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