/*

 * Copyright 2014-2026 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

 */

/* Custom extension utility functions */

#include <openssl/ct.h>

#include "../ssl_local.h"

#include "internal/cryptlib.h"

#include "internal/ssl_unwrap.h"

#include "statem_local.h"

typedef struct {

    void *add_arg;

    custom_ext_add_cb add_cb;

    custom_ext_free_cb free_cb;

} custom_ext_add_cb_wrap;

typedef struct {

    void *parse_arg;

    custom_ext_parse_cb parse_cb;

} custom_ext_parse_cb_wrap;

/*

 * Provide thin wrapper callbacks which convert new style arguments to old style

 */

static int custom_ext_add_old_cb_wrap(SSL *s, unsigned int ext_type,

    unsigned int context,

    const unsigned char **out,

    size_t *outlen, X509 *x, size_t chainidx,

    int *al, void *add_arg)

{

    custom_ext_add_cb_wrap *add_cb_wrap = (custom_ext_add_cb_wrap *)add_arg;

    if (add_cb_wrap->add_cb == NULL)

        return 1;

    return add_cb_wrap->add_cb(s, ext_type, out, outlen, al,

        add_cb_wrap->add_arg);

}

static void custom_ext_free_old_cb_wrap(SSL *s, unsigned int ext_type,

    unsigned int context,

    const unsigned char *out, void *add_arg)

{

    custom_ext_add_cb_wrap *add_cb_wrap = (custom_ext_add_cb_wrap *)add_arg;

    if (add_cb_wrap->free_cb == NULL)

        return;

    add_cb_wrap->free_cb(s, ext_type, out, add_cb_wrap->add_arg);

}

static int custom_ext_parse_old_cb_wrap(SSL *s, unsigned int ext_type,

    unsigned int context,

    const unsigned char *in,

    size_t inlen, X509 *x, size_t chainidx,

    int *al, void *parse_arg)

{

    custom_ext_parse_cb_wrap *parse_cb_wrap = (custom_ext_parse_cb_wrap *)parse_arg;

    if (parse_cb_wrap->parse_cb == NULL)

        return 1;

    return parse_cb_wrap->parse_cb(s, ext_type, in, inlen, al,

        parse_cb_wrap->parse_arg);

}

/*

 * Find a custom extension from the list. The |role| param is there to

 * support the legacy API where custom extensions for client and server could

 * be set independently on the same SSL_CTX. It is set to ENDPOINT_SERVER if we

 * are trying to find a method relevant to the server, ENDPOINT_CLIENT for the

 * client, or ENDPOINT_BOTH for either

 */

custom_ext_method *custom_ext_find(const custom_ext_methods *exts,

    ENDPOINT role, unsigned int ext_type,

    size_t *idx)

{

    size_t i;

    custom_ext_method *meth = exts->meths;

    for (i = 0; i < exts->meths_count; i++, meth++) {

        if (ext_type == meth->ext_type

            && (role == ENDPOINT_BOTH || role == meth->role

                || meth->role == ENDPOINT_BOTH)) {

            if (idx != NULL)

                *idx = i;

            return meth;

        }

    }

    return NULL;

}

/*

 * Initialise custom extensions flags to indicate neither sent nor received.

 */

void custom_ext_init(custom_ext_methods *exts)

{

    size_t i;

    custom_ext_method *meth = exts->meths;

    for (i = 0; i < exts->meths_count; i++, meth++)

        meth->ext_flags = 0;

}

/* Pass received custom extension data to the application for parsing. */

int custom_ext_parse(SSL_CONNECTION *s, unsigned int context,

    unsigned int ext_type,

    const unsigned char *ext_data, size_t ext_size, X509 *x,

    size_t chainidx)

{

    int al = 0;

    custom_ext_methods *exts = &s->cert->custext;

    custom_ext_method *meth;

    ENDPOINT role = ENDPOINT_BOTH;

    if ((context & (SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO)) != 0)

        role = s->server ? ENDPOINT_SERVER : ENDPOINT_CLIENT;

    meth = custom_ext_find(exts, role, ext_type, NULL);

    /* If not found return success */

    if (!meth)

        return 1;

    /* Check if extension is defined for our protocol. If not, skip */

    if (!extension_is_relevant(s, meth->context, context))

        return 1;

    if ((context & (SSL_EXT_TLS1_2_SERVER_HELLO | SSL_EXT_TLS1_3_SERVER_HELLO | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS)) != 0) {

        /*

         * If it's ServerHello or EncryptedExtensions we can't have any

         * extensions not sent in ClientHello.

         */

        if ((meth->ext_flags & SSL_EXT_FLAG_SENT) == 0) {

            SSLfatal(s, TLS1_AD_UNSUPPORTED_EXTENSION, SSL_R_BAD_EXTENSION);

            return 0;

        }

    }

    /*

     * Extensions received in the ClientHello or CertificateRequest are marked

     * with the SSL_EXT_FLAG_RECEIVED. This is so we know to add the equivalent

     * extensions in the response messages

     */

    if ((context & (SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_CERTIFICATE_REQUEST))

        != 0)

        meth->ext_flags |= SSL_EXT_FLAG_RECEIVED;

    /* If no parse function set return success */

    if (meth->parse_cb == NULL)

        return 1;

    if (meth->parse_cb(SSL_CONNECTION_GET_USER_SSL(s), ext_type, context, ext_data,

            ext_size, x, chainidx, &al, meth->parse_arg)

        <= 0) {

        SSLfatal(s, al, SSL_R_BAD_EXTENSION);

        return 0;

    }

    return 1;

}

/*

 * Request custom extension data from the application and add to the return

 * buffer.

 */

int custom_ext_add(SSL_CONNECTION *s, int context, WPACKET *pkt, X509 *x,

    size_t chainidx, int maxversion)

{

    custom_ext_methods *exts = &s->cert->custext;

    custom_ext_method *meth;

    size_t i;

    int al;

    int for_comp = (context & SSL_EXT_TLS1_3_CERTIFICATE_COMPRESSION) != 0;

    for (i = 0; i < exts->meths_count; i++) {

        const unsigned char *out = NULL;

        size_t outlen = 0;

        meth = exts->meths + i;

        if (!should_add_extension(s, meth->context, context, maxversion))

            continue;

        if ((context & (SSL_EXT_TLS1_2_SERVER_HELLO | SSL_EXT_TLS1_3_SERVER_HELLO | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS | SSL_EXT_TLS1_3_CERTIFICATE | SSL_EXT_TLS1_3_RAW_PUBLIC_KEY | SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST)) != 0) {

            /* Only send extensions present in ClientHello/CertificateRequest */

            if (!(meth->ext_flags & SSL_EXT_FLAG_RECEIVED))

                continue;

        }

#ifndef OPENSSL_NO_ECH

        if ((context & SSL_EXT_CLIENT_HELLO) != 0

            && s->ext.ech.attempted == 1) {

            if (s->ext.ech.ch_depth == 1) {

                /* mark custom CH ext for ECH compression, if doing ECH */

                if (s->ext.ech.n_outer_only >= OSSL_ECH_OUTERS_MAX) {

                    OSSL_TRACE_BEGIN(TLS)

                    {

                        BIO_printf(trc_out,

                            "Too many outers to compress (max=%d)\n",

                            OSSL_ECH_OUTERS_MAX);

                    }

                    OSSL_TRACE_END(TLS);

                    SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_R_BAD_EXTENSION);

                    return 0;

                }

                s->ext.ech.outer_only[s->ext.ech.n_outer_only] = meth->ext_type;

                s->ext.ech.n_outer_only++;

                OSSL_TRACE_BEGIN(TLS)

                {

                    BIO_printf(trc_out, "ECH compressing type "

                                        "0x%04x (tot: %d)\n",

                        (int)meth->ext_type,

                        (int)s->ext.ech.n_outer_only);

                }

                OSSL_TRACE_END(TLS);

            }

            if (s->ext.ech.ch_depth == 0) {

                /*

                 * We store/access the index of the extension handler in

                 * s->ext.ech.ext_ind, as we'd otherwise not know it here.

                 * Be nice were there a better way to handle that.

                 */

                /* copy over the extension octets (if any) to outer */

                int j, tind = -1;

                RAW_EXTENSION *raws = NULL;

                /* we gotta find the relevant index to copy over this ext */

                if (s->clienthello == NULL

                    || s->clienthello->pre_proc_exts == NULL) {

                    SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_R_BAD_EXTENSION);

                    return 0;

                }

                raws = s->clienthello->pre_proc_exts;

                for (j = 0; j != (int)s->clienthello->pre_proc_exts_len; j++) {

                    if (raws[j].type == meth->ext_type) {

                        tind = j;

                        break;

                    }

                }

                if (tind == -1) {

                    SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_R_BAD_EXTENSION);

                    return 0;

                }

                if (ossl_ech_copy_inner2outer(s, meth->ext_type, tind,

                        pkt)

                    != OSSL_ECH_SAME_EXT_DONE) {

                    /* for custom exts, we really should have found it */

                    SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_R_BAD_EXTENSION);

                    return 0;

                }

                /* we're done with that one now */

                continue;

            }

        }

#endif

        /*

         * We skip it if the callback is absent - except for a ClientHello where

         * we add an empty extension.

         */

        if ((context & SSL_EXT_CLIENT_HELLO) == 0 && meth->add_cb == NULL)

            continue;

        if (meth->add_cb != NULL) {

            int cb_retval = meth->add_cb(SSL_CONNECTION_GET_USER_SSL(s),

                meth->ext_type, context, &out,

                &outlen, x, chainidx, &al,

                meth->add_arg);

            if (cb_retval < 0) {

                if (!for_comp)

                    SSLfatal(s, al, SSL_R_CALLBACK_FAILED);

                return 0; /* error */

            }

            if (cb_retval == 0)

                continue; /* skip this extension */

        }

        if (!WPACKET_put_bytes_u16(pkt, meth->ext_type)

            || !WPACKET_start_sub_packet_u16(pkt)

            || (outlen > 0 && !WPACKET_memcpy(pkt, out, outlen))

            || !WPACKET_close(pkt)) {

            if (meth->free_cb != NULL)

                meth->free_cb(SSL_CONNECTION_GET_USER_SSL(s), meth->ext_type,

                    context, out, meth->add_arg);

            if (!for_comp)

                SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);

            return 0;

        }

        if ((context & SSL_EXT_CLIENT_HELLO) != 0) {

            /*

             * We can't send duplicates: code logic should prevent this.

             */

            if (!ossl_assert((meth->ext_flags & SSL_EXT_FLAG_SENT) == 0)) {

                if (meth->free_cb != NULL)

                    meth->free_cb(SSL_CONNECTION_GET_USER_SSL(s), meth->ext_type,

                        context, out, meth->add_arg);

                if (!for_comp)

                    SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);

                return 0;

            }

            /*

             * Indicate extension has been sent: this is both a sanity check to

             * ensure we don't send duplicate extensions and indicates that it

             * is not an error if the extension is present in ServerHello.

             */

            meth->ext_flags |= SSL_EXT_FLAG_SENT;

        }

        if (meth->free_cb != NULL)

            meth->free_cb(SSL_CONNECTION_GET_USER_SSL(s), meth->ext_type,

                context, out, meth->add_arg);

    }

    return 1;

}

/* Copy the flags from src to dst for any extensions that exist in both */

int custom_exts_copy_flags(custom_ext_methods *dst,

    const custom_ext_methods *src)

{

    size_t i;

    custom_ext_method *methsrc = src->meths;

    for (i = 0; i < src->meths_count; i++, methsrc++) {

        custom_ext_method *methdst = custom_ext_find(dst, methsrc->role,

            methsrc->ext_type, NULL);

        if (methdst == NULL)

            continue;

        methdst->ext_flags = methsrc->ext_flags;

    }

    return 1;

}

/* Copy old style API wrapper arguments */

static void custom_ext_copy_old_cb(custom_ext_method *methdst,

    const custom_ext_method *methsrc,

    int *err)

{

    if (methsrc->add_cb != custom_ext_add_old_cb_wrap)

        return;

    if (*err) {

        methdst->add_arg = NULL;

        methdst->parse_arg = NULL;

        return;

    }

    methdst->add_arg = OPENSSL_memdup(methsrc->add_arg,

        sizeof(custom_ext_add_cb_wrap));

    methdst->parse_arg = OPENSSL_memdup(methsrc->parse_arg,

        sizeof(custom_ext_parse_cb_wrap));

    if (methdst->add_arg == NULL || methdst->parse_arg == NULL)

        *err = 1;

    return;

}

/* Copy table of custom extensions */

int custom_exts_copy(custom_ext_methods *dst, const custom_ext_methods *src)

{

    size_t i;

    int err = 0;

    if (src->meths_count > 0) {

        dst->meths = OPENSSL_memdup(src->meths,

            sizeof(*src->meths) * src->meths_count);

        if (dst->meths == NULL)

            return 0;

        dst->meths_count = src->meths_count;

        for (i = 0; i < src->meths_count; i++)

            custom_ext_copy_old_cb(&dst->meths[i], &src->meths[i], &err);

    }

    if (err) {

        custom_exts_free(dst);

        return 0;

    }

    return 1;

}

void custom_exts_free(custom_ext_methods *exts)

{

    size_t i;

    custom_ext_method *meth;

    for (i = 0, meth = exts->meths; i < exts->meths_count; i++, meth++) {

        if (meth->add_cb != custom_ext_add_old_cb_wrap)

            continue;

        /* Old style API wrapper. Need to free the arguments too */

        OPENSSL_free(meth->add_arg);

        OPENSSL_free(meth->parse_arg);

    }

    OPENSSL_free(exts->meths);

    exts->meths = NULL;

    exts->meths_count = 0;

}

/* Return true if a client custom extension exists, false otherwise */

int SSL_CTX_has_client_custom_ext(const SSL_CTX *ctx, unsigned int ext_type)

{

    return custom_ext_find(&ctx->cert->custext, ENDPOINT_CLIENT, ext_type,

               NULL)

        != NULL;

}

int ossl_tls_add_custom_ext_intern(SSL_CTX *ctx, custom_ext_methods *exts,

    ENDPOINT role, unsigned int ext_type,

    unsigned int context,

    SSL_custom_ext_add_cb_ex add_cb,

    SSL_custom_ext_free_cb_ex free_cb,

    void *add_arg,

    SSL_custom_ext_parse_cb_ex parse_cb,

    void *parse_arg)

{

    custom_ext_method *meth, *tmp;

    /*

     * Check application error: if add_cb is not set free_cb will never be

     * called.

     */

    if (add_cb == NULL && free_cb != NULL)

        return 0;

    if (exts == NULL)

        exts = &ctx->cert->custext;

#ifndef OPENSSL_NO_CT

    /*

     * We don't want applications registering callbacks for SCT extensions

     * whilst simultaneously using the built-in SCT validation features, as

     * these two things may not play well together.

     */

    if (ext_type == TLSEXT_TYPE_signed_certificate_timestamp

        && (context & SSL_EXT_CLIENT_HELLO) != 0

        && ctx != NULL

        && SSL_CTX_ct_is_enabled(ctx))

        return 0;

#endif

    /*

     * Don't add if extension supported internally, but make exception

     * for extension types that previously were not supported, but now are.

     */

    if (SSL_extension_supported(ext_type)

        && ext_type != TLSEXT_TYPE_signed_certificate_timestamp)

        return 0;

    /* Extension type must fit in 16 bits */

    if (ext_type > 0xffff)

        return 0;

    /* Search for duplicate */

    if (custom_ext_find(exts, role, ext_type, NULL))

        return 0;

    tmp = OPENSSL_realloc(exts->meths,

        (exts->meths_count + 1) * sizeof(custom_ext_method));

    if (tmp == NULL)

        return 0;

    exts->meths = tmp;

    meth = exts->meths + exts->meths_count;

    memset(meth, 0, sizeof(*meth));

    meth->role = role;

    meth->context = context;

    meth->parse_cb = parse_cb;

    meth->add_cb = add_cb;

    meth->free_cb = free_cb;

    meth->ext_type = ext_type;

    meth->add_arg = add_arg;

    meth->parse_arg = parse_arg;

    exts->meths_count++;

    return 1;

}

static int add_old_custom_ext(SSL_CTX *ctx, ENDPOINT role,

    unsigned int ext_type,

    unsigned int context,

    custom_ext_add_cb add_cb,

    custom_ext_free_cb free_cb,

    void *add_arg,

    custom_ext_parse_cb parse_cb, void *parse_arg)

{

    custom_ext_add_cb_wrap *add_cb_wrap

        = OPENSSL_malloc(sizeof(*add_cb_wrap));

    custom_ext_parse_cb_wrap *parse_cb_wrap

        = OPENSSL_malloc(sizeof(*parse_cb_wrap));

    int ret;

    if (add_cb_wrap == NULL || parse_cb_wrap == NULL) {

        OPENSSL_free(add_cb_wrap);

        OPENSSL_free(parse_cb_wrap);

        return 0;

    }

    add_cb_wrap->add_arg = add_arg;

    add_cb_wrap->add_cb = add_cb;

    add_cb_wrap->free_cb = free_cb;

    parse_cb_wrap->parse_arg = parse_arg;

    parse_cb_wrap->parse_cb = parse_cb;

    ret = ossl_tls_add_custom_ext_intern(ctx, NULL, role, ext_type,

        context,

        custom_ext_add_old_cb_wrap,

        custom_ext_free_old_cb_wrap,

        add_cb_wrap,

        custom_ext_parse_old_cb_wrap,

        parse_cb_wrap);

    if (!ret) {

        OPENSSL_free(add_cb_wrap);

        OPENSSL_free(parse_cb_wrap);

    }

    return ret;

}

/* Application level functions to add the old custom extension callbacks */

int SSL_CTX_add_client_custom_ext(SSL_CTX *ctx, unsigned int ext_type,

    custom_ext_add_cb add_cb,

    custom_ext_free_cb free_cb,

    void *add_arg,

    custom_ext_parse_cb parse_cb, void *parse_arg)

{

    return add_old_custom_ext(ctx, ENDPOINT_CLIENT, ext_type,

        SSL_EXT_TLS1_2_AND_BELOW_ONLY

            | SSL_EXT_CLIENT_HELLO

            | SSL_EXT_TLS1_2_SERVER_HELLO

            | SSL_EXT_IGNORE_ON_RESUMPTION,

        add_cb, free_cb, add_arg, parse_cb, parse_arg);

}

int SSL_CTX_add_server_custom_ext(SSL_CTX *ctx, unsigned int ext_type,

    custom_ext_add_cb add_cb,

    custom_ext_free_cb free_cb,

    void *add_arg,

    custom_ext_parse_cb parse_cb, void *parse_arg)

{

    return add_old_custom_ext(ctx, ENDPOINT_SERVER, ext_type,

        SSL_EXT_TLS1_2_AND_BELOW_ONLY

            | SSL_EXT_CLIENT_HELLO

            | SSL_EXT_TLS1_2_SERVER_HELLO

            | SSL_EXT_IGNORE_ON_RESUMPTION,

        add_cb, free_cb, add_arg, parse_cb, parse_arg);

}

int SSL_CTX_add_custom_ext(SSL_CTX *ctx, unsigned int ext_type,

    unsigned int context,

    SSL_custom_ext_add_cb_ex add_cb,

    SSL_custom_ext_free_cb_ex free_cb,

    void *add_arg,

    SSL_custom_ext_parse_cb_ex parse_cb, void *parse_arg)

{

    return ossl_tls_add_custom_ext_intern(ctx, NULL, ENDPOINT_BOTH, ext_type,

        context, add_cb, free_cb, add_arg,

        parse_cb, parse_arg);

}

int SSL_extension_supported(unsigned int ext_type)

{

    switch (ext_type) {

        /* Internally supported extensions. */

    case TLSEXT_TYPE_application_layer_protocol_negotiation:

    case TLSEXT_TYPE_ec_point_formats:

    case TLSEXT_TYPE_supported_groups:

    case TLSEXT_TYPE_key_share:

#ifndef OPENSSL_NO_NEXTPROTONEG

    case TLSEXT_TYPE_next_proto_neg:

#endif

    case TLSEXT_TYPE_padding:

    case TLSEXT_TYPE_renegotiate:

    case TLSEXT_TYPE_max_fragment_length:

    case TLSEXT_TYPE_server_name:

    case TLSEXT_TYPE_session_ticket:

    case TLSEXT_TYPE_signature_algorithms:

#ifndef OPENSSL_NO_SRP

    case TLSEXT_TYPE_srp:

#endif

#ifndef OPENSSL_NO_OCSP

    case TLSEXT_TYPE_status_request:

#endif

#ifndef OPENSSL_NO_CT

    case TLSEXT_TYPE_signed_certificate_timestamp:

#endif

#ifndef OPENSSL_NO_SRTP

    case TLSEXT_TYPE_use_srtp:

#endif

    case TLSEXT_TYPE_encrypt_then_mac:

    case TLSEXT_TYPE_supported_versions:

    case TLSEXT_TYPE_extended_master_secret:

    case TLSEXT_TYPE_psk_kex_modes:

    case TLSEXT_TYPE_cookie:

    case TLSEXT_TYPE_early_data:

    case TLSEXT_TYPE_certificate_authorities:

    case TLSEXT_TYPE_psk:

    case TLSEXT_TYPE_post_handshake_auth:

    case TLSEXT_TYPE_compress_certificate:

    case TLSEXT_TYPE_client_cert_type:

    case TLSEXT_TYPE_server_cert_type:

#ifndef OPENSSL_NO_ECH

    case TLSEXT_TYPE_ech:

    case TLSEXT_TYPE_outer_extensions:

#endif

        return 1;

    default:

        return 0;

    }

}