diff options
Diffstat (limited to 'crypto/openssh/sshd.c')
| -rw-r--r-- | crypto/openssh/sshd.c | 1645 |
1 files changed, 1645 insertions, 0 deletions
diff --git a/crypto/openssh/sshd.c b/crypto/openssh/sshd.c new file mode 100644 index 0000000..5073465 --- /dev/null +++ b/crypto/openssh/sshd.c @@ -0,0 +1,1645 @@ +/* + * Author: Tatu Ylonen <ylo@cs.hut.fi> + * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland + * All rights reserved + * This program is the ssh daemon. It listens for connections from clients, + * and performs authentication, executes use commands or shell, and forwards + * information to/from the application to the user client over an encrypted + * connection. This can also handle forwarding of X11, TCP/IP, and + * authentication agent connections. + * + * As far as I am concerned, the code I have written for this software + * can be used freely for any purpose. Any derived versions of this + * software must be clearly marked as such, and if the derived work is + * incompatible with the protocol description in the RFC file, it must be + * called by a name other than "ssh" or "Secure Shell". + * + * SSH2 implementation: + * + * Copyright (c) 2000 Markus Friedl. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "includes.h" +RCSID("$OpenBSD: sshd.c,v 1.132 2000/10/13 18:34:46 markus Exp $"); +RCSID("$FreeBSD$"); + +#include "xmalloc.h" +#include "rsa.h" +#include "ssh.h" +#include "pty.h" +#include "packet.h" +#include "mpaux.h" +#include "servconf.h" +#include "uidswap.h" +#include "compat.h" +#include "buffer.h" +#include <poll.h> +#include <time.h> + +#include "ssh2.h" +#include <openssl/dh.h> +#include <openssl/bn.h> +#include <openssl/hmac.h> +#include "kex.h" +#include <openssl/dsa.h> +#include <openssl/rsa.h> +#include "key.h" +#include "dsa.h" +#include "dh.h" + +#include "auth.h" +#include "myproposal.h" +#include "authfile.h" + +#ifdef LIBWRAP +#include <tcpd.h> +#include <syslog.h> +int allow_severity = LOG_INFO; +int deny_severity = LOG_WARNING; +#endif /* LIBWRAP */ + +#ifndef O_NOCTTY +#define O_NOCTTY 0 +#endif + +#ifdef KRB5 +#include <krb5.h> +#endif /* KRB5 */ + +/* Server configuration options. */ +ServerOptions options; + +/* Name of the server configuration file. */ +char *config_file_name = SERVER_CONFIG_FILE; + +/* + * Flag indicating whether IPv4 or IPv6. This can be set on the command line. + * Default value is AF_UNSPEC means both IPv4 and IPv6. + */ +int IPv4or6 = AF_UNSPEC; + +/* + * Debug mode flag. This can be set on the command line. If debug + * mode is enabled, extra debugging output will be sent to the system + * log, the daemon will not go to background, and will exit after processing + * the first connection. + */ +int debug_flag = 0; + +/* Flag indicating that the daemon is being started from inetd. */ +int inetd_flag = 0; + +/* debug goes to stderr unless inetd_flag is set */ +int log_stderr = 0; + +/* argv[0] without path. */ +char *av0; + +/* Saved arguments to main(). */ +char **saved_argv; + +/* + * The sockets that the server is listening; this is used in the SIGHUP + * signal handler. + */ +#define MAX_LISTEN_SOCKS 16 +int listen_socks[MAX_LISTEN_SOCKS]; +int num_listen_socks = 0; + +/* + * the client's version string, passed by sshd2 in compat mode. if != NULL, + * sshd will skip the version-number exchange + */ +char *client_version_string = NULL; +char *server_version_string = NULL; + +/* + * Any really sensitive data in the application is contained in this + * structure. The idea is that this structure could be locked into memory so + * that the pages do not get written into swap. However, there are some + * problems. The private key contains BIGNUMs, and we do not (in principle) + * have access to the internals of them, and locking just the structure is + * not very useful. Currently, memory locking is not implemented. + */ +struct { + RSA *private_key; /* Private part of empheral server key. */ + RSA *host_key; /* Private part of host key. */ + Key *dsa_host_key; /* Private DSA host key. */ +} sensitive_data; + +/* + * Flag indicating whether the current session key has been used. This flag + * is set whenever the key is used, and cleared when the key is regenerated. + */ +int key_used = 0; + +/* This is set to true when SIGHUP is received. */ +int received_sighup = 0; + +/* Public side of the server key. This value is regenerated regularly with + the private key. */ +RSA *public_key; + +/* session identifier, used by RSA-auth */ +unsigned char session_id[16]; + +/* same for ssh2 */ +unsigned char *session_id2 = NULL; +int session_id2_len = 0; + +/* record remote hostname or ip */ +unsigned int utmp_len = MAXHOSTNAMELEN; + +/* Prototypes for various functions defined later in this file. */ +void do_ssh1_kex(); +void do_ssh2_kex(); + +void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *); +void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *); + +/* + * Close all listening sockets + */ +void +close_listen_socks(void) +{ + int i; + for (i = 0; i < num_listen_socks; i++) + close(listen_socks[i]); + num_listen_socks = -1; +} + +/* + * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; + * the effect is to reread the configuration file (and to regenerate + * the server key). + */ +void +sighup_handler(int sig) +{ + received_sighup = 1; + signal(SIGHUP, sighup_handler); +} + +/* + * Called from the main program after receiving SIGHUP. + * Restarts the server. + */ +void +sighup_restart() +{ + log("Received SIGHUP; restarting."); + close_listen_socks(); + execv(saved_argv[0], saved_argv); + execv("/proc/curproc/file", saved_argv); + log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno)); + exit(1); +} + +/* + * Generic signal handler for terminating signals in the master daemon. + * These close the listen socket; not closing it seems to cause "Address + * already in use" problems on some machines, which is inconvenient. + */ +void +sigterm_handler(int sig) +{ + log("Received signal %d; terminating.", sig); + close_listen_socks(); + unlink(options.pid_file); + exit(255); +} + +/* + * SIGCHLD handler. This is called whenever a child dies. This will then + * reap any zombies left by exited c. + */ +void +main_sigchld_handler(int sig) +{ + int save_errno = errno; + int status; + + while (waitpid(-1, &status, WNOHANG) > 0) + ; + + signal(SIGCHLD, main_sigchld_handler); + errno = save_errno; +} + +/* + * Signal handler for the alarm after the login grace period has expired. + */ +void +grace_alarm_handler(int sig) +{ + /* Close the connection. */ + packet_close(); + + /* Log error and exit. */ + fatal("Timeout before authentication for %s.", get_remote_ipaddr()); +} + +/* + * Signal handler for the key regeneration alarm. Note that this + * alarm only occurs in the daemon waiting for connections, and it does not + * do anything with the private key or random state before forking. + * Thus there should be no concurrency control/asynchronous execution + * problems. + */ +/* XXX do we really want this work to be done in a signal handler ? -m */ +void +key_regeneration_alarm(int sig) +{ + int save_errno = errno; + + /* Check if we should generate a new key. */ + if (key_used) { + /* This should really be done in the background. */ + log("Generating new %d bit RSA key.", options.server_key_bits); + + if (sensitive_data.private_key != NULL) + RSA_free(sensitive_data.private_key); + sensitive_data.private_key = RSA_new(); + + if (public_key != NULL) + RSA_free(public_key); + public_key = RSA_new(); + + rsa_generate_key(sensitive_data.private_key, public_key, + options.server_key_bits); + arc4random_stir(); + key_used = 0; + log("RSA key generation complete."); + } + /* Reschedule the alarm. */ + signal(SIGALRM, key_regeneration_alarm); + alarm(options.key_regeneration_time); + errno = save_errno; +} + +void +sshd_exchange_identification(int sock_in, int sock_out) +{ + int i, mismatch; + int remote_major, remote_minor; + int major, minor; + char *s; + char buf[256]; /* Must not be larger than remote_version. */ + char remote_version[256]; /* Must be at least as big as buf. */ + + if ((options.protocol & SSH_PROTO_1) && + (options.protocol & SSH_PROTO_2)) { + major = PROTOCOL_MAJOR_1; + minor = 99; + } else if (options.protocol & SSH_PROTO_2) { + major = PROTOCOL_MAJOR_2; + minor = PROTOCOL_MINOR_2; + } else { + major = PROTOCOL_MAJOR_1; + minor = PROTOCOL_MINOR_1; + } + snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); + server_version_string = xstrdup(buf); + + if (client_version_string == NULL) { + /* Send our protocol version identification. */ + if (atomicio(write, sock_out, server_version_string, strlen(server_version_string)) + != strlen(server_version_string)) { + log("Could not write ident string to %s.", get_remote_ipaddr()); + fatal_cleanup(); + } + + /* Read other side\'s version identification. */ + for (i = 0; i < sizeof(buf) - 1; i++) { + if (atomicio(read, sock_in, &buf[i], 1) != 1) { + log("Did not receive ident string from %s.", get_remote_ipaddr()); + fatal_cleanup(); + } + if (buf[i] == '\r') { + buf[i] = '\n'; + buf[i + 1] = 0; + /* Kludge for F-Secure Macintosh < 1.0.2 */ + if (i == 12 && + strncmp(buf, "SSH-1.5-W1.0", 12) == 0) + break; + continue; + } + if (buf[i] == '\n') { + /* buf[i] == '\n' */ + buf[i + 1] = 0; + break; + } + } + buf[sizeof(buf) - 1] = 0; + client_version_string = xstrdup(buf); + } + + /* + * Check that the versions match. In future this might accept + * several versions and set appropriate flags to handle them. + */ + if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", + &remote_major, &remote_minor, remote_version) != 3) { + s = "Protocol mismatch.\n"; + (void) atomicio(write, sock_out, s, strlen(s)); + close(sock_in); + close(sock_out); + log("Bad protocol version identification '%.100s' from %s", + client_version_string, get_remote_ipaddr()); + fatal_cleanup(); + } + debug("Client protocol version %d.%d; client software version %.100s", + remote_major, remote_minor, remote_version); + + compat_datafellows(remote_version); + + mismatch = 0; + switch(remote_major) { + case 1: + if (remote_minor == 99) { + if (options.protocol & SSH_PROTO_2) + enable_compat20(); + else + mismatch = 1; + break; + } + if (!(options.protocol & SSH_PROTO_1)) { + mismatch = 1; + break; + } + if (remote_minor < 3) { + packet_disconnect("Your ssh version is too old and " + "is no longer supported. Please install a newer version."); + } else if (remote_minor == 3) { + /* note that this disables agent-forwarding */ + enable_compat13(); + } + break; + case 2: + if (options.protocol & SSH_PROTO_2) { + enable_compat20(); + break; + } + /* FALLTHROUGH */ + default: + mismatch = 1; + break; + } + chop(server_version_string); + chop(client_version_string); + debug("Local version string %.200s", server_version_string); + + if (mismatch) { + s = "Protocol major versions differ.\n"; + (void) atomicio(write, sock_out, s, strlen(s)); + close(sock_in); + close(sock_out); + log("Protocol major versions differ for %s: %.200s vs. %.200s", + get_remote_ipaddr(), + server_version_string, client_version_string); + fatal_cleanup(); + } + if (compat20) + packet_set_ssh2_format(); +} + + +void +destroy_sensitive_data(void) +{ + /* Destroy the private and public keys. They will no longer be needed. */ + if (public_key) + RSA_free(public_key); + if (sensitive_data.private_key) + RSA_free(sensitive_data.private_key); + if (sensitive_data.host_key) + RSA_free(sensitive_data.host_key); + if (sensitive_data.dsa_host_key != NULL) + key_free(sensitive_data.dsa_host_key); +} + +/* + * returns 1 if connection should be dropped, 0 otherwise. + * dropping starts at connection #max_startups_begin with a probability + * of (max_startups_rate/100). the probability increases linearly until + * all connections are dropped for startups > max_startups + */ +int +drop_connection(int startups) +{ + double p, r; + + if (startups < options.max_startups_begin) + return 0; + if (startups >= options.max_startups) + return 1; + if (options.max_startups_rate == 100) + return 1; + + p = 100 - options.max_startups_rate; + p *= startups - options.max_startups_begin; + p /= (double) (options.max_startups - options.max_startups_begin); + p += options.max_startups_rate; + p /= 100.0; + r = arc4random() / (double) UINT_MAX; + + debug("drop_connection: p %g, r %g", p, r); + return (r < p) ? 1 : 0; +} + +int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */ +int startup_pipe; /* in child */ + +/* + * Main program for the daemon. + */ +int +main(int ac, char **av) +{ + extern char *optarg; + extern int optind; + int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1; + pid_t pid; + socklen_t fromlen; + int silent = 0; + fd_set *fdset; + struct sockaddr_storage from; + const char *remote_ip; + int remote_port; + FILE *f; + struct linger linger; + struct addrinfo *ai; + char ntop[NI_MAXHOST], strport[NI_MAXSERV]; + int listen_sock, maxfd; + int startup_p[2]; + int startups = 0; + + /* Save argv[0]. */ + saved_argv = av; + if (strchr(av[0], '/')) + av0 = strrchr(av[0], '/') + 1; + else + av0 = av[0]; + + /* Initialize configuration options to their default values. */ + initialize_server_options(&options); + + /* Parse command-line arguments. */ + while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:diqQ46")) != EOF) { + switch (opt) { + case '4': + IPv4or6 = AF_INET; + break; + case '6': + IPv4or6 = AF_INET6; + break; + case 'f': + config_file_name = optarg; + break; + case 'd': + if (0 == debug_flag) { + debug_flag = 1; + options.log_level = SYSLOG_LEVEL_DEBUG1; + } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) { + options.log_level++; + } else { + fprintf(stderr, "Too high debugging level.\n"); + exit(1); + } + break; + case 'i': + inetd_flag = 1; + break; + case 'Q': + silent = 1; + break; + case 'q': + options.log_level = SYSLOG_LEVEL_QUIET; + break; + case 'b': + options.server_key_bits = atoi(optarg); + break; + case 'p': + options.ports_from_cmdline = 1; + if (options.num_ports >= MAX_PORTS) { + fprintf(stderr, "too many ports.\n"); + exit(1); + } + options.ports[options.num_ports++] = atoi(optarg); + break; + case 'g': + options.login_grace_time = atoi(optarg); + break; + case 'k': + options.key_regeneration_time = atoi(optarg); + break; + case 'h': + options.host_key_file = optarg; + break; + case 'V': + client_version_string = optarg; + /* only makes sense with inetd_flag, i.e. no listen() */ + inetd_flag = 1; + break; + case 'u': + utmp_len = atoi(optarg); + break; + case '?': + default: + fprintf(stderr, "sshd version %s\n", SSH_VERSION); + fprintf(stderr, "Usage: %s [options]\n", av0); + fprintf(stderr, "Options:\n"); + fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE); + fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n"); + fprintf(stderr, " -i Started from inetd\n"); + fprintf(stderr, " -q Quiet (no logging)\n"); + fprintf(stderr, " -p port Listen on the specified port (default: 22)\n"); + fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n"); + fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n"); + fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n"); + fprintf(stderr, " -h file File from which to read host key (default: %s)\n", + HOST_KEY_FILE); + fprintf(stderr, " -u len Maximum hostname length for utmp recording\n"); + fprintf(stderr, " -4 Use IPv4 only\n"); + fprintf(stderr, " -6 Use IPv6 only\n"); + exit(1); + } + } + + /* + * Force logging to stderr until we have loaded the private host + * key (unless started from inetd) + */ + log_init(av0, + options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level, + options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility, + !silent && !inetd_flag); + + /* Read server configuration options from the configuration file. */ + read_server_config(&options, config_file_name); + + /* Fill in default values for those options not explicitly set. */ + fill_default_server_options(&options); + + /* Check that there are no remaining arguments. */ + if (optind < ac) { + fprintf(stderr, "Extra argument %s.\n", av[optind]); + exit(1); + } + + debug("sshd version %.100s", SSH_VERSION); + + sensitive_data.dsa_host_key = NULL; + sensitive_data.host_key = NULL; + + /* check if RSA support exists */ + if ((options.protocol & SSH_PROTO_1) && + rsa_alive() == 0) { + log("no RSA support in libssl and libcrypto. See ssl(8)"); + log("Disabling protocol version 1"); + options.protocol &= ~SSH_PROTO_1; + } + /* Load the RSA/DSA host key. It must have empty passphrase. */ + if (options.protocol & SSH_PROTO_1) { + Key k; + sensitive_data.host_key = RSA_new(); + k.type = KEY_RSA; + k.rsa = sensitive_data.host_key; + errno = 0; + if (!load_private_key(options.host_key_file, "", &k, NULL)) { + error("Could not load host key: %.200s: %.100s", + options.host_key_file, strerror(errno)); + log("Disabling protocol version 1"); + options.protocol &= ~SSH_PROTO_1; + } + k.rsa = NULL; + } + if (options.protocol & SSH_PROTO_2) { + sensitive_data.dsa_host_key = key_new(KEY_DSA); + if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) { + + error("Could not load DSA host key: %.200s", options.host_dsa_key_file); + log("Disabling protocol version 2"); + options.protocol &= ~SSH_PROTO_2; + } + } + if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) { + if (silent == 0) + fprintf(stderr, "sshd: no hostkeys available -- exiting.\n"); + log("sshd: no hostkeys available -- exiting.\n"); + exit(1); + } + + /* Check certain values for sanity. */ + if (options.protocol & SSH_PROTO_1) { + if (options.server_key_bits < 512 || + options.server_key_bits > 32768) { + fprintf(stderr, "Bad server key size.\n"); + exit(1); + } + /* + * Check that server and host key lengths differ sufficiently. This + * is necessary to make double encryption work with rsaref. Oh, I + * hate software patents. I dont know if this can go? Niels + */ + if (options.server_key_bits > + BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED && + options.server_key_bits < + BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) { + options.server_key_bits = + BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED; + debug("Forcing server key to %d bits to make it differ from host key.", + options.server_key_bits); + } + } + + /* Initialize the log (it is reinitialized below in case we forked). */ + if (debug_flag && !inetd_flag) + log_stderr = 1; + log_init(av0, options.log_level, options.log_facility, log_stderr); + + /* + * If not in debugging mode, and not started from inetd, disconnect + * from the controlling terminal, and fork. The original process + * exits. + */ + if (!debug_flag && !inetd_flag) { +#ifdef TIOCNOTTY + int fd; +#endif /* TIOCNOTTY */ + if (daemon(0, 0) < 0) + fatal("daemon() failed: %.200s", strerror(errno)); + + /* Disconnect from the controlling tty. */ +#ifdef TIOCNOTTY + fd = open("/dev/tty", O_RDWR | O_NOCTTY); + if (fd >= 0) { + (void) ioctl(fd, TIOCNOTTY, NULL); + close(fd); + } +#endif /* TIOCNOTTY */ + } + /* Reinitialize the log (because of the fork above). */ + log_init(av0, options.log_level, options.log_facility, log_stderr); + + /* Do not display messages to stdout in RSA code. */ + rsa_set_verbose(0); + + /* Initialize the random number generator. */ + arc4random_stir(); + + /* Chdir to the root directory so that the current disk can be + unmounted if desired. */ + chdir("/"); + + /* Start listening for a socket, unless started from inetd. */ + if (inetd_flag) { + int s1, s2; + s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ + s2 = dup(s1); + sock_in = dup(0); + sock_out = dup(1); + startup_pipe = -1; + /* + * We intentionally do not close the descriptors 0, 1, and 2 + * as our code for setting the descriptors won\'t work if + * ttyfd happens to be one of those. + */ + debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); + + if (options.protocol & SSH_PROTO_1) { + public_key = RSA_new(); + sensitive_data.private_key = RSA_new(); + log("Generating %d bit RSA key.", options.server_key_bits); + rsa_generate_key(sensitive_data.private_key, public_key, + options.server_key_bits); + arc4random_stir(); + log("RSA key generation complete."); + } + } else { + for (ai = options.listen_addrs; ai; ai = ai->ai_next) { + if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) + continue; + if (num_listen_socks >= MAX_LISTEN_SOCKS) + fatal("Too many listen sockets. " + "Enlarge MAX_LISTEN_SOCKS"); + if (getnameinfo(ai->ai_addr, ai->ai_addrlen, + ntop, sizeof(ntop), strport, sizeof(strport), + NI_NUMERICHOST|NI_NUMERICSERV) != 0) { + error("getnameinfo failed"); + continue; + } + /* Create socket for listening. */ + listen_sock = socket(ai->ai_family, SOCK_STREAM, 0); + if (listen_sock < 0) { + /* kernel may not support ipv6 */ + verbose("socket: %.100s", strerror(errno)); + continue; + } + if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { + error("listen_sock O_NONBLOCK: %s", strerror(errno)); + close(listen_sock); + continue; + } + /* + * Set socket options. We try to make the port + * reusable and have it close as fast as possible + * without waiting in unnecessary wait states on + * close. + */ + setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, + (void *) &on, sizeof(on)); + linger.l_onoff = 1; + linger.l_linger = 5; + setsockopt(listen_sock, SOL_SOCKET, SO_LINGER, + (void *) &linger, sizeof(linger)); + + debug("Bind to port %s on %s.", strport, ntop); + + /* Bind the socket to the desired port. */ + if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { + error("Bind to port %s on %s failed: %.200s.", + strport, ntop, strerror(errno)); + close(listen_sock); + continue; + } + listen_socks[num_listen_socks] = listen_sock; + num_listen_socks++; + + /* Start listening on the port. */ + log("Server listening on %s port %s.", ntop, strport); + if (listen(listen_sock, 5) < 0) + fatal("listen: %.100s", strerror(errno)); + + } + freeaddrinfo(options.listen_addrs); + + if (!num_listen_socks) + fatal("Cannot bind any address."); + + if (!debug_flag) { + /* + * Record our pid in /etc/sshd_pid to make it easier + * to kill the correct sshd. We don\'t want to do + * this before the bind above because the bind will + * fail if there already is a daemon, and this will + * overwrite any old pid in the file. + */ + f = fopen(options.pid_file, "w"); + if (f) { + fprintf(f, "%u\n", (unsigned int) getpid()); + fclose(f); + } + } + if (options.protocol & SSH_PROTO_1) { + public_key = RSA_new(); + sensitive_data.private_key = RSA_new(); + + log("Generating %d bit RSA key.", options.server_key_bits); + rsa_generate_key(sensitive_data.private_key, public_key, + options.server_key_bits); + arc4random_stir(); + log("RSA key generation complete."); + + /* Schedule server key regeneration alarm. */ + signal(SIGALRM, key_regeneration_alarm); + alarm(options.key_regeneration_time); + } + + /* Arrange to restart on SIGHUP. The handler needs listen_sock. */ + signal(SIGHUP, sighup_handler); + + signal(SIGTERM, sigterm_handler); + signal(SIGQUIT, sigterm_handler); + + /* Arrange SIGCHLD to be caught. */ + signal(SIGCHLD, main_sigchld_handler); + + /* setup fd set for listen */ + fdset = NULL; + maxfd = 0; + for (i = 0; i < num_listen_socks; i++) + if (listen_socks[i] > maxfd) + maxfd = listen_socks[i]; + /* pipes connected to unauthenticated childs */ + startup_pipes = xmalloc(options.max_startups * sizeof(int)); + for (i = 0; i < options.max_startups; i++) + startup_pipes[i] = -1; + + /* + * Stay listening for connections until the system crashes or + * the daemon is killed with a signal. + */ + for (;;) { + if (received_sighup) + sighup_restart(); + if (fdset != NULL) + xfree(fdset); + fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask); + fdset = (fd_set *)xmalloc(fdsetsz); + memset(fdset, 0, fdsetsz); + + for (i = 0; i < num_listen_socks; i++) + FD_SET(listen_socks[i], fdset); + for (i = 0; i < options.max_startups; i++) + if (startup_pipes[i] != -1) + FD_SET(startup_pipes[i], fdset); + + /* Wait in select until there is a connection. */ + if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) { + if (errno != EINTR) + error("select: %.100s", strerror(errno)); + continue; + } + for (i = 0; i < options.max_startups; i++) + if (startup_pipes[i] != -1 && + FD_ISSET(startup_pipes[i], fdset)) { + /* + * the read end of the pipe is ready + * if the child has closed the pipe + * after successfull authentication + * or if the child has died + */ + close(startup_pipes[i]); + startup_pipes[i] = -1; + startups--; + } + for (i = 0; i < num_listen_socks; i++) { + if (!FD_ISSET(listen_socks[i], fdset)) + continue; + fromlen = sizeof(from); + newsock = accept(listen_socks[i], (struct sockaddr *)&from, + &fromlen); + if (newsock < 0) { + if (errno != EINTR && errno != EWOULDBLOCK) + error("accept: %.100s", strerror(errno)); + continue; + } + if (fcntl(newsock, F_SETFL, 0) < 0) { + error("newsock del O_NONBLOCK: %s", strerror(errno)); + continue; + } + if (drop_connection(startups) == 1) { + debug("drop connection #%d", startups); + close(newsock); + continue; + } + if (pipe(startup_p) == -1) { + close(newsock); + continue; + } + + for (j = 0; j < options.max_startups; j++) + if (startup_pipes[j] == -1) { + startup_pipes[j] = startup_p[0]; + if (maxfd < startup_p[0]) + maxfd = startup_p[0]; + startups++; + break; + } + + + /* + * Got connection. Fork a child to handle it, unless + * we are in debugging mode. + */ + if (debug_flag) { + /* + * In debugging mode. Close the listening + * socket, and start processing the + * connection without forking. + */ + debug("Server will not fork when running in debugging mode."); + close_listen_socks(); + sock_in = newsock; + sock_out = newsock; + startup_pipe = -1; + pid = getpid(); + break; + } else { + /* + * Normal production daemon. Fork, and have + * the child process the connection. The + * parent continues listening. + */ + if ((pid = fork()) == 0) { + /* + * Child. Close the listening and max_startup + * sockets. Start using the accepted socket. + * Reinitialize logging (since our pid has + * changed). We break out of the loop to handle + * the connection. + */ + startup_pipe = startup_p[1]; + for (j = 0; j < options.max_startups; j++) + if (startup_pipes[j] != -1) + close(startup_pipes[j]); + close_listen_socks(); + sock_in = newsock; + sock_out = newsock; + log_init(av0, options.log_level, options.log_facility, log_stderr); + break; + } + } + + /* Parent. Stay in the loop. */ + if (pid < 0) + error("fork: %.100s", strerror(errno)); + else + debug("Forked child %d.", pid); + + close(startup_p[1]); + + /* Mark that the key has been used (it was "given" to the child). */ + key_used = 1; + + arc4random_stir(); + + /* Close the new socket (the child is now taking care of it). */ + close(newsock); + } + /* child process check (or debug mode) */ + if (num_listen_socks < 0) + break; + } + } + + /* This is the child processing a new connection. */ + + /* + * Disable the key regeneration alarm. We will not regenerate the + * key since we are no longer in a position to give it to anyone. We + * will not restart on SIGHUP since it no longer makes sense. + */ + alarm(0); + signal(SIGALRM, SIG_DFL); + signal(SIGHUP, SIG_DFL); + signal(SIGTERM, SIG_DFL); + signal(SIGQUIT, SIG_DFL); + signal(SIGCHLD, SIG_DFL); + signal(SIGPIPE, SIG_IGN); + + /* + * Set socket options for the connection. We want the socket to + * close as fast as possible without waiting for anything. If the + * connection is not a socket, these will do nothing. + */ + /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */ + linger.l_onoff = 1; + linger.l_linger = 5; + setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger)); + + /* + * Register our connection. This turns encryption off because we do + * not have a key. + */ + packet_set_connection(sock_in, sock_out); + + remote_port = get_remote_port(); + remote_ip = get_remote_ipaddr(); + + /* Check whether logins are denied from this host. */ +#ifdef LIBWRAP + { + struct request_info req; + + request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL); + fromhost(&req); + + if (!hosts_access(&req)) { + close(sock_in); + close(sock_out); + refuse(&req); + } + verbose("Connection from %.500s port %d", eval_client(&req), remote_port); + } +#endif /* LIBWRAP */ + /* Log the connection. */ + verbose("Connection from %.500s port %d", remote_ip, remote_port); + + /* + * We don\'t want to listen forever unless the other side + * successfully authenticates itself. So we set up an alarm which is + * cleared after successful authentication. A limit of zero + * indicates no limit. Note that we don\'t set the alarm in debugging + * mode; it is just annoying to have the server exit just when you + * are about to discover the bug. + */ + signal(SIGALRM, grace_alarm_handler); + if (!debug_flag) + alarm(options.login_grace_time); + + sshd_exchange_identification(sock_in, sock_out); + /* + * Check that the connection comes from a privileged port. Rhosts- + * and Rhosts-RSA-Authentication only make sense from priviledged + * programs. Of course, if the intruder has root access on his local + * machine, he can connect from any port. So do not use these + * authentication methods from machines that you do not trust. + */ + if (remote_port >= IPPORT_RESERVED || + remote_port < IPPORT_RESERVED / 2) { + options.rhosts_authentication = 0; + options.rhosts_rsa_authentication = 0; + } +#ifdef KRB4 + if (!packet_connection_is_ipv4() && + options.krb4_authentication) { + debug("Kerberos Authentication disabled, only available for IPv4."); + options.krb4_authentication = 0; + } +#endif /* KRB4 */ + + packet_set_nonblocking(); + + /* perform the key exchange */ + /* authenticate user and start session */ + if (compat20) { + do_ssh2_kex(); + do_authentication2(); + } else { + do_ssh1_kex(); + do_authentication(); + } + +#ifdef KRB4 + /* Cleanup user's ticket cache file. */ + if (options.krb4_ticket_cleanup) + (void) dest_tkt(); +#endif /* KRB4 */ + + /* The connection has been terminated. */ + verbose("Closing connection to %.100s", remote_ip); + +#ifdef USE_PAM + finish_pam(); +#endif /* USE_PAM */ + + packet_close(); + exit(0); +} + +/* + * SSH1 key exchange + */ +void +do_ssh1_kex() +{ + int i, len; + int plen, slen; + int rsafail = 0; + BIGNUM *session_key_int; + unsigned char session_key[SSH_SESSION_KEY_LENGTH]; + unsigned char cookie[8]; + unsigned int cipher_type, auth_mask, protocol_flags; + u_int32_t rand = 0; + + /* + * Generate check bytes that the client must send back in the user + * packet in order for it to be accepted; this is used to defy ip + * spoofing attacks. Note that this only works against somebody + * doing IP spoofing from a remote machine; any machine on the local + * network can still see outgoing packets and catch the random + * cookie. This only affects rhosts authentication, and this is one + * of the reasons why it is inherently insecure. + */ + for (i = 0; i < 8; i++) { + if (i % 4 == 0) + rand = arc4random(); + cookie[i] = rand & 0xff; + rand >>= 8; + } + + /* + * Send our public key. We include in the packet 64 bits of random + * data that must be matched in the reply in order to prevent IP + * spoofing. + */ + packet_start(SSH_SMSG_PUBLIC_KEY); + for (i = 0; i < 8; i++) + packet_put_char(cookie[i]); + + /* Store our public server RSA key. */ + packet_put_int(BN_num_bits(public_key->n)); + packet_put_bignum(public_key->e); + packet_put_bignum(public_key->n); + + /* Store our public host RSA key. */ + packet_put_int(BN_num_bits(sensitive_data.host_key->n)); + packet_put_bignum(sensitive_data.host_key->e); + packet_put_bignum(sensitive_data.host_key->n); + + /* Put protocol flags. */ + packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); + + /* Declare which ciphers we support. */ + packet_put_int(cipher_mask_ssh1(0)); + + /* Declare supported authentication types. */ + auth_mask = 0; + if (options.rhosts_authentication) + auth_mask |= 1 << SSH_AUTH_RHOSTS; + if (options.rhosts_rsa_authentication) + auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; + if (options.rsa_authentication) + auth_mask |= 1 << SSH_AUTH_RSA; +#ifdef KRB4 + if (options.krb4_authentication) + auth_mask |= 1 << SSH_AUTH_KRB4; +#endif +#ifdef KRB5 + if (options.krb5_authentication) { + auth_mask |= 1 << SSH_AUTH_KRB5; + /* compatibility with MetaCentre ssh */ + auth_mask |= 1 << SSH_AUTH_KRB4; + } + if (options.krb5_tgt_passing) + auth_mask |= 1 << SSH_PASS_KRB5_TGT; +#endif /* KRB5 */ + +#ifdef AFS + if (options.krb4_tgt_passing) + auth_mask |= 1 << SSH_PASS_KRB4_TGT; + if (options.afs_token_passing) + auth_mask |= 1 << SSH_PASS_AFS_TOKEN; +#endif +#ifdef SKEY + if (options.skey_authentication == 1) + auth_mask |= 1 << SSH_AUTH_TIS; +#endif + if (options.password_authentication) + auth_mask |= 1 << SSH_AUTH_PASSWORD; + packet_put_int(auth_mask); + + /* Send the packet and wait for it to be sent. */ + packet_send(); + packet_write_wait(); + + debug("Sent %d bit public key and %d bit host key.", + BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n)); + + /* Read clients reply (cipher type and session key). */ + packet_read_expect(&plen, SSH_CMSG_SESSION_KEY); + + /* Get cipher type and check whether we accept this. */ + cipher_type = packet_get_char(); + + if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) + packet_disconnect("Warning: client selects unsupported cipher."); + + /* Get check bytes from the packet. These must match those we + sent earlier with the public key packet. */ + for (i = 0; i < 8; i++) + if (cookie[i] != packet_get_char()) + packet_disconnect("IP Spoofing check bytes do not match."); + + debug("Encryption type: %.200s", cipher_name(cipher_type)); + + /* Get the encrypted integer. */ + session_key_int = BN_new(); + packet_get_bignum(session_key_int, &slen); + + protocol_flags = packet_get_int(); + packet_set_protocol_flags(protocol_flags); + + packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY); + + /* + * Decrypt it using our private server key and private host key (key + * with larger modulus first). + */ + if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) { + /* Server key has bigger modulus. */ + if (BN_num_bits(sensitive_data.private_key->n) < + BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) { + fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", + get_remote_ipaddr(), + BN_num_bits(sensitive_data.private_key->n), + BN_num_bits(sensitive_data.host_key->n), + SSH_KEY_BITS_RESERVED); + } + if (rsa_private_decrypt(session_key_int, session_key_int, + sensitive_data.private_key) <= 0) + rsafail++; + if (rsa_private_decrypt(session_key_int, session_key_int, + sensitive_data.host_key) <= 0) + rsafail++; + } else { + /* Host key has bigger modulus (or they are equal). */ + if (BN_num_bits(sensitive_data.host_key->n) < + BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) { + fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d", + get_remote_ipaddr(), + BN_num_bits(sensitive_data.host_key->n), + BN_num_bits(sensitive_data.private_key->n), + SSH_KEY_BITS_RESERVED); + } + if (rsa_private_decrypt(session_key_int, session_key_int, + sensitive_data.host_key) < 0) + rsafail++; + if (rsa_private_decrypt(session_key_int, session_key_int, + sensitive_data.private_key) < 0) + rsafail++; + } + + compute_session_id(session_id, cookie, + sensitive_data.host_key->n, + sensitive_data.private_key->n); + + /* Destroy the private and public keys. They will no longer be needed. */ + destroy_sensitive_data(); + + /* + * Extract session key from the decrypted integer. The key is in the + * least significant 256 bits of the integer; the first byte of the + * key is in the highest bits. + */ + if (!rsafail) { + BN_mask_bits(session_key_int, sizeof(session_key) * 8); + len = BN_num_bytes(session_key_int); + if (len < 0 || len > sizeof(session_key)) { + error("do_connection: bad session key len from %s: " + "session_key_int %d > sizeof(session_key) %d", + get_remote_ipaddr(), len, sizeof(session_key)); + rsafail++; + } else { + memset(session_key, 0, sizeof(session_key)); + BN_bn2bin(session_key_int, + session_key + sizeof(session_key) - len); + } + } + if (rsafail) { + log("do_connection: generating a fake encryption key"); + for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { + if (i % 4 == 0) + rand = arc4random(); + session_key[i] = rand & 0xff; + rand >>= 8; + } + } + + /* Destroy the decrypted integer. It is no longer needed. */ + BN_clear_free(session_key_int); + + /* Xor the first 16 bytes of the session key with the session id. */ + for (i = 0; i < 16; i++) + session_key[i] ^= session_id[i]; + + /* Set the session key. From this on all communications will be encrypted. */ + packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); + + /* Destroy our copy of the session key. It is no longer needed. */ + memset(session_key, 0, sizeof(session_key)); + + debug("Received session key; encryption turned on."); + + /* Send an acknowledgement packet. Note that this packet is sent encrypted. */ + packet_start(SSH_SMSG_SUCCESS); + packet_send(); + packet_write_wait(); +} + +/* + * SSH2 key exchange: diffie-hellman-group1-sha1 + */ +void +do_ssh2_kex() +{ + Buffer *server_kexinit; + Buffer *client_kexinit; + int payload_len; + int i; + Kex *kex; + char *cprop[PROPOSAL_MAX]; + +/* KEXINIT */ + + if (options.ciphers != NULL) { + myproposal[PROPOSAL_ENC_ALGS_CTOS] = + myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; + } + server_kexinit = kex_init(myproposal); + client_kexinit = xmalloc(sizeof(*client_kexinit)); + buffer_init(client_kexinit); + + /* algorithm negotiation */ + kex_exchange_kexinit(server_kexinit, client_kexinit, cprop); + kex = kex_choose_conf(cprop, myproposal, 1); + for (i = 0; i < PROPOSAL_MAX; i++) + xfree(cprop[i]); + + switch (kex->kex_type) { + case DH_GRP1_SHA1: + ssh_dh1_server(kex, client_kexinit, server_kexinit); + break; + case DH_GEX_SHA1: + ssh_dhgex_server(kex, client_kexinit, server_kexinit); + break; + default: + fatal("Unsupported key exchange %d", kex->kex_type); + } + + debug("send SSH2_MSG_NEWKEYS."); + packet_start(SSH2_MSG_NEWKEYS); + packet_send(); + packet_write_wait(); + debug("done: send SSH2_MSG_NEWKEYS."); + + debug("Wait SSH2_MSG_NEWKEYS."); + packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS); + debug("GOT SSH2_MSG_NEWKEYS."); + +#ifdef DEBUG_KEXDH + /* send 1st encrypted/maced/compressed message */ + packet_start(SSH2_MSG_IGNORE); + packet_put_cstring("markus"); + packet_send(); + packet_write_wait(); +#endif + + debug("done: KEX2."); +} + +/* + * SSH2 key exchange + */ + +/* diffie-hellman-group1-sha1 */ + +void +ssh_dh1_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit) +{ +#ifdef DEBUG_KEXDH + int i; +#endif + int payload_len, dlen; + int slen; + unsigned char *signature = NULL; + unsigned char *server_host_key_blob = NULL; + unsigned int sbloblen; + unsigned int klen, kout; + unsigned char *kbuf; + unsigned char *hash; + BIGNUM *shared_secret = 0; + DH *dh; + BIGNUM *dh_client_pub = 0; + +/* KEXDH */ + debug("Wait SSH2_MSG_KEXDH_INIT."); + packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT); + + /* key, cert */ + dh_client_pub = BN_new(); + if (dh_client_pub == NULL) + fatal("dh_client_pub == NULL"); + packet_get_bignum2(dh_client_pub, &dlen); + +#ifdef DEBUG_KEXDH + fprintf(stderr, "\ndh_client_pub= "); + BN_print_fp(stderr, dh_client_pub); + fprintf(stderr, "\n"); + debug("bits %d", BN_num_bits(dh_client_pub)); +#endif + + /* generate DH key */ + dh = dh_new_group1(); /* XXX depends on 'kex' */ + +#ifdef DEBUG_KEXDH + fprintf(stderr, "\np= "); + BN_print_fp(stderr, dh->p); + fprintf(stderr, "\ng= "); + bn_print(dh->g); + fprintf(stderr, "\npub= "); + BN_print_fp(stderr, dh->pub_key); + fprintf(stderr, "\n"); + DHparams_print_fp(stderr, dh); +#endif + if (!dh_pub_is_valid(dh, dh_client_pub)) + packet_disconnect("bad client public DH value"); + + klen = DH_size(dh); + kbuf = xmalloc(klen); + kout = DH_compute_key(kbuf, dh_client_pub, dh); + +#ifdef DEBUG_KEXDH + debug("shared secret: len %d/%d", klen, kout); + fprintf(stderr, "shared secret == "); + for (i = 0; i< kout; i++) + fprintf(stderr, "%02x", (kbuf[i])&0xff); + fprintf(stderr, "\n"); +#endif + shared_secret = BN_new(); + + BN_bin2bn(kbuf, kout, shared_secret); + memset(kbuf, 0, klen); + xfree(kbuf); + + /* XXX precompute? */ + dsa_make_key_blob(sensitive_data.dsa_host_key, + &server_host_key_blob, &sbloblen); + + /* calc H */ /* XXX depends on 'kex' */ + hash = kex_hash( + client_version_string, + server_version_string, + buffer_ptr(client_kexinit), buffer_len(client_kexinit), + buffer_ptr(server_kexinit), buffer_len(server_kexinit), + (char *)server_host_key_blob, sbloblen, + dh_client_pub, + dh->pub_key, + shared_secret + ); + buffer_free(client_kexinit); + buffer_free(server_kexinit); + xfree(client_kexinit); + xfree(server_kexinit); +#ifdef DEBUG_KEXDH + fprintf(stderr, "hash == "); + for (i = 0; i< 20; i++) + fprintf(stderr, "%02x", (hash[i])&0xff); + fprintf(stderr, "\n"); +#endif + /* save session id := H */ + /* XXX hashlen depends on KEX */ + session_id2_len = 20; + session_id2 = xmalloc(session_id2_len); + memcpy(session_id2, hash, session_id2_len); + + /* sign H */ + /* XXX hashlen depends on KEX */ + dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20); + + destroy_sensitive_data(); + + /* send server hostkey, DH pubkey 'f' and singed H */ + packet_start(SSH2_MSG_KEXDH_REPLY); + packet_put_string((char *)server_host_key_blob, sbloblen); + packet_put_bignum2(dh->pub_key); /* f */ + packet_put_string((char *)signature, slen); + packet_send(); + xfree(signature); + xfree(server_host_key_blob); + packet_write_wait(); + + kex_derive_keys(kex, hash, shared_secret); + packet_set_kex(kex); + + /* have keys, free DH */ + DH_free(dh); +} + +/* diffie-hellman-group-exchange-sha1 */ + +void +ssh_dhgex_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit) +{ +#ifdef DEBUG_KEXDH + int i; +#endif + int payload_len, dlen; + int slen, nbits; + unsigned char *signature = NULL; + unsigned char *server_host_key_blob = NULL; + unsigned int sbloblen; + unsigned int klen, kout; + unsigned char *kbuf; + unsigned char *hash; + BIGNUM *shared_secret = 0; + DH *dh; + BIGNUM *dh_client_pub = 0; + +/* KEXDHGEX */ + debug("Wait SSH2_MSG_KEX_DH_GEX_REQUEST."); + packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_REQUEST); + nbits = packet_get_int(); + dh = choose_dh(nbits); + + debug("Sending SSH2_MSG_KEX_DH_GEX_GROUP."); + packet_start(SSH2_MSG_KEX_DH_GEX_GROUP); + packet_put_bignum2(dh->p); + packet_put_bignum2(dh->g); + packet_send(); + packet_write_wait(); + + debug("Wait SSH2_MSG_KEX_DH_GEX_INIT."); + packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_INIT); + + /* key, cert */ + dh_client_pub = BN_new(); + if (dh_client_pub == NULL) + fatal("dh_client_pub == NULL"); + packet_get_bignum2(dh_client_pub, &dlen); + +#ifdef DEBUG_KEXDH + fprintf(stderr, "\ndh_client_pub= "); + BN_print_fp(stderr, dh_client_pub); + fprintf(stderr, "\n"); + debug("bits %d", BN_num_bits(dh_client_pub)); +#endif + +#ifdef DEBUG_KEXDH + fprintf(stderr, "\np= "); + BN_print_fp(stderr, dh->p); + fprintf(stderr, "\ng= "); + bn_print(dh->g); + fprintf(stderr, "\npub= "); + BN_print_fp(stderr, dh->pub_key); + fprintf(stderr, "\n"); + DHparams_print_fp(stderr, dh); +#endif + if (!dh_pub_is_valid(dh, dh_client_pub)) + packet_disconnect("bad client public DH value"); + + klen = DH_size(dh); + kbuf = xmalloc(klen); + kout = DH_compute_key(kbuf, dh_client_pub, dh); + +#ifdef DEBUG_KEXDH + debug("shared secret: len %d/%d", klen, kout); + fprintf(stderr, "shared secret == "); + for (i = 0; i< kout; i++) + fprintf(stderr, "%02x", (kbuf[i])&0xff); + fprintf(stderr, "\n"); +#endif + shared_secret = BN_new(); + + BN_bin2bn(kbuf, kout, shared_secret); + memset(kbuf, 0, klen); + xfree(kbuf); + + /* XXX precompute? */ + dsa_make_key_blob(sensitive_data.dsa_host_key, + &server_host_key_blob, &sbloblen); + + /* calc H */ /* XXX depends on 'kex' */ + hash = kex_hash_gex( + client_version_string, + server_version_string, + buffer_ptr(client_kexinit), buffer_len(client_kexinit), + buffer_ptr(server_kexinit), buffer_len(server_kexinit), + (char *)server_host_key_blob, sbloblen, + nbits, dh->p, dh->g, + dh_client_pub, + dh->pub_key, + shared_secret + ); + buffer_free(client_kexinit); + buffer_free(server_kexinit); + xfree(client_kexinit); + xfree(server_kexinit); +#ifdef DEBUG_KEXDH + fprintf(stderr, "hash == "); + for (i = 0; i< 20; i++) + fprintf(stderr, "%02x", (hash[i])&0xff); + fprintf(stderr, "\n"); +#endif + /* save session id := H */ + /* XXX hashlen depends on KEX */ + session_id2_len = 20; + session_id2 = xmalloc(session_id2_len); + memcpy(session_id2, hash, session_id2_len); + + /* sign H */ + /* XXX hashlen depends on KEX */ + dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20); + + destroy_sensitive_data(); + + /* send server hostkey, DH pubkey 'f' and singed H */ + packet_start(SSH2_MSG_KEX_DH_GEX_REPLY); + packet_put_string((char *)server_host_key_blob, sbloblen); + packet_put_bignum2(dh->pub_key); /* f */ + packet_put_string((char *)signature, slen); + packet_send(); + xfree(signature); + xfree(server_host_key_blob); + packet_write_wait(); + + kex_derive_keys(kex, hash, shared_secret); + packet_set_kex(kex); + + /* have keys, free DH */ + DH_free(dh); +} + |
