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
  26 // Set the private key and certificate chain for the global SSL Context.
  27 // This is called during initialization, and can be called again later if the certificate changes.
  28 void bind_to_key_and_certificate(void) {
  29
  30         SSL_CTX *old_ctx, *new_ctx;
  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         if (!(new_ctx = SSL_CTX_new(SSLv23_server_method()))) {
  40                 syslog(LOG_WARNING, "SSL_CTX_new failed: %s", ERR_reason_error_string(ERR_get_error()));
  41                 return;
  42         }
  43
  44         syslog(LOG_INFO, "Requesting cipher list: %s", ssl_cipher_list);
  45         if (!(SSL_CTX_set_cipher_list(new_ctx, ssl_cipher_list))) {
  46                 syslog(LOG_WARNING, "SSL_CTX_set_cipher_list failed: %s", ERR_reason_error_string(ERR_get_error()));
  47                 return;
  48         }
  49
  50         syslog(LOG_DEBUG, "crypto: [re]installing key \"%s\" and certificate \"%s\"", key_file, cert_file);
  51
  52         SSL_CTX_use_certificate_chain_file(new_ctx, cert_file);
  53         SSL_CTX_use_PrivateKey_file(new_ctx, key_file, SSL_FILETYPE_PEM);
  54
  55         if ( !SSL_CTX_check_private_key(new_ctx) ) {
  56                 syslog(LOG_WARNING, "crypto: cannot install certificate: %s", ERR_reason_error_string(ERR_get_error()));
  57         }
  58
  59         old_ctx = ssl_ctx;
  60         ssl_ctx = new_ctx;
  61         sleep(1);
  62         SSL_CTX_free(old_ctx);
  63 }
  64
  65
  66 // initialize ssl engine, load certs and initialize openssl internals
  67 void init_ssl(void) {
  68
  69         // Initialize the OpenSSL library
  70         SSL_load_error_strings();
  71         ERR_load_crypto_strings();
  72         OpenSSL_add_all_algorithms();
  73         SSL_library_init();
  74
  75         // Now try to bind to the key and certificate.
  76         bind_to_key_and_certificate();
  77 }
  78
  79
  80 // Check the modification time of the key and certificate -- reload if either one changed
  81 void update_key_and_cert_if_needed(void) {
  82         static time_t previous_mtime = 0;
  83         struct stat keystat;
  84         struct stat certstat;
  85
  86         if (stat(key_file, &keystat) != 0) {
  87                 syslog(LOG_ERR, "%s: %s", key_file, strerror(errno));
  88                 return;
  89         }
  90         if (stat(cert_file, &certstat) != 0) {
  91                 syslog(LOG_ERR, "%s: %s", cert_file, strerror(errno));
  92                 return;
  93         }
  94
  95         if ((keystat.st_mtime + certstat.st_mtime) != previous_mtime) {
  96                 bind_to_key_and_certificate();
  97                 previous_mtime = keystat.st_mtime + certstat.st_mtime;
  98         }
  99 }
 100
 101
 102 // starts SSL/TLS encryption for the current session.
 103 int starttls(int sock) {
 104         SSL *newssl;
 105         int retval, bits, alg_bits;
 106
 107         // Check the modification time of the key and certificate -- reload if they changed
 108         update_key_and_cert_if_needed();
 109
 110         // SSL is a thread-specific thing, I think.
 111         pthread_setspecific(ThreadSSL, NULL);
 112
 113         if (!ssl_ctx) {
 114                 return(1);
 115         }
 116         if (!(newssl = SSL_new(ssl_ctx))) {
 117                 syslog(LOG_WARNING, "SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 118                 return(2);
 119         }
 120         if (!(SSL_set_fd(newssl, sock))) {
 121                 syslog(LOG_WARNING, "SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 122                 SSL_free(newssl);
 123                 return(3);
 124         }
 125         retval = SSL_accept(newssl);
 126         if (retval < 1) {
 127                 // Can't notify the client of an error here; they will
 128                 // discover the problem at the SSL layer and should
 129                 // revert to unencrypted communications.
 130                 long errval;
 131                 const char *ssl_error_reason = NULL;
 132
 133                 errval = SSL_get_error(newssl, retval);
 134                 ssl_error_reason = ERR_reason_error_string(ERR_get_error());
 135                 if (ssl_error_reason == NULL) {
 136                         syslog(LOG_WARNING, "first SSL_accept failed: errval=%ld, retval=%d %s", errval, retval, strerror(errval));
 137                 }
 138                 else {
 139                         syslog(LOG_WARNING, "first SSL_accept failed: %s", ssl_error_reason);
 140                 }
 141         }
 142         else {
 143                 syslog(LOG_INFO, "SSL_accept success");
 144         }
 145         BIO_set_close(SSL_get_rbio(newssl), BIO_NOCLOSE);
 146         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(newssl), &alg_bits);
 147         syslog(LOG_INFO, "SSL/TLS using %s on %s (%d of %d bits)",
 148                 SSL_CIPHER_get_name(SSL_get_current_cipher(newssl)),
 149                 SSL_CIPHER_get_version(SSL_get_current_cipher(newssl)),
 150                 bits, alg_bits);
 151
 152         pthread_setspecific(ThreadSSL, newssl);
 153         syslog(LOG_INFO, "SSL started");
 154         return(0);
 155 }
 156
 157
 158 // shuts down the TLS connection
 159 //
 160 // WARNING:  This may make your session vulnerable to a known plaintext
 161 // attack in the current implmentation.
 162 void endtls(void) {
 163
 164         if (THREADSSL == NULL) {
 165                 return;
 166         }
 167
 168         syslog(LOG_INFO, "Ending SSL/TLS");
 169         SSL_shutdown(THREADSSL);
 170         SSL_get_SSL_CTX(THREADSSL);
 171         SSL_free(THREADSSL);
 172         pthread_setspecific(ThreadSSL, NULL);
 173 }
 174
 175
 176 // Send binary data to the client encrypted.
 177 int client_write_ssl(const StrBuf *Buf) {
 178         const char *buf;
 179         int retval;
 180         int nremain;
 181         long nbytes;
 182         char junk[1];
 183
 184         if (THREADSSL == NULL) return -1;
 185
 186         nbytes = nremain = StrLength(Buf);
 187         buf = ChrPtr(Buf);
 188
 189         while (nremain > 0) {
 190                 if (SSL_want_write(THREADSSL)) {
 191                         if ((SSL_read(THREADSSL, junk, 0)) < 1) {
 192                                 syslog(LOG_WARNING, "SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 193                         }
 194                 }
 195                 retval = SSL_write(THREADSSL, &buf[nbytes - nremain], nremain);
 196                 if (retval < 1) {
 197                         long errval;
 198
 199                         errval = SSL_get_error(THREADSSL, retval);
 200                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 201                                 sleeeeeeeeeep(1);
 202                                 continue;
 203                         }
 204                         syslog(LOG_WARNING, "SSL_write: %s", ERR_reason_error_string(ERR_get_error()));
 205                         if (retval == -1) {
 206                                 syslog(LOG_WARNING, "errno is %d\n", errno);
 207                         }
 208                         endtls();
 209                         return -1;
 210                 }
 211                 nremain -= retval;
 212         }
 213         return 0;
 214 }
 215
 216
 217 // read data from the encrypted layer.
 218 int client_read_sslbuffer(StrBuf *buf, int timeout) {
 219         char sbuf[16384];       // OpenSSL communicates in 16k blocks, so let's speak its native tongue.
 220         int rlen;
 221         char junk[1];
 222         SSL *pssl = THREADSSL;
 223
 224         if (pssl == NULL) return(-1);
 225
 226         while (1) {
 227                 if (SSL_want_read(pssl)) {
 228                         if ((SSL_write(pssl, junk, 0)) < 1) {
 229                                 syslog(LOG_WARNING, "SSL_write in client_read");
 230                         }
 231                 }
 232                 rlen = SSL_read(pssl, sbuf, sizeof(sbuf));
 233                 if (rlen < 1) {
 234                         long errval;
 235
 236                         errval = SSL_get_error(pssl, rlen);
 237                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 238                                 sleeeeeeeeeep(1);
 239                                 continue;
 240                         }
 241                         syslog(LOG_WARNING, "SSL_read in client_read: %s", ERR_reason_error_string(ERR_get_error()));
 242                         endtls();
 243                         return (-1);
 244                 }
 245                 StrBufAppendBufPlain(buf, sbuf, rlen, 0);
 246                 return rlen;
 247         }
 248         return (0);
 249 }
 250
 251 #endif                          /* HAVE_OPENSSL */