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         RSA *rsa = NULL;
  48         X509_REQ *req = NULL;
  49         X509 *cer = NULL;
  50         EVP_PKEY *pk = NULL;
  51         EVP_PKEY *req_pkey = NULL;
  52         X509_NAME *name = NULL;
  53         FILE *fp;
  54         char buf[SIZ];
  55         int rv = 0;
  56
  57         // Initialize SSL transport layer
  58         SSL_library_init();
  59         SSL_load_error_strings();
  60         if (!(ssl_ctx = SSL_CTX_new(SSLv23_server_method()))) {
  61                 syslog(LOG_WARNING, "SSL_CTX_new failed: %s", ERR_reason_error_string(ERR_get_error()));
  62                 return;
  63         }
  64
  65         syslog(LOG_INFO, "Requesting cipher list: %s", ssl_cipher_list);
  66         if (!(SSL_CTX_set_cipher_list(ssl_ctx, ssl_cipher_list))) {
  67                 syslog(LOG_WARNING, "SSL_CTX_set_cipher_list failed: %s", ERR_reason_error_string(ERR_get_error()));
  68                 return;
  69         }
  70
  71         // Now try to bind to the key and certificate.
  72         bind_to_key_and_certificate();
  73 }
  74
  75
  76 // Check the modification time of the key and certificate -- reload if they changed
  77 void update_key_and_cert_if_needed(void) {
  78         static time_t previous_mtime = 0;
  79         struct stat keystat;
  80         struct stat certstat;
  81
  82         if (stat(key_file, &keystat) != 0) {
  83                 syslog(LOG_ERR, "%s: %s", key_file, strerror(errno));
  84                 return;
  85         }
  86         if (stat(cert_file, &certstat) != 0) {
  87                 syslog(LOG_ERR, "%s: %s", cert_file, strerror(errno));
  88                 return;
  89         }
  90
  91         if ((keystat.st_mtime + certstat.st_mtime) != previous_mtime) {
  92                 bind_to_key_and_certificate();
  93                 previous_mtime = keystat.st_mtime + certstat.st_mtime;
  94         }
  95 }
  96
  97
  98 // starts SSL/TLS encryption for the current session.
  99 void starttls(struct client_handle *ch) {
 100         int retval, bits, alg_bits;
 101
 102         if (!ssl_ctx) {
 103                 return;
 104         }
 105
 106         // Check the modification time of the key and certificate -- reload if they changed
 107         update_key_and_cert_if_needed();
 108
 109         if (!(ch->ssl_handle = SSL_new(ssl_ctx))) {
 110                 syslog(LOG_WARNING, "SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 111                 return;
 112         }
 113         if (!(SSL_set_fd(ch->ssl_handle, ch->sock))) {
 114                 syslog(LOG_WARNING, "SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 115                 SSL_free(ch->ssl_handle);
 116                 return;
 117         }
 118         retval = SSL_accept(ch->ssl_handle);
 119         if (retval < 1) {
 120                 syslog(LOG_WARNING, "SSL_accept failed: %s", ERR_reason_error_string(ERR_get_error()));
 121         }
 122         else {
 123                 syslog(LOG_INFO, "SSL_accept success");
 124         }
 125         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(ch->ssl_handle), &alg_bits);
 126         syslog(LOG_INFO, "SSL/TLS using %s on %s (%d of %d bits)",
 127                SSL_CIPHER_get_name(SSL_get_current_cipher(ch->ssl_handle)),
 128                SSL_CIPHER_get_version(SSL_get_current_cipher(ch->ssl_handle)), bits, alg_bits);
 129         syslog(LOG_INFO, "SSL started");
 130 }
 131
 132
 133 // shuts down the TLS connection
 134 void endtls(struct client_handle *ch) {
 135         syslog(LOG_INFO, "Ending SSL/TLS");
 136         if (ch->ssl_handle != NULL) {
 137                 SSL_shutdown(ch->ssl_handle);
 138                 SSL_get_SSL_CTX(ch->ssl_handle);
 139                 SSL_free(ch->ssl_handle);
 140         }
 141         ch->ssl_handle = NULL;
 142 }
 143
 144
 145 // Send binary data to the client encrypted.
 146 int client_write_ssl(struct client_handle *ch, char *buf, int nbytes) {
 147         int retval;
 148         int nremain;
 149         char junk[1];
 150
 151         if (ch->ssl_handle == NULL)
 152                 return (-1);
 153
 154         nremain = nbytes;
 155         while (nremain > 0) {
 156                 if (SSL_want_write(ch->ssl_handle)) {
 157                         if ((SSL_read(ch->ssl_handle, junk, 0)) < 1) {
 158                                 syslog(LOG_WARNING, "SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 159                         }
 160                 }
 161                 retval = SSL_write(ch->ssl_handle, &buf[nbytes - nremain], nremain);
 162                 if (retval < 1) {
 163                         long errval;
 164
 165                         errval = SSL_get_error(ch->ssl_handle, retval);
 166                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 167                                 sleep(1);
 168                                 continue;
 169                         }
 170                         syslog(LOG_WARNING, "SSL_write: %s", ERR_reason_error_string(ERR_get_error()));
 171                         if (retval == -1) {
 172                                 syslog(LOG_WARNING, "errno is %d", errno);
 173                                 endtls(ch);
 174                         }
 175                         return -1;
 176                 }
 177                 nremain -= retval;
 178         }
 179         return 0;
 180 }
 181
 182
 183 // read data from the encrypted layer
 184 int client_read_ssl(struct client_handle *ch, char *buf, int nbytes) {
 185         int bytes_read = 0;
 186         int rlen = 0;
 187         char junk[1];
 188
 189         if (ch->ssl_handle == NULL)
 190                 return (-1);
 191
 192         while (bytes_read < nbytes) {
 193                 if (SSL_want_read(ch->ssl_handle)) {
 194                         if ((SSL_write(ch->ssl_handle, junk, 0)) < 1) {
 195                                 syslog(LOG_WARNING, "SSL_write in client_read");
 196                         }
 197                 }
 198                 rlen = SSL_read(ch->ssl_handle, &buf[bytes_read], nbytes - bytes_read);
 199                 if (rlen < 1) {
 200                         long errval;
 201                         errval = SSL_get_error(ch->ssl_handle, rlen);
 202                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 203                                 sleep(1);
 204                                 continue;
 205                         }
 206                         syslog(LOG_WARNING, "SSL_read error %ld", errval);
 207                         endtls(ch);
 208                         return (-1);
 209                 }
 210                 bytes_read += rlen;
 211         }
 212         return (bytes_read);
 213 }