PRIVKEY_TOO_SMALL;
+        goto err;
+    }
+    if (BN_cmp(priv, upper) >= 0) {
+        *ret |= FFC_ERROR_PRIVKEY_TOO_LARGE;
+        goto err;
+    }
+    ok = 1;
+err:
+    return ok;
+}