webcit/crypto.c

   1 // Copyright (c) 1996-2022 by the citadel.org team
   2 //
   3 // This program is open source software.  You can redistribute it and/or
   4 // modify it under the terms of the GNU General Public License, version 3.
   5 //
   6 // This program is distributed in the hope that it will be useful,
   7 // but WITHOUT ANY WARRANTY; without even the implied warranty of
   8 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   9 // GNU General Public License for more details.
  10
  11 #include "sysdep.h"
  12 #ifdef HAVE_OPENSSL
  13
  14 #include "webcit.h"
  15 #include "webserver.h"
  16
  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 pthread_key_t ThreadSSL;        // Per-thread SSL context
  24
  25 void shutdown_ssl(void) {
  26         ERR_free_strings();
  27 }
  28
  29
  30 // Set the private key and certificate chain for the global SSL Context.
  31 // This is called during initialization, and can be called again later if the certificate changes.
  32 void bind_to_key_and_certificate(void) {
  33
  34         SSL_CTX *old_ctx, *new_ctx;
  35
  36         if (IsEmptyStr(key_file)) {
  37                 snprintf(key_file, sizeof key_file, "%s/keys/citadel.key", ctdl_dir);
  38         }
  39         if (IsEmptyStr(cert_file)) {
  40                 snprintf(cert_file, sizeof key_file, "%s/keys/citadel.cer", ctdl_dir);
  41         }
  42
  43         if (!(new_ctx = SSL_CTX_new(TLS_server_method()))) {
  44                 syslog(LOG_WARNING, "SSL_CTX_new failed: %s", ERR_reason_error_string(ERR_get_error()));
  45                 return;
  46         }
  47
  48         syslog(LOG_INFO, "Requesting cipher list: %s", ssl_cipher_list);
  49         if (!(SSL_CTX_set_cipher_list(new_ctx, ssl_cipher_list))) {
  50                 syslog(LOG_WARNING, "SSL_CTX_set_cipher_list failed: %s", ERR_reason_error_string(ERR_get_error()));
  51                 return;
  52         }
  53
  54         syslog(LOG_DEBUG, "crypto: [re]installing key \"%s\" and certificate \"%s\"", key_file, cert_file);
  55
  56         SSL_CTX_use_certificate_chain_file(new_ctx, cert_file);
  57         SSL_CTX_use_PrivateKey_file(new_ctx, key_file, SSL_FILETYPE_PEM);
  58
  59         if ( !SSL_CTX_check_private_key(new_ctx) ) {
  60                 syslog(LOG_WARNING, "crypto: cannot install certificate: %s", ERR_reason_error_string(ERR_get_error()));
  61         }
  62
  63         old_ctx = ssl_ctx;
  64         ssl_ctx = new_ctx;
  65         sleep(1);
  66         SSL_CTX_free(old_ctx);
  67 }
  68
  69
  70 // initialize ssl engine, load certs and initialize openssl internals
  71 void init_ssl(void) {
  72
  73         // Initialize SSL transport layer
  74         SSL_library_init();
  75         SSL_load_error_strings();
  76
  77         // Now try to bind to the key and certificate.
  78         bind_to_key_and_certificate();
  79 }
  80
  81
  82 // Check the modification time of the key and certificate -- reload if either one changed
  83 void update_key_and_cert_if_needed(void) {
  84         static time_t previous_mtime = 0;
  85         struct stat keystat;
  86         struct stat certstat;
  87
  88         if (stat(key_file, &keystat) != 0) {
  89                 syslog(LOG_ERR, "%s: %s", key_file, strerror(errno));
  90                 return;
  91         }
  92         if (stat(cert_file, &certstat) != 0) {
  93                 syslog(LOG_ERR, "%s: %s", cert_file, strerror(errno));
  94                 return;
  95         }
  96
  97         if ((keystat.st_mtime + certstat.st_mtime) != previous_mtime) {
  98                 bind_to_key_and_certificate();
  99                 previous_mtime = keystat.st_mtime + certstat.st_mtime;
 100         }
 101 }
 102
 103
 104 // starts SSL/TLS encryption for the current session.
 105 int starttls(int sock) {
 106         SSL *newssl;
 107         int retval, bits, alg_bits;
 108
 109         // Check the modification time of the key and certificate -- reload if they changed
 110         update_key_and_cert_if_needed();
 111
 112         // SSL is a thread-specific thing, I think.
 113         pthread_setspecific(ThreadSSL, NULL);
 114
 115         if (!ssl_ctx) {
 116                 return(1);
 117         }
 118         if (!(newssl = SSL_new(ssl_ctx))) {
 119                 syslog(LOG_WARNING, "SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 120                 return(2);
 121         }
 122         if (!(SSL_set_fd(newssl, sock))) {
 123                 syslog(LOG_WARNING, "SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 124                 SSL_free(newssl);
 125                 return(3);
 126         }
 127         retval = SSL_accept(newssl);
 128         if (retval < 1) {
 129                 // Can't notify the client of an error here; they will
 130                 // discover the problem at the SSL layer and should
 131                 // revert to unencrypted communications.
 132                 long errval;
 133                 const char *ssl_error_reason = NULL;
 134
 135                 errval = SSL_get_error(newssl, retval);
 136                 ssl_error_reason = ERR_reason_error_string(ERR_get_error());
 137                 if (ssl_error_reason == NULL) {
 138                         syslog(LOG_WARNING, "first SSL_accept failed: errval=%ld, retval=%d %s", errval, retval, strerror(errval));
 139                 }
 140                 else {
 141                         syslog(LOG_WARNING, "first SSL_accept failed: %s", ssl_error_reason);
 142                 }
 143         }
 144         else {
 145                 syslog(LOG_INFO, "SSL_accept success");
 146         }
 147         BIO_set_close(SSL_get_rbio(newssl), BIO_NOCLOSE);
 148         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(newssl), &alg_bits);
 149         syslog(LOG_INFO, "SSL/TLS using %s on %s (%d of %d bits)",
 150                 SSL_CIPHER_get_name(SSL_get_current_cipher(newssl)),
 151                 SSL_CIPHER_get_version(SSL_get_current_cipher(newssl)),
 152                 bits, alg_bits);
 153
 154         pthread_setspecific(ThreadSSL, newssl);
 155         syslog(LOG_INFO, "SSL started");
 156         return(0);
 157 }
 158
 159
 160 // shuts down the TLS connection
 161 //
 162 // WARNING:  This may make your session vulnerable to a known plaintext
 163 // attack in the current implmentation.
 164 void endtls(void) {
 165
 166         if (THREADSSL == NULL) {
 167                 return;
 168         }
 169
 170         syslog(LOG_INFO, "Ending SSL/TLS");
 171         SSL_shutdown(THREADSSL);
 172         SSL_get_SSL_CTX(THREADSSL);
 173         SSL_free(THREADSSL);
 174         pthread_setspecific(ThreadSSL, NULL);
 175 }
 176
 177
 178 // Send binary data to the client encrypted.
 179 int client_write_ssl(const StrBuf *Buf) {
 180         const char *buf;
 181         int retval;
 182         int nremain;
 183         long nbytes;
 184         char junk[1];
 185
 186         if (THREADSSL == NULL) return -1;
 187
 188         nbytes = nremain = StrLength(Buf);
 189         buf = ChrPtr(Buf);
 190
 191         while (nremain > 0) {
 192                 if (SSL_want_write(THREADSSL)) {
 193                         if ((SSL_read(THREADSSL, junk, 0)) < 1) {
 194                                 syslog(LOG_WARNING, "SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 195                         }
 196                 }
 197                 retval = SSL_write(THREADSSL, &buf[nbytes - nremain], nremain);
 198                 if (retval < 1) {
 199                         long errval;
 200
 201                         errval = SSL_get_error(THREADSSL, retval);
 202                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 203                                 sleeeeeeeeeep(1);
 204                                 continue;
 205                         }
 206                         syslog(LOG_WARNING, "SSL_write: %s", ERR_reason_error_string(ERR_get_error()));
 207                         if (retval == -1) {
 208                                 syslog(LOG_WARNING, "errno is %d\n", errno);
 209                         }
 210                         endtls();
 211                         return -1;
 212                 }
 213                 nremain -= retval;
 214         }
 215         return 0;
 216 }
 217
 218
 219 // read data from the encrypted layer.
 220 int client_read_sslbuffer(StrBuf *buf, int timeout) {
 221         char sbuf[16384];       // OpenSSL communicates in 16k blocks, so let's speak its native tongue.
 222         int rlen;
 223         char junk[1];
 224         SSL *pssl = THREADSSL;
 225
 226         if (pssl == NULL) return(-1);
 227
 228         while (1) {
 229                 if (SSL_want_read(pssl)) {
 230                         if ((SSL_write(pssl, junk, 0)) < 1) {
 231                                 syslog(LOG_WARNING, "SSL_write in client_read");
 232                         }
 233                 }
 234                 rlen = SSL_read(pssl, sbuf, sizeof(sbuf));
 235                 if (rlen < 1) {
 236                         long errval;
 237
 238                         errval = SSL_get_error(pssl, rlen);
 239                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 240                                 sleeeeeeeeeep(1);
 241                                 continue;
 242                         }
 243                         syslog(LOG_WARNING, "SSL_read in client_read: %s", ERR_reason_error_string(ERR_get_error()));
 244                         endtls();
 245                         return (-1);
 246                 }
 247                 StrBufAppendBufPlain(buf, sbuf, rlen, 0);
 248                 return rlen;
 249         }
 250         return (0);
 251 }
 252
 253 #endif                          /* HAVE_OPENSSL */