Casey Marshall wrote: I've been hacking together a way to use rsync with OpenSSL, and have attached my current patch against a recent CVS tree. The details of this implementation are: 1. The SSL code is added as a "layer" that is forked into its own process. 2. An SSL connection is established by the client issuing the command: #starttls And, if the daemon allows SSL, it replies with @RSYNCD: starttls At which point both sides begin negotiating the SSL connection. Servers that can't or don't want to use SSL just treat it as a normal unknown command. 3. The SSL code is meant to be unobtrusive, and when this patch is applied the program may still be built with no SSL code. 4. There are a number of details not implemented. All warnings apply; I don't do C programming all that often, so I can't say if I've left any cleanup/compatibility errors in the code. To use this patch, run these commands for a successful build: patch -p1 +#include +#endif + struct hashtable { void *nodes; int32 size, entries; diff --git a/ssl.c b/ssl.c new file mode 100644 --- /dev/null +++ b/ssl.c @@ -0,0 +1,369 @@ +/* -*- c-file-style: "linux" -*- + * ssl.c: operations for negotiating SSL rsync connections. + * + * Copyright (C) 2003 Casey Marshall + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#include "rsync.h" + +#ifdef HAVE_SYS_SELECT_H +#include +#else +#include +#include +#include +#endif +#include + +#define BUF_SIZE 1024 + +extern int am_daemon; +extern int am_server; + +extern char *ssl_cert_path; +extern char *ssl_key_path; +extern char *ssl_key_passwd; +extern char *ssl_ca_path; + +static SSL_CTX *ssl_ctx; +static SSL *ssl; +static int tls_read[2] = { -1, -1 }; +static int tls_write[2] = { -1, -1 }; +static int ssl_running; +static int ssl_pid = -1; + +#ifdef HAVE_SIGACTION +static struct sigaction sigact; +#endif + +/** + * A non-interactive callback to be passed to SSL_CTX_set_default_password_cb, + * which merely copies the value of ssl_key_passwd into buf. This is + * used for when the private key password is supplied via an option. + */ +static int default_password_cb(char *buf, int n, UNUSED(int f), UNUSED(void *u)) +{ + if (ssl_key_passwd == NULL || n < (int)strlen(ssl_key_passwd)) + return 0; + strncpy(buf, ssl_key_passwd, n-1); + return strlen(ssl_key_passwd); +} + +/** + * If verbose, this method traces the status of the SSL handshake. + */ +static void info_callback(const SSL *ssl, int cb, int val) +{ + char buf[128]; + char *cbs; + + switch (cb) { + case SSL_CB_LOOP: + cbs = "SSL_CB_LOOP"; + break; + case SSL_CB_EXIT: + cbs = "SSL_CB_EXIT"; + break; + case SSL_CB_READ: + cbs = "SSL_CB_READ"; + break; + case SSL_CB_WRITE: + cbs = "SSL_CB_WRITE"; + break; + case SSL_CB_ALERT: + cbs = "SSL_CB_ALERT"; + break; + case SSL_CB_READ_ALERT: + cbs = "SSL_CB_READ_ALERT"; + break; + case SSL_CB_WRITE_ALERT: + cbs = "SSL_CB_WRITE_ALERT"; + break; + case SSL_CB_ACCEPT_LOOP: + cbs = "SSL_CB_ACCEPT_LOOP"; + break; + case SSL_CB_ACCEPT_EXIT: + cbs = "SSL_CB_ACCEPT_EXIT"; + break; + case SSL_CB_CONNECT_LOOP: + cbs = "SSL_CB_CONNECT_LOOP"; + break; + case SSL_CB_CONNECT_EXIT: + cbs = "SSL_CB_CONNECT_EXIT"; + break; + case SSL_CB_HANDSHAKE_START: + cbs = "SSL_CB_HANDSHAKE_START"; + break; + case SSL_CB_HANDSHAKE_DONE: + cbs = "SSL_CB_HANDSHAKE_DONE"; + break; + default: + snprintf(buf, sizeof buf, "??? (%d)", cb); + cbs = buf; + break; + } + if (DEBUG_GTE(CONNECT, 1)) { + rprintf(FLOG, "SSL: info_callback(%p,%s,%d)\n", ssl, cbs, val); + if (cb == SSL_CB_HANDSHAKE_DONE) { + SSL_CIPHER_description(SSL_get_current_cipher((SSL*)ssl), + buf, sizeof buf); + rprintf(FLOG, "SSL: cipher: %s", buf); + } + } +} + +/** + * Initializes the SSL context for TLSv1 connections; returns zero on + * success. + */ +int init_tls(void) +{ + if (ssl_ctx) + return 0; + SSL_library_init(); + SSL_load_error_strings(); + ssl_ctx = SSL_CTX_new(TLSv1_method()); + if (!ssl_ctx) + return 1; + SSL_CTX_set_info_callback(ssl_ctx, info_callback); + + /* Sets the certificate sent to the other party. */ + if (ssl_cert_path != NULL + && SSL_CTX_use_certificate_file(ssl_ctx, ssl_cert_path, + SSL_FILETYPE_PEM) != 1) + return 1; + /* Set up the simple non-interactive callback if the password + * was supplied on the command line. */ + if (ssl_key_passwd != NULL) + SSL_CTX_set_default_passwd_cb(ssl_ctx, default_password_cb); + /* Sets the private key that matches the public certificate. */ + if (ssl_key_path != NULL) { + if (SSL_CTX_use_PrivateKey_file(ssl_ctx, ssl_key_path, + SSL_FILETYPE_PEM) != 1) + return 1; + if (SSL_CTX_check_private_key(ssl_ctx) != 1) + return 1; + } + if (ssl_ca_path != NULL + && !SSL_CTX_load_verify_locations(ssl_ctx, ssl_ca_path, NULL)) + return 1; + + return 0; +} + +/** + * Returns the error string for the current SSL error, if any. + */ +char *get_ssl_error(void) +{ + return ERR_error_string(ERR_get_error(), NULL); +} + +/** + * Returns the input file descriptor for the SSL connection. + */ +int get_tls_rfd(void) +{ + return tls_read[0]; +} + +/** + * Returns the output file descriptor for the SSL connection. + */ +int get_tls_wfd(void) +{ + return tls_write[1]; +} + +/** + * Signal handler that ends the SSL connection. + */ +static RETSIGTYPE tls_sigusr1(int UNUSED(val)) +{ + if (ssl) { + SSL_shutdown(ssl); + SSL_free(ssl); + ssl = NULL; + } + ssl_running = 0; +} + +/** + * Negotiates the TLS connection, creates a socket pair for communicating + * with the rsync process, then forks into a new process that will handle + * the communication. + * + * 0 is returned on success. + */ +int start_tls(int f_in, int f_out) +{ + int tls_fd; + int n = 0, r; + unsigned char buf1[BUF_SIZE], buf2[BUF_SIZE]; + int avail1 = 0, avail2 = 0, write1 = 0, write2 = 0; + fd_set rd, wd; + + if (fd_pair(tls_read)) + return 1; + if (fd_pair(tls_write)) + return 1; + + set_blocking(tls_read[0]); + set_blocking(tls_read[1]); + set_blocking(tls_write[0]); + set_blocking(tls_write[1]); + set_blocking(f_in); + set_blocking(f_out); + + ssl_pid = do_fork(); + if (ssl_pid < 0) + return -1; + if (ssl_pid != 0) { + close(tls_write[0]); + close(tls_read[1]); + return 0; + } + + SIGACTION(SIGUSR1, tls_sigusr1); + ssl = SSL_new(ssl_ctx); + if (!ssl) + goto closed; + if (am_daemon || am_server) + SSL_set_accept_state(ssl); + else + SSL_set_connect_state(ssl); + SSL_set_rfd(ssl, f_in); + SSL_set_wfd(ssl, f_out); + + tls_fd = SSL_get_fd(ssl); + n = tls_write[0]; + n = MAX(tls_read[1], n); + n = MAX(tls_fd, n) + 1; + + ssl_running = 1; + while (ssl_running) { + FD_ZERO(&rd); + FD_ZERO(&wd); + FD_SET(tls_write[0], &rd); + FD_SET(tls_read[1], &wd); + FD_SET(tls_fd, &rd); + FD_SET(tls_fd, &wd); + + r = select(n, &rd, &wd, NULL, NULL); + + if (r == -1 && errno == EINTR) + continue; + if (FD_ISSET(tls_write[0], &rd)) { + r = read(tls_write[0], buf1+avail1, BUF_SIZE-avail1); + if (r >= 0) + avail1 += r; + else { + rprintf(FERROR, "pipe read error: %s\n", + strerror(errno)); + break; + } + } + if (FD_ISSET(tls_fd, &rd)) { + r = SSL_read(ssl, buf2+avail2, BUF_SIZE-avail2); + if (r > 0) + avail2 += r; + else { + switch (SSL_get_error(ssl, r)) { + case SSL_ERROR_ZERO_RETURN: + goto closed; + case SSL_ERROR_WANT_READ: + case SSL_ERROR_WANT_WRITE: + break; + case SSL_ERROR_SYSCALL: + if (r == 0) + rprintf(FERROR, "SSL spurious EOF\n"); + else + rprintf(FERROR, "SSL I/O error: %s\n", + strerror(errno)); + goto closed; + case SSL_ERROR_SSL: + rprintf(FERROR, "SSL: %s\n", + ERR_error_string(ERR_get_error(), NULL)); + goto closed; + default: + rprintf(FERROR, "unexpected ssl error %d\n", r); + goto closed; + } + } + } + if (FD_ISSET(tls_read[1], &wd) && write2 < avail2) { + r = write(tls_read[1], buf2+write2, avail2-write2); + if (r >= 0) + write2 += r; + else { + rprintf(FERROR, "pipe write error: %s\n", + strerror(errno)); + break; + } + } + if (FD_ISSET(tls_fd, &wd) && write1 < avail1) { + r = SSL_write(ssl, buf1+write1, avail1-write1); + if (r > 0) + write1 += r; + else { + switch (SSL_get_error(ssl, r)) { + case SSL_ERROR_ZERO_RETURN: + goto closed; + case SSL_ERROR_WANT_READ: + case SSL_ERROR_WANT_WRITE: + break; + case SSL_ERROR_SYSCALL: + if (r == 0) + rprintf(FERROR, "SSL: spurious EOF\n"); + else + rprintf(FERROR, "SSL: I/O error: %s\n", + strerror(errno)); + goto closed; + case SSL_ERROR_SSL: + rprintf(FERROR, "SSL: %s\n", + ERR_error_string(ERR_get_error(), NULL)); + goto closed; + default: + rprintf(FERROR, "unexpected ssl error %d\n", r); + goto closed; + } + } + } + if (avail1 == write1) + avail1 = write1 = 0; + if (avail2 == write2) + avail2 = write2 = 0; + } + + /* XXX I'm pretty sure that there is a lot that I am not considering + here. Bugs? Yes, probably. */ + + /* We're finished. */ + closed: + close(tls_read[1]); + close(tls_write[0]); + exit(0); +} + +/** + * Ends the TLS connection. + */ +void end_tls(void) +{ + if (ssl_pid > 0) + kill(ssl_pid, SIGUSR1); +}