authfd.c - platform/external/openssh - Gitiles

 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
  * Functions for connecting the local authentication agent.
  *
  * 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: authfd.c,v 1.35 2001/02/04 15:32:22 stevesk Exp $");

 #include <openssl/evp.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 "cipher.h"
 #include "kex.h"
 #include "compat.h"
 #include "log.h"
 #include "atomicio.h"

 /* helper */
 int	decode_reply(int type);

 /* macro to check for "agent failure" message */
 #define agent_failed(x) \
     ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE))

 /* Returns the number of the authentication fd, or -1 if there is none. */

 int
 ssh_get_authentication_socket(void)
 {
 	const char *authsocket;
 	int sock, len;
 	struct sockaddr_un sunaddr;

 	authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
 	if (!authsocket)
 		return -1;

 	sunaddr.sun_family = AF_UNIX;
 	strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
 #ifdef HAVE_SUN_LEN_IN_SOCKADDR_UN
 	sunaddr.sun_len = len = SUN_LEN(&sunaddr)+1;
 #else /* HAVE_SUN_LEN_IN_SOCKADDR_UN */
 	len = SUN_LEN(&sunaddr)+1;
 #endif /* HAVE_SUN_LEN_IN_SOCKADDR_UN */

 	sock = socket(AF_UNIX, SOCK_STREAM, 0);
 	if (sock < 0)
 		return -1;

 	/* close on exec */
 	if (fcntl(sock, F_SETFD, 1) == -1) {
 		close(sock);
 		return -1;
 	}
 	if (connect(sock, (struct sockaddr *) & sunaddr, len) < 0) {
 		close(sock);
 		return -1;
 	}
 	return sock;
 }

 int
 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply)
 {
 	int l, len;
 	char buf[1024];

 	/* Get the length of the message, and format it in the buffer. */
 	len = buffer_len(request);
 	PUT_32BIT(buf, len);

 	/* Send the length and then the packet to the agent. */
 	if (atomicio(write, auth->fd, buf, 4) != 4 ||
 	    atomicio(write, auth->fd, buffer_ptr(request),
 	    buffer_len(request)) != buffer_len(request)) {
 		error("Error writing to authentication socket.");
 		return 0;
 	}
 	/*
 	 * Wait for response from the agent.  First read the length of the
 	 * response packet.
 	 */
 	len = 4;
 	while (len > 0) {
 		l = read(auth->fd, buf + 4 - len, len);
 		if (l <= 0) {
 			error("Error reading response length from authentication socket.");
 			return 0;
 		}
 		len -= l;
 	}

 	/* Extract the length, and check it for sanity. */
 	len = GET_32BIT(buf);
 	if (len > 256 * 1024)
 		fatal("Authentication response too long: %d", len);

 	/* Read the rest of the response in to the buffer. */
 	buffer_clear(reply);
 	while (len > 0) {
 		l = len;
 		if (l > sizeof(buf))
 			l = sizeof(buf);
 		l = read(auth->fd, buf, l);
 		if (l <= 0) {
 			error("Error reading response from authentication socket.");
 			return 0;
 		}
 		buffer_append(reply, (char *) buf, l);
 		len -= l;
 	}
 	return 1;
 }

 /*
  * Closes the agent socket if it should be closed (depends on how it was
  * obtained).  The argument must have been returned by
  * ssh_get_authentication_socket().
  */

 void
 ssh_close_authentication_socket(int sock)
 {
 	if (getenv(SSH_AUTHSOCKET_ENV_NAME))
 		close(sock);
 }

 /*
  * Opens and connects a private socket for communication with the
  * authentication agent.  Returns the file descriptor (which must be
  * shut down and closed by the caller when no longer needed).
  * Returns NULL if an error occurred and the connection could not be
  * opened.
  */

 AuthenticationConnection *
 ssh_get_authentication_connection(void)
 {
 	AuthenticationConnection *auth;
 	int sock;

 	sock = ssh_get_authentication_socket();

 	/*
 	 * Fail if we couldn't obtain a connection.  This happens if we
 	 * exited due to a timeout.
 	 */
 	if (sock < 0)
 		return NULL;

 	auth = xmalloc(sizeof(*auth));
 	auth->fd = sock;
 	buffer_init(&auth->identities);
 	auth->howmany = 0;

 	return auth;
 }

 /*
  * Closes the connection to the authentication agent and frees any associated
  * memory.
  */

 void
 ssh_close_authentication_connection(AuthenticationConnection *auth)
 {
 	buffer_free(&auth->identities);
 	close(auth->fd);
 	xfree(auth);
 }

 /*
  * Returns the first authentication identity held by the agent.
  */

 int
 ssh_get_num_identities(AuthenticationConnection *auth, int version)
 {
 	int type, code1 = 0, code2 = 0;
 	Buffer request;

 	switch(version){
 	case 1:
 		code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
 		code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER;
 		break;
 	case 2:
 		code1 = SSH2_AGENTC_REQUEST_IDENTITIES;
 		code2 = SSH2_AGENT_IDENTITIES_ANSWER;
 		break;
 	default:
 		return 0;
 	}

 	/*
 	 * Send a message to the agent requesting for a list of the
 	 * identities it can represent.
 	 */
 	buffer_init(&request);
 	buffer_put_char(&request, code1);

 	buffer_clear(&auth->identities);
 	if (ssh_request_reply(auth, &request, &auth->identities) == 0) {
 		buffer_free(&request);
 		return 0;
 	}
 	buffer_free(&request);

 	/* Get message type, and verify that we got a proper answer. */
 	type = buffer_get_char(&auth->identities);
 	if (agent_failed(type)) {
 		return 0;
 	} else if (type != code2) {
 		fatal("Bad authentication reply message type: %d", type);
 	}

 	/* Get the number of entries in the response and check it for sanity. */
 	auth->howmany = buffer_get_int(&auth->identities);
 	if (auth->howmany > 1024)
 		fatal("Too many identities in authentication reply: %d\n",
 		    auth->howmany);

 	return auth->howmany;
 }

 Key *
 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version)
 {
 	/* get number of identities and return the first entry (if any). */
 	if (ssh_get_num_identities(auth, version) > 0)
 		return ssh_get_next_identity(auth, comment, version);
 	return NULL;
 }

 Key *
 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version)
 {
 	u_int bits;
 	u_char *blob;
 	u_int blen;
 	Key *key = NULL;

 	/* Return failure if no more entries. */
 	if (auth->howmany <= 0)
 		return NULL;

 	/*
 	 * Get the next entry from the packet.  These will abort with a fatal
 	 * error if the packet is too short or contains corrupt data.
 	 */
 	switch(version){
 	case 1:
 		key = key_new(KEY_RSA1);
 		bits = buffer_get_int(&auth->identities);
 		buffer_get_bignum(&auth->identities, key->rsa->e);
 		buffer_get_bignum(&auth->identities, key->rsa->n);
 		*comment = buffer_get_string(&auth->identities, NULL);
 		if (bits != BN_num_bits(key->rsa->n))
 			log("Warning: identity keysize mismatch: actual %d, announced %u",
 			    BN_num_bits(key->rsa->n), bits);
 		break;
 	case 2:
 		blob = buffer_get_string(&auth->identities, &blen);
 		*comment = buffer_get_string(&auth->identities, NULL);
 		key = key_from_blob(blob, blen);
 		xfree(blob);
 		break;
 	default:
 		return NULL;
 		break;
 	}
 	/* Decrement the number of remaining entries. */
 	auth->howmany--;
 	return key;
 }

 /*
  * Generates a random challenge, sends it to the agent, and waits for
  * response from the agent.  Returns true (non-zero) if the agent gave the
  * correct answer, zero otherwise.  Response type selects the style of
  * response desired, with 0 corresponding to protocol version 1.0 (no longer
  * supported) and 1 corresponding to protocol version 1.1.
  */

 int
 ssh_decrypt_challenge(AuthenticationConnection *auth,
     Key* key, BIGNUM *challenge,
     u_char session_id[16],
     u_int response_type,
     u_char response[16])
 {
 	Buffer buffer;
 	int success = 0;
 	int i;
 	int type;

 	if (key->type != KEY_RSA1)
 		return 0;
 	if (response_type == 0) {
 		log("Compatibility with ssh protocol version 1.0 no longer supported.");
 		return 0;
 	}
 	buffer_init(&buffer);
 	buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE);
 	buffer_put_int(&buffer, BN_num_bits(key->rsa->n));
 	buffer_put_bignum(&buffer, key->rsa->e);
 	buffer_put_bignum(&buffer, key->rsa->n);
 	buffer_put_bignum(&buffer, challenge);
 	buffer_append(&buffer, (char *) session_id, 16);
 	buffer_put_int(&buffer, response_type);

 	if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
 		buffer_free(&buffer);
 		return 0;
 	}
 	type = buffer_get_char(&buffer);

 	if (agent_failed(type)) {
 		log("Agent admitted failure to authenticate using the key.");
 	} else if (type != SSH_AGENT_RSA_RESPONSE) {
 		fatal("Bad authentication response: %d", type);
 	} else {
 		success = 1;
 		/*
 		 * Get the response from the packet.  This will abort with a
 		 * fatal error if the packet is corrupt.
 		 */
 		for (i = 0; i < 16; i++)
 			response[i] = buffer_get_char(&buffer);
 	}
 	buffer_free(&buffer);
 	return success;
 }

 /* ask agent to sign data, returns -1 on error, 0 on success */
 int
 ssh_agent_sign(AuthenticationConnection *auth,
     Key *key,
     u_char **sigp, int *lenp,
     u_char *data, int datalen)
 {
 	extern int datafellows;
 	Buffer msg;
 	u_char *blob;
 	u_int blen;
 	int type, flags = 0;
 	int ret = -1;

 	if (key_to_blob(key, &blob, &blen) == 0)
 		return -1;

 	if (datafellows & SSH_BUG_SIGBLOB)
 		flags = SSH_AGENT_OLD_SIGNATURE;

 	buffer_init(&msg);
 	buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST);
 	buffer_put_string(&msg, blob, blen);
 	buffer_put_string(&msg, data, datalen);
 	buffer_put_int(&msg, flags);
 	xfree(blob);

 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
 		buffer_free(&msg);
 		return -1;
 	}
 	type = buffer_get_char(&msg);
 	if (agent_failed(type)) {
 		log("Agent admitted failure to sign using the key.");
 	} else if (type != SSH2_AGENT_SIGN_RESPONSE) {
 		fatal("Bad authentication response: %d", type);
 	} else {
 		ret = 0;
 		*sigp = buffer_get_string(&msg, lenp);
 	}
 	buffer_free(&msg);
 	return ret;
 }

 /* Encode key for a message to the agent. */

 void
 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment)
 {
 	buffer_clear(b);
 	buffer_put_char(b, SSH_AGENTC_ADD_RSA_IDENTITY);
 	buffer_put_int(b, BN_num_bits(key->n));
 	buffer_put_bignum(b, key->n);
 	buffer_put_bignum(b, key->e);
 	buffer_put_bignum(b, key->d);
 	/* To keep within the protocol: p < q for ssh. in SSL p > q */
 	buffer_put_bignum(b, key->iqmp);	/* ssh key->u */
 	buffer_put_bignum(b, key->q);	/* ssh key->p, SSL key->q */
 	buffer_put_bignum(b, key->p);	/* ssh key->q, SSL key->p */
 	buffer_put_string(b, comment, strlen(comment));
 }

 void
 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment)
 {
 	buffer_clear(b);
 	buffer_put_char(b, SSH2_AGENTC_ADD_IDENTITY);
 	buffer_put_cstring(b, key_ssh_name(key));
 	switch(key->type){
 	case KEY_RSA:
 		buffer_put_bignum2(b, key->rsa->n);
 		buffer_put_bignum2(b, key->rsa->e);
 		buffer_put_bignum2(b, key->rsa->d);
 		buffer_put_bignum2(b, key->rsa->iqmp);
 		buffer_put_bignum2(b, key->rsa->p);
 		buffer_put_bignum2(b, key->rsa->q);
 		break;
 	case KEY_DSA:
 		buffer_put_bignum2(b, key->dsa->p);
 		buffer_put_bignum2(b, key->dsa->q);
 		buffer_put_bignum2(b, key->dsa->g);
 		buffer_put_bignum2(b, key->dsa->pub_key);
 		buffer_put_bignum2(b, key->dsa->priv_key);
 		break;
 	}
 	buffer_put_cstring(b, comment);
 }

 /*
  * Adds an identity to the authentication server.  This call is not meant to
  * be used by normal applications.
  */

 int
 ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment)
 {
 	Buffer msg;
 	int type;

 	buffer_init(&msg);

 	switch (key->type) {
 	case KEY_RSA1:
 		ssh_encode_identity_rsa1(&msg, key->rsa, comment);
 		break;
 	case KEY_RSA:
 	case KEY_DSA:
 		ssh_encode_identity_ssh2(&msg, key, comment);
 		break;
 	default:
 		buffer_free(&msg);
 		return 0;
 		break;
 	}
 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
 		buffer_free(&msg);
 		return 0;
 	}
 	type = buffer_get_char(&msg);
 	buffer_free(&msg);
 	return decode_reply(type);
 }

 /*
  * Removes an identity from the authentication server.  This call is not
  * meant to be used by normal applications.
  */

 int
 ssh_remove_identity(AuthenticationConnection *auth, Key *key)
 {
 	Buffer msg;
 	int type;
 	u_char *blob;
 	u_int blen;

 	buffer_init(&msg);

 	if (key->type == KEY_RSA1) {
 		buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY);
 		buffer_put_int(&msg, BN_num_bits(key->rsa->n));
 		buffer_put_bignum(&msg, key->rsa->e);
 		buffer_put_bignum(&msg, key->rsa->n);
 	} else if (key->type == KEY_DSA || key->type == KEY_RSA) {
 		key_to_blob(key, &blob, &blen);
 		buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY);
 		buffer_put_string(&msg, blob, blen);
 		xfree(blob);
 	} else {
 		buffer_free(&msg);
 		return 0;
 	}
 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
 		buffer_free(&msg);
 		return 0;
 	}
 	type = buffer_get_char(&msg);
 	buffer_free(&msg);
 	return decode_reply(type);
 }

 /*
  * Removes all identities from the agent.  This call is not meant to be used
  * by normal applications.
  */

 int
 ssh_remove_all_identities(AuthenticationConnection *auth, int version)
 {
 	Buffer msg;
 	int type;
 	int code = (version==1) ?
 		SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
 		SSH2_AGENTC_REMOVE_ALL_IDENTITIES;

 	buffer_init(&msg);
 	buffer_put_char(&msg, code);

 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
 		buffer_free(&msg);
 		return 0;
 	}
 	type = buffer_get_char(&msg);
 	buffer_free(&msg);
 	return decode_reply(type);
 }

 int
 decode_reply(int type)
 {
 	switch (type) {
 	case SSH_AGENT_FAILURE:
 	case SSH_COM_AGENT2_FAILURE:
 		log("SSH_AGENT_FAILURE");
 		return 0;
 	case SSH_AGENT_SUCCESS:
 		return 1;
 	default:
 		fatal("Bad response from authentication agent: %d", type);
 	}
 	/* NOTREACHED */
 	return 0;
 }
	/*
	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	* All rights reserved
	* Functions for connecting the local authentication agent.
	*
	* 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: authfd.c,v 1.35 2001/02/04 15:32:22 stevesk Exp $");

	#include <openssl/evp.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 "cipher.h"
	#include "kex.h"
	#include "compat.h"
	#include "log.h"
	#include "atomicio.h"

	/* helper */
	int decode_reply(int type);

	/* macro to check for "agent failure" message */
	#define agent_failed(x) \
	((x == SSH_AGENT_FAILURE) \|\| (x == SSH_COM_AGENT2_FAILURE))

	/* Returns the number of the authentication fd, or -1 if there is none. */

	int
	ssh_get_authentication_socket(void)
	{
	const char *authsocket;
	int sock, len;
	struct sockaddr_un sunaddr;

	authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
	if (!authsocket)
	return -1;

	sunaddr.sun_family = AF_UNIX;
	strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
	#ifdef HAVE_SUN_LEN_IN_SOCKADDR_UN
	sunaddr.sun_len = len = SUN_LEN(&sunaddr)+1;
	#else /* HAVE_SUN_LEN_IN_SOCKADDR_UN */
	len = SUN_LEN(&sunaddr)+1;
	#endif /* HAVE_SUN_LEN_IN_SOCKADDR_UN */

	sock = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sock < 0)
	return -1;

	/* close on exec */
	if (fcntl(sock, F_SETFD, 1) == -1) {
	close(sock);
	return -1;
	}
	if (connect(sock, (struct sockaddr *) & sunaddr, len) < 0) {
	close(sock);
	return -1;
	}
	return sock;
	}

	int
	ssh_request_reply(AuthenticationConnection auth, Buffer request, Buffer *reply)
	{
	int l, len;
	char buf[1024];

	/* Get the length of the message, and format it in the buffer. */
	len = buffer_len(request);
	PUT_32BIT(buf, len);

	/* Send the length and then the packet to the agent. */
	if (atomicio(write, auth->fd, buf, 4) != 4 \|\|
	atomicio(write, auth->fd, buffer_ptr(request),
	buffer_len(request)) != buffer_len(request)) {
	error("Error writing to authentication socket.");
	return 0;
	}
	/*
	* Wait for response from the agent. First read the length of the
	* response packet.
	*/
	len = 4;
	while (len > 0) {
	l = read(auth->fd, buf + 4 - len, len);
	if (l <= 0) {
	error("Error reading response length from authentication socket.");
	return 0;
	}
	len -= l;
	}

	/* Extract the length, and check it for sanity. */
	len = GET_32BIT(buf);
	if (len > 256 * 1024)
	fatal("Authentication response too long: %d", len);

	/* Read the rest of the response in to the buffer. */
	buffer_clear(reply);
	while (len > 0) {
	l = len;
	if (l > sizeof(buf))
	l = sizeof(buf);
	l = read(auth->fd, buf, l);
	if (l <= 0) {
	error("Error reading response from authentication socket.");
	return 0;
	}
	buffer_append(reply, (char *) buf, l);
	len -= l;
	}
	return 1;
	}

	/*
	* Closes the agent socket if it should be closed (depends on how it was
	* obtained). The argument must have been returned by
	* ssh_get_authentication_socket().
	*/

	void
	ssh_close_authentication_socket(int sock)
	{
	if (getenv(SSH_AUTHSOCKET_ENV_NAME))
	close(sock);
	}

	/*
	* Opens and connects a private socket for communication with the
	* authentication agent. Returns the file descriptor (which must be
	* shut down and closed by the caller when no longer needed).
	* Returns NULL if an error occurred and the connection could not be
	* opened.
	*/

	AuthenticationConnection *
	ssh_get_authentication_connection(void)
	{
	AuthenticationConnection *auth;
	int sock;

	sock = ssh_get_authentication_socket();

	/*
	* Fail if we couldn't obtain a connection. This happens if we
	* exited due to a timeout.
	*/
	if (sock < 0)
	return NULL;

	auth = xmalloc(sizeof(*auth));
	auth->fd = sock;
	buffer_init(&auth->identities);
	auth->howmany = 0;

	return auth;
	}

	/*
	* Closes the connection to the authentication agent and frees any associated
	* memory.
	*/

	void
	ssh_close_authentication_connection(AuthenticationConnection *auth)
	{
	buffer_free(&auth->identities);
	close(auth->fd);
	xfree(auth);
	}

	/*
	* Returns the first authentication identity held by the agent.
	*/

	int
	ssh_get_num_identities(AuthenticationConnection *auth, int version)
	{
	int type, code1 = 0, code2 = 0;
	Buffer request;

	switch(version){
	case 1:
	code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
	code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER;
	break;
	case 2:
	code1 = SSH2_AGENTC_REQUEST_IDENTITIES;
	code2 = SSH2_AGENT_IDENTITIES_ANSWER;
	break;
	default:
	return 0;
	}

	/*
	* Send a message to the agent requesting for a list of the
	* identities it can represent.
	*/
	buffer_init(&request);
	buffer_put_char(&request, code1);

	buffer_clear(&auth->identities);
	if (ssh_request_reply(auth, &request, &auth->identities) == 0) {
	buffer_free(&request);
	return 0;
	}
	buffer_free(&request);

	/* Get message type, and verify that we got a proper answer. */
	type = buffer_get_char(&auth->identities);
	if (agent_failed(type)) {
	return 0;
	} else if (type != code2) {
	fatal("Bad authentication reply message type: %d", type);
	}

	/* Get the number of entries in the response and check it for sanity. */
	auth->howmany = buffer_get_int(&auth->identities);
	if (auth->howmany > 1024)
	fatal("Too many identities in authentication reply: %d\n",
	auth->howmany);

	return auth->howmany;
	}

	Key *
	ssh_get_first_identity(AuthenticationConnection auth, char *comment, int version)
	{
	/* get number of identities and return the first entry (if any). */
	if (ssh_get_num_identities(auth, version) > 0)
	return ssh_get_next_identity(auth, comment, version);
	return NULL;
	}

	Key *
	ssh_get_next_identity(AuthenticationConnection auth, char *comment, int version)
	{
	u_int bits;
	u_char *blob;
	u_int blen;
	Key *key = NULL;

	/* Return failure if no more entries. */
	if (auth->howmany <= 0)
	return NULL;

	/*
	* Get the next entry from the packet. These will abort with a fatal
	* error if the packet is too short or contains corrupt data.
	*/
	switch(version){
	case 1:
	key = key_new(KEY_RSA1);
	bits = buffer_get_int(&auth->identities);
	buffer_get_bignum(&auth->identities, key->rsa->e);
	buffer_get_bignum(&auth->identities, key->rsa->n);
	*comment = buffer_get_string(&auth->identities, NULL);
	if (bits != BN_num_bits(key->rsa->n))
	log("Warning: identity keysize mismatch: actual %d, announced %u",
	BN_num_bits(key->rsa->n), bits);
	break;
	case 2:
	blob = buffer_get_string(&auth->identities, &blen);
	*comment = buffer_get_string(&auth->identities, NULL);
	key = key_from_blob(blob, blen);
	xfree(blob);
	break;
	default:
	return NULL;
	break;
	}
	/* Decrement the number of remaining entries. */
	auth->howmany--;
	return key;
	}

	/*
	* Generates a random challenge, sends it to the agent, and waits for
	* response from the agent. Returns true (non-zero) if the agent gave the
	* correct answer, zero otherwise. Response type selects the style of
	* response desired, with 0 corresponding to protocol version 1.0 (no longer
	* supported) and 1 corresponding to protocol version 1.1.
	*/

	int
	ssh_decrypt_challenge(AuthenticationConnection *auth,
	Key* key, BIGNUM *challenge,
	u_char session_id[16],
	u_int response_type,
	u_char response[16])
	{
	Buffer buffer;
	int success = 0;
	int i;
	int type;

	if (key->type != KEY_RSA1)
	return 0;
	if (response_type == 0) {
	log("Compatibility with ssh protocol version 1.0 no longer supported.");
	return 0;
	}
	buffer_init(&buffer);
	buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE);
	buffer_put_int(&buffer, BN_num_bits(key->rsa->n));
	buffer_put_bignum(&buffer, key->rsa->e);
	buffer_put_bignum(&buffer, key->rsa->n);
	buffer_put_bignum(&buffer, challenge);
	buffer_append(&buffer, (char *) session_id, 16);
	buffer_put_int(&buffer, response_type);

	if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
	buffer_free(&buffer);
	return 0;
	}
	type = buffer_get_char(&buffer);

	if (agent_failed(type)) {
	log("Agent admitted failure to authenticate using the key.");
	} else if (type != SSH_AGENT_RSA_RESPONSE) {
	fatal("Bad authentication response: %d", type);
	} else {
	success = 1;
	/*
	* Get the response from the packet. This will abort with a
	* fatal error if the packet is corrupt.
	*/
	for (i = 0; i < 16; i++)
	response[i] = buffer_get_char(&buffer);
	}
	buffer_free(&buffer);
	return success;
	}

	/* ask agent to sign data, returns -1 on error, 0 on success */
	int
	ssh_agent_sign(AuthenticationConnection *auth,
	Key *key,
	u_char *sigp, int lenp,
	u_char *data, int datalen)
	{
	extern int datafellows;
	Buffer msg;
	u_char *blob;
	u_int blen;
	int type, flags = 0;
	int ret = -1;

	if (key_to_blob(key, &blob, &blen) == 0)
	return -1;

	if (datafellows & SSH_BUG_SIGBLOB)
	flags = SSH_AGENT_OLD_SIGNATURE;

	buffer_init(&msg);
	buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST);
	buffer_put_string(&msg, blob, blen);
	buffer_put_string(&msg, data, datalen);
	buffer_put_int(&msg, flags);
	xfree(blob);

	if (ssh_request_reply(auth, &msg, &msg) == 0) {
	buffer_free(&msg);
	return -1;
	}
	type = buffer_get_char(&msg);
	if (agent_failed(type)) {
	log("Agent admitted failure to sign using the key.");
	} else if (type != SSH2_AGENT_SIGN_RESPONSE) {
	fatal("Bad authentication response: %d", type);
	} else {
	ret = 0;
	*sigp = buffer_get_string(&msg, lenp);
	}
	buffer_free(&msg);
	return ret;
	}

	/* Encode key for a message to the agent. */

	void
	ssh_encode_identity_rsa1(Buffer b, RSA key, const char *comment)
	{
	buffer_clear(b);
	buffer_put_char(b, SSH_AGENTC_ADD_RSA_IDENTITY);
	buffer_put_int(b, BN_num_bits(key->n));
	buffer_put_bignum(b, key->n);
	buffer_put_bignum(b, key->e);
	buffer_put_bignum(b, key->d);
	/* To keep within the protocol: p < q for ssh. in SSL p > q */
	buffer_put_bignum(b, key->iqmp); /* ssh key->u */
	buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */
	buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */
	buffer_put_string(b, comment, strlen(comment));
	}

	void
	ssh_encode_identity_ssh2(Buffer b, Key key, const char *comment)
	{
	buffer_clear(b);
	buffer_put_char(b, SSH2_AGENTC_ADD_IDENTITY);
	buffer_put_cstring(b, key_ssh_name(key));
	switch(key->type){
	case KEY_RSA:
	buffer_put_bignum2(b, key->rsa->n);
	buffer_put_bignum2(b, key->rsa->e);
	buffer_put_bignum2(b, key->rsa->d);
	buffer_put_bignum2(b, key->rsa->iqmp);
	buffer_put_bignum2(b, key->rsa->p);
	buffer_put_bignum2(b, key->rsa->q);
	break;
	case KEY_DSA:
	buffer_put_bignum2(b, key->dsa->p);
	buffer_put_bignum2(b, key->dsa->q);
	buffer_put_bignum2(b, key->dsa->g);
	buffer_put_bignum2(b, key->dsa->pub_key);
	buffer_put_bignum2(b, key->dsa->priv_key);
	break;
	}
	buffer_put_cstring(b, comment);
	}

	/*
	* Adds an identity to the authentication server. This call is not meant to
	* be used by normal applications.
	*/

	int
	ssh_add_identity(AuthenticationConnection auth, Key key, const char *comment)
	{
	Buffer msg;
	int type;

	buffer_init(&msg);

	switch (key->type) {
	case KEY_RSA1:
	ssh_encode_identity_rsa1(&msg, key->rsa, comment);
	break;
	case KEY_RSA:
	case KEY_DSA:
	ssh_encode_identity_ssh2(&msg, key, comment);
	break;
	default:
	buffer_free(&msg);
	return 0;
	break;
	}
	if (ssh_request_reply(auth, &msg, &msg) == 0) {
	buffer_free(&msg);
	return 0;
	}
	type = buffer_get_char(&msg);
	buffer_free(&msg);
	return decode_reply(type);
	}

	/*
	* Removes an identity from the authentication server. This call is not
	* meant to be used by normal applications.
	*/

	int
	ssh_remove_identity(AuthenticationConnection auth, Key key)
	{
	Buffer msg;
	int type;
	u_char *blob;
	u_int blen;

	buffer_init(&msg);

	if (key->type == KEY_RSA1) {
	buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY);
	buffer_put_int(&msg, BN_num_bits(key->rsa->n));
	buffer_put_bignum(&msg, key->rsa->e);
	buffer_put_bignum(&msg, key->rsa->n);
	} else if (key->type == KEY_DSA \|\| key->type == KEY_RSA) {
	key_to_blob(key, &blob, &blen);
	buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY);
	buffer_put_string(&msg, blob, blen);
	xfree(blob);
	} else {
	buffer_free(&msg);
	return 0;
	}
	if (ssh_request_reply(auth, &msg, &msg) == 0) {
	buffer_free(&msg);
	return 0;
	}
	type = buffer_get_char(&msg);
	buffer_free(&msg);
	return decode_reply(type);
	}

	/*
	* Removes all identities from the agent. This call is not meant to be used
	* by normal applications.
	*/

	int
	ssh_remove_all_identities(AuthenticationConnection *auth, int version)
	{
	Buffer msg;
	int type;
	int code = (version==1) ?
	SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
	SSH2_AGENTC_REMOVE_ALL_IDENTITIES;

	buffer_init(&msg);
	buffer_put_char(&msg, code);

	if (ssh_request_reply(auth, &msg, &msg) == 0) {
	buffer_free(&msg);
	return 0;
	}
	type = buffer_get_char(&msg);
	buffer_free(&msg);
	return decode_reply(type);
	}

	int
	decode_reply(int type)
	{
	switch (type) {
	case SSH_AGENT_FAILURE:
	case SSH_COM_AGENT2_FAILURE:
	log("SSH_AGENT_FAILURE");
	return 0;
	case SSH_AGENT_SUCCESS:
	return 1;
	default:
	fatal("Bad response from authentication agent: %d", type);
	}
	/* NOTREACHED */
	return 0;
	}