ssh-agent.c

OpenSSL Source code for SFTP, SSH, and many others

/*
 * Author: Tatu Ylonen <[e-mail]>
 * Copyright (c) 1995 Tatu Ylonen <[e-mail]>, Espoo, Finland
 *                    All rights reserved
 * The authentication agent program.
 *
 * 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".
 *
 * Copyright (c) 2000, 2001 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"
#include "openbsd-compat/fake-queue.h"
RCSID("$OpenBSD: ssh-agent.c,v 1.95 2002/06/19 00:27:55 deraadt Exp $");

#include <openssl/evp.h>
#include <openssl/md5.h>

#include "ssh.h"
#include "rsa.h"
#include "buffer.h"
#include "bufaux.h"
#include "xmalloc.h"
#include "getput.h"
#include "key.h"
#include "authfd.h"
#include "compat.h"
#include "log.h"

#ifdef SMARTCARD
#include "scard.h"
#endif

typedef enum {
	AUTH_UNUSED,
	AUTH_SOCKET,
	AUTH_CONNECTION
} sock_type;

typedef struct {
	int fd;
	sock_type type;
	Buffer input;
	Buffer output;
	Buffer request;
} SocketEntry;

u_int sockets_alloc = 0;
SocketEntry *sockets = NULL;

typedef struct identity {
	TAILQ_ENTRY(identity) next;
	Key *key;
	char *comment;
	u_int death;
} Identity;

typedef struct {
	int nentries;
	TAILQ_HEAD(idqueue, identity) idlist;
} Idtab;

/* private key table, one per protocol version */
Idtab idtable[3];

int max_fd = 0;

/* pid of shell == parent of agent */
pid_t parent_pid = -1;

/* pathname and directory for AUTH_SOCKET */
char socket_name[1024];
char socket_dir[1024];

/* locking */
int locked = 0;
char *lock_passwd = NULL;

#ifdef HAVE___PROGNAME
extern char *__progname;
#else
char *__progname;
#endif

static void
idtab_init(void)
{
	int i;
	for (i = 0; i <=2; i++) {
		TAILQ_INIT(&idtable[i].idlist);
		idtable[i].nentries = 0;
	}
}

/* return private key table for requested protocol version */
static Idtab *
idtab_lookup(int version)
{
	if (version < 1 || version > 2)
		fatal("internal error, bad protocol version %d", version);
	return &idtable[version];
}

static void
free_identity(Identity *id)
{
	key_free(id->key);
	xfree(id->comment);
	xfree(id);
}

/* return matching private key for given public key */
static Identity *
lookup_identity(Key *key, int version)
{
	Identity *id;

	Idtab *tab = idtab_lookup(version);
	TAILQ_FOREACH(id, &tab->idlist, next) {
		if (key_equal(key, id->key))
			return (id);
	}
	return (NULL);
}

/* send list of supported public keys to 'client' */
static void
process_request_identities(SocketEntry *e, int version)
{
	Idtab *tab = idtab_lookup(version);
	Buffer msg;
	Identity *id;

	buffer_init(&msg);
	buffer_put_char(&msg, (version == 1) ?
	    SSH_AGENT_RSA_IDENTITIES_ANSWER : SSH2_AGENT_IDENTITIES_ANSWER);
	buffer_put_int(&msg, tab->nentries);
	TAILQ_FOREACH(id, &tab->idlist, next) {
		if (id->key->type == KEY_RSA1) {
			buffer_put_int(&msg, BN_num_bits(id->key->rsa->n));
			buffer_put_bignum(&msg, id->key->rsa->e);
			buffer_put_bignum(&msg, id->key->rsa->n);
		} else {
			u_char *blob;
			u_int blen;
			key_to_blob(id->key, &blob, &blen);
			buffer_put_string(&msg, blob, blen);
			xfree(blob);
		}
		buffer_put_cstring(&msg, id->comment);
	}
	buffer_put_int(&e->output, buffer_len(&msg));
	buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
	buffer_free(&msg);
}

/* ssh1 only */
static void
process_authentication_challenge1(SocketEntry *e)
{
	Identity *id;
	Key *key;
	BIGNUM *challenge;
	int i, len;
	Buffer msg;
	MD5_CTX md;
	u_char buf[32], mdbuf[16], session_id[16];
	u_int response_type;

	buffer_init(&msg);
	key = key_new(KEY_RSA1);
	if ((challenge = BN_new()) == NULL)
		fatal("process_authentication_challenge1: BN_new failed");

	buffer_get_int(&e->request);				/* ignored */
	buffer_get_bignum(&e->request, key->rsa->e);
	buffer_get_bignum(&e->request, key->rsa->n);
	buffer_get_bignum(&e->request, challenge);

	/* Only protocol 1.1 is supported */
	if (buffer_len(&e->request) == 0)
		goto failure;
	buffer_get(&e->request, session_id, 16);
	response_type = buffer_get_int(&e->request);
	if (response_type != 1)
		goto failure;

	id = lookup_identity(key, 1);
	if (id != NULL) {
		Key *private = id->key;
		/* Decrypt the challenge using the private key. */
		if (rsa_private_decrypt(challenge, challenge, private->rsa) <= 0)
			goto failure;

		/* The response is MD5 of decrypted challenge plus session id. */
		len = BN_num_bytes(challenge);
		if (len <= 0 || len > 32) {
			log("process_authentication_challenge: bad challenge length %d", len);
			goto failure;
		}
		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);

		/* 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;
	}

failure:
	/* Unknown identity or protocol error.  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));
	key_free(key);
	BN_clear_free(challenge);
	buffer_free(&msg);
}

/* ssh2 only */
static void
process_sign_request2(SocketEntry *e)
{
	extern int datafellows;
	Key *key;
	u_char *blob, *data, *signature = NULL;
	u_int blen, dlen, slen = 0;
	int flags;
	Buffer msg;
	int ok = -1;

	datafellows = 0;

	blob = buffer_get_string(&e->request, &blen);
	data = buffer_get_string(&e->request, &dlen);

	flags = buffer_get_int(&e->request);
	if (flags & SSH_AGENT_OLD_SIGNATURE)
		datafellows = SSH_BUG_SIGBLOB;

	key = key_from_blob(blob, blen);
	if (key != NULL) {
		Identity *id = lookup_identity(key, 2);
		if (id != NULL)
			ok = key_sign(id->key, &signature, &slen, data, dlen);
	}
	key_free(key);
	buffer_init(&msg);
	if (ok == 0) {
		buffer_put_char(&msg, SSH2_AGENT_SIGN_RESPONSE);
		buffer_put_string(&msg, signature, slen);
	} else {
		buffer_put_char(&msg, SSH_AGENT_FAILURE);
	}
	buffer_put_int(&e->output, buffer_len(&msg));
	buffer_append(&e->output, buffer_ptr(&msg),
	    buffer_len(&msg));
	buffer_free(&msg);
	xfree(data);
	xfree(blob);
	if (signature != NULL)
		xfree(signature);
}

/* shared */
static void
process_remove_identity(SocketEntry *e, int version)
{
	Key *key = NULL;
	u_char *blob;
	u_int blen;
	u_int bits;
	int success = 0;

	switch (version) {
	case 1:
		key = key_new(KEY_RSA1);
		bits = buffer_get_int(&e->request);
		buffer_get_bignum(&e->request, key->rsa->e);
		buffer_get_bignum(&e->request, key->rsa->n);

		if (bits != key_size(key))
			log("Warning: identity keysize mismatch: actual %d, announced %d",
			    key_size(key), bits);
		break;
	case 2:
		blob = buffer_get_string(&e->request, &blen);
		key = key_from_blob(blob, blen);
		xfree(blob);
		break;
	}
	if (key != NULL) {
		Identity *id = lookup_identity(key, version);
		if (id != NULL) {
			/*
			 * 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 move
			 * all the entries between the empty slot and the end
			 * of the array.
			 */
			Idtab *tab = idtab_lookup(version);
			if (tab->nentries < 1)
				fatal("process_remove_identity: "
				    "internal error: tab->nentries %d",
				    tab->nentries);
			TAILQ_REMOVE(&tab->idlist, id, next);
			free_identity(id);
			tab->nentries--;
			success = 1;
		}
		key_free(key);
	}
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output,
	    success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
}

static void
process_remove_all_identities(SocketEntry *e, int version)
{
	Idtab *tab = idtab_lookup(version);
	Identity *id;

	/* Loop over all identities and clear the keys. */
	for (id = TAILQ_FIRST(&tab->idlist); id;
	    id = TAILQ_FIRST(&tab->idlist)) {
		TAILQ_REMOVE(&tab->idlist, id, next);
		free_identity(id);
	}

	/* Mark that there are no identities. */
	tab->nentries = 0;

	/* Send success. */
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
}

static void
reaper(void)
{
	Idtab *tab;
	Identity *id, *nxt;
	int version;
	u_int now = time(NULL);

	for (version = 1; version < 3; version++) {
		tab = idtab_lookup(version);
		for (id = TAILQ_FIRST(&tab->idlist); id; id = nxt) {
			nxt = TAILQ_NEXT(id, next);
			if (id->death != 0 && now >= id->death) {
				TAILQ_REMOVE(&tab->idlist, id, next);
				free_identity(id);
				tab->nentries--;
			}
		}
	}
}

static void
process_add_identity(SocketEntry *e, int version)
{
	Key *k = NULL;
	char *type_name;
	char *comment;
	int type, success = 0, death = 0;
	Idtab *tab = idtab_lookup(version);

	switch (version) {
	case 1:
		k = key_new_private(KEY_RSA1);
		buffer_get_int(&e->request);			/* ignored */
		buffer_get_bignum(&e->request, k->rsa->n);
		buffer_get_bignum(&e->request, k->rsa->e);
		buffer_get_bignum(&e->request, k->rsa->d);
		buffer_get_bignum(&e->request, k->rsa->iqmp);

		/* SSH and SSL have p and q swapped */
		buffer_get_bignum(&e->request, k->rsa->q);	/* p */
		buffer_get_bignum(&e->request, k->rsa->p);	/* q */

		/* Generate additional parameters */
		rsa_generate_additional_parameters(k->rsa);
		break;
	case 2:
		type_name = buffer_get_string(&e->request, NULL);
		type = key_type_from_name(type_name);
		xfree(type_name);
		switch (type) {
		case KEY_DSA:
			k = key_new_private(type);
			buffer_get_bignum2(&e->request, k->dsa->p);
			buffer_get_bignum2(&e->request, k->dsa->q);
			buffer_get_bignum2(&e->request, k->dsa->g);
			buffer_get_bignum2(&e->request, k->dsa->pub_key);
			buffer_get_bignum2(&e->request, k->dsa->priv_key);
			break;
		case KEY_RSA:
			k = key_new_private(type);
			buffer_get_bignum2(&e->request, k->rsa->n);
			buffer_get_bignum2(&e->request, k->rsa->e);
			buffer_get_bignum2(&e->request, k->rsa->d);
			buffer_get_bignum2(&e->request, k->rsa->iqmp);
			buffer_get_bignum2(&e->request, k->rsa->p);
			buffer_get_bignum2(&e->request, k->rsa->q);

			/* Generate additional parameters */
			rsa_generate_additional_parameters(k->rsa);
			break;
		default:
			buffer_clear(&e->request);
			goto send;
		}
		break;
	}
	comment = buffer_get_string(&e->request, NULL);
	if (k == NULL) {
		xfree(comment);
		goto send;
	}
	success = 1;
	while (buffer_len(&e->request)) {
		switch (buffer_get_char(&e->request)) {
		case SSH_AGENT_CONSTRAIN_LIFETIME:
			death = time(NULL) + buffer_get_int(&e->request);
			break;
		default:
			break;
		}
	}
	if (lookup_identity(k, version) == NULL) {
		Identity *id = xmalloc(sizeof(Identity));
		id->key = k;
		id->comment = comment;
		id->death = death;
		TAILQ_INSERT_TAIL(&tab->idlist, id, next);
		/* Increment the number of identities. */
		tab->nentries++;
	} else {
		key_free(k);
		xfree(comment);
	}
send:
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output,
	    success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
}

/* XXX todo: encrypt sensitive data with passphrase */
static void
process_lock_agent(SocketEntry *e, int lock)
{
	char *passwd;
	int success = 0;

	passwd = buffer_get_string(&e->request, NULL);
	if (locked && !lock && strcmp(passwd, lock_passwd) == 0) {
		locked = 0;
		memset(lock_passwd, 0, strlen(lock_passwd));
		xfree(lock_passwd);
		lock_passwd = NULL;
		success = 1;
	} else if (!locked && lock) {
		locked = 1;
		lock_passwd = xstrdup(passwd);
		success = 1;
	}
	memset(passwd, 0, strlen(passwd));
	xfree(passwd);

	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output,
	    success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
}

static void
no_identities(SocketEntry *e, u_int type)
{
	Buffer msg;

	buffer_init(&msg);
	buffer_put_char(&msg,
	    (type == SSH_AGENTC_REQUEST_RSA_IDENTITIES) ?
	    SSH_AGENT_RSA_IDENTITIES_ANSWER : SSH2_AGENT_IDENTITIES_ANSWER);
	buffer_put_int(&msg, 0);
	buffer_put_int(&e->output, buffer_len(&msg));
	buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
	buffer_free(&msg);
}

#ifdef SMARTCARD
static void
process_add_smartcard_key (SocketEntry *e)
{
	Identity *id;
	Idtab *tab;
	Key **keys, *k;
	char *sc_reader_id = NULL, *pin;
	int i, version, success = 0;

	sc_reader_id = buffer_get_string(&e->request, NULL);
	pin = buffer_get_string(&e->request, NULL);
	keys = sc_get_keys(sc_reader_id, pin);
	xfree(sc_reader_id);
	xfree(pin);

	if (keys == NULL || keys[0] == NULL) {
		error("sc_get_keys failed");
		goto send;
	}
	for (i = 0; keys[i] != NULL; i++) {
		k = keys[i];
		version = k->type == KEY_RSA1 ? 1 : 2;
		tab = idtab_lookup(version);
		if (lookup_identity(k, version) == NULL) {
			id = xmalloc(sizeof(Identity));
			id->key = k;
			id->comment = xstrdup("smartcard key");
			id->death = 0;
			TAILQ_INSERT_TAIL(&tab->idlist, id, next);
			tab->nentries++;
			success = 1;
		} else {
			key_free(k);
		}
		keys[i] = NULL;
	}
	xfree(keys);
send:
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output,
	    success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
}

static void
process_remove_smartcard_key(SocketEntry *e)
{
	Identity *id;
	Idtab *tab;
	Key **keys, *k = NULL;
	char *sc_reader_id = NULL, *pin;
	int i, version, success = 0;