/* $OpenBSD: tls_server.c,v 1.44 2018/03/19 16:34:47 jsing Exp $ */
/*
 * Copyright (c) 2014 Joel Sing <jsing@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/socket.h>

#include <arpa/inet.h>

#include <openssl/ec.h>
#include <openssl/err.h>
#include <openssl/ssl.h>

#include <tls.h>
#include "tls_internal.h"

struct tls *
tls_server(void)
{
   struct tls *ctx;

   if (tls_init() == -1)
      return (NULL);

   if ((ctx = tls_new()) == NULL)
      return (NULL);

   ctx->flags |= TLS_SERVER;

   return (ctx);
}

struct tls *
tls_server_conn(struct tls *ctx)
{
   struct tls *conn_ctx;

   if ((conn_ctx = tls_new()) == NULL)
      return (NULL);

   conn_ctx->flags |= TLS_SERVER_CONN;

   ctx->config->refcount++;

   conn_ctx->config = ctx->config;
   conn_ctx->keypair = ctx->config->keypair;

   return (conn_ctx);
}

static int
tls_server_alpn_cb(SSL *ssl, const unsigned char **out, unsigned char *outlen,
    const unsigned char *in, unsigned int inlen, void *arg)
{
   struct tls *ctx = arg;

   if (SSL_select_next_proto((unsigned char**)out, outlen,
#ifndef __VMS
      ctx->config->alpn, ctx->config->alpn_len, in, inlen) ==
#else
      (const unsigned char*)ctx->config->alpn, ctx->config->alpn_len, in, inlen) ==
#endif      
         OPENSSL_NPN_NEGOTIATED)
      return (SSL_TLSEXT_ERR_OK);

   return (SSL_TLSEXT_ERR_NOACK);
}

static int
tls_servername_cb(SSL *ssl, int *al, void *arg)
{
   struct tls *ctx = (struct tls *)arg;
   struct tls_sni_ctx *sni_ctx;
   union tls_addr addrbuf;
   struct tls *conn_ctx;
   const char *name;
   int match;

   if ((conn_ctx = SSL_get_app_data(ssl)) == NULL)
      goto err;

   if ((name = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name)) ==
       NULL) {
      /*
       * The servername callback gets called even when there is no
       * TLS servername extension provided by the client. Sigh!
       */
      return (SSL_TLSEXT_ERR_NOACK);
   }

   /*
    * Per RFC 6066 section 3: ensure that name is not an IP literal.
    *
    * While we should treat this as an error, a number of clients
    * (Python, Ruby and Safari) are not RFC compliant. To avoid handshake
    * failures, pretend that we did not receive the extension.
    */
   if (inet_pton(AF_INET, name, &addrbuf) == 1 ||
            inet_pton(AF_INET6, name, &addrbuf) == 1)
      return (SSL_TLSEXT_ERR_NOACK);

   free((char *)conn_ctx->servername);
   if ((conn_ctx->servername = strdup(name)) == NULL)
      goto err;

   /* Find appropriate SSL context for requested servername. */
   for (sni_ctx = ctx->sni_ctx; sni_ctx != NULL; sni_ctx = sni_ctx->next) {
      if (tls_check_name(ctx, sni_ctx->ssl_cert, name,
          &match) == -1)
         goto err;
      if (match) {
         conn_ctx->keypair = sni_ctx->keypair;
         SSL_set_SSL_CTX(conn_ctx->ssl_conn, sni_ctx->ssl_ctx);
         return (SSL_TLSEXT_ERR_OK);
      }
   }

   /* No match, use the existing context/certificate. */
   return (SSL_TLSEXT_ERR_OK);

 err:
   /*
    * There is no way to tell libssl that an internal failure occurred.
    * The only option we have is to return a fatal alert.
    */
   *al = TLS1_AD_INTERNAL_ERROR;
   return (SSL_TLSEXT_ERR_ALERT_FATAL);
}

static struct tls_ticket_key *
tls_server_ticket_key(struct tls_config *config, unsigned char *keyname)
{
   struct tls_ticket_key *key = NULL;
   time_t now;
   int i;

   now = time(NULL);
   if (config->ticket_autorekey == 1) {
      if (now - 3 * (config->session_lifetime / 4) >
          config->ticket_keys[0].time) {
         if (tls_config_ticket_autorekey(config) == -1)
            return (NULL);
      }
   }
   for (i = 0; i < TLS_NUM_TICKETS; i++) {
      struct tls_ticket_key *tk = &config->ticket_keys[i];
      if (now - config->session_lifetime > tk->time)
         continue;
      if (keyname == NULL || timingsafe_memcmp(keyname,
          tk->key_name, sizeof(tk->key_name)) == 0) {
         key = tk;
         break;
      }
   }
   return (key);
}

static int
tls_server_ticket_cb(SSL *ssl, unsigned char *keyname, unsigned char *iv,
    EVP_CIPHER_CTX *ctx, HMAC_CTX *hctx, int mode)
{
   struct tls_ticket_key *key;
   struct tls *tls_ctx;

   if ((tls_ctx = SSL_get_app_data(ssl)) == NULL)
      return (-1);

   if (mode == 1) {
      /* create new session */
      key = tls_server_ticket_key(tls_ctx->config, NULL);
      if (key == NULL) {
         tls_set_errorx(tls_ctx, "no valid ticket key found");
         return (-1);
      }

      memcpy(keyname, key->key_name, sizeof(key->key_name));
      arc4random_buf(iv, EVP_MAX_IV_LENGTH);
      EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL,
          key->aes_key, iv);
      HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
          EVP_sha256(), NULL);
      return (0);
   } else {
      /* get key by name */
      key = tls_server_ticket_key(tls_ctx->config, keyname);
      if (key == NULL)
         return (0);

      EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL,
          key->aes_key, iv);
      HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
          EVP_sha256(), NULL);

      /* time to renew the ticket? is it the primary key? */
      if (key != &tls_ctx->config->ticket_keys[0])
         return (2);
      return (1);
   }
}

static int
tls_configure_server_ssl(struct tls *ctx, SSL_CTX **ssl_ctx,
    struct tls_keypair *keypair)
{
   SSL_CTX_free(*ssl_ctx);

#if WCME_OPENSSL_SINCE_110
   if ((*ssl_ctx = SSL_CTX_new(TLS_server_method())) == NULL) {
      tls_set_errorx(ctx, "ssl context failure");
      goto err;
   }
   if (!SSL_CTX_set_min_proto_version (*ssl_ctx, TLS1_VERSION))
   {
      tls_set_errorx(ctx, "set_min_proto_version failure");
      goto err;
   }
   if (!SSL_CTX_set_max_proto_version (*ssl_ctx, TLS_MAX_VERSION))
   {
      tls_set_errorx(ctx, "set_max_proto_version failure");
      goto err;
   }
#else
   if ((*ssl_ctx = SSL_CTX_new(SSLv23_server_method())) == NULL) {
      tls_set_errorx(ctx, "ssl context failure");
      goto err;
   }
#endif

#ifndef __VMS
   SSL_CTX_set_options(*ssl_ctx, SSL_OP_NO_CLIENT_RENEGOTIATION);
#else
#ifdef SSL_OP_NO_CLIENT_RENEGOTIATION
   SSL_CTX_set_options(*ssl_ctx, SSL_OP_NO_CLIENT_RENEGOTIATION);
#endif
#endif

   if (SSL_CTX_set_tlsext_servername_callback(*ssl_ctx,
       tls_servername_cb) != 1) {
      tls_set_error(ctx, "failed to set servername callback");
      goto err;
   }
   if (SSL_CTX_set_tlsext_servername_arg(*ssl_ctx, ctx) != 1) {
      tls_set_error(ctx, "failed to set servername callback arg");
      goto err;
   }

   if (tls_configure_ssl(ctx, *ssl_ctx) != 0)
      goto err;
   if (tls_configure_ssl_keypair(ctx, *ssl_ctx, keypair, 1) != 0)
      goto err;
   if (ctx->config->verify_client != 0) {
      int verify = SSL_VERIFY_PEER;
      if (ctx->config->verify_client == 1)
         verify |= SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
      if (tls_configure_ssl_verify(ctx, *ssl_ctx, verify) == -1)
         goto err;
   }

   if (ctx->config->alpn != NULL)
      SSL_CTX_set_alpn_select_cb(*ssl_ctx, tls_server_alpn_cb,
          ctx);

#ifdef __VMS
#ifdef SSL_CTRL_SET_DH_AUTO
        if (ctx->config->dheparams == -1)
                SSL_CTX_set_dh_auto(*ssl_ctx, 1);
        else if (ctx->config->dheparams == 1024)
                SSL_CTX_set_dh_auto(*ssl_ctx, 2);
#endif
#endif

   if (ctx->config->ecdhecurves != NULL) {
      SSL_CTX_set_ecdh_auto(*ssl_ctx, 1);
#if WCME_OPENSSL_SINCE_110
      if (SSL_CTX_set1_groups(ctx->ssl_ctx, ctx->config->ecdhecurves,
          ctx->config->ecdhecurves_len) != 1) {
#else
      if (SSL_CTX_set1_curves(ctx->ssl_ctx, ctx->config->ecdhecurves,
          ctx->config->ecdhecurves_len) != 1) {
#endif
         tls_set_errorx(ctx, "failed to set ecdhe curves");
         goto err;
      }
   }

   if (ctx->config->ciphers_server == 1)
      SSL_CTX_set_options(*ssl_ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);

   if (SSL_CTX_set_tlsext_status_cb(*ssl_ctx, tls_ocsp_stapling_cb) != 1) {
      tls_set_errorx(ctx, "failed to add OCSP stapling callback");
      goto err;
   }

   if (ctx->config->session_lifetime > 0) {
      /* set the session lifetime and enable tickets */
      SSL_CTX_set_timeout(*ssl_ctx, ctx->config->session_lifetime);
      SSL_CTX_clear_options(*ssl_ctx, SSL_OP_NO_TICKET);
      if (!SSL_CTX_set_tlsext_ticket_key_cb(*ssl_ctx,
          tls_server_ticket_cb)) {
         tls_set_error(ctx,
             "failed to set the TLS ticket callback");
         goto err;
      }
   }

   if (SSL_CTX_set_session_id_context(*ssl_ctx, ctx->config->session_id,
       sizeof(ctx->config->session_id)) != 1) {
      tls_set_error(ctx, "failed to set session id context");
      goto err;
   }

   return (0);

  err:
   SSL_CTX_free(*ssl_ctx);
   *ssl_ctx = NULL;

   return (-1);
}

static int
tls_configure_server_sni(struct tls *ctx)
{
   struct tls_sni_ctx **sni_ctx;
   struct tls_keypair *kp;

   if (ctx->config->keypair->next == NULL)
      return (0);

   /* Set up additional SSL contexts for SNI. */
   sni_ctx = &ctx->sni_ctx;
   for (kp = ctx->config->keypair->next; kp != NULL; kp = kp->next) {
      if ((*sni_ctx = tls_sni_ctx_new()) == NULL) {
         tls_set_errorx(ctx, "out of memory");
         goto err;
      }
      (*sni_ctx)->keypair = kp;
      if (tls_configure_server_ssl(ctx, &(*sni_ctx)->ssl_ctx, kp) == -1)
         goto err;
      if (tls_keypair_load_cert(kp, &ctx->error,
          &(*sni_ctx)->ssl_cert) == -1)
         goto err;
      sni_ctx = &(*sni_ctx)->next;
   }

   return (0);

 err:
   return (-1);
}

int
tls_configure_server(struct tls *ctx)
{
   if (tls_configure_server_ssl(ctx, &ctx->ssl_ctx,
       ctx->config->keypair) == -1)
      goto err;
   if (tls_configure_server_sni(ctx) == -1)
      goto err;

   return (0);

 err:
   return (-1);
}

static struct tls *
tls_accept_common(struct tls *ctx)
{
   struct tls *conn_ctx = NULL;

   if ((ctx->flags & TLS_SERVER) == 0) {
      tls_set_errorx(ctx, "not a server context");
      goto err;
   }

   if ((conn_ctx = tls_server_conn(ctx)) == NULL) {
      tls_set_errorx(ctx, "connection context failure");
      goto err;
   }

   if ((conn_ctx->ssl_conn = SSL_new(ctx->ssl_ctx)) == NULL) {
      tls_set_errorx(ctx, "ssl failure");
      goto err;
   }

   if (SSL_set_app_data(conn_ctx->ssl_conn, conn_ctx) != 1) {
      tls_set_errorx(ctx, "ssl application data failure");
      goto err;
   }

   return conn_ctx;

 err:
   tls_free(conn_ctx);

   return (NULL);
}

int
tls_accept_socket(struct tls *ctx, struct tls **cctx, int s)
{
   return (tls_accept_fds(ctx, cctx, s, s));
}

int
tls_accept_fds(struct tls *ctx, struct tls **cctx, int fd_read, int fd_write)
{
   struct tls *conn_ctx;

   if ((conn_ctx = tls_accept_common(ctx)) == NULL)
      goto err;

   if (SSL_set_rfd(conn_ctx->ssl_conn, fd_read) != 1 ||
       SSL_set_wfd(conn_ctx->ssl_conn, fd_write) != 1) {
      tls_set_errorx(ctx, "ssl file descriptor failure");
      goto err;
   }

   *cctx = conn_ctx;

   return (0);
 err:
   tls_free(conn_ctx);
   *cctx = NULL;

   return (-1);
}

int
tls_accept_cbs(struct tls *ctx, struct tls **cctx,
    tls_read_cb read_cb, tls_write_cb write_cb, void *cb_arg)
{
   struct tls *conn_ctx;

   if ((conn_ctx = tls_accept_common(ctx)) == NULL)
      goto err;

   if (tls_set_cbs(conn_ctx, read_cb, write_cb, cb_arg) != 0)
      goto err;

   *cctx = conn_ctx;

   return (0);
 err:
   tls_free(conn_ctx);
   *cctx = NULL;

   return (-1);
}

int
tls_handshake_server(struct tls *ctx)
{
   int ssl_ret;
   int rv = -1;

   if ((ctx->flags & TLS_SERVER_CONN) == 0) {
      tls_set_errorx(ctx, "not a server connection context");
      goto err;
   }

   ctx->state |= TLS_SSL_NEEDS_SHUTDOWN;

   ERR_clear_error();
   if ((ssl_ret = SSL_accept(ctx->ssl_conn)) != 1) {
      rv = tls_ssl_error(ctx, ctx->ssl_conn, ssl_ret, "handshake");
      goto err;
   }

   ctx->state |= TLS_HANDSHAKE_COMPLETE;
   rv = 0;

 err:
   return (rv);
}