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/* $OpenBSD: ssh-agent.c,v 1.25 2000/01/02 21:51:03 markus Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* Created: Wed Mar 29 03:46:59 1995 ylo
* The authentication agent program.
*/
#include "includes.h"
RCSID("$OpenBSD: ssh-agent.c,v 1.25 2000/01/02 21:51:03 markus Exp $");
#include "ssh.h"
#include "rsa.h"
#include "authfd.h"
#include "buffer.h"
#include "bufaux.h"
#include "xmalloc.h"
#include "packet.h"
#include "getput.h"
#include "mpaux.h"
#ifdef HAVE_OPENSSL
#include <openssl/md5.h>
#endif
#ifdef HAVE_SSL
#include <ssl/md5.h>
#endif
typedef struct {
int fd;
enum {
AUTH_UNUSED, AUTH_SOCKET, AUTH_CONNECTION
} type;
Buffer input;
Buffer output;
} SocketEntry;
unsigned int sockets_alloc = 0;
SocketEntry *sockets = NULL;
typedef struct {
RSA *key;
char *comment;
} Identity;
unsigned int num_identities = 0;
Identity *identities = NULL;
int max_fd = 0;
/* pid of shell == parent of agent */
int parent_pid = -1;
/* pathname and directory for AUTH_SOCKET */
char socket_name[1024];
char socket_dir[1024];
#ifdef HAVE___PROGNAME
extern char *__progname;
#else /* HAVE___PROGNAME */
const char *__progname = "ssh-agent";
#endif /* HAVE___PROGNAME */
void
process_request_identity(SocketEntry *e)
{
Buffer msg;
int i;
buffer_init(&msg);
buffer_put_char(&msg, SSH_AGENT_RSA_IDENTITIES_ANSWER);
buffer_put_int(&msg, num_identities);
for (i = 0; i < num_identities; i++) {
buffer_put_int(&msg, BN_num_bits(identities[i].key->n));
buffer_put_bignum(&msg, identities[i].key->e);
buffer_put_bignum(&msg, identities[i].key->n);
buffer_put_string(&msg, identities[i].comment,
strlen(identities[i].comment));
}
buffer_put_int(&e->output, buffer_len(&msg));
buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
buffer_free(&msg);
}
void
process_authentication_challenge(SocketEntry *e)
{
int i, pub_bits, len;
BIGNUM *pub_e, *pub_n, *challenge;
Buffer msg;
MD5_CTX md;
unsigned char buf[32], mdbuf[16], session_id[16];
unsigned int response_type;
buffer_init(&msg);
pub_e = BN_new();
pub_n = BN_new();
challenge = BN_new();
pub_bits = buffer_get_int(&e->input);
buffer_get_bignum(&e->input, pub_e);
buffer_get_bignum(&e->input, pub_n);
buffer_get_bignum(&e->input, challenge);
if (buffer_len(&e->input) == 0) {
/* Compatibility code for old servers. */
memset(session_id, 0, 16);
response_type = 0;
} else {
/* New code. */
buffer_get(&e->input, (char *) session_id, 16);
response_type = buffer_get_int(&e->input);
}
for (i = 0; i < num_identities; i++)
if (pub_bits == BN_num_bits(identities[i].key->n) &&
BN_cmp(pub_e, identities[i].key->e) == 0 &&
BN_cmp(pub_n, identities[i].key->n) == 0) {
/* Decrypt the challenge using the private key. */
rsa_private_decrypt(challenge, challenge, identities[i].key);
/* Compute the desired response. */
switch (response_type) {
case 0:/* As of protocol 1.0 */
/* This response type is no longer supported. */
log("Compatibility with ssh protocol 1.0 no longer supported.");
buffer_put_char(&msg, SSH_AGENT_FAILURE);
goto send;
case 1:/* As of protocol 1.1 */
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
if (len <= 0 || len > 32) {
fatal("process_authentication_challenge: "
"bad challenge length %d", len);
}
memset(buf, 0, 32);
BN_bn2bin(challenge, buf + 32 - len);
MD5_Init(&md);
MD5_Update(&md, buf, 32);
MD5_Update(&md, session_id, 16);
MD5_Final(mdbuf, &md);
break;
default:
fatal("process_authentication_challenge: bad response_type %d",
response_type);
break;
}
/* Send the response. */
buffer_put_char(&msg, SSH_AGENT_RSA_RESPONSE);
for (i = 0; i < 16; i++)
buffer_put_char(&msg, mdbuf[i]);
goto send;
}
/* Unknown identity. Send failure. */
buffer_put_char(&msg, SSH_AGENT_FAILURE);
send:
buffer_put_int(&e->output, buffer_len(&msg));
buffer_append(&e->output, buffer_ptr(&msg),
buffer_len(&msg));
buffer_free(&msg);
BN_clear_free(pub_e);
BN_clear_free(pub_n);
BN_clear_free(challenge);
}
void
process_remove_identity(SocketEntry *e)
{
unsigned int bits;
unsigned int i;
BIGNUM *dummy, *n;
dummy = BN_new();
n = BN_new();
/* Get the key from the packet. */
bits = buffer_get_int(&e->input);
buffer_get_bignum(&e->input, dummy);
buffer_get_bignum(&e->input, n);
if (bits != BN_num_bits(n))
error("Warning: identity keysize mismatch: actual %d, announced %d",
BN_num_bits(n), bits);
/* Check if we have the key. */
for (i = 0; i < num_identities; i++)
if (BN_cmp(identities[i].key->n, n) == 0) {
/*
* We have this key. Free the old key. Since we
* don\'t want to leave empty slots in the middle of
* the array, we actually free the key there and copy
* data from the last entry.
*/
RSA_free(identities[i].key);
xfree(identities[i].comment);
if (i < num_identities - 1)
identities[i] = identities[num_identities - 1];
num_identities--;
BN_clear_free(dummy);
BN_clear_free(n);
/* Send success. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
return;
}
/* We did not have the key. */
BN_clear(dummy);
BN_clear(n);
/* Send failure. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_FAILURE);
}
/*
* Removes all identities from the agent.
*/
void
process_remove_all_identities(SocketEntry *e)
{
unsigned int i;
/* Loop over all identities and clear the keys. */
for (i = 0; i < num_identities; i++) {
RSA_free(identities[i].key);
xfree(identities[i].comment);
}
/* Mark that there are no identities. */
num_identities = 0;
/* Send success. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
return;
}
/*
* Adds an identity to the agent.
*/
void
process_add_identity(SocketEntry *e)
{
RSA *k;
int i;
BIGNUM *aux;
BN_CTX *ctx;
if (num_identities == 0)
identities = xmalloc(sizeof(Identity));
else
identities = xrealloc(identities, (num_identities + 1) * sizeof(Identity));
identities[num_identities].key = RSA_new();
k = identities[num_identities].key;
buffer_get_int(&e->input); /* bits */
k->n = BN_new();
buffer_get_bignum(&e->input, k->n);
k->e = BN_new();
buffer_get_bignum(&e->input, k->e);
k->d = BN_new();
buffer_get_bignum(&e->input, k->d);
k->iqmp = BN_new();
buffer_get_bignum(&e->input, k->iqmp);
/* SSH and SSL have p and q swapped */
k->q = BN_new();
buffer_get_bignum(&e->input, k->q); /* p */
k->p = BN_new();
buffer_get_bignum(&e->input, k->p); /* q */
/* Generate additional parameters */
aux = BN_new();
ctx = BN_CTX_new();
BN_sub(aux, k->q, BN_value_one());
k->dmq1 = BN_new();
BN_mod(k->dmq1, k->d, aux, ctx);
BN_sub(aux, k->p, BN_value_one());
k->dmp1 = BN_new();
BN_mod(k->dmp1, k->d, aux, ctx);
BN_clear_free(aux);
BN_CTX_free(ctx);
identities[num_identities].comment = buffer_get_string(&e->input, NULL);
/* Check if we already have the key. */
for (i = 0; i < num_identities; i++)
if (BN_cmp(identities[i].key->n, k->n) == 0) {
/*
* We already have this key. Clear and free the new
* data and return success.
*/
RSA_free(k);
xfree(identities[num_identities].comment);
/* Send success. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
return;
}
/* Increment the number of identities. */
num_identities++;
/* Send a success message. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
}
void
process_message(SocketEntry *e)
{
unsigned int msg_len;
unsigned int type;
unsigned char *cp;
if (buffer_len(&e->input) < 5)
return; /* Incomplete message. */
cp = (unsigned char *) buffer_ptr(&e->input);
msg_len = GET_32BIT(cp);
if (msg_len > 256 * 1024) {
shutdown(e->fd, SHUT_RDWR);
close(e->fd);
e->type = AUTH_UNUSED;
return;
}
if (buffer_len(&e->input) < msg_len + 4)
return;
buffer_consume(&e->input, 4);
type = buffer_get_char(&e->input);
switch (type) {
case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
process_request_identity(e);
break;
case SSH_AGENTC_RSA_CHALLENGE:
process_authentication_challenge(e);
break;
case SSH_AGENTC_ADD_RSA_IDENTITY:
process_add_identity(e);
break;
case SSH_AGENTC_REMOVE_RSA_IDENTITY:
process_remove_identity(e);
break;
case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
process_remove_all_identities(e);
break;
default:
/* Unknown message. Respond with failure. */
error("Unknown message %d", type);
buffer_clear(&e->input);
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_FAILURE);
break;
}
}
void
new_socket(int type, int fd)
{
unsigned int i, old_alloc;
if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0)
error("fcntl O_NONBLOCK: %s", strerror(errno));
if (fd > max_fd)
max_fd = fd;
for (i = 0; i < sockets_alloc; i++)
if (sockets[i].type == AUTH_UNUSED) {
sockets[i].fd = fd;
sockets[i].type = type;
buffer_init(&sockets[i].input);
buffer_init(&sockets[i].output);
return;
}
old_alloc = sockets_alloc;
sockets_alloc += 10;
if (sockets)
sockets = xrealloc(sockets, sockets_alloc * sizeof(sockets[0]));
else
sockets = xmalloc(sockets_alloc * sizeof(sockets[0]));
for (i = old_alloc; i < sockets_alloc; i++)
sockets[i].type = AUTH_UNUSED;
sockets[old_alloc].type = type;
sockets[old_alloc].fd = fd;
buffer_init(&sockets[old_alloc].input);
buffer_init(&sockets[old_alloc].output);
}
void
prepare_select(fd_set *readset, fd_set *writeset)
{
unsigned int i;
for (i = 0; i < sockets_alloc; i++)
switch (sockets[i].type) {
case AUTH_SOCKET:
case AUTH_CONNECTION:
FD_SET(sockets[i].fd, readset);
if (buffer_len(&sockets[i].output) > 0)
FD_SET(sockets[i].fd, writeset);
break;
case AUTH_UNUSED:
break;
default:
fatal("Unknown socket type %d", sockets[i].type);
break;
}
}
void
after_select(fd_set *readset, fd_set *writeset)
{
unsigned int i;
int len, sock;
char buf[1024];
struct sockaddr_un sunaddr;
for (i = 0; i < sockets_alloc; i++)
switch (sockets[i].type) {
case AUTH_UNUSED:
break;
case AUTH_SOCKET:
if (FD_ISSET(sockets[i].fd, readset)) {
len = sizeof(sunaddr);
sock = accept(sockets[i].fd, (struct sockaddr *) & sunaddr, &len);
if (sock < 0) {
perror("accept from AUTH_SOCKET");
break;
}
new_socket(AUTH_CONNECTION, sock);
}
break;
case AUTH_CONNECTION:
if (buffer_len(&sockets[i].output) > 0 &&
FD_ISSET(sockets[i].fd, writeset)) {
len = write(sockets[i].fd, buffer_ptr(&sockets[i].output),
buffer_len(&sockets[i].output));
if (len <= 0) {
shutdown(sockets[i].fd, SHUT_RDWR);
close(sockets[i].fd);
sockets[i].type = AUTH_UNUSED;
break;
}
buffer_consume(&sockets[i].output, len);
}
if (FD_ISSET(sockets[i].fd, readset)) {
len = read(sockets[i].fd, buf, sizeof(buf));
if (len <= 0) {
shutdown(sockets[i].fd, SHUT_RDWR);
close(sockets[i].fd);
sockets[i].type = AUTH_UNUSED;
break;
}
buffer_append(&sockets[i].input, buf, len);
process_message(&sockets[i]);
}
break;
default:
fatal("Unknown type %d", sockets[i].type);
}
}
void
check_parent_exists(int sig)
{
if (kill(parent_pid, 0) < 0) {
/* printf("Parent has died - Authentication agent exiting.\n"); */
exit(1);
}
signal(SIGALRM, check_parent_exists);
alarm(10);
}
void
cleanup_socket(void)
{
remove(socket_name);
rmdir(socket_dir);
}
void
cleanup_exit(int i)
{
cleanup_socket();
exit(i);
}
void
usage()
{
fprintf(stderr, "ssh-agent version %s\n", SSH_VERSION);
fprintf(stderr, "Usage: %s [-c | -s] [-k] [command {args...]]\n",
__progname);
exit(1);
}
int
main(int ac, char **av)
{
fd_set readset, writeset;
int sock, c_flag = 0, k_flag = 0, s_flag = 0, ch;
struct sockaddr_un sunaddr;
pid_t pid;
char *shell, *format, *pidstr, pidstrbuf[1 + 3 * sizeof pid];
/* check if RSA support exists */
if (rsa_alive() == 0) {
fprintf(stderr,
"%s: no RSA support in libssl and libcrypto. See ssl(8).\n",
__progname);
exit(1);
}
while ((ch = getopt(ac, av, "cks")) != -1) {
switch (ch) {
case 'c':
if (s_flag)
usage();
c_flag++;
break;
case 'k':
k_flag++;
break;
case 's':
if (c_flag)
usage();
s_flag++;
break;
default:
usage();
}
}
ac -= optind;
av += optind;
if (ac > 0 && (c_flag || k_flag || s_flag))
usage();
if (ac == 0 && !c_flag && !k_flag && !s_flag) {
shell = getenv("SHELL");
if (shell != NULL && strncmp(shell + strlen(shell) - 3, "csh", 3) == 0)
c_flag = 1;
}
if (k_flag) {
pidstr = getenv(SSH_AGENTPID_ENV_NAME);
if (pidstr == NULL) {
fprintf(stderr, "%s not set, cannot kill agent\n",
SSH_AGENTPID_ENV_NAME);
exit(1);
}
pid = atoi(pidstr);
if (pid < 1) { /* XXX PID_MAX check too */
fprintf(stderr, "%s=\"%s\", which is not a good PID\n",
SSH_AGENTPID_ENV_NAME, pidstr);
exit(1);
}
if (kill(pid, SIGTERM) == -1) {
perror("kill");
exit(1);
}
format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
printf(format, SSH_AUTHSOCKET_ENV_NAME);
printf(format, SSH_AGENTPID_ENV_NAME);
printf("echo Agent pid %d killed;\n", pid);
exit(0);
}
parent_pid = getpid();
/* Create private directory for agent socket */
strlcpy(socket_dir, "/tmp/ssh-XXXXXXXX", sizeof socket_dir);
if (mkdtemp(socket_dir) == NULL) {
perror("mkdtemp: private socket dir");
exit(1);
}
snprintf(socket_name, sizeof socket_name, "%s/agent.%d", socket_dir,
parent_pid);
/*
* Create socket early so it will exist before command gets run from
* the parent.
*/
sock = socket(AF_UNIX, SOCK_STREAM, 0);
if (sock < 0) {
perror("socket");
cleanup_exit(1);
}
memset(&sunaddr, 0, sizeof(sunaddr));
sunaddr.sun_family = AF_UNIX;
strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path));
if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0) {
perror("bind");
cleanup_exit(1);
}
if (listen(sock, 5) < 0) {
perror("listen");
cleanup_exit(1);
}
/*
* Fork, and have the parent execute the command, if any, or present
* the socket data. The child continues as the authentication agent.
*/
pid = fork();
if (pid == -1) {
perror("fork");
exit(1);
}
if (pid != 0) { /* Parent - execute the given command. */
close(sock);
snprintf(pidstrbuf, sizeof pidstrbuf, "%d", pid);
if (ac == 0) {
format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
SSH_AUTHSOCKET_ENV_NAME);
printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
SSH_AGENTPID_ENV_NAME);
printf("echo Agent pid %d;\n", pid);
exit(0);
}
setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1);
setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1);
execvp(av[0], av);
perror(av[0]);
exit(1);
}
close(0);
close(1);
close(2);
if (setsid() == -1) {
perror("setsid");
cleanup_exit(1);
}
if (atexit(cleanup_socket) < 0) {
perror("atexit");
cleanup_exit(1);
}
new_socket(AUTH_SOCKET, sock);
if (ac > 0) {
signal(SIGALRM, check_parent_exists);
alarm(10);
}
signal(SIGINT, SIG_IGN);
signal(SIGPIPE, SIG_IGN);
signal(SIGHUP, cleanup_exit);
signal(SIGTERM, cleanup_exit);
while (1) {
FD_ZERO(&readset);
FD_ZERO(&writeset);
prepare_select(&readset, &writeset);
if (select(max_fd + 1, &readset, &writeset, NULL, NULL) < 0) {
if (errno == EINTR)
continue;
exit(1);
}
after_select(&readset, &writeset);
}
/* NOTREACHED */
}