/*
 * Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the OpenSSL license (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 <stdio.h>
#include <openssl/crypto.h>
#include <openssl/bio.h>
#include <openssl/x509.h>
#include <openssl/pem.h>
#include <openssl/err.h>

static STACK_OF(X509) *load_certs_from_file(const char *filename)
{
    STACK_OF(X509) *certs;
    BIO *bio;
    X509 *x;

    bio = BIO_new_file(filename, "r");

    if (bio == NULL) {
        return NULL;
    }

    certs = sk_X509_new_null();
    if (certs == NULL) {
        BIO_free(bio);
        return NULL;
    }

    ERR_set_mark();
    do {
        x = PEM_read_bio_X509(bio, NULL, 0, NULL);
        if (x != NULL && !sk_X509_push(certs, x)) {
            sk_X509_pop_free(certs, X509_free);
            BIO_free(bio);
            return NULL;
        } else if (x == NULL) {
            /*
             * We probably just ran out of certs, so ignore any errors
             * generated
             */
            ERR_pop_to_mark();
        }
    } while (x != NULL);

    BIO_free(bio);

    return certs;
}

/*
 * Test for CVE-2015-1793 (Alternate Chains Certificate Forgery)
 *
 * Chain is as follows:
 *
 * rootCA (self-signed)
 *   |
 * interCA
 *   |
 * subinterCA       subinterCA (self-signed)
 *   |                   |
 * leaf ------------------
 *   |
 * bad
 *
 * rootCA, interCA, subinterCA, subinterCA (ss) all have CA=TRUE
 * leaf and bad have CA=FALSE
 *
 * subinterCA and subinterCA (ss) have the same subject name and keys
 *
 * interCA (but not rootCA) and subinterCA (ss) are in the trusted store
 * (roots.pem)
 * leaf and subinterCA are in the untrusted list (untrusted.pem)
 * bad is the certificate being verified (bad.pem)
 *
 * Versions vulnerable to CVE-2015-1793 will fail to detect that leaf has
 * CA=FALSE, and will therefore incorrectly verify bad
 *
 */
static int test_alt_chains_cert_forgery(const char *roots_f,
                                        const char *untrusted_f,
                                        const char *bad_f)
{
    int ret = 0;
    int i;
    X509 *x = NULL;
    STACK_OF(X509) *untrusted = NULL;
    BIO *bio = NULL;
    X509_STORE_CTX *sctx = NULL;
    X509_STORE *store = NULL;
    X509_LOOKUP *lookup = NULL;

    store = X509_STORE_new();
    if (store == NULL)
        goto err;

    lookup = X509_STORE_add_lookup(store, X509_LOOKUP_file());
    if (lookup == NULL)
        goto err;
    if(!X509_LOOKUP_load_file(lookup, roots_f, X509_FILETYPE_PEM))
        goto err;

    untrusted = load_certs_from_file(untrusted_f);

    if ((bio = BIO_new_file(bad_f, "r")) == NULL)
        goto err;

    if((x = PEM_read_bio_X509(bio, NULL, 0, NULL)) == NULL)
        goto err;

    sctx = X509_STORE_CTX_new();
    if (sctx == NULL)
        goto err;

    if (!X509_STORE_CTX_init(sctx, store, x, untrusted))
        goto err;

    i = X509_verify_cert(sctx);

    if(i == 0 && X509_STORE_CTX_get_error(sctx) == X509_V_ERR_INVALID_CA) {
        /* This is the result we were expecting: Test passed */
        ret = 1;
    }
 err:
    X509_STORE_CTX_free(sctx);
    X509_free(x);
    BIO_free(bio);
    sk_X509_pop_free(untrusted, X509_free);
    X509_STORE_free(store);
    if (ret != 1)
        ERR_print_errors_fp(stderr);
    return ret;
}

int main(int argc, char **argv)
{
    CRYPTO_set_mem_debug(1);
    CRYPTO_mem_ctrl(CRYPTO_MEM_CHECK_ON);

    if (argc != 4) {
        fprintf(stderr, "usage: verify_extra_test roots.pem untrusted.pem bad.pem\n");
        return 1;
    }

    if (!test_alt_chains_cert_forgery(argv[1], argv[2], argv[3])) {
        fprintf(stderr, "Test alt chains cert forgery failed\n");
        return 1;
    }

#ifndef OPENSSL_NO_CRYPTO_MDEBUG
    if (CRYPTO_mem_leaks_fp(stderr) <= 0)
        return 1;
#endif

    printf("PASS\n");
    return 0;
}
