path: root/ssl/statem/extensions_cust.c

/*
 * Copyright 2014-2018 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_locl.h"
#include "internal/cryptlib.h"
#include "statem_locl.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 *s, unsigned int context, unsigned int ext_type,
                     const unsigned char *ext_data, size_t ext_size, X509 *x,
                     size_t chainidx)
{
    int al;
    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_F_CUSTOM_EXT_PARSE,
                     SSL_R_BAD_EXTENSION);
            return 0;
        }
    }

    /*
     * Extensions received in the ClientHello are marked with the
     * SSL_EXT_FLAG_RECEIVED. This is so we know to add the equivalent
     * extensions in the ServerHello/EncryptedExtensions message
     */
    if ((context & SSL_EXT_CLIENT_HELLO) != 0)
        meth->ext_flags |= SSL_EXT_FLAG_RECEIVED;

    /* If no parse function set return success */
    if (!meth->parse_cb)
        return 1;

    if (meth->parse_cb(s, ext_type, context, ext_data, ext_size, x, chainidx,
                       &al, meth->parse_arg) <= 0) {
        SSLfatal(s, al, SSL_F_CUSTOM_EXT_PARSE, 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 *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;

    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_HELLO_RETRY_REQUEST)) != 0) {
            /* Only send extensions present in ClientHello. */
            if (!(meth->ext_flags & SSL_EXT_FLAG_RECEIVED))
                continue;
        }
        /*
         * 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(s, meth->ext_type, <