test_provider.c

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/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2021-2025 Selva Nair <selva.nair@gmail.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by the
 *  Free Software Foundation, either version 2 of the License,
 *  or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, see <https://www.gnu.org/licenses/>.
 */
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include "syshead.h"
#include "manage.h"
#include "integer.h"
#include "xkey_common.h"
 
#ifdef HAVE_XKEY_PROVIDER
 
#include <setjmp.h>
#include <cmocka.h>
#include <openssl/bio.h>
#include <openssl/pem.h>
#include <openssl/core_names.h>
#include <openssl/evp.h>
 
#include "test_common.h"
 
struct management *management; /* global */
static int mgmt_callback_called;
 
#ifndef _countof
#define _countof(x) sizeof((x)) / sizeof(*(x))
#endif
 
static OSSL_PROVIDER *prov[2];
 
/* public keys for testing -- RSA and EC */
static const char pubkey1[] = "-----BEGIN PUBLIC KEY-----\n"
                              "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA7GWP6RLCGlvmVioIqYI6\n"
                              "LUR4owA7sJ/nJxBAk+/xzD6gqgSigBsTqeb+gdZwkKjY1N4w2DUA0r5i8Eja/BWN\n"
                              "xMZtC5nxK4MACtMqIwvlzfk130NhFXKtlZj2cyFBXqDdRyeg1ZrUQagcHVcgcReP\n"
                              "9yiePgfO7NUOQk8edEeOR53SFCgnLBQQ9dGWtZN0hO/5BN6NSm/fd6vq0VjTRP5a\n"
                              "BAH/BnqX9/3jV0jh8N9AE59mI1rjVVQ9VDnuAPkS8dLfdC661/CNxt0YWByTIgt1\n"
                              "+qjW4LUvLbnU/rlPhuJ1SBZg+z/JtDBCKfs7syu5WYFqRvNFg7/91Rr/NwxvW/1h\n"
                              "8QIDAQAB\n"
                              "-----END PUBLIC KEY-----\n";
 
static const char pubkey2[] = "-----BEGIN PUBLIC KEY-----\n"
                              "MFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAEO85iXW+HgnUkwlj1DohNVw0GsnGIh1gZ\n"
                              "u95ff1JiUaJIkYNIkZA+hwIPFVH5aJcSCv3SPIeDS2VUAESNKHZJBQ==\n"
                              "-----END PUBLIC KEY-----\n";
 
static const char pubkey3[] = "-----BEGIN PUBLIC KEY-----\n"
                              "MCowBQYDK2VwAyEA+q5xjF5hGyyqYZidJdz/0saEQabL3N4wIZJBxNGbgJE=\n"
                              "-----END PUBLIC KEY-----";
 
static const char *pubkeys[] = { pubkey1, pubkey2, pubkey3 };
 
static const char *prov_name = "ovpn.xkey";
 
static const char *test_msg = "Lorem ipsum dolor sit amet, consectetur "
                              "adipisici elit, sed eiusmod tempor incidunt "
                              "ut labore et dolore magna aliqua.";
 
static const char *test_msg_b64 =
    "TG9yZW0gaXBzdW0gZG9sb3Igc2l0IGFtZXQsIGNvbnNlY3RldHVyIGFkaXBpc2ljaS"
    "BlbGl0LCBzZWQgZWl1c21vZCB0ZW1wb3IgaW5jaWR1bnQgdXQgbGFib3JlIGV0IGRv"
    "bG9yZSBtYWduYSBhbGlxdWEu";
 
/* Sha256 digest of test_msg excluding NUL terminator */
static const uint8_t test_digest[] = { 0x77, 0x38, 0x65, 0x00, 0x1e, 0x96, 0x48, 0xc6,
                                       0x57, 0x0b, 0xae, 0xc0, 0xb7, 0x96, 0xf9, 0x66,
                                       0x4d, 0x5f, 0xd0, 0xb7, 0xdb, 0xf3, 0x3a, 0xbf,
                                       0x02, 0xcc, 0x78, 0x61, 0x83, 0x20, 0x20, 0xee };
 
static const char *test_digest_b64 = "dzhlAB6WSMZXC67At5b5Zk1f0Lfb8zq/Asx4YYMgIO4=";
 
/* Dummy signature used only to check that the expected callback
 * was successfully exercised. Keep this shorter than 64 bytes
 * --- the smallest size of the actual signature with the above
 * keys.
 */
static const uint8_t good_sig[] = { 0xd8, 0xa7, 0xd9, 0x81, 0xd8, 0xaa, 0xd8, 0xad,
                                    0x20, 0xd9, 0x8a, 0xd8, 0xa7, 0x20, 0xd8, 0xb3,
                                    0xd9, 0x85, 0xd8, 0xb3, 0xd9, 0x85, 0x0 };
 
static const char *good_sig_b64 = "2KfZgdiq2K0g2YrYpyDYs9mF2LPZhQA=";
 
static EVP_PKEY *
load_pubkey(const char *pem)
{
    BIO *in = BIO_new_mem_buf(pem, -1);
    assert_non_null(in);
 
    EVP_PKEY *pkey = PEM_read_bio_PUBKEY(in, NULL, NULL, NULL);
    assert_non_null(pkey);
 
    BIO_free(in);
    return pkey;
}
 
static void
init_test(void)
{
    openvpn_unit_test_setup();
    prov[0] = OSSL_PROVIDER_load(NULL, "default");
    OSSL_PROVIDER_add_builtin(NULL, prov_name, xkey_provider_init);
    prov[1] = OSSL_PROVIDER_load(NULL, prov_name);
 
    /* set default propq matching what we use in ssl_openssl.c */
    EVP_set_default_properties(NULL, "?provider!=ovpn.xkey");
 
#ifdef ENABLE_MANAGEMENT
    management = test_calloc(sizeof(*management), 1);
#endif
}
 
static void
uninit_test(void)
{
    for (size_t i = 0; i < _countof(prov); i++)
    {
        if (prov[i])
        {
            OSSL_PROVIDER_unload(prov[i]);
        }
    }
    test_free(management);
}
 
/* Mock management callback for signature.
 * We check that the received data to sign matches test_msg or
 * test_digest and return a predefined string as signature so that
 * the caller can validate all steps up to sending the data to
 * the management client.
 */
char *
management_query_pk_sig(struct management *man, const char *b64_data, const char *algorithm)
{
    char *out = NULL;
 
    /* indicate entry to the callback */
    mgmt_callback_called = 1;
 
    const char *expected_tbs = test_digest_b64;
    if (strstr(algorithm, "data=message"))
    {
        expected_tbs = test_msg_b64;
        /* ED25519 does not have a hash algorithm even though it goes via
         * the DigestSign path (data=message) */
        if (!strstr(algorithm, "ED25519"))
        {
            assert_non_null(strstr(algorithm, "hashalg=SHA256"));
        }
    }
    assert_string_equal(b64_data, expected_tbs);
 
    /* We test using ED25519, ECDSA or PSS with saltlen = digest */
    if (!strstr(algorithm, "ECDSA") && !strstr(algorithm, "ED25519"))
    {
        assert_non_null(strstr(algorithm, "RSA_PKCS1_PSS_PADDING,hashalg=SHA256,saltlen=digest"));
    }
 
    /* Return a predefined string as sig so that the caller
     * can confirm that this callback was exercised.
     */
    out = strdup(good_sig_b64);
    assert_non_null(out);
 
    return out;
}
 
/* Check signature and keymgmt methods can be fetched from the provider */
static void
xkey_provider_test_fetch(void **state)
{
    assert_true(OSSL_PROVIDER_available(NULL, prov_name));
 
    const char *algs[] = { "RSA", "ECDSA" };
 
    for (size_t i = 0; i < _countof(algs); i++)
    {
        EVP_SIGNATURE *sig = EVP_SIGNATURE_fetch(NULL, algs[i], "provider=ovpn.xkey");
        assert_non_null(sig);
        assert_string_equal(OSSL_PROVIDER_get0_name(EVP_SIGNATURE_get0_provider(sig)), prov_name);
 
        EVP_SIGNATURE_free(sig);
    }
 
    const char *names[] = { "RSA", "EC" };
 
    for (size_t i = 0; i < _countof(names); i++)
    {
        EVP_KEYMGMT *km = EVP_KEYMGMT_fetch(NULL, names[i], "provider=ovpn.xkey");
        assert_non_null(km);
        assert_string_equal(OSSL_PROVIDER_get0_name(EVP_KEYMGMT_get0_provider(km)), prov_name);
 
        EVP_KEYMGMT_free(km);
    }
}
 
/* sign a test message using pkey -- caller must free the returned sig */
static uint8_t *
digest_sign(EVP_PKEY *pkey)
{
    uint8_t *sig = NULL;
    size_t siglen = 0;
 
    OSSL_PARAM params[6] = { OSSL_PARAM_END };
 
    const char *mdname = "SHA256";
    const char *padmode = "pss";
    const char *saltlen = "digest";
 
    if (EVP_PKEY_get_id(pkey) == EVP_PKEY_RSA)
    {
        params[0] =
            OSSL_PARAM_construct_utf8_string(OSSL_SIGNATURE_PARAM_DIGEST, (char *)mdname, 0);
        params[1] =
            OSSL_PARAM_construct_utf8_string(OSSL_SIGNATURE_PARAM_PAD_MODE, (char *)padmode, 0);
        params[2] =
            OSSL_PARAM_construct_utf8_string(OSSL_SIGNATURE_PARAM_PSS_SALTLEN, (char *)saltlen, 0);
        /* same digest for mgf1 */
        params[3] =
            OSSL_PARAM_construct_utf8_string(OSSL_SIGNATURE_PARAM_MGF1_DIGEST, (char *)saltlen, 0);
        params[4] = OSSL_PARAM_construct_end();
    }
    else if (EVP_PKEY_get_id(pkey) == EVP_PKEY_ED25519)
    {
        mdname = NULL;
        params[0] = OSSL_PARAM_construct_end();
    }
 
 
    EVP_PKEY_CTX *pctx = NULL;
    EVP_MD_CTX *mctx = EVP_MD_CTX_new();
 
    if (!mctx || EVP_DigestSignInit_ex(mctx, &pctx, mdname, NULL, NULL, pkey, params) <= 0)
    {
        fail_msg("Failed to initialize EVP_DigestSignInit_ex()");
        goto done;
    }
 
    /* sign with sig = NULL to get required siglen */
    assert_int_equal(EVP_DigestSign(mctx, sig, &siglen, (uint8_t *)test_msg, strlen(test_msg)), 1);
    assert_true(siglen > 0);
 
    if ((sig = test_calloc(1, siglen)) == NULL)
    {
        fail_msg("Out of memory");
    }
    assert_int_equal(EVP_DigestSign(mctx, sig, &siglen, (uint8_t *)test_msg, strlen(test_msg)), 1);
 
done:
    if (mctx)
    {
        EVP_MD_CTX_free(mctx); /* pctx is internally allocated and freed by mctx */
    }
    return sig;
}
 
#ifdef ENABLE_MANAGEMENT
/* Check loading of management external key and have sign callback exercised
 * for RSA and EC keys with and without digest support in management client.
 * Sha256 digest used for both cases with pss padding for RSA.
 */
static void
xkey_provider_test_mgmt_sign_cb(void **state)
{
    EVP_PKEY *pubkey;
    for (size_t i = 0; i < _countof(pubkeys); i++)
    {
        pubkey = load_pubkey(pubkeys[i]);
        assert_true(pubkey != NULL);
        EVP_PKEY *privkey = xkey_load_management_key(NULL, pubkey);
        assert_true(privkey != NULL);
 
        management->settings.flags = MF_EXTERNAL_KEY | MF_EXTERNAL_KEY_PSSPAD;
 
        /* first without digest support in management client */
again:
        mgmt_callback_called = 0;
        uint8_t *sig = digest_sign(privkey);
        assert_non_null(sig);
 
        /* check callback for signature got exercised */
        assert_int_equal(mgmt_callback_called, 1);
        assert_memory_equal(sig, good_sig, sizeof(good_sig));
        test_free(sig);
 
        if (!(management->settings.flags & MF_EXTERNAL_KEY_DIGEST))
        {
            management->settings.flags |= MF_EXTERNAL_KEY_DIGEST;
            goto again; /* this time with digest support announced */
        }
 
        EVP_PKEY_free(pubkey);
        EVP_PKEY_free(privkey);
    }
}
#endif /* ifdef ENABLE_MANAGEMENT */
 
/* helpers for testing generic key load and sign */
static int xkey_free_called;
static int xkey_sign_called;
static void
xkey_free(void *handle)
{
    xkey_free_called = 1;
    /* We use a dummy string as handle -- check its value */
    assert_string_equal(handle, "xkey_handle");
}
 
static int
xkey_sign(void *handle, unsigned char *sig, size_t *siglen, const unsigned char *tbs, size_t tbslen,
          XKEY_SIGALG s)
{
    if (!sig)
    {
        *siglen = 256; /* some arbitrary size */
        return 1;
    }
 
    xkey_sign_called = 1; /* called with non-null sig */
 
    if (!strcmp(s.op, "DigestSign"))
    {
        assert_memory_equal(tbs, test_msg, strlen(test_msg));
    }
    else
    {
        assert_memory_equal(tbs, test_digest, sizeof(test_digest));
    }
 
    /* For the test use sha256 and PSS padding for RSA and none for EDDSA */
    if (!strcmp(s.keytype, "ED25519"))
    {
        assert_string_equal(s.mdname, "none");
    }
    else
    {
        assert_int_equal(OBJ_sn2nid(s.mdname), NID_sha256);
    }
    if (!strcmp(s.keytype, "RSA"))
    {
        assert_string_equal(s.padmode, "pss"); /* we use PSS for the test */
    }
    else if (strcmp(s.keytype, "EC") && strcmp(s.keytype, "ED25519"))
    {
        fail_msg("Unknown keytype: %s", s.keytype);
    }
 
    /* return a predefined string as sig */
    memcpy(sig, good_sig, min_size(sizeof(good_sig), *siglen));
 
    return 1;
}
 
/* Load a key as a generic key and check its sign op gets
 * called for signature.
 */
static void
xkey_provider_test_generic_sign_cb(void **state)
{
    EVP_PKEY *pubkey;
    const char *dummy = "xkey_handle"; /* a dummy handle for the external key */
 
    for (size_t i = 0; i < _countof(pubkeys); i++)
    {
        pubkey = load_pubkey(pubkeys[i]);
        assert_true(pubkey != NULL);
 
        EVP_PKEY *privkey =
            xkey_load_generic_key(NULL, (void *)dummy, pubkey, xkey_sign, xkey_free);
        assert_true(privkey != NULL);
 
        xkey_sign_called = 0;
        xkey_free_called = 0;
        uint8_t *sig = digest_sign(privkey);
        assert_non_null(sig);
 
        /* check callback for signature got exercised */
        assert_int_equal(xkey_sign_called, 1);
        assert_memory_equal(sig, good_sig, sizeof(good_sig));
        test_free(sig);
 
        EVP_PKEY_free(pubkey);
        EVP_PKEY_free(privkey);
 
        /* check key's free-op got called */
        assert_int_equal(xkey_free_called, 1);
    }
}
 
int
main(void)
{
    init_test();
 
    const struct CMUnitTest tests[] = {
        cmocka_unit_test(xkey_provider_test_fetch),
#ifdef ENABLE_MANAGEMENT
        cmocka_unit_test(xkey_provider_test_mgmt_sign_cb),
#endif
        cmocka_unit_test(xkey_provider_test_generic_sign_cb),
    };
 
    int ret = cmocka_run_group_tests_name("xkey provider tests", tests, NULL, NULL);
 
    uninit_test();
    return ret;
}
#else  /* ifdef HAVE_XKEY_PROVIDER */
int
main(void)
{
    return 0;
}
#endif /* HAVE_XKEY_PROVIDER */