/*

 * 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

 */

#include <string.h>

#include <openssl/ct.h>

#include <openssl/err.h>

#include <openssl/evp.h>

#include <openssl/x509.h>

#include "ct_local.h"

typedef enum sct_signature_type_t {

    SIGNATURE_TYPE_NOT_SET = -1,

    SIGNATURE_TYPE_CERT_TIMESTAMP,

    SIGNATURE_TYPE_TREE_HASH

} SCT_SIGNATURE_TYPE;

/*

 * Update encoding for SCT signature verification/generation to supplied

 * EVP_MD_CTX.

 */

static int sct_ctx_update(EVP_MD_CTX *ctx, const SCT_CTX *sctx, const SCT *sct)

{

    unsigned char tmpbuf[12];

    unsigned char *p, *der;

    size_t derlen;

    /*+

     * digitally-signed struct {

     *   (1 byte) Version sct_version;

     *   (1 byte) SignatureType signature_type = certificate_timestamp;

     *   (8 bytes) uint64 timestamp;

     *   (2 bytes) LogEntryType entry_type;

     *   (? bytes) select(entry_type) {

     *     case x509_entry: ASN.1Cert;

     *     case precert_entry: PreCert;

     *   } signed_entry;

     *   (2 bytes + sct->ext_len) CtExtensions extensions;

     * }

     */

    if (sct->entry_type == CT_LOG_ENTRY_TYPE_NOT_SET)

        return 0;

    if (sct->entry_type == CT_LOG_ENTRY_TYPE_PRECERT && sctx->ihash == NULL)

        return 0;

    p = tmpbuf;

    *p++ = sct->version;

    *p++ = SIGNATURE_TYPE_CERT_TIMESTAMP;

    l2n8(sct->timestamp, p);

    s2n(sct->entry_type, p);

    if (!EVP_DigestUpdate(ctx, tmpbuf, p - tmpbuf))

        return 0;

    if (sct->entry_type == CT_LOG_ENTRY_TYPE_X509) {

        der = sctx->certder;

        derlen = sctx->certderlen;

    } else {

        if (!EVP_DigestUpdate(ctx, sctx->ihash, sctx->ihashlen))

            return 0;

        der = sctx->preder;

        derlen = sctx->prederlen;

    }

    /* If no encoding available, fatal error */

    if (der == NULL)

        return 0;

    /* Include length first */

    p = tmpbuf;

    l2n3(derlen, p);

    if (!EVP_DigestUpdate(ctx, tmpbuf, 3))

        return 0;

    if (!EVP_DigestUpdate(ctx, der, derlen))

        return 0;

    /* Add any extensions */

    p = tmpbuf;

    s2n(sct->ext_len, p);

    if (!EVP_DigestUpdate(ctx, tmpbuf, 2))

        return 0;

    if (sct->ext_len && !EVP_DigestUpdate(ctx, sct->ext, sct->ext_len))

        return 0;

    return 1;

}

int SCT_CTX_verify(const SCT_CTX *sctx, const SCT *sct)

{

    EVP_MD_CTX *ctx = NULL;

    int ret = 0;

    if (!SCT_is_complete(sct) || sctx->pkey == NULL ||

        sct->entry_type == CT_LOG_ENTRY_TYPE_NOT_SET ||

        (sct->entry_type == CT_LOG_ENTRY_TYPE_PRECERT && sctx->ihash == NULL)) {

        ERR_raise(ERR_LIB_CT, CT_R_SCT_NOT_SET);

        return 0;

    }

    if (sct->version != SCT_VERSION_V1) {

        ERR_raise(ERR_LIB_CT, CT_R_SCT_UNSUPPORTED_VERSION);

        return 0;

    }

    if (sct->log_id_len != sctx->pkeyhashlen ||

        memcmp(sct->log_id, sctx->pkeyhash, sctx->pkeyhashlen) != 0) {

        ERR_raise(ERR_LIB_CT, CT_R_SCT_LOG_ID_MISMATCH);

        return 0;

    }

    if (sct->timestamp > sctx->epoch_time_in_ms) {

        ERR_raise(ERR_LIB_CT, CT_R_SCT_FUTURE_TIMESTAMP);

        return 0;

    }

    ctx = EVP_MD_CTX_new();

    if (ctx == NULL)

        goto end;

    if (!EVP_DigestVerifyInit_ex(ctx, NULL, "SHA2-256", sctx->libctx,

                                 sctx->propq, sctx->pkey, NULL))

        goto end;

    if (!sct_ctx_update(ctx, sctx, sct))

        goto end;

    /* Verify signature */

    ret = EVP_DigestVerifyFinal(ctx, sct->sig, sct->sig_len);

    /* If ret < 0 some other error: fall through without setting error */

    if (ret == 0)

        ERR_raise(ERR_LIB_CT, CT_R_SCT_INVALID_SIGNATURE);

end:

    EVP_MD_CTX_free(ctx);

    return ret;

}