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/* -*- coding: utf-8 -*- */
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* Mandos client - get and decrypt data from a Mandos server
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* This program is partly derived from an example program for an Avahi
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* service browser, downloaded from
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* <http://avahi.org/browser/examples/core-browse-services.c>. This
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* includes the following functions: "resolve_callback",
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* "browse_callback", and parts of "main".
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* Everything else is Copyright © 2007-2008 Teddy Hogeborn and Björn
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* This program is free software: you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see
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* <http://www.gnu.org/licenses/>.
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* Contact the authors at <https://www.fukt.bsnet.se/~belorn/> and
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* <https://www.fukt.bsnet.se/~teddy/>.
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#define _FORTIFY_SOURCE 2
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#define _LARGEFILE_SOURCE
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#define _FILE_OFFSET_BITS 64
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#include <net/if.h> /* if_nametoindex */
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#include <avahi-core/core.h>
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#include <avahi-core/lookup.h>
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#include <avahi-core/log.h>
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#include <avahi-common/simple-watch.h>
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#include <avahi-common/malloc.h>
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#include <avahi-common/error.h>
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#include <sys/types.h> /* socket(), inet_pton() */
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#include <sys/socket.h> /* socket(), struct sockaddr_in6,
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struct in6_addr, inet_pton() */
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#include <gnutls/gnutls.h> /* All GnuTLS stuff */
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#include <gnutls/openpgp.h> /* GnuTLS with openpgp stuff */
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#include <unistd.h> /* close() */
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#include <netinet/in.h>
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#include <stdbool.h> /* true */
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#include <string.h> /* memset */
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#include <arpa/inet.h> /* inet_pton() */
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#include <iso646.h> /* not */
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#include <errno.h> /* perror() */
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#define CERT_ROOT "/conf/conf.d/cryptkeyreq/"
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#define CERTFILE CERT_ROOT "openpgp-client.txt"
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#define KEYFILE CERT_ROOT "openpgp-client-key.txt"
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#define BUFFER_SIZE 256
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gnutls_session_t session;
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gnutls_certificate_credentials_t cred;
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gnutls_dh_params_t dh_params;
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ssize_t pgp_packet_decrypt (char *packet, size_t packet_size,
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char **new_packet, const char *homedir){
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gpgme_data_t dh_crypto, dh_plain;
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ssize_t new_packet_capacity = 0;
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ssize_t new_packet_length = 0;
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gpgme_engine_info_t engine_info;
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fprintf(stderr, "Trying to decrypt OpenPGP packet\n");
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gpgme_check_version(NULL);
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gpgme_engine_check_version(GPGME_PROTOCOL_OpenPGP);
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/* Set GPGME home directory */
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rc = gpgme_get_engine_info (&engine_info);
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if (rc != GPG_ERR_NO_ERROR){
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fprintf(stderr, "bad gpgme_get_engine_info: %s: %s\n",
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gpgme_strsource(rc), gpgme_strerror(rc));
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while(engine_info != NULL){
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if(engine_info->protocol == GPGME_PROTOCOL_OpenPGP){
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gpgme_set_engine_info(GPGME_PROTOCOL_OpenPGP,
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engine_info->file_name, homedir);
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engine_info = engine_info->next;
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if(engine_info == NULL){
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fprintf(stderr, "Could not set home dir to %s\n", homedir);
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/* Create new GPGME data buffer from packet buffer */
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rc = gpgme_data_new_from_mem(&dh_crypto, packet, packet_size, 0);
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if (rc != GPG_ERR_NO_ERROR){
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fprintf(stderr, "bad gpgme_data_new_from_mem: %s: %s\n",
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gpgme_strsource(rc), gpgme_strerror(rc));
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/* Create new empty GPGME data buffer for the plaintext */
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rc = gpgme_data_new(&dh_plain);
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if (rc != GPG_ERR_NO_ERROR){
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fprintf(stderr, "bad gpgme_data_new: %s: %s\n",
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gpgme_strsource(rc), gpgme_strerror(rc));
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/* Create new GPGME "context" */
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rc = gpgme_new(&ctx);
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if (rc != GPG_ERR_NO_ERROR){
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fprintf(stderr, "bad gpgme_new: %s: %s\n",
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gpgme_strsource(rc), gpgme_strerror(rc));
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/* Decrypt data from the FILE pointer to the plaintext data
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rc = gpgme_op_decrypt(ctx, dh_crypto, dh_plain);
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if (rc != GPG_ERR_NO_ERROR){
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fprintf(stderr, "bad gpgme_op_decrypt: %s: %s\n",
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gpgme_strsource(rc), gpgme_strerror(rc));
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fprintf(stderr, "Decryption of OpenPGP packet succeeded\n");
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gpgme_decrypt_result_t result;
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result = gpgme_op_decrypt_result(ctx);
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fprintf(stderr, "gpgme_op_decrypt_result failed\n");
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fprintf(stderr, "Unsupported algorithm: %s\n",
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result->unsupported_algorithm);
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fprintf(stderr, "Wrong key usage: %d\n",
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result->wrong_key_usage);
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if(result->file_name != NULL){
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fprintf(stderr, "File name: %s\n", result->file_name);
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gpgme_recipient_t recipient;
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recipient = result->recipients;
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while(recipient != NULL){
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fprintf(stderr, "Public key algorithm: %s\n",
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gpgme_pubkey_algo_name(recipient->pubkey_algo));
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fprintf(stderr, "Key ID: %s\n", recipient->keyid);
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fprintf(stderr, "Secret key available: %s\n",
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recipient->status == GPG_ERR_NO_SECKEY
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recipient = recipient->next;
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/* Delete the GPGME FILE pointer cryptotext data buffer */
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gpgme_data_release(dh_crypto);
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/* Seek back to the beginning of the GPGME plaintext data buffer */
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gpgme_data_seek(dh_plain, (off_t) 0, SEEK_SET);
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if (new_packet_length + BUFFER_SIZE > new_packet_capacity){
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*new_packet = realloc(*new_packet,
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(unsigned int)new_packet_capacity
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if (*new_packet == NULL){
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new_packet_capacity += BUFFER_SIZE;
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ret = gpgme_data_read(dh_plain, *new_packet + new_packet_length,
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/* Print the data, if any */
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perror("gpgme_data_read");
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new_packet_length += ret;
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/* FIXME: check characters before printing to screen so to not print
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terminal control characters */
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/* fprintf(stderr, "decrypted password is: "); */
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/* fwrite(*new_packet, 1, new_packet_length, stderr); */
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/* fprintf(stderr, "\n"); */
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/* Delete the GPGME plaintext data buffer */
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gpgme_data_release(dh_plain);
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return new_packet_length;
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static const char * safer_gnutls_strerror (int value) {
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const char *ret = gnutls_strerror (value);
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void debuggnutls(__attribute__((unused)) int level,
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fprintf(stderr, "%s", string);
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int initgnutls(encrypted_session *es){
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fprintf(stderr, "Initializing GnuTLS\n");
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if ((ret = gnutls_global_init ())
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!= GNUTLS_E_SUCCESS) {
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fprintf (stderr, "global_init: %s\n", safer_gnutls_strerror(ret));
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gnutls_global_set_log_level(11);
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gnutls_global_set_log_function(debuggnutls);
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/* openpgp credentials */
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if ((ret = gnutls_certificate_allocate_credentials (&es->cred))
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!= GNUTLS_E_SUCCESS) {
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fprintf (stderr, "memory error: %s\n",
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safer_gnutls_strerror(ret));
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fprintf(stderr, "Attempting to use OpenPGP certificate %s"
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" and keyfile %s as GnuTLS credentials\n", CERTFILE,
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ret = gnutls_certificate_set_openpgp_key_file
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(es->cred, CERTFILE, KEYFILE, GNUTLS_OPENPGP_FMT_BASE64);
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if (ret != GNUTLS_E_SUCCESS) {
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(stderr, "Error[%d] while reading the OpenPGP key pair ('%s',"
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ret, CERTFILE, KEYFILE);
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fprintf(stdout, "The Error is: %s\n",
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safer_gnutls_strerror(ret));
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//GnuTLS server initialization
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if ((ret = gnutls_dh_params_init (&es->dh_params))
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!= GNUTLS_E_SUCCESS) {
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fprintf (stderr, "Error in dh parameter initialization: %s\n",
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safer_gnutls_strerror(ret));
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if ((ret = gnutls_dh_params_generate2 (es->dh_params, DH_BITS))
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!= GNUTLS_E_SUCCESS) {
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fprintf (stderr, "Error in prime generation: %s\n",
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safer_gnutls_strerror(ret));
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gnutls_certificate_set_dh_params (es->cred, es->dh_params);
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// GnuTLS session creation
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if ((ret = gnutls_init (&es->session, GNUTLS_SERVER))
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!= GNUTLS_E_SUCCESS){
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fprintf(stderr, "Error in GnuTLS session initialization: %s\n",
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safer_gnutls_strerror(ret));
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if ((ret = gnutls_priority_set_direct (es->session, "NORMAL", &err))
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!= GNUTLS_E_SUCCESS) {
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fprintf(stderr, "Syntax error at: %s\n", err);
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fprintf(stderr, "GnuTLS error: %s\n",
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safer_gnutls_strerror(ret));
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if ((ret = gnutls_credentials_set
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(es->session, GNUTLS_CRD_CERTIFICATE, es->cred))
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!= GNUTLS_E_SUCCESS) {
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fprintf(stderr, "Error setting a credentials set: %s\n",
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safer_gnutls_strerror(ret));
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/* ignore client certificate if any. */
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gnutls_certificate_server_set_request (es->session,
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gnutls_dh_set_prime_bits (es->session, DH_BITS);
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void empty_log(__attribute__((unused)) AvahiLogLevel level,
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__attribute__((unused)) const char *txt){}
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int start_mandos_communication(const char *ip, uint16_t port,
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unsigned int if_index){
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struct sockaddr_in6 to;
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encrypted_session es;
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char *decrypted_buffer;
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size_t buffer_length = 0;
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size_t buffer_capacity = 0;
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ssize_t decrypted_buffer_size;
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char interface[IF_NAMESIZE];
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fprintf(stderr, "Setting up a tcp connection to %s\n", ip);
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tcp_sd = socket(PF_INET6, SOCK_STREAM, 0);
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if(if_indextoname(if_index, interface) == NULL){
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perror("if_indextoname");
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fprintf(stderr, "Binding to interface %s\n", interface);
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memset(&to,0,sizeof(to)); /* Spurious warning */
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to.sin6_family = AF_INET6;
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ret = inet_pton(AF_INET6, ip, &to.sin6_addr);
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fprintf(stderr, "Bad address: %s\n", ip);
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to.sin6_port = htons(port); /* Spurious warning */
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to.sin6_scope_id = (uint32_t)if_index;
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fprintf(stderr, "Connection to: %s\n", ip);
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ret = connect(tcp_sd, (struct sockaddr *) &to, sizeof(to));
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ret = initgnutls (&es);
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gnutls_transport_set_ptr (es.session,
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(gnutls_transport_ptr_t) tcp_sd);
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fprintf(stderr, "Establishing TLS session with %s\n", ip);
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ret = gnutls_handshake (es.session);
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if (ret != GNUTLS_E_SUCCESS){
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fprintf(stderr, "\n*** Handshake failed ***\n");
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//Retrieve OpenPGP packet that contains the wanted password
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fprintf(stderr, "Retrieving pgp encrypted password from %s\n",
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if (buffer_length + BUFFER_SIZE > buffer_capacity){
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buffer = realloc(buffer, buffer_capacity + BUFFER_SIZE);
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buffer_capacity += BUFFER_SIZE;
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ret = gnutls_record_recv
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(es.session, buffer+buffer_length, BUFFER_SIZE);
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case GNUTLS_E_INTERRUPTED:
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case GNUTLS_E_REHANDSHAKE:
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ret = gnutls_handshake (es.session);
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fprintf(stderr, "\n*** Handshake failed ***\n");
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fprintf(stderr, "Unknown error while reading data from"
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" encrypted session with mandos server\n");
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gnutls_bye (es.session, GNUTLS_SHUT_RDWR);
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buffer_length += (size_t) ret;
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if (buffer_length > 0){
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decrypted_buffer_size = pgp_packet_decrypt(buffer,
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if (decrypted_buffer_size >= 0){
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while(written < decrypted_buffer_size){
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ret = (int)fwrite (decrypted_buffer + written, 1,
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(size_t)decrypted_buffer_size - written,
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if(ret == 0 and ferror(stdout)){
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fprintf(stderr, "Error writing encrypted data: %s\n",
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written += (size_t)ret;
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free(decrypted_buffer);
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fprintf(stderr, "Closing TLS session\n");
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gnutls_bye (es.session, GNUTLS_SHUT_RDWR);
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gnutls_deinit (es.session);
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gnutls_certificate_free_credentials (es.cred);
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gnutls_global_deinit ();
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static AvahiSimplePoll *simple_poll = NULL;
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static AvahiServer *server = NULL;
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static void resolve_callback(
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AvahiSServiceResolver *r,
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AvahiIfIndex interface,
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AVAHI_GCC_UNUSED AvahiProtocol protocol,
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AvahiResolverEvent event,
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const char *host_name,
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const AvahiAddress *address,
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AVAHI_GCC_UNUSED AvahiStringList *txt,
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AVAHI_GCC_UNUSED AvahiLookupResultFlags flags,
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AVAHI_GCC_UNUSED void* userdata) {
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assert(r); /* Spurious warning */
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/* Called whenever a service has been resolved successfully or
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case AVAHI_RESOLVER_FAILURE:
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fprintf(stderr, "(Resolver) Failed to resolve service '%s' of"
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" type '%s' in domain '%s': %s\n", name, type, domain,
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avahi_strerror(avahi_server_errno(server)));
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case AVAHI_RESOLVER_FOUND:
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char ip[AVAHI_ADDRESS_STR_MAX];
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avahi_address_snprint(ip, sizeof(ip), address);
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fprintf(stderr, "Mandos server found on %s (%s) on port %d\n",
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host_name, ip, port);
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int ret = start_mandos_communication(ip, port,
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(unsigned int) interface);
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avahi_s_service_resolver_free(r);
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static void browse_callback(
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AvahiSServiceBrowser *b,
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AvahiIfIndex interface,
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AvahiProtocol protocol,
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AvahiBrowserEvent event,
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AVAHI_GCC_UNUSED AvahiLookupResultFlags flags,
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AvahiServer *s = userdata;
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assert(b); /* Spurious warning */
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/* Called whenever a new services becomes available on the LAN or
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is removed from the LAN */
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case AVAHI_BROWSER_FAILURE:
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fprintf(stderr, "(Browser) %s\n",
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avahi_strerror(avahi_server_errno(server)));
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avahi_simple_poll_quit(simple_poll);
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case AVAHI_BROWSER_NEW:
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/* We ignore the returned resolver object. In the callback
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function we free it. If the server is terminated before
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the callback function is called the server will free
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the resolver for us. */
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if (!(avahi_s_service_resolver_new(s, interface, protocol, name,
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AVAHI_PROTO_INET6, 0,
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resolve_callback, s)))
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fprintf(stderr, "Failed to resolve service '%s': %s\n", name,
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avahi_strerror(avahi_server_errno(s)));
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case AVAHI_BROWSER_REMOVE:
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case AVAHI_BROWSER_ALL_FOR_NOW:
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case AVAHI_BROWSER_CACHE_EXHAUSTED:
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int main(AVAHI_GCC_UNUSED int argc, AVAHI_GCC_UNUSED char*argv[]) {
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AvahiServerConfig config;
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AvahiSServiceBrowser *sb = NULL;
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int returncode = EXIT_SUCCESS;
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const char *interface = "eth0";
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static struct option long_options[] = {
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{"debug", no_argument, (int *)&debug, 1},
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{"interface", required_argument, 0, 'i'},
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int option_index = 0;
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ret = getopt_long (argc, argv, "i:", long_options,
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avahi_set_log_function(empty_log);
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/* Initialize the psuedo-RNG */
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srand((unsigned int) time(NULL));
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/* Allocate main loop object */
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if (!(simple_poll = avahi_simple_poll_new())) {
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fprintf(stderr, "Failed to create simple poll object.\n");
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/* Do not publish any local records */
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avahi_server_config_init(&config);
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config.publish_hinfo = 0;
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config.publish_addresses = 0;
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config.publish_workstation = 0;
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config.publish_domain = 0;
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/* Allocate a new server */
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server = avahi_server_new(avahi_simple_poll_get(simple_poll),
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&config, NULL, NULL, &error);
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/* Free the configuration data */
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avahi_server_config_free(&config);
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/* Check if creating the server object succeeded */
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fprintf(stderr, "Failed to create server: %s\n",
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avahi_strerror(error));
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returncode = EXIT_FAILURE;
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/* Create the service browser */
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sb = avahi_s_service_browser_new(server,
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if_nametoindex(interface),
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"_mandos._tcp", NULL, 0,
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browse_callback, server);
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fprintf(stderr, "Failed to create service browser: %s\n",
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avahi_strerror(avahi_server_errno(server)));
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returncode = EXIT_FAILURE;
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/* Run the main loop */
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fprintf(stderr, "Starting avahi loop search\n");
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avahi_simple_poll_loop(simple_poll);
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fprintf(stderr, "%s exiting\n", argv[0]);
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avahi_s_service_browser_free(sb);
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avahi_server_free(server);
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avahi_simple_poll_free(simple_poll);