webcit-ng/tls.c

   1 // Functions in this module handle SSL encryption when WebCit is running
   2 // as an HTTPS server.
   3 //
   4 // Copyright (c) 1996-2022 by the citadel.org team
   5 //
   6 // This program is open source software.  It runs great on the
   7 // Linux operating system (and probably elsewhere).  You can use,
   8 // copy, and run it under the terms of the GNU General Public
   9 // License version 3.
  10 //
  11 // This program is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 #include "webcit.h"
  17
  18 SSL_CTX *ssl_ctx;               // global SSL context
  19 char key_file[PATH_MAX] = "";
  20 char cert_file[PATH_MAX] = "";
  21 char *ssl_cipher_list = DEFAULT_SSL_CIPHER_LIST;
  22
  23
  24 // Set the private key and certificate chain for the global SSL Context.
  25 // This is called during initialization, and can be called again later if the certificate changes.
  26 void bind_to_key_and_certificate(void) {
  27         if (IsEmptyStr(key_file)) {
  28                 snprintf(key_file, sizeof key_file, "%s/keys/citadel.key", ctdl_dir);
  29         }
  30         if (IsEmptyStr(cert_file)) {
  31                 snprintf(cert_file, sizeof key_file, "%s/keys/citadel.cer", ctdl_dir);
  32         }
  33
  34         syslog(LOG_DEBUG, "crypto: [re]installing key \"%s\" and certificate \"%s\"", key_file, cert_file);
  35
  36         SSL_CTX_use_certificate_chain_file(ssl_ctx, cert_file);
  37         SSL_CTX_use_PrivateKey_file(ssl_ctx, key_file, SSL_FILETYPE_PEM);
  38
  39         if ( !SSL_CTX_check_private_key(ssl_ctx) ) {
  40                 syslog(LOG_WARNING, "crypto: cannot install certificate: %s", ERR_reason_error_string(ERR_get_error()));
  41         }
  42 }
  43
  44
  45 // Initialize ssl engine, load certs and initialize openssl internals
  46 void init_ssl(void) {
  47
  48         // Initialize SSL transport layer
  49         SSL_library_init();
  50         SSL_load_error_strings();
  51         if (!(ssl_ctx = SSL_CTX_new(SSLv23_server_method()))) {
  52                 syslog(LOG_WARNING, "SSL_CTX_new failed: %s", ERR_reason_error_string(ERR_get_error()));
  53                 return;
  54         }
  55
  56         syslog(LOG_INFO, "Requesting cipher list: %s", ssl_cipher_list);
  57         if (!(SSL_CTX_set_cipher_list(ssl_ctx, ssl_cipher_list))) {
  58                 syslog(LOG_WARNING, "SSL_CTX_set_cipher_list failed: %s", ERR_reason_error_string(ERR_get_error()));
  59                 return;
  60         }
  61
  62         // Now try to bind to the key and certificate.
  63         bind_to_key_and_certificate();
  64 }
  65
  66
  67 // Check the modification time of the key and certificate -- reload if they changed
  68 void update_key_and_cert_if_needed(void) {
  69         static time_t previous_mtime = 0;
  70         struct stat keystat;
  71         struct stat certstat;
  72
  73         if (stat(key_file, &keystat) != 0) {
  74                 syslog(LOG_ERR, "%s: %s", key_file, strerror(errno));
  75                 return;
  76         }
  77         if (stat(cert_file, &certstat) != 0) {
  78                 syslog(LOG_ERR, "%s: %s", cert_file, strerror(errno));
  79                 return;
  80         }
  81
  82         if ((keystat.st_mtime + certstat.st_mtime) != previous_mtime) {
  83                 bind_to_key_and_certificate();
  84                 previous_mtime = keystat.st_mtime + certstat.st_mtime;
  85         }
  86 }
  87
  88
  89 // starts SSL/TLS encryption for the current session.
  90 void starttls(struct client_handle *ch) {
  91         int retval, bits, alg_bits;
  92
  93         if (!ssl_ctx) {
  94                 return;
  95         }
  96
  97         // Check the modification time of the key and certificate -- reload if they changed
  98         update_key_and_cert_if_needed();
  99
 100         if (!(ch->ssl_handle = SSL_new(ssl_ctx))) {
 101                 syslog(LOG_WARNING, "SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 102                 return;
 103         }
 104         if (!(SSL_set_fd(ch->ssl_handle, ch->sock))) {
 105                 syslog(LOG_WARNING, "SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 106                 SSL_free(ch->ssl_handle);
 107                 return;
 108         }
 109         retval = SSL_accept(ch->ssl_handle);
 110         if (retval < 1) {
 111                 syslog(LOG_WARNING, "SSL_accept failed: %s", ERR_reason_error_string(ERR_get_error()));
 112         }
 113         else {
 114                 syslog(LOG_INFO, "SSL_accept success");
 115         }
 116         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(ch->ssl_handle), &alg_bits);
 117         syslog(LOG_INFO, "SSL/TLS using %s on %s (%d of %d bits)",
 118                SSL_CIPHER_get_name(SSL_get_current_cipher(ch->ssl_handle)),
 119                SSL_CIPHER_get_version(SSL_get_current_cipher(ch->ssl_handle)), bits, alg_bits);
 120         syslog(LOG_INFO, "SSL started");
 121 }
 122
 123
 124 // shuts down the TLS connection
 125 void endtls(struct client_handle *ch) {
 126         syslog(LOG_INFO, "Ending SSL/TLS");
 127         if (ch->ssl_handle != NULL) {
 128                 SSL_shutdown(ch->ssl_handle);
 129                 SSL_get_SSL_CTX(ch->ssl_handle);
 130                 SSL_free(ch->ssl_handle);
 131         }
 132         ch->ssl_handle = NULL;
 133 }
 134
 135
 136 // Send binary data to the client encrypted.
 137 int client_write_ssl(struct client_handle *ch, char *buf, int nbytes) {
 138         int retval;
 139         int nremain;
 140         char junk[1];
 141
 142         if (ch->ssl_handle == NULL)
 143                 return (-1);
 144
 145         nremain = nbytes;
 146         while (nremain > 0) {
 147                 if (SSL_want_write(ch->ssl_handle)) {
 148                         if ((SSL_read(ch->ssl_handle, junk, 0)) < 1) {
 149                                 syslog(LOG_WARNING, "SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 150                         }
 151                 }
 152                 retval = SSL_write(ch->ssl_handle, &buf[nbytes - nremain], nremain);
 153                 if (retval < 1) {
 154                         long errval;
 155
 156                         errval = SSL_get_error(ch->ssl_handle, retval);
 157                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 158                                 sleep(1);
 159                                 continue;
 160                         }
 161                         syslog(LOG_WARNING, "SSL_write: %s", ERR_reason_error_string(ERR_get_error()));
 162                         if (retval == -1) {
 163                                 syslog(LOG_WARNING, "errno is %d", errno);
 164                                 endtls(ch);
 165                         }
 166                         return -1;
 167                 }
 168                 nremain -= retval;
 169         }
 170         return 0;
 171 }
 172
 173
 174 // read data from the encrypted layer
 175 int client_read_ssl(struct client_handle *ch, char *buf, int nbytes) {
 176         int bytes_read = 0;
 177         int rlen = 0;
 178         char junk[1];
 179
 180         if (ch->ssl_handle == NULL)
 181                 return (-1);
 182
 183         while (bytes_read < nbytes) {
 184                 if (SSL_want_read(ch->ssl_handle)) {
 185                         if ((SSL_write(ch->ssl_handle, junk, 0)) < 1) {
 186                                 syslog(LOG_WARNING, "SSL_write in client_read");
 187                         }
 188                 }
 189                 rlen = SSL_read(ch->ssl_handle, &buf[bytes_read], nbytes - bytes_read);
 190                 if (rlen < 1) {
 191                         long errval;
 192                         errval = SSL_get_error(ch->ssl_handle, rlen);
 193                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 194                                 sleep(1);
 195                                 continue;
 196                         }
 197                         syslog(LOG_WARNING, "SSL_read error %ld", errval);
 198                         endtls(ch);
 199                         return (-1);
 200                 }
 201                 bytes_read += rlen;
 202         }
 203         return (bytes_read);
 204 }