/*

 * Copyright 2016-2021 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

 */

#ifdef OPENSSL_NO_CT

# error "CT is disabled"

#endif

#include <stddef.h>

#include <string.h>

#include <openssl/err.h>

#include <openssl/obj_mac.h>

#include <openssl/x509.h>

#include "ct_local.h"

SCT_CTX *SCT_CTX_new(OSSL_LIB_CTX *libctx, const char *propq)

{

    SCT_CTX *sctx = OPENSSL_zalloc(sizeof(*sctx));

    if (sctx == NULL)

        return NULL;

    sctx->libctx = libctx;

    if (propq != NULL) {

        sctx->propq = OPENSSL_strdup(propq);

        if (sctx->propq == NULL) {

            OPENSSL_free(sctx);

            return NULL;

        }

    }

    return sctx;

}

void SCT_CTX_free(SCT_CTX *sctx)

{

    if (sctx == NULL)

        return;

    EVP_PKEY_free(sctx->pkey);

    OPENSSL_free(sctx->pkeyhash);

    OPENSSL_free(sctx->ihash);

    OPENSSL_free(sctx->certder);

    OPENSSL_free(sctx->preder);

    OPENSSL_free(sctx->propq);

    OPENSSL_free(sctx);

}

/*

 * Finds the index of the first extension with the given NID in cert.

 * If there is more than one extension with that NID, *is_duplicated is set to

 * 1, otherwise 0 (unless it is NULL).

 */

static int ct_x509_get_ext(X509 *cert, int nid, int *is_duplicated)

{

    int ret = X509_get_ext_by_NID(cert, nid, -1);

    if (is_duplicated != NULL)

        *is_duplicated = ret >= 0 && X509_get_ext_by_NID(cert, nid, ret) >= 0;

    return ret;

}

/*

 * Modifies a certificate by deleting extensions and copying the issuer and

 * AKID from the presigner certificate, if necessary.

 * Returns 1 on success, 0 otherwise.

 */

__owur static int ct_x509_cert_fixup(X509 *cert, X509 *presigner)

{

    int preidx, certidx;

    int pre_akid_ext_is_dup, cert_akid_ext_is_dup;

    if (presigner == NULL)

        return 1;

    preidx = ct_x509_get_ext(presigner, NID_authority_key_identifier,

                             &pre_akid_ext_is_dup);

    certidx = ct_x509_get_ext(cert, NID_authority_key_identifier,

                              &cert_akid_ext_is_dup);

    /* An error occurred whilst searching for the extension */

    if (preidx < -1 || certidx < -1)

        return 0;

    /* Invalid certificate if they contain duplicate extensions */

    if (pre_akid_ext_is_dup || cert_akid_ext_is_dup)

        return 0;

    /* AKID must be present in both certificate or absent in both */

    if (preidx >= 0 && certidx == -1)

        return 0;

    if (preidx == -1 && certidx >= 0)

        return 0;

    /* Copy issuer name */

    if (!X509_set_issuer_name(cert, X509_get_issuer_name(presigner)))

        return 0;

    if (preidx != -1) {

        /* Retrieve and copy AKID encoding */

        X509_EXTENSION *preext = X509_get_ext(presigner, preidx);

        X509_EXTENSION *certext = X509_get_ext(cert, certidx);

        ASN1_OCTET_STRING *preextdata;

        /* Should never happen */

        if (preext == NULL || certext == NULL)

            return 0;

        preextdata = X509_EXTENSION_get_data(preext);

        if (preextdata == NULL ||

            !X509_EXTENSION_set_data(certext, preextdata))

            return 0;

    }

    return 1;

}

int SCT_CTX_set1_cert(SCT_CTX *sctx, X509 *cert, X509 *presigner)

{

    unsigned char *certder = NULL, *preder = NULL;

    X509 *pretmp = NULL;

    int certderlen = 0, prederlen = 0;

    int idx = -1;

    int poison_ext_is_dup, sct_ext_is_dup;

    int poison_idx = ct_x509_get_ext(cert, NID_ct_precert_poison, &poison_ext_is_dup);

    /* Duplicate poison extensions are present - error */

    if (poison_ext_is_dup)

        goto err;

    /* If *cert doesn't have a poison extension, it isn't a precert */

    if (poison_idx == -1) {

        /* cert isn't a precert, so we shouldn't have a presigner */

        if (presigner != NULL)

            goto err;

        certderlen = i2d_X509(cert, &certder);

        if (certderlen < 0)

            goto err;

    }

    /* See if cert has a precert SCTs extension */

    idx = ct_x509_get_ext(cert, NID_ct_precert_scts, &sct_ext_is_dup);

    /* Duplicate SCT extensions are present - error */

    if (sct_ext_is_dup)

        goto err;

    if (idx >= 0 && poison_idx >= 0) {

        /*

         * cert can't both contain SCTs (i.e. have an SCT extension) and be a

         * precert (i.e. have a poison extension).

         */

        goto err;

    }

    if (idx == -1) {

        idx = poison_idx;

    }

    /*

     * If either a poison or SCT extension is present, remove it before encoding

     * cert. This, along with ct_x509_cert_fixup(), gets a TBSCertificate (see

     * RFC5280) from cert, which is what the CT log signed when it produced the

     * SCT.

     */

    if (idx >= 0) {

        /* Take a copy of certificate so we don't modify passed version */

        pretmp = X509_dup(cert);

        if (pretmp == NULL)

            goto err;

        X509_EXTENSION_free(X509_delete_ext(pretmp, idx));

        if (!ct_x509_cert_fixup(pretmp, presigner))

            goto err;

        prederlen = i2d_re_X509_tbs(pretmp, &preder);

        if (prederlen <= 0)

            goto err;

    }

    X509_free(pretmp);

    OPENSSL_free(sctx->certder);

    sctx->certder = certder;

    sctx->certderlen = certderlen;

    OPENSSL_free(sctx->preder);

    sctx->preder = preder;

    sctx->prederlen = prederlen;

    return 1;

err:

    OPENSSL_free(certder);

    OPENSSL_free(preder);

    X509_free(pretmp);

    return 0;

}

__owur static int ct_public_key_hash(SCT_CTX *sctx, X509_PUBKEY *pkey,

                                     unsigned char **hash, size_t *hash_len)

{

    int ret = 0;

    unsigned char *md = NULL, *der = NULL;

    int der_len;

    unsigned int md_len;

    EVP_MD *sha256 = EVP_MD_fetch(sctx->libctx, "SHA2-256", sctx->propq);

    if (sha256 == NULL)

        goto err;

    /* Reuse buffer if possible */

    if (*hash != NULL && *hash_len >= SHA256_DIGEST_LENGTH) {

        md = *hash;

    } else {

        md = OPENSSL_malloc(SHA256_DIGEST_LENGTH);

        if (md == NULL)

            goto err;

    }

    /* Calculate key hash */

    der_len = i2d_X509_PUBKEY(pkey, &der);

    if (der_len <= 0)

        goto err;

    if (!EVP_Digest(der, der_len, md, &md_len, sha256, NULL))

        goto err;

    if (md != *hash) {

        OPENSSL_free(*hash);

        *hash = md;

        *hash_len = SHA256_DIGEST_LENGTH;

    }

    md = NULL;

    ret = 1;

 err:

    EVP_MD_free(sha256);

    OPENSSL_free(md);

    OPENSSL_free(der);

    return ret;

}

int SCT_CTX_set1_issuer(SCT_CTX *sctx, const X509 *issuer)

{

    return SCT_CTX_set1_issuer_pubkey(sctx, X509_get_X509_PUBKEY(issuer));

}

int SCT_CTX_set1_issuer_pubkey(SCT_CTX *sctx, X509_PUBKEY *pubkey)

{

    return ct_public_key_hash(sctx, pubkey, &sctx->ihash, &sctx->ihashlen);

}

int SCT_CTX_set1_pubkey(SCT_CTX *sctx, X509_PUBKEY *pubkey)

{

    EVP_PKEY *pkey = X509_PUBKEY_get(pubkey);

    if (pkey == NULL)

        return 0;

    if (!ct_public_key_hash(sctx, pubkey, &sctx->pkeyhash, &sctx->pkeyhashlen)) {

        EVP_PKEY_free(pkey);

        return 0;

    }

    EVP_PKEY_free(sctx->pkey);

    sctx->pkey = pkey;

    return 1;

}

void SCT_CTX_set_time(SCT_CTX *sctx, uint64_t time_in_ms)

{

    sctx->epoch_time_in_ms = time_in_ms;

}