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         SSL_CTX *old_ctx, *new_ctx;
  28
  29         if (!(new_ctx = SSL_CTX_new(TLS_server_method()))) {
  30                 syslog(LOG_WARNING, "SSL_CTX_new failed: %s", ERR_reason_error_string(ERR_get_error()));
  31                 return;
  32         }
  33
  34         syslog(LOG_INFO, "Requesting cipher list: %s", ssl_cipher_list);
  35         if (!(SSL_CTX_set_cipher_list(new_ctx, ssl_cipher_list))) {
  36                 syslog(LOG_WARNING, "SSL_CTX_set_cipher_list failed: %s", ERR_reason_error_string(ERR_get_error()));
  37                 return;
  38         }
  39
  40         if (IsEmptyStr(key_file)) {
  41                 snprintf(key_file, sizeof key_file, "%s/keys/citadel.key", ctdl_dir);
  42         }
  43         if (IsEmptyStr(cert_file)) {
  44                 snprintf(cert_file, sizeof key_file, "%s/keys/citadel.cer", ctdl_dir);
  45         }
  46
  47         syslog(LOG_DEBUG, "crypto: [re]installing key \"%s\" and certificate \"%s\"", key_file, cert_file);
  48
  49         SSL_CTX_use_certificate_chain_file(new_ctx, cert_file);
  50         SSL_CTX_use_PrivateKey_file(new_ctx, key_file, SSL_FILETYPE_PEM);
  51
  52         if ( !SSL_CTX_check_private_key(new_ctx) ) {
  53                 syslog(LOG_WARNING, "crypto: cannot install certificate: %s", ERR_reason_error_string(ERR_get_error()));
  54         }
  55
  56         old_ctx = ssl_ctx;
  57         ssl_ctx = new_ctx;
  58         sleep(1);
  59         SSL_CTX_free(old_ctx);
  60 }
  61
  62
  63 // Initialize ssl engine, load certs and initialize openssl internals
  64 void init_ssl(void) {
  65
  66         // Initialize SSL transport layer
  67         SSL_library_init();
  68         SSL_load_error_strings();
  69
  70         // Now try to bind to the key and certificate.
  71         bind_to_key_and_certificate();
  72 }
  73
  74
  75 // Check the modification time of the key and certificate -- reload if they changed
  76 void update_key_and_cert_if_needed(void) {
  77         static time_t previous_mtime = 0;
  78         struct stat keystat;
  79         struct stat certstat;
  80
  81         if (stat(key_file, &keystat) != 0) {
  82                 syslog(LOG_ERR, "%s: %s", key_file, strerror(errno));
  83                 return;
  84         }
  85         if (stat(cert_file, &certstat) != 0) {
  86                 syslog(LOG_ERR, "%s: %s", cert_file, strerror(errno));
  87                 return;
  88         }
  89
  90         if ((keystat.st_mtime + certstat.st_mtime) != previous_mtime) {
  91                 bind_to_key_and_certificate();
  92                 previous_mtime = keystat.st_mtime + certstat.st_mtime;
  93         }
  94 }
  95
  96
  97 // starts SSL/TLS encryption for the current session.
  98 void starttls(struct client_handle *ch) {
  99         int retval, bits, alg_bits;
 100
 101         if (!ssl_ctx) {
 102                 return;
 103         }
 104
 105         // Check the modification time of the key and certificate -- reload if they changed
 106         update_key_and_cert_if_needed();
 107
 108         if (!(ch->ssl_handle = SSL_new(ssl_ctx))) {
 109                 syslog(LOG_WARNING, "SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 110                 return;
 111         }
 112         if (!(SSL_set_fd(ch->ssl_handle, ch->sock))) {
 113                 syslog(LOG_WARNING, "SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 114                 SSL_free(ch->ssl_handle);
 115                 return;
 116         }
 117         retval = SSL_accept(ch->ssl_handle);
 118         if (retval < 1) {
 119                 syslog(LOG_WARNING, "SSL_accept failed: %s", ERR_reason_error_string(ERR_get_error()));
 120         }
 121         else {
 122                 syslog(LOG_INFO, "SSL_accept success");
 123         }
 124         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(ch->ssl_handle), &alg_bits);
 125         syslog(LOG_INFO, "SSL/TLS using %s on %s (%d of %d bits)",
 126                SSL_CIPHER_get_name(SSL_get_current_cipher(ch->ssl_handle)),
 127                SSL_CIPHER_get_version(SSL_get_current_cipher(ch->ssl_handle)), bits, alg_bits);
 128         syslog(LOG_INFO, "SSL started");
 129 }
 130
 131
 132 // shuts down the TLS connection
 133 void endtls(struct client_handle *ch) {
 134         syslog(LOG_INFO, "Ending SSL/TLS");
 135         if (ch->ssl_handle != NULL) {
 136                 SSL_shutdown(ch->ssl_handle);
 137                 SSL_get_SSL_CTX(ch->ssl_handle);
 138                 SSL_free(ch->ssl_handle);
 139         }
 140         ch->ssl_handle = NULL;
 141 }
 142
 143
 144 // Send binary data to the client encrypted.
 145 int client_write_ssl(struct client_handle *ch, char *buf, int nbytes) {
 146         int retval;
 147         int nremain;
 148         char junk[1];
 149
 150         if (ch->ssl_handle == NULL)
 151                 return (-1);
 152
 153         nremain = nbytes;
 154         while (nremain > 0) {
 155                 if (SSL_want_write(ch->ssl_handle)) {
 156                         if ((SSL_read(ch->ssl_handle, junk, 0)) < 1) {
 157                                 syslog(LOG_WARNING, "SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 158                         }
 159                 }
 160                 retval = SSL_write(ch->ssl_handle, &buf[nbytes - nremain], nremain);
 161                 if (retval < 1) {
 162                         long errval;
 163
 164                         errval = SSL_get_error(ch->ssl_handle, retval);
 165                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 166                                 sleep(1);
 167                                 continue;
 168                         }
 169                         syslog(LOG_WARNING, "SSL_write: %s", ERR_reason_error_string(ERR_get_error()));
 170                         if (retval == -1) {
 171                                 syslog(LOG_WARNING, "errno is %d", errno);
 172                                 endtls(ch);
 173                         }
 174                         return -1;
 175                 }
 176                 nremain -= retval;
 177         }
 178         return 0;
 179 }
 180
 181
 182 // read data from the encrypted layer
 183 int client_read_ssl(struct client_handle *ch, char *buf, int nbytes) {
 184         int bytes_read = 0;
 185         int rlen = 0;
 186         char junk[1];
 187
 188         if (ch->ssl_handle == NULL)
 189                 return (-1);
 190
 191         while (bytes_read < nbytes) {
 192                 if (SSL_want_read(ch->ssl_handle)) {
 193                         if ((SSL_write(ch->ssl_handle, junk, 0)) < 1) {
 194                                 syslog(LOG_WARNING, "SSL_write in client_read");
 195                         }
 196                 }
 197                 rlen = SSL_read(ch->ssl_handle, &buf[bytes_read], nbytes - bytes_read);
 198                 if (rlen < 1) {
 199                         long errval;
 200                         errval = SSL_get_error(ch->ssl_handle, rlen);
 201                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 202                                 sleep(1);
 203                                 continue;
 204                         }
 205                         syslog(LOG_WARNING, "SSL_read error %ld", errval);
 206                         endtls(ch);
 207                         return (-1);
 208                 }
 209                 bytes_read += rlen;
 210         }
 211         return (bytes_read);
 212 }