fixup! Implement HKDF expand function based on RFC 8446

Change-Id: If7fc7984b2262a8ee8558435296ac8512d4cc33a

src/openvpn/crypto_epoch.c

@@ -90,14 +90,20 @@ ovpn_expand_label(const uint8_t *secret, size_t secret_len,
     }
 
     struct gc_arena gc = gc_new();
-    /* 2 byte for the outlen encoded as uint16, 5 bytes for "ovpn " */
-    int hkdf_label_len = 2 + 5 + label_len + context_len;
+    /* 2 byte for the outlen encoded as uint16, 5 bytes for "ovpn ",
+     * 1 byte for context len byte and 1 byte for label len byte */
+    int hkdf_label_len = 2 + 5 + label_len + 1 + context_len;
     struct buffer hkdf_label = alloc_buf_gc(hkdf_label_len, &gc);
 
+    const uint8_t *label_prefix = (const uint8_t *) ("ovpn ");
+    int prefix_len = 5;
 
     buf_write_u16(&hkdf_label, out_len);
-    buf_write(&hkdf_label, "ovpn ", 5);
+    buf_write_u8(&hkdf_label, prefix_len + label_len);
+    buf_write(&hkdf_label, label_prefix, prefix_len);
     buf_write(&hkdf_label, label, label_len);
+
+    buf_write_u8(&hkdf_label, context_len);
     if (context_len > 0)
     {
         buf_write(&hkdf_label, context, context_len);

tests/unit_tests/openvpn/test_crypto.c

@@ -42,6 +42,12 @@
 #include "mss.h"
 #include "test_common.h"
 
+
+#if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x30000000L
+#include <openssl/core_names.h>
+#include <openssl/kdf.h>
+#endif
+
 static const char testtext[] = "Dummy text to test PEM encoding";
 
 static void
@@ -586,6 +592,75 @@ crypto_test_ovpn_label_expand(void **state)
     assert_memory_equal(out, out_expected, 16);
 }
 
+void
+crypto_test_ovpn_expand_openssl3(void **state)
+{
+#if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x30000000L
+    OSSL_LIB_CTX *libctx = NULL;
+    const char *properties = NULL;
+
+    uint8_t secret[32] =
+    {0x07, 0x77, 0x09, 0x36, 0x2c, 0x2e, 0x32, 0xdf,
+     0x0d, 0xdc, 0x3f, 0x0d, 0xc4, 0x7b, 0xba, 0x63,
+     0x90, 0xb6, 0xc7, 0x3b, 0xb5, 0x0f, 0x9c, 0x31,
+     0x22, 0xec, 0x84, 0x4a, 0xd7, 0xc2, 0xb3, 0xe5};
+
+    const uint8_t *label_prefix = (const uint8_t *) ("ovpn ");
+    const size_t label_prefix_len = 5;
+    const uint8_t *label = (const uint8_t *) ("unit test");
+    const size_t labellen = 9;
+    uint8_t out[27];
+    size_t outlen = sizeof(out);
+
+    EVP_KDF *kdf = EVP_KDF_fetch(libctx, OSSL_KDF_NAME_TLS1_3_KDF, properties);
+    assert_non_null(kdf);
+
+    const char *mdname = "SHA-256";
+
+    size_t hashlen = SHA256_DIGEST_LENGTH;
+
+    EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
+    assert_non_null(kctx);
+
+    OSSL_PARAM params[7];
+    OSSL_PARAM *p = params;
+
+    int mode = EVP_PKEY_HKDEF_MODE_EXPAND_ONLY;
+
+    *p++ = OSSL_PARAM_construct_int(OSSL_KDF_PARAM_MODE, &mode);
+    *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
+                                            (char *) mdname, 0);
+    *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
+                                             (unsigned char *) secret, hashlen);
+    *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_PREFIX,
+                                             (unsigned char *) label_prefix,
+                                             label_prefix_len);
+    *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_LABEL,
+                                             (unsigned char *) label, labellen);
+
+    /*
+     * *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_DATA,
+     *                                            (unsigned char *)data,
+     *                                           datalen);
+     */
+    *p++ = OSSL_PARAM_construct_end();
+
+    int ret = EVP_KDF_derive(kctx, out, outlen, params);
+    EVP_KDF_CTX_free(kctx);
+
+    assert_int_equal(ret, 1);
+
+    /* Do the same derivation with our own function */
+    uint8_t out_ovpn[27];
+
+    ovpn_expand_label(secret, sizeof(secret), label, 9, NULL, 0, out_ovpn, sizeof(out_ovpn));
+    assert_memory_equal(out_ovpn, out, sizeof(out_ovpn));
+
+#else  /* if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x30000000L */
+    skip();
+#endif /* if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x30000000L */
+}
+
 struct epoch_test_state
 {
     struct key_type kt;
@@ -831,6 +906,7 @@ main(void)
         cmocka_unit_test(crypto_test_hkdf_expand_testa2),
         cmocka_unit_test(crypto_test_hkdf_expand_testa3),
         cmocka_unit_test(crypto_test_ovpn_label_expand),
+        cmocka_unit_test(crypto_test_ovpn_expand_openssl3),
         cmocka_unit_test_prestate_setup_teardown(crypto_test_epoch_key_generation,
                                                  crypto_test_epoch_setup,
                                                  crypto_test_epoch_teardown,