authfd.c - third_party/openssh-portable - Git at Google

 /*
  *
  * authfd.c
  *
  * 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 01:30:28 1995 ylo
  *
  * Functions for connecting the local authentication agent.
  *
  */

 #include "includes.h"
 RCSID("$OpenBSD: authfd.c,v 1.20 2000/06/20 01:39:38 markus Exp $");

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

 #include <openssl/rsa.h>

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

 int
 ssh_get_authentication_socket()
 {
 	const char *authsocket;
 	int sock;
 	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));

 	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, sizeof(sunaddr)) < 0) {
 		close(sock);
 		return -1;
 	}
 	return sock;
 }

 /*
  * 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()
 {
 	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->packet);
 	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 *ac)
 {
 	buffer_free(&ac->packet);
 	buffer_free(&ac->identities);
 	close(ac->fd);
 	xfree(ac);
 }

 /*
  * Returns the first authentication identity held by the agent.
  * Returns true if an identity is available, 0 otherwise.
  * The caller must initialize the integers before the call, and free the
  * comment after a successful call (before calling ssh_get_next_identity).
  */

 int
 ssh_get_first_identity(AuthenticationConnection *auth,
 		       BIGNUM *e, BIGNUM *n, char **comment)
 {
 	unsigned char msg[8192];
 	int len, l;

 	/*
 	 * Send a message to the agent requesting for a list of the
 	 * identities it can represent.
 	 */
 	msg[0] = 0;
 	msg[1] = 0;
 	msg[2] = 0;
 	msg[3] = 1;
 	msg[4] = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
 	if (atomicio(write, auth->fd, msg, 5) != 5) {
 		error("write auth->fd: %.100s", strerror(errno));
 		return 0;
 	}
 	/* Read the length of the response.  XXX implement timeouts here. */
 	len = 4;
 	while (len > 0) {
 		l = read(auth->fd, msg + 4 - len, len);
 		if (l <= 0) {
 			error("read auth->fd: %.100s", strerror(errno));
 			return 0;
 		}
 		len -= l;
 	}

 	/*
 	 * Extract the length, and check it for sanity.  (We cannot trust
 	 * authentication agents).
 	 */
 	len = GET_32BIT(msg);
 	if (len < 1 || len > 256 * 1024)
 		fatal("Authentication reply message too long: %d\n", len);

 	/* Read the packet itself. */
 	buffer_clear(&auth->identities);
 	while (len > 0) {
 		l = len;
 		if (l > sizeof(msg))
 			l = sizeof(msg);
 		l = read(auth->fd, msg, l);
 		if (l <= 0)
 			fatal("Incomplete authentication reply.");
 		buffer_append(&auth->identities, (char *) msg, l);
 		len -= l;
 	}

 	/* Get message type, and verify that we got a proper answer. */
 	buffer_get(&auth->identities, (char *) msg, 1);
 	if (msg[0] != SSH_AGENT_RSA_IDENTITIES_ANSWER)
 		fatal("Bad authentication reply message type: %d", msg[0]);

 	/* 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 the first entry (if any). */
 	return ssh_get_next_identity(auth, e, n, comment);
 }

 /*
  * Returns the next authentication identity for the agent.  Other functions
  * can be called between this and ssh_get_first_identity or two calls of this
  * function.  This returns 0 if there are no more identities.  The caller
  * must free comment after a successful return.
  */

 int
 ssh_get_next_identity(AuthenticationConnection *auth,
 		      BIGNUM *e, BIGNUM *n, char **comment)
 {
 	unsigned int bits;

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

 	/*
 	 * Get the next entry from the packet.  These will abort with a fatal
 	 * error if the packet is too short or contains corrupt data.
 	 */
 	bits = buffer_get_int(&auth->identities);
 	buffer_get_bignum(&auth->identities, e);
 	buffer_get_bignum(&auth->identities, n);
 	*comment = buffer_get_string(&auth->identities, NULL);

 	if (bits != BN_num_bits(n))
 		log("Warning: identity keysize mismatch: actual %d, announced %u",
 		    BN_num_bits(n), bits);

 	/* Decrement the number of remaining entries. */
 	auth->howmany--;

 	return 1;
 }

 /*
  * 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,
 		      BIGNUM* e, BIGNUM *n, BIGNUM *challenge,
 		      unsigned char session_id[16],
 		      unsigned int response_type,
 		      unsigned char response[16])
 {
 	Buffer buffer;
 	unsigned char buf[8192];
 	int len, l, i;

 	/* Response type 0 is no longer supported. */
 	if (response_type == 0)
 		fatal("Compatibility with ssh protocol version 1.0 no longer supported.");

 	/* Format a message to the agent. */
 	buf[0] = SSH_AGENTC_RSA_CHALLENGE;
 	buffer_init(&buffer);
 	buffer_append(&buffer, (char *) buf, 1);
 	buffer_put_int(&buffer, BN_num_bits(n));
 	buffer_put_bignum(&buffer, e);
 	buffer_put_bignum(&buffer, n);
 	buffer_put_bignum(&buffer, challenge);
 	buffer_append(&buffer, (char *) session_id, 16);
 	buffer_put_int(&buffer, response_type);

 	/* Get the length of the message, and format it in the buffer. */
 	len = buffer_len(&buffer);
 	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(&buffer),
 	    buffer_len(&buffer)) != buffer_len(&buffer)) {
 		error("Error writing to authentication socket.");
 error_cleanup:
 		buffer_free(&buffer);
 		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.");
 			goto error_cleanup;
 		}
 		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 tothe buffer. */
 	buffer_clear(&buffer);
 	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.");
 			goto error_cleanup;
 		}
 		buffer_append(&buffer, (char *) buf, l);
 		len -= l;
 	}

 	/* Get the type of the packet. */
 	buffer_get(&buffer, (char *) buf, 1);

 	/* Check for agent failure message. */
 	if (buf[0] == SSH_AGENT_FAILURE) {
 		log("Agent admitted failure to authenticate using the key.");
 		goto error_cleanup;
 	}
 	/* Now it must be an authentication response packet. */
 	if (buf[0] != SSH_AGENT_RSA_RESPONSE)
 		fatal("Bad authentication response: %d", buf[0]);

 	/*
 	 * 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);

 	/* The buffer containing the packet is no longer needed. */
 	buffer_free(&buffer);

 	/* Correct answer. */
 	return 1;
 }

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

 int
 ssh_add_identity(AuthenticationConnection *auth,
 		 RSA * key, const char *comment)
 {
 	Buffer buffer;
 	unsigned char buf[8192];
 	int len, l, type;

 	/* Format a message to the agent. */
 	buffer_init(&buffer);
 	buffer_put_char(&buffer, SSH_AGENTC_ADD_RSA_IDENTITY);
 	buffer_put_int(&buffer, BN_num_bits(key->n));
 	buffer_put_bignum(&buffer, key->n);
 	buffer_put_bignum(&buffer, key->e);
 	buffer_put_bignum(&buffer, key->d);
 	/* To keep within the protocol: p < q for ssh. in SSL p > q */
 	buffer_put_bignum(&buffer, key->iqmp);	/* ssh key->u */
 	buffer_put_bignum(&buffer, key->q);	/* ssh key->p, SSL key->q */
 	buffer_put_bignum(&buffer, key->p);	/* ssh key->q, SSL key->p */
 	buffer_put_string(&buffer, comment, strlen(comment));

 	/* Get the length of the message, and format it in the buffer. */
 	len = buffer_len(&buffer);
 	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(&buffer),
 	    buffer_len(&buffer)) != buffer_len(&buffer)) {
 		error("Error writing to authentication socket.");
 error_cleanup:
 		buffer_free(&buffer);
 		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.");
 			goto error_cleanup;
 		}
 		len -= l;
 	}

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

 	/* Read the rest of the response in tothe buffer. */
 	buffer_clear(&buffer);
 	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.");
 			goto error_cleanup;
 		}
 		buffer_append(&buffer, (char *) buf, l);
 		len -= l;
 	}

 	/* Get the type of the packet. */
 	type = buffer_get_char(&buffer);
 	switch (type) {
 	case SSH_AGENT_FAILURE:
 		buffer_free(&buffer);
 		return 0;
 	case SSH_AGENT_SUCCESS:
 		buffer_free(&buffer);
 		return 1;
 	default:
 		fatal("Bad response to add identity from authentication agent: %d",
 		      type);
 	}
 	/* NOTREACHED */
 	return 0;
 }

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

 int
 ssh_remove_identity(AuthenticationConnection *auth, RSA *key)
 {
 	Buffer buffer;
 	unsigned char buf[8192];
 	int len, l, type;

 	/* Format a message to the agent. */
 	buffer_init(&buffer);
 	buffer_put_char(&buffer, SSH_AGENTC_REMOVE_RSA_IDENTITY);
 	buffer_put_int(&buffer, BN_num_bits(key->n));
 	buffer_put_bignum(&buffer, key->e);
 	buffer_put_bignum(&buffer, key->n);

 	/* Get the length of the message, and format it in the buffer. */
 	len = buffer_len(&buffer);
 	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(&buffer),
 	    buffer_len(&buffer)) != buffer_len(&buffer)) {
 		error("Error writing to authentication socket.");
 error_cleanup:
 		buffer_free(&buffer);
 		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.");
 			goto error_cleanup;
 		}
 		len -= l;
 	}

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

 	/* Read the rest of the response in tothe buffer. */
 	buffer_clear(&buffer);
 	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.");
 			goto error_cleanup;
 		}
 		buffer_append(&buffer, (char *) buf, l);
 		len -= l;
 	}

 	/* Get the type of the packet. */
 	type = buffer_get_char(&buffer);
 	switch (type) {
 	case SSH_AGENT_FAILURE:
 		buffer_free(&buffer);
 		return 0;
 	case SSH_AGENT_SUCCESS:
 		buffer_free(&buffer);
 		return 1;
 	default:
 		fatal("Bad response to remove identity from authentication agent: %d",
 		      type);
 	}
 	/* NOTREACHED */
 	return 0;
 }

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

 int
 ssh_remove_all_identities(AuthenticationConnection *auth)
 {
 	Buffer buffer;
 	unsigned char buf[8192];
 	int len, l, type;

 	/* Get the length of the message, and format it in the buffer. */
 	PUT_32BIT(buf, 1);
 	buf[4] = SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES;

 	/* Send the length and then the packet to the agent. */
 	if (atomicio(write, auth->fd, buf, 5) != 5) {
 		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("Remove identity response too long: %d", len);

 	/* Read the rest of the response into the buffer. */
 	buffer_init(&buffer);
 	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.");
 			buffer_free(&buffer);
 			return 0;
 		}
 		buffer_append(&buffer, (char *) buf, l);
 		len -= l;
 	}

 	/* Get the type of the packet. */
 	type = buffer_get_char(&buffer);
 	switch (type) {
 	case SSH_AGENT_FAILURE:
 		buffer_free(&buffer);
 		return 0;
 	case SSH_AGENT_SUCCESS:
 		buffer_free(&buffer);
 		return 1;
 	default:
 		fatal("Bad response to remove identity from authentication agent: %d",
 		      type);
 	}
 	/* NOTREACHED */
 	return 0;
 }
	/*
	*
	* authfd.c
	*
	* 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 01:30:28 1995 ylo
	*
	* Functions for connecting the local authentication agent.
	*
	*/

	#include "includes.h"
	RCSID("$OpenBSD: authfd.c,v 1.20 2000/06/20 01:39:38 markus Exp $");

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

	#include <openssl/rsa.h>

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

	int
	ssh_get_authentication_socket()
	{
	const char *authsocket;
	int sock;
	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));

	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, sizeof(sunaddr)) < 0) {
	close(sock);
	return -1;
	}
	return sock;
	}

	/*
	* 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()
	{
	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->packet);
	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 *ac)
	{
	buffer_free(&ac->packet);
	buffer_free(&ac->identities);
	close(ac->fd);
	xfree(ac);
	}

	/*
	* Returns the first authentication identity held by the agent.
	* Returns true if an identity is available, 0 otherwise.
	* The caller must initialize the integers before the call, and free the
	* comment after a successful call (before calling ssh_get_next_identity).
	*/

	int
	ssh_get_first_identity(AuthenticationConnection *auth,
	BIGNUM e, BIGNUM n, char **comment)
	{
	unsigned char msg[8192];
	int len, l;

	/*
	* Send a message to the agent requesting for a list of the
	* identities it can represent.
	*/
	msg[0] = 0;
	msg[1] = 0;
	msg[2] = 0;
	msg[3] = 1;
	msg[4] = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
	if (atomicio(write, auth->fd, msg, 5) != 5) {
	error("write auth->fd: %.100s", strerror(errno));
	return 0;
	}
	/* Read the length of the response. XXX implement timeouts here. */
	len = 4;
	while (len > 0) {
	l = read(auth->fd, msg + 4 - len, len);
	if (l <= 0) {
	error("read auth->fd: %.100s", strerror(errno));
	return 0;
	}
	len -= l;
	}

	/*
	* Extract the length, and check it for sanity. (We cannot trust
	* authentication agents).
	*/
	len = GET_32BIT(msg);
	if (len < 1 \|\| len > 256 * 1024)
	fatal("Authentication reply message too long: %d\n", len);

	/* Read the packet itself. */
	buffer_clear(&auth->identities);
	while (len > 0) {
	l = len;
	if (l > sizeof(msg))
	l = sizeof(msg);
	l = read(auth->fd, msg, l);
	if (l <= 0)
	fatal("Incomplete authentication reply.");
	buffer_append(&auth->identities, (char *) msg, l);
	len -= l;
	}

	/* Get message type, and verify that we got a proper answer. */
	buffer_get(&auth->identities, (char *) msg, 1);
	if (msg[0] != SSH_AGENT_RSA_IDENTITIES_ANSWER)
	fatal("Bad authentication reply message type: %d", msg[0]);

	/* 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 the first entry (if any). */
	return ssh_get_next_identity(auth, e, n, comment);
	}

	/*
	* Returns the next authentication identity for the agent. Other functions
	* can be called between this and ssh_get_first_identity or two calls of this
	* function. This returns 0 if there are no more identities. The caller
	* must free comment after a successful return.
	*/

	int
	ssh_get_next_identity(AuthenticationConnection *auth,
	BIGNUM e, BIGNUM n, char **comment)
	{
	unsigned int bits;

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

	/*
	* Get the next entry from the packet. These will abort with a fatal
	* error if the packet is too short or contains corrupt data.
	*/
	bits = buffer_get_int(&auth->identities);
	buffer_get_bignum(&auth->identities, e);
	buffer_get_bignum(&auth->identities, n);
	*comment = buffer_get_string(&auth->identities, NULL);

	if (bits != BN_num_bits(n))
	log("Warning: identity keysize mismatch: actual %d, announced %u",
	BN_num_bits(n), bits);

	/* Decrement the number of remaining entries. */
	auth->howmany--;

	return 1;
	}

	/*
	* 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,
	BIGNUM* e, BIGNUM n, BIGNUM challenge,
	unsigned char session_id[16],
	unsigned int response_type,
	unsigned char response[16])
	{
	Buffer buffer;
	unsigned char buf[8192];
	int len, l, i;

	/* Response type 0 is no longer supported. */
	if (response_type == 0)
	fatal("Compatibility with ssh protocol version 1.0 no longer supported.");

	/* Format a message to the agent. */
	buf[0] = SSH_AGENTC_RSA_CHALLENGE;
	buffer_init(&buffer);
	buffer_append(&buffer, (char *) buf, 1);
	buffer_put_int(&buffer, BN_num_bits(n));
	buffer_put_bignum(&buffer, e);
	buffer_put_bignum(&buffer, n);
	buffer_put_bignum(&buffer, challenge);
	buffer_append(&buffer, (char *) session_id, 16);
	buffer_put_int(&buffer, response_type);

	/* Get the length of the message, and format it in the buffer. */
	len = buffer_len(&buffer);
	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(&buffer),
	buffer_len(&buffer)) != buffer_len(&buffer)) {
	error("Error writing to authentication socket.");
	error_cleanup:
	buffer_free(&buffer);
	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.");
	goto error_cleanup;
	}
	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 tothe buffer. */
	buffer_clear(&buffer);
	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.");
	goto error_cleanup;
	}
	buffer_append(&buffer, (char *) buf, l);
	len -= l;
	}

	/* Get the type of the packet. */
	buffer_get(&buffer, (char *) buf, 1);

	/* Check for agent failure message. */
	if (buf[0] == SSH_AGENT_FAILURE) {
	log("Agent admitted failure to authenticate using the key.");
	goto error_cleanup;
	}
	/* Now it must be an authentication response packet. */
	if (buf[0] != SSH_AGENT_RSA_RESPONSE)
	fatal("Bad authentication response: %d", buf[0]);

	/*
	* 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);

	/* The buffer containing the packet is no longer needed. */
	buffer_free(&buffer);

	/* Correct answer. */
	return 1;
	}

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

	int
	ssh_add_identity(AuthenticationConnection *auth,
	RSA * key, const char *comment)
	{
	Buffer buffer;
	unsigned char buf[8192];
	int len, l, type;

	/* Format a message to the agent. */
	buffer_init(&buffer);
	buffer_put_char(&buffer, SSH_AGENTC_ADD_RSA_IDENTITY);
	buffer_put_int(&buffer, BN_num_bits(key->n));
	buffer_put_bignum(&buffer, key->n);
	buffer_put_bignum(&buffer, key->e);
	buffer_put_bignum(&buffer, key->d);
	/* To keep within the protocol: p < q for ssh. in SSL p > q */
	buffer_put_bignum(&buffer, key->iqmp); /* ssh key->u */
	buffer_put_bignum(&buffer, key->q); /* ssh key->p, SSL key->q */
	buffer_put_bignum(&buffer, key->p); /* ssh key->q, SSL key->p */
	buffer_put_string(&buffer, comment, strlen(comment));

	/* Get the length of the message, and format it in the buffer. */
	len = buffer_len(&buffer);
	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(&buffer),
	buffer_len(&buffer)) != buffer_len(&buffer)) {
	error("Error writing to authentication socket.");
	error_cleanup:
	buffer_free(&buffer);
	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.");
	goto error_cleanup;
	}
	len -= l;
	}

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

	/* Read the rest of the response in tothe buffer. */
	buffer_clear(&buffer);
	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.");
	goto error_cleanup;
	}
	buffer_append(&buffer, (char *) buf, l);
	len -= l;
	}

	/* Get the type of the packet. */
	type = buffer_get_char(&buffer);
	switch (type) {
	case SSH_AGENT_FAILURE:
	buffer_free(&buffer);
	return 0;
	case SSH_AGENT_SUCCESS:
	buffer_free(&buffer);
	return 1;
	default:
	fatal("Bad response to add identity from authentication agent: %d",
	type);
	}
	/* NOTREACHED */
	return 0;
	}

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

	int
	ssh_remove_identity(AuthenticationConnection auth, RSA key)
	{
	Buffer buffer;
	unsigned char buf[8192];
	int len, l, type;

	/* Format a message to the agent. */
	buffer_init(&buffer);
	buffer_put_char(&buffer, SSH_AGENTC_REMOVE_RSA_IDENTITY);
	buffer_put_int(&buffer, BN_num_bits(key->n));
	buffer_put_bignum(&buffer, key->e);
	buffer_put_bignum(&buffer, key->n);

	/* Get the length of the message, and format it in the buffer. */
	len = buffer_len(&buffer);
	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(&buffer),
	buffer_len(&buffer)) != buffer_len(&buffer)) {
	error("Error writing to authentication socket.");
	error_cleanup:
	buffer_free(&buffer);
	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.");
	goto error_cleanup;
	}
	len -= l;
	}

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

	/* Read the rest of the response in tothe buffer. */
	buffer_clear(&buffer);
	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.");
	goto error_cleanup;
	}
	buffer_append(&buffer, (char *) buf, l);
	len -= l;
	}

	/* Get the type of the packet. */
	type = buffer_get_char(&buffer);
	switch (type) {
	case SSH_AGENT_FAILURE:
	buffer_free(&buffer);
	return 0;
	case SSH_AGENT_SUCCESS:
	buffer_free(&buffer);
	return 1;
	default:
	fatal("Bad response to remove identity from authentication agent: %d",
	type);
	}
	/* NOTREACHED */
	return 0;
	}

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

	int
	ssh_remove_all_identities(AuthenticationConnection *auth)
	{
	Buffer buffer;
	unsigned char buf[8192];
	int len, l, type;

	/* Get the length of the message, and format it in the buffer. */
	PUT_32BIT(buf, 1);
	buf[4] = SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES;

	/* Send the length and then the packet to the agent. */
	if (atomicio(write, auth->fd, buf, 5) != 5) {
	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("Remove identity response too long: %d", len);

	/* Read the rest of the response into the buffer. */
	buffer_init(&buffer);
	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.");
	buffer_free(&buffer);
	return 0;
	}
	buffer_append(&buffer, (char *) buf, l);
	len -= l;
	}

	/* Get the type of the packet. */
	type = buffer_get_char(&buffer);
	switch (type) {
	case SSH_AGENT_FAILURE:
	buffer_free(&buffer);
	return 0;
	case SSH_AGENT_SUCCESS:
	buffer_free(&buffer);
	return 1;
	default:
	fatal("Bad response to remove identity from authentication agent: %d",
	type);
	}
	/* NOTREACHED */
	return 0;
	}