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/* $OpenBSD: authfd.c,v 1.80 2006/08/03 03:34:41 deraadt Exp $ */

/*

 * 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"

#include <sys/types.h>

#include <sys/un.h>

#include <sys/socket.h>

#include <openssl/evp.h>

#include <openssl/crypto.h>

#include <fcntl.h>

#include <stdlib.h>

#include <signal.h>

#include <stdarg.h>

#include <string.h>

#include <unistd.h>

#include "xmalloc.h"

#include "ssh.h"

#include "rsa.h"

#include "buffer.h"

#include "key.h"

#include "authfd.h"

#include "cipher.h"

#include "kex.h"

#include "compat.h"

#include "log.h"

#include "atomicio.h"

#include "misc.h"

static int agent_present = 0;

/* 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) || \

    (x == SSH2_AGENT_FAILURE))

int

ssh_agent_present(void)

{

	int authfd;

	if (agent_present)

		return 1;

	if ((authfd = ssh_get_authentication_socket()) == -1)

		return 0;

	else {

		ssh_close_authentication_socket(authfd);

		return 1;

	}

}

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

int

ssh_get_authentication_socket(void)

{

	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;

	}

	agent_present = 1;

	return sock;

}

static int

ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply)

{

	u_int l, len;

	char buf[1024];

	/* Get the length of the message, and format it in the buffer. */

	len = buffer_len(request);

	put_u32(buf, len);

	/* Send the length and then the packet to the agent. */

	if (atomicio(vwrite, auth->fd, buf, 4) != 4 ||

	    atomicio(vwrite, 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.

	 */

	if (atomicio(read, auth->fd, buf, 4) != 4) {

	    error("Error reading response length from authentication socket.");

	    return 0;

	}

	/* Extract the length, and check it for sanity. */

	len = get_u32(buf);

	if (len > 256 * 1024)

		fatal("Authentication response too long: %u", 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);

		if (atomicio(read, auth->fd, buf, l) != l) {

			error("Error reading response from authentication socket.");

			return 0;

		}

		buffer_append(reply, 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);

}

/* Lock/unlock agent */

int

ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password)

{

	int type;

	Buffer msg;

	buffer_init(&msg);

	buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK);

	buffer_put_cstring(&msg, password);

	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);

}

/*

 * 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 ((u_int)auth->howmany > 1024)

		fatal("Too many identities in authentication reply: %d",

		    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)

{

	int keybits;

	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);

		keybits = BN_num_bits(key->rsa->n);

		if (keybits < 0 || bits != (u_int)keybits)

			logit("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;

	}

	/* 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) {

		logit("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, 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)) {

		logit("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] = (u_char)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, u_int *lenp,

    u_char *data, u_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)) {

		logit("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. */

static void

ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment)

{

	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_cstring(b, comment);

}

static void

ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment)

{

	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_constrained(AuthenticationConnection *auth, Key *key,

    const char *comment, u_int life, u_int confirm)

{

	Buffer msg;

	int type, constrained = (life || confirm);

	buffer_init(&msg);

	switch (key->type) {

	case KEY_RSA1:

		type = constrained ?

		    SSH_AGENTC_ADD_RSA_ID_CONSTRAINED :

		    SSH_AGENTC_ADD_RSA_IDENTITY;

		buffer_put_char(&msg, type);

		ssh_encode_identity_rsa1(&msg, key->rsa, comment);

		break;

	case KEY_RSA:

	case KEY_DSA:

		type = constrained ?

		    SSH2_AGENTC_ADD_ID_CONSTRAINED :

		    SSH2_AGENTC_ADD_IDENTITY;

		buffer_put_char(&msg, type);

		ssh_encode_identity_ssh2(&msg, key, comment);

		break;

	default:

		buffer_free(&msg);

		return 0;

	}

	if (constrained) {

		if (life != 0) {

			buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);

			buffer_put_int(&msg, life);

		}

		if (confirm != 0)

			buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);

	}

	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

ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment)

{

	return ssh_add_identity_constrained(auth, key, comment, 0, 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, 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);

}

int

ssh_update_card(AuthenticationConnection *auth, int add,

    const char *reader_id, const char *pin, u_int life, u_int confirm)

{

	Buffer msg;

	int type, constrained = (life || confirm);

	if (add) {

		type = constrained ?

		    SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED :

		    SSH_AGENTC_ADD_SMARTCARD_KEY;

	} else

		type = SSH_AGENTC_REMOVE_SMARTCARD_KEY;

	buffer_init(&msg);

	buffer_put_char(&msg, type);

	buffer_put_cstring(&msg, reader_id);

	buffer_put_cstring(&msg, pin);

	if (constrained) {

		if (life != 0) {

			buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);

			buffer_put_int(&msg, life);

		}

		if (confirm != 0)

			buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);

	}

	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:

	case SSH2_AGENT_FAILURE:

		logit("SSH_AGENT_FAILURE");

		return 0;

	case SSH_AGENT_SUCCESS:

		return 1;

	default:

		fatal("Bad response from authentication agent: %d", type);

	}

	/* NOTREACHED */

	return 0;

}