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(SSLv23_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 the OpenSSL library
  67         SSL_load_error_strings();
  68         ERR_load_crypto_strings();
  69         OpenSSL_add_all_algorithms();
  70         SSL_library_init();
  71
  72         // Now try to bind to the key and certificate.
  73         bind_to_key_and_certificate();
  74 }
  75
  76
  77 // Check the modification time of the key and certificate -- reload if they changed
  78 void update_key_and_cert_if_needed(void) {
  79         static time_t previous_mtime = 0;
  80         struct stat keystat;
  81         struct stat certstat;
  82
  83         if (stat(key_file, &keystat) != 0) {
  84                 syslog(LOG_ERR, "%s: %s", key_file, strerror(errno));
  85                 return;
  86         }
  87         if (stat(cert_file, &certstat) != 0) {
  88                 syslog(LOG_ERR, "%s: %s", cert_file, strerror(errno));
  89                 return;
  90         }
  91
  92         if ((keystat.st_mtime + certstat.st_mtime) != previous_mtime) {
  93                 bind_to_key_and_certificate();
  94                 previous_mtime = keystat.st_mtime + certstat.st_mtime;
  95         }
  96 }
  97
  98
  99 // starts SSL/TLS encryption for the current session.
 100 void starttls(struct client_handle *ch) {
 101         int retval, bits, alg_bits;
 102
 103         if (!ssl_ctx) {
 104                 return;
 105         }
 106
 107         // Check the modification time of the key and certificate -- reload if they changed
 108         update_key_and_cert_if_needed();
 109
 110         if (!(ch->ssl_handle = SSL_new(ssl_ctx))) {
 111                 syslog(LOG_WARNING, "SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 112                 return;
 113         }
 114         if (!(SSL_set_fd(ch->ssl_handle, ch->sock))) {
 115                 syslog(LOG_WARNING, "SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 116                 SSL_free(ch->ssl_handle);
 117                 return;
 118         }
 119         retval = SSL_accept(ch->ssl_handle);
 120         if (retval < 1) {
 121                 syslog(LOG_WARNING, "SSL_accept failed: %s", ERR_reason_error_string(ERR_get_error()));
 122         }
 123         else {
 124                 syslog(LOG_INFO, "SSL_accept success");
 125         }
 126         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(ch->ssl_handle), &alg_bits);
 127         syslog(LOG_INFO, "SSL/TLS using %s on %s (%d of %d bits)",
 128                SSL_CIPHER_get_name(SSL_get_current_cipher(ch->ssl_handle)),
 129                SSL_CIPHER_get_version(SSL_get_current_cipher(ch->ssl_handle)), bits, alg_bits);
 130         syslog(LOG_INFO, "SSL started");
 131 }
 132
 133
 134 // shuts down the TLS connection
 135 void endtls(struct client_handle *ch) {
 136         syslog(LOG_INFO, "Ending SSL/TLS");
 137         if (ch->ssl_handle != NULL) {
 138                 SSL_shutdown(ch->ssl_handle);
 139                 SSL_get_SSL_CTX(ch->ssl_handle);
 140                 SSL_free(ch->ssl_handle);
 141         }
 142         ch->ssl_handle = NULL;
 143 }
 144
 145
 146 // Send binary data to the client encrypted.
 147 int client_write_ssl(struct client_handle *ch, char *buf, int nbytes) {
 148         int retval;
 149         int nremain;
 150         char junk[1];
 151
 152         if (ch->ssl_handle == NULL)
 153                 return (-1);
 154
 155         nremain = nbytes;
 156         while (nremain > 0) {
 157                 if (SSL_want_write(ch->ssl_handle)) {
 158                         if ((SSL_read(ch->ssl_handle, junk, 0)) < 1) {
 159                                 syslog(LOG_WARNING, "SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 160                         }
 161                 }
 162                 retval = SSL_write(ch->ssl_handle, &buf[nbytes - nremain], nremain);
 163                 if (retval < 1) {
 164                         long errval;
 165
 166                         errval = SSL_get_error(ch->ssl_handle, retval);
 167                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 168                                 sleep(1);
 169                                 continue;
 170                         }
 171                         syslog(LOG_WARNING, "SSL_write: %s", ERR_reason_error_string(ERR_get_error()));
 172                         if (retval == -1) {
 173                                 syslog(LOG_WARNING, "errno is %d", errno);
 174                                 endtls(ch);
 175                         }
 176                         return -1;
 177                 }
 178                 nremain -= retval;
 179         }
 180         return 0;
 181 }
 182
 183
 184 // read data from the encrypted layer
 185 int client_read_ssl(struct client_handle *ch, char *buf, int nbytes) {
 186         int bytes_read = 0;
 187         int rlen = 0;
 188         char junk[1];
 189
 190         if (ch->ssl_handle == NULL)
 191                 return (-1);
 192
 193         while (bytes_read < nbytes) {
 194                 if (SSL_want_read(ch->ssl_handle)) {
 195                         if ((SSL_write(ch->ssl_handle, junk, 0)) < 1) {
 196                                 syslog(LOG_WARNING, "SSL_write in client_read");
 197                         }
 198                 }
 199                 rlen = SSL_read(ch->ssl_handle, &buf[bytes_read], nbytes - bytes_read);
 200                 if (rlen < 1) {
 201                         long errval;
 202                         errval = SSL_get_error(ch->ssl_handle, rlen);
 203                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 204                                 sleep(1);
 205                                 continue;
 206                         }
 207                         syslog(LOG_WARNING, "SSL_read error %ld", errval);
 208                         endtls(ch);
 209                         return (-1);
 210                 }
 211                 bytes_read += rlen;
 212         }
 213         return (bytes_read);
 214 }