Marshalling/Unmarshalling DH public keys (aws#1916)

### Issues:
Addresses: CryptoAlg-2696

### Description of changes: 
* Support marshalling/unmarshalling of DH public keys.

### Testing:
Added test `DHTest.DHMarshalPubKey`

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license and the ISC license.

crypto/dh_extra/dh_test.cc

@@ -1051,3 +1051,110 @@ TEST(DHTest, DHCheckForStandardParams) {
   ASSERT_TRUE(DH_check(dh2.get(), &flags));
   EXPECT_EQ(flags, 0);
 }
+
+TEST(DHTest, DHMarshalPubKey) {
+  const char* dh512_pem =
+    "-----BEGIN DH PARAMETERS-----\n"
+    "MEYCQQDqvLe5oX3p+Dw8T7NWG7nlWVFK58Ev74xvxYH72DC4kqfPEFPvNnCpFoRB\n"
+    "RdxOz7DZ6JO/GxobSRyAAI766+GDAgEC\n"
+    "-----END DH PARAMETERS-----";
+  const uint64_t encoded_g = 2;
+  const char encoded_p_dec_str[] = "12294183602774786812319504504704470077603616440910559765086569005477513835495488680341310019770549315448633656928525381740662262980129138358936697450520963";
+
+  bssl::UniquePtr<EVP_PKEY> epkey_dh_params(nullptr);
+  {
+    const size_t pem_len = OPENSSL_strnlen(dh512_pem, 1024);
+    bssl::UniquePtr<BIO> in_bio(BIO_new_mem_buf(dh512_pem, pem_len));
+    ASSERT_TRUE(in_bio);
+
+    epkey_dh_params.reset(PEM_read_bio_Parameters(in_bio.get(), nullptr));
+    ASSERT_TRUE(epkey_dh_params);
+  }
+
+  // Sanity check the Param parsing
+  {
+    DH *dh_params = EVP_PKEY_get0_DH(epkey_dh_params.get());
+    const BIGNUM *p = DH_get0_p(dh_params);
+    const BIGNUM *g = DH_get0_g(dh_params);
+    uint64_t parsed_g = 0;
+    ASSERT_TRUE(BN_get_u64(g, &parsed_g));
+    ASSERT_EQ(parsed_g, encoded_g);
+    const char *parsed_p_dec_str = BN_bn2dec(p);
+    ASSERT_NE(parsed_p_dec_str, nullptr);
+    ASSERT_EQ(OPENSSL_strcasecmp(encoded_p_dec_str, parsed_p_dec_str), 0);
+    OPENSSL_free((void *)parsed_p_dec_str);
+  }
+
+  // Perform keygen operation
+  bssl::UniquePtr<EVP_PKEY> gen_dh(nullptr);
+  {
+    bssl::UniquePtr<EVP_PKEY_CTX> epkey_ctx(
+        EVP_PKEY_CTX_new(epkey_dh_params.get(), nullptr));
+    ASSERT_TRUE(epkey_ctx);
+
+    ASSERT_TRUE(EVP_PKEY_keygen_init(epkey_ctx.get()));
+    EVP_PKEY *gen_dh_raw = nullptr;
+    ASSERT_TRUE(EVP_PKEY_keygen(epkey_ctx.get(), &gen_dh_raw));
+    gen_dh.reset(gen_dh_raw);
+    ASSERT_TRUE(gen_dh);
+  }
+
+  // Marshall pubkey to der
+  const uint8_t* pubkey_der = NULL;
+  size_t pubkey_der_len = 0;
+  {
+    bssl::UniquePtr<BIO> out_bio(BIO_new(BIO_s_mem()));
+    ASSERT_TRUE(out_bio);
+    ASSERT_TRUE(i2d_PUBKEY_bio(out_bio.get(), gen_dh.get()));
+    ASSERT_TRUE(BIO_flush(out_bio.get()));
+    ASSERT_TRUE(BIO_mem_contents(out_bio.get(), &pubkey_der, &pubkey_der_len));
+    ASSERT_GT(pubkey_der_len, (size_t)0);
+    ASSERT_NE(pubkey_der, nullptr);
+    // We own the allocation after this
+    pubkey_der = (const uint8_t*)OPENSSL_memdup(pubkey_der, pubkey_der_len);
+  }
+
+  // Parse der to pubkey
+  bssl::UniquePtr<EVP_PKEY> parsed_der_pubkey(nullptr);
+  {
+    bssl::UniquePtr<BIO> in_bio(BIO_new_mem_buf(pubkey_der, pubkey_der_len));
+    ASSERT_TRUE(in_bio);
+    EVP_PKEY* parsed_dh_pubkey_raw = nullptr;
+    ASSERT_TRUE(d2i_PUBKEY_bio(in_bio.get(), &parsed_dh_pubkey_raw));
+    parsed_der_pubkey.reset(parsed_dh_pubkey_raw);
+    ASSERT_TRUE(parsed_der_pubkey);
+  }
+
+  ASSERT_TRUE(EVP_PKEY_cmp(gen_dh.get(), parsed_der_pubkey.get()));
+
+  // Marshall pubkey to PEM
+  const uint8_t* pubkey_pem = NULL;
+  size_t pubkey_pem_len = 0;
+  {
+    bssl::UniquePtr<BIO> out_bio(BIO_new(BIO_s_mem()));
+    ASSERT_TRUE(out_bio);
+    ASSERT_TRUE(PEM_write_bio_PUBKEY(out_bio.get(), gen_dh.get()));
+    ASSERT_TRUE(BIO_flush(out_bio.get()));
+    ASSERT_TRUE(BIO_mem_contents(out_bio.get(), &pubkey_pem, &pubkey_pem_len));
+    ASSERT_GT(pubkey_pem_len, (size_t)0);
+    ASSERT_TRUE(pubkey_pem);
+    // We own the allocation after this
+    pubkey_pem = (const uint8_t*)OPENSSL_memdup(pubkey_pem, pubkey_pem_len);
+  }
+
+  // Parse PEM to pubkey
+  bssl::UniquePtr<EVP_PKEY> parsed_pem_pubkey(nullptr);
+  {
+    bssl::UniquePtr<BIO> in_bio(BIO_new_mem_buf(pubkey_pem, pubkey_pem_len));
+    ASSERT_TRUE(in_bio);
+    EVP_PKEY* pem_pubkey_raw = NULL;
+    ASSERT_TRUE(PEM_read_bio_PUBKEY(in_bio.get(), &pem_pubkey_raw, NULL, NULL));
+    parsed_pem_pubkey.reset(pem_pubkey_raw);
+    ASSERT_TRUE(parsed_pem_pubkey);
+  }
+
+  ASSERT_TRUE(EVP_PKEY_cmp(gen_dh.get(), parsed_pem_pubkey.get()));
+
+  OPENSSL_free((void*)pubkey_der);
+  OPENSSL_free((void*)pubkey_pem);
+}

crypto/evp_extra/evp_asn1.c

@@ -142,6 +142,8 @@ EVP_PKEY *EVP_parse_public_key(CBS *cbs) {
 }
 
 int EVP_marshal_public_key(CBB *cbb, const EVP_PKEY *key) {
+  GUARD_PTR(cbb);
+  GUARD_PTR(key);
   if (key->ameth == NULL || key->ameth->pub_encode == NULL) {
     OPENSSL_PUT_ERROR(EVP, EVP_R_UNSUPPORTED_ALGORITHM);
     return 0;

crypto/evp_extra/p_dh_asn1.c

@@ -12,10 +12,71 @@
 #include <openssl/bn.h>
 #include <openssl/dh.h>
 #include <openssl/err.h>
+#include <openssl/x509.h>
 
-#include "internal.h"
-#include "../internal.h"
 #include "../fipsmodule/cpucap/internal.h"
+#include "../fipsmodule/dh/internal.h"
+#include "../internal.h"
+#include "internal.h"
+
+static int dh_pub_encode(CBB *out, const EVP_PKEY *key) {
+  CBB spki, algorithm, oid, key_bitstring;
+  if (!CBB_add_asn1(out, &spki, CBS_ASN1_SEQUENCE) ||
+      !CBB_add_asn1(&spki, &algorithm, CBS_ASN1_SEQUENCE) ||
+      !CBB_add_asn1(&algorithm, &oid, CBS_ASN1_OBJECT) ||
+      !CBB_add_bytes(&oid, dh_asn1_meth.oid, dh_asn1_meth.oid_len) ||
+      !DH_marshal_parameters(&algorithm, key->pkey.dh) ||
+      !CBB_add_asn1(&spki, &key_bitstring, CBS_ASN1_BITSTRING) ||
+      !CBB_add_u8(&key_bitstring, 0 /* padding */) ||
+      !BN_marshal_asn1(&key_bitstring, key->pkey.dh->pub_key) ||
+      !CBB_flush(out)) {
+    OPENSSL_PUT_ERROR(EVP, EVP_R_ENCODE_ERROR);
+    return 0;
+  }
+
+  return 1;
+}
+
+static int dh_pub_decode(EVP_PKEY *out, CBS *params, CBS *key) {
+  // RFC 2786
+  BIGNUM *pubkey = NULL;
+  DH *dh = NULL;
+  if (out == NULL || params == NULL || CBS_len(params) == 0 || key == NULL ||
+      CBS_len(key) == 0) {
+    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
+    goto err;
+  }
+
+  dh = DH_parse_parameters(params);
+  if (dh == NULL) {
+    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
+    goto err;
+  }
+
+  pubkey = BN_new();
+  if (pubkey == NULL || !BN_parse_asn1_unsigned(key, pubkey)) {
+    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
+    goto err;
+  }
+
+  int out_flags = 0;
+  if (!DH_check_pub_key(dh, pubkey, &out_flags) || out_flags != 0) {
+    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
+    goto err;
+  }
+  dh->pub_key = pubkey;
+
+  if (!EVP_PKEY_assign_DH(out, dh)) {
+    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
+    goto err;
+  }
+  return 1;
+
+err:
+  DH_free(dh);
+  BN_free(pubkey);
+  return 0;
+}
 
 
 static void dh_free(EVP_PKEY *pkey) {
@@ -80,13 +141,23 @@ static int dh_pub_cmp(const EVP_PKEY *a, const EVP_PKEY *b) {
 
 const EVP_PKEY_ASN1_METHOD dh_asn1_meth = {
     .pkey_id = EVP_PKEY_DH,
+    // 1.2.840.113549.1.3.1
+    // ((1)*40 + (2)) = 42 = 0x2a
+    // 840 = 0b_0000110_1001000 => 0b_1000_0110_0100_1000 = 0x86 0x48
+    // 113549 = 0b_0000110_1110111_0001101 => 0b_1000_0110_1111_0111_0000_1101 = 0x86 0xF7 0x0D
+    .oid = {0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x03, 0x01},
+    .oid_len = 9,
+    .pem_str = "DH",
+    .info = "OpenSSL PKCS#3 DH method",
     .pub_cmp = dh_pub_cmp,
     .pkey_size = dh_size,
     .pkey_bits = dh_bits,
     .param_missing = dh_param_missing,
     .param_copy = dh_param_copy,
     .param_cmp = dh_param_cmp,
     .pkey_free = dh_free,
+    .pub_encode = dh_pub_encode,
+    .pub_decode = dh_pub_decode,
 };
 
 int EVP_PKEY_set1_DH(EVP_PKEY *pkey, DH *key) {

crypto/evp_extra/p_methods.c

@@ -27,7 +27,8 @@ const EVP_PKEY_ASN1_METHOD *const asn1_evp_pkey_methods[] = {
   &dilithium3_asn1_meth,
 #endif
   &kem_asn1_meth,
-  &hmac_asn1_meth
+  &hmac_asn1_meth,
+  &dh_asn1_meth
 };
 const size_t asn1_evp_pkey_methods_size = sizeof(asn1_evp_pkey_methods)/sizeof(asn1_evp_pkey_methods[0]);
 

crypto/fipsmodule/evp/internal.h

@@ -375,10 +375,10 @@ void evp_pkey_set_cb_translate(BN_GENCB *cb, EVP_PKEY_CTX *ctx);
 
 #ifdef ENABLE_DILITHIUM
 #define NON_FIPS_EVP_PKEY_METHODS 3
-#define ASN1_EVP_PKEY_METHODS 9
+#define ASN1_EVP_PKEY_METHODS 10
 #else
 #define NON_FIPS_EVP_PKEY_METHODS 2
-#define ASN1_EVP_PKEY_METHODS 8
+#define ASN1_EVP_PKEY_METHODS 9
 #endif
 
 struct fips_evp_pkey_methods {