webcit-ng/server/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.  Use, duplication, or
   7 // disclosure are subject to the GNU General Public License v3.
   8
   9 #include "webcit.h"
  10
  11 SSL_CTX *ssl_ctx;               // global SSL context
  12 char key_file[PATH_MAX] = "";
  13 char cert_file[PATH_MAX] = "";
  14 char *ssl_cipher_list = DEFAULT_SSL_CIPHER_LIST;
  15
  16
  17 // Set the private key and certificate chain for the global SSL Context.
  18 // This is called during initialization, and can be called again later if the certificate changes.
  19 void bind_to_key_and_certificate(void) {
  20         SSL_CTX *old_ctx, *new_ctx;
  21
  22         if (!(new_ctx = SSL_CTX_new(SSLv23_server_method()))) {
  23                 syslog(LOG_WARNING, "SSL_CTX_new failed: %s", ERR_reason_error_string(ERR_get_error()));
  24                 return;
  25         }
  26
  27         syslog(LOG_INFO, "Requesting cipher list: %s", ssl_cipher_list);
  28         if (!(SSL_CTX_set_cipher_list(new_ctx, ssl_cipher_list))) {
  29                 syslog(LOG_WARNING, "SSL_CTX_set_cipher_list failed: %s", ERR_reason_error_string(ERR_get_error()));
  30                 return;
  31         }
  32
  33         if (IsEmptyStr(key_file)) {
  34                 snprintf(key_file, sizeof key_file, "%s/keys/citadel.key", ctdl_dir);
  35         }
  36         if (IsEmptyStr(cert_file)) {
  37                 snprintf(cert_file, sizeof key_file, "%s/keys/citadel.cer", ctdl_dir);
  38         }
  39
  40         syslog(LOG_DEBUG, "crypto: [re]installing key \"%s\" and certificate \"%s\"", key_file, cert_file);
  41
  42         SSL_CTX_use_certificate_chain_file(new_ctx, cert_file);
  43         SSL_CTX_use_PrivateKey_file(new_ctx, key_file, SSL_FILETYPE_PEM);
  44
  45         if ( !SSL_CTX_check_private_key(new_ctx) ) {
  46                 syslog(LOG_WARNING, "crypto: cannot install certificate: %s", ERR_reason_error_string(ERR_get_error()));
  47         }
  48
  49         old_ctx = ssl_ctx;
  50         ssl_ctx = new_ctx;
  51         sleep(1);
  52         SSL_CTX_free(old_ctx);
  53 }
  54
  55
  56 // Initialize ssl engine, load certs and initialize openssl internals
  57 void init_ssl(void) {
  58
  59         // Initialize the OpenSSL library
  60         SSL_load_error_strings();
  61         ERR_load_crypto_strings();
  62         OpenSSL_add_all_algorithms();
  63         SSL_library_init();
  64
  65         // Now try to bind to the key and certificate.
  66         bind_to_key_and_certificate();
  67 }
  68
  69
  70 // Check the modification time of the key and certificate -- reload if they changed
  71 void update_key_and_cert_if_needed(void) {
  72         static time_t previous_mtime = 0;
  73         struct stat keystat;
  74         struct stat certstat;
  75
  76         if (stat(key_file, &keystat) != 0) {
  77                 syslog(LOG_ERR, "%s: %s", key_file, strerror(errno));
  78                 return;
  79         }
  80         if (stat(cert_file, &certstat) != 0) {
  81                 syslog(LOG_ERR, "%s: %s", cert_file, strerror(errno));
  82                 return;
  83         }
  84
  85         if ((keystat.st_mtime + certstat.st_mtime) != previous_mtime) {
  86                 bind_to_key_and_certificate();
  87                 previous_mtime = keystat.st_mtime + certstat.st_mtime;
  88         }
  89 }
  90
  91
  92 // starts SSL/TLS encryption for the current session.
  93 void starttls(struct client_handle *ch) {
  94         int retval, bits, alg_bits;
  95
  96         if (!ssl_ctx) {
  97                 return;
  98         }
  99
 100         // Check the modification time of the key and certificate -- reload if they changed
 101         update_key_and_cert_if_needed();
 102
 103         if (!(ch->ssl_handle = SSL_new(ssl_ctx))) {
 104                 syslog(LOG_WARNING, "SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 105                 return;
 106         }
 107         if (!(SSL_set_fd(ch->ssl_handle, ch->sock))) {
 108                 syslog(LOG_WARNING, "SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 109                 SSL_free(ch->ssl_handle);
 110                 return;
 111         }
 112         retval = SSL_accept(ch->ssl_handle);
 113         if (retval < 1) {
 114                 syslog(LOG_WARNING, "SSL_accept failed: %s", ERR_reason_error_string(ERR_get_error()));
 115         }
 116         else {
 117                 syslog(LOG_INFO, "SSL_accept success");
 118         }
 119         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(ch->ssl_handle), &alg_bits);
 120         syslog(LOG_INFO, "SSL/TLS using %s on %s (%d of %d bits)",
 121                SSL_CIPHER_get_name(SSL_get_current_cipher(ch->ssl_handle)),
 122                SSL_CIPHER_get_version(SSL_get_current_cipher(ch->ssl_handle)), bits, alg_bits);
 123         syslog(LOG_INFO, "SSL started");
 124 }
 125
 126
 127 // shuts down the TLS connection
 128 void endtls(struct client_handle *ch) {
 129         syslog(LOG_INFO, "Ending SSL/TLS");
 130         if (ch->ssl_handle != NULL) {
 131                 SSL_shutdown(ch->ssl_handle);
 132                 SSL_get_SSL_CTX(ch->ssl_handle);
 133                 SSL_free(ch->ssl_handle);
 134         }
 135         ch->ssl_handle = NULL;
 136 }
 137
 138
 139 // Send binary data to the client encrypted.
 140 int client_write_ssl(struct client_handle *ch, char *buf, int nbytes) {
 141         int retval;
 142         int nremain;
 143         char junk[1];
 144
 145         if (ch->ssl_handle == NULL)
 146                 return (-1);
 147
 148         nremain = nbytes;
 149         while (nremain > 0) {
 150                 if (SSL_want_write(ch->ssl_handle)) {
 151                         if ((SSL_read(ch->ssl_handle, junk, 0)) < 1) {
 152                                 syslog(LOG_WARNING, "SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 153                         }
 154                 }
 155                 retval = SSL_write(ch->ssl_handle, &buf[nbytes - nremain], nremain);
 156                 if (retval < 1) {
 157                         long errval;
 158
 159                         errval = SSL_get_error(ch->ssl_handle, retval);
 160                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 161                                 sleep(1);
 162                                 continue;
 163                         }
 164                         syslog(LOG_WARNING, "SSL_write: %s", ERR_reason_error_string(ERR_get_error()));
 165                         if (retval == -1) {
 166                                 syslog(LOG_WARNING, "errno is %d", errno);
 167                                 endtls(ch);
 168                         }
 169                         return -1;
 170                 }
 171                 nremain -= retval;
 172         }
 173         return 0;
 174 }
 175
 176
 177 // read data from the encrypted layer
 178 int client_read_ssl(struct client_handle *ch, char *buf, int nbytes) {
 179         int bytes_read = 0;
 180         int rlen = 0;
 181         char junk[1];
 182
 183         if (ch->ssl_handle == NULL)
 184                 return (-1);
 185
 186         while (bytes_read < nbytes) {
 187                 if (SSL_want_read(ch->ssl_handle)) {
 188                         if ((SSL_write(ch->ssl_handle, junk, 0)) < 1) {
 189                                 syslog(LOG_WARNING, "SSL_write in client_read");
 190                         }
 191                 }
 192                 rlen = SSL_read(ch->ssl_handle, &buf[bytes_read], nbytes - bytes_read);
 193                 if (rlen < 1) {
 194                         long errval;
 195                         errval = SSL_get_error(ch->ssl_handle, rlen);
 196                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 197                                 sleep(1);
 198                                 continue;
 199                         }
 200                         syslog(LOG_WARNING, "SSL_read error %ld", errval);
 201                         endtls(ch);
 202                         return (-1);
 203                 }
 204                 bytes_read += rlen;
 205         }
 206         return (bytes_read);
 207 }