sshconnect2.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  * 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: sshconnect2.c,v 1.20 2000/09/21 11:25:07 markus Exp $");

 #include <openssl/bn.h>
 #include <openssl/rsa.h>
 #include <openssl/dsa.h>
 #include <openssl/md5.h>
 #include <openssl/dh.h>
 #include <openssl/hmac.h>

 #include "ssh.h"
 #include "xmalloc.h"
 #include "rsa.h"
 #include "buffer.h"
 #include "packet.h"
 #include "cipher.h"
 #include "uidswap.h"
 #include "compat.h"
 #include "readconf.h"
 #include "bufaux.h"
 #include "ssh2.h"
 #include "kex.h"
 #include "myproposal.h"
 #include "key.h"
 #include "dsa.h"
 #include "sshconnect.h"
 #include "authfile.h"
 #include "dispatch.h"
 #include "authfd.h"

 /* import */
 extern char *client_version_string;
 extern char *server_version_string;
 extern Options options;

 /*
  * SSH2 key exchange
  */

 unsigned char *session_id2 = NULL;
 int session_id2_len = 0;

 void
 ssh_kex_dh(Kex *kex, char *host, struct sockaddr *hostaddr,
     Buffer *client_kexinit, Buffer *server_kexinit)
 {
 #ifdef DEBUG_KEXDH
 	int i;
 #endif
 	int plen, dlen;
 	unsigned int klen, kout;
 	char *signature = NULL;
 	unsigned int slen;
 	char *server_host_key_blob = NULL;
 	Key *server_host_key;
 	unsigned int sbloblen;
 	DH *dh;
 	BIGNUM *dh_server_pub = 0;
 	BIGNUM *shared_secret = 0;
 	unsigned char *kbuf;
 	unsigned char *hash;

 	debug("Sending SSH2_MSG_KEXDH_INIT.");
 	/* generate and send 'e', client DH public key */
 	dh = dh_new_group1();
 	packet_start(SSH2_MSG_KEXDH_INIT);
 	packet_put_bignum2(dh->pub_key);
 	packet_send();
 	packet_write_wait();

 #ifdef DEBUG_KEXDH
 	fprintf(stderr, "\np= ");
 	BN_print_fp(stderr, dh->p);
 	fprintf(stderr, "\ng= ");
 	BN_print_fp(stderr, dh->g);
 	fprintf(stderr, "\npub= ");
 	BN_print_fp(stderr, dh->pub_key);
 	fprintf(stderr, "\n");
 	DHparams_print_fp(stderr, dh);
 #endif

 	debug("Wait SSH2_MSG_KEXDH_REPLY.");

 	packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);

 	debug("Got SSH2_MSG_KEXDH_REPLY.");

 	/* key, cert */
 	server_host_key_blob = packet_get_string(&sbloblen);
 	server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen);
 	if (server_host_key == NULL)
 		fatal("cannot decode server_host_key_blob");

 	check_host_key(host, hostaddr, server_host_key,
 	    options.user_hostfile2, options.system_hostfile2);

 	/* DH paramter f, server public DH key */
 	dh_server_pub = BN_new();
 	if (dh_server_pub == NULL)
 		fatal("dh_server_pub == NULL");
 	packet_get_bignum2(dh_server_pub, &dlen);

 #ifdef DEBUG_KEXDH
 	fprintf(stderr, "\ndh_server_pub= ");
 	BN_print_fp(stderr, dh_server_pub);
 	fprintf(stderr, "\n");
 	debug("bits %d", BN_num_bits(dh_server_pub));
 #endif

 	/* signed H */
 	signature = packet_get_string(&slen);
 	packet_done();

 	if (!dh_pub_is_valid(dh, dh_server_pub))
 		packet_disconnect("bad server public DH value");

 	klen = DH_size(dh);
 	kbuf = xmalloc(klen);
 	kout = DH_compute_key(kbuf, dh_server_pub, dh);
 #ifdef DEBUG_KEXDH
 	debug("shared secret: len %d/%d", klen, kout);
 	fprintf(stderr, "shared secret == ");
 	for (i = 0; i< kout; i++)
 		fprintf(stderr, "%02x", (kbuf[i])&0xff);
 	fprintf(stderr, "\n");
 #endif
 	shared_secret = BN_new();

 	BN_bin2bn(kbuf, kout, shared_secret);
 	memset(kbuf, 0, klen);
 	xfree(kbuf);

 	/* calc and verify H */
 	hash = kex_hash(
 	    client_version_string,
 	    server_version_string,
 	    buffer_ptr(client_kexinit), buffer_len(client_kexinit),
 	    buffer_ptr(server_kexinit), buffer_len(server_kexinit),
 	    server_host_key_blob, sbloblen,
 	    dh->pub_key,
 	    dh_server_pub,
 	    shared_secret
 	);
 	xfree(server_host_key_blob);
 	DH_free(dh);
 #ifdef DEBUG_KEXDH
 	fprintf(stderr, "hash == ");
 	for (i = 0; i< 20; i++)
 		fprintf(stderr, "%02x", (hash[i])&0xff);
 	fprintf(stderr, "\n");
 #endif
 	if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1)
 		fatal("dsa_verify failed for server_host_key");
 	key_free(server_host_key);

 	kex_derive_keys(kex, hash, shared_secret);
 	packet_set_kex(kex);

 	/* save session id */
 	session_id2_len = 20;
 	session_id2 = xmalloc(session_id2_len);
 	memcpy(session_id2, hash, session_id2_len);
 }

 void
 ssh_kex2(char *host, struct sockaddr *hostaddr)
 {
 	int i, plen;
 	Kex *kex;
 	Buffer *client_kexinit, *server_kexinit;
 	char *sprop[PROPOSAL_MAX];

 	if (options.ciphers != NULL) {
 		myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 		myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
 	} else if (options.cipher == SSH_CIPHER_3DES) {
 		myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 		myproposal[PROPOSAL_ENC_ALGS_STOC] =
 		    (char *) cipher_name(SSH_CIPHER_3DES_CBC);
 	} else if (options.cipher == SSH_CIPHER_BLOWFISH) {
 		myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 		myproposal[PROPOSAL_ENC_ALGS_STOC] =
 		    (char *) cipher_name(SSH_CIPHER_BLOWFISH_CBC);
 	}
 	if (options.compression) {
 		myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib";
 		myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
 	} else {
 		myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none";
 		myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
 	}

 	/* buffers with raw kexinit messages */
 	server_kexinit = xmalloc(sizeof(*server_kexinit));
 	buffer_init(server_kexinit);
 	client_kexinit = kex_init(myproposal);

 	/* algorithm negotiation */
 	kex_exchange_kexinit(client_kexinit, server_kexinit, sprop);
 	kex = kex_choose_conf(myproposal, sprop, 0);
 	for (i = 0; i < PROPOSAL_MAX; i++)
 		xfree(sprop[i]);

 	/* server authentication and session key agreement */
 	ssh_kex_dh(kex, host, hostaddr, client_kexinit, server_kexinit);

 	buffer_free(client_kexinit);
 	buffer_free(server_kexinit);
 	xfree(client_kexinit);
 	xfree(server_kexinit);

 	debug("Wait SSH2_MSG_NEWKEYS.");
 	packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
 	packet_done();
 	debug("GOT SSH2_MSG_NEWKEYS.");

 	debug("send SSH2_MSG_NEWKEYS.");
 	packet_start(SSH2_MSG_NEWKEYS);
 	packet_send();
 	packet_write_wait();
 	debug("done: send SSH2_MSG_NEWKEYS.");

 #ifdef DEBUG_KEXDH
 	/* send 1st encrypted/maced/compressed message */
 	packet_start(SSH2_MSG_IGNORE);
 	packet_put_cstring("markus");
 	packet_send();
 	packet_write_wait();
 #endif
 	debug("done: KEX2.");
 }

 /*
  * Authenticate user
  */

 typedef struct Authctxt Authctxt;
 typedef struct Authmethod Authmethod;

 typedef int sign_cb_fn(
     Authctxt *authctxt, Key *key,
     unsigned char **sigp, int *lenp, unsigned char *data, int datalen);

 struct Authctxt {
 	const char *server_user;
 	const char *host;
 	const char *service;
 	AuthenticationConnection *agent;
 	int success;
 	Authmethod *method;
 };
 struct Authmethod {
 	char	*name;		/* string to compare against server's list */
 	int	(*userauth)(Authctxt *authctxt);
 	int	*enabled;	/* flag in option struct that enables method */
 	int	*batch_flag;	/* flag in option struct that disables method */
 };

 void	input_userauth_success(int type, int plen, void *ctxt);
 void	input_userauth_failure(int type, int plen, void *ctxt);
 void	input_userauth_error(int type, int plen, void *ctxt);
 int	userauth_pubkey(Authctxt *authctxt);
 int	userauth_passwd(Authctxt *authctxt);

 void	authmethod_clear();
 Authmethod *authmethod_get(char *auth_list);

 Authmethod authmethods[] = {
 	{"publickey",
 		userauth_pubkey,
 		&options.dsa_authentication,
 		NULL},
 	{"password",
 		userauth_passwd,
 		&options.password_authentication,
 		&options.batch_mode},
 	{NULL, NULL, NULL, NULL}
 };

 void
 ssh_userauth2(const char *server_user, char *host)
 {
 	Authctxt authctxt;
 	int type;
 	int plen;

 	debug("send SSH2_MSG_SERVICE_REQUEST");
 	packet_start(SSH2_MSG_SERVICE_REQUEST);
 	packet_put_cstring("ssh-userauth");
 	packet_send();
 	packet_write_wait();
 	type = packet_read(&plen);
 	if (type != SSH2_MSG_SERVICE_ACCEPT) {
 		fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
 	}
 	if (packet_remaining() > 0) {
 		char *reply = packet_get_string(&plen);
 		debug("service_accept: %s", reply);
 		xfree(reply);
 		packet_done();
 	} else {
 		debug("buggy server: service_accept w/o service");
 	}
 	packet_done();
 	debug("got SSH2_MSG_SERVICE_ACCEPT");

 	/* setup authentication context */
 	authctxt.agent = ssh_get_authentication_connection();
 	authctxt.server_user = server_user;
 	authctxt.host = host;
 	authctxt.service = "ssh-connection";		/* service name */
 	authctxt.success = 0;
 	authctxt.method = NULL;

 	/* initial userauth request */
 	packet_start(SSH2_MSG_USERAUTH_REQUEST);
 	packet_put_cstring(authctxt.server_user);
 	packet_put_cstring(authctxt.service);
 	packet_put_cstring("none");
 	packet_send();
 	packet_write_wait();

 	authmethod_clear();

 	dispatch_init(&input_userauth_error);
 	dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
 	dispatch_set(SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
 	dispatch_run(DISPATCH_BLOCK, &authctxt.success, &authctxt);	/* loop until success */

 	if (authctxt.agent != NULL)
 		ssh_close_authentication_connection(authctxt.agent);

 	debug("ssh-userauth2 successfull");
 }
 void
 input_userauth_error(int type, int plen, void *ctxt)
 {
 	fatal("input_userauth_error: bad message during authentication");
 }
 void
 input_userauth_success(int type, int plen, void *ctxt)
 {
 	Authctxt *authctxt = ctxt;
 	if (authctxt == NULL)
 		fatal("input_userauth_success: no authentication context");
 	authctxt->success = 1;			/* break out */
 }
 void
 input_userauth_failure(int type, int plen, void *ctxt)
 {
 	Authmethod *method = NULL;
 	Authctxt *authctxt = ctxt;
 	char *authlist = NULL;
 	int partial;
 	int dlen;

 	if (authctxt == NULL)
 		fatal("input_userauth_failure: no authentication context");

 	authlist = packet_get_string(&dlen);
 	partial = packet_get_char();
 	packet_done();

 	if (partial != 0)
 		debug("partial success");
 	debug("authentications that can continue: %s", authlist);

 	for (;;) {
 		/* try old method or get next method */
 		method = authmethod_get(authlist);
 		if (method == NULL)
                         fatal("Unable to find an authentication method");
 		if (method->userauth(authctxt) != 0) {
 			debug2("we sent a packet, wait for reply");
 			break;
 		} else {
 			debug2("we did not send a packet, disable method");
 			method->enabled = NULL;
 		}
 	}
 	xfree(authlist);
 }

 int
 userauth_passwd(Authctxt *authctxt)
 {
 	static int attempt = 0;
 	char prompt[80];
 	char *password;

 	if (attempt++ >= options.number_of_password_prompts)
 		return 0;

 	if(attempt != 1)
 		error("Permission denied, please try again.");

 	snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
 	    authctxt->server_user, authctxt->host);
 	password = read_passphrase(prompt, 0);
 	packet_start(SSH2_MSG_USERAUTH_REQUEST);
 	packet_put_cstring(authctxt->server_user);
 	packet_put_cstring(authctxt->service);
 	packet_put_cstring("password");
 	packet_put_char(0);
 	packet_put_cstring(password);
 	memset(password, 0, strlen(password));
 	xfree(password);
 	packet_send();
 	packet_write_wait();
 	return 1;
 }

 int
 sign_and_send_pubkey(Authctxt *authctxt, Key *k, sign_cb_fn *sign_callback)
 {
 	Buffer b;
 	unsigned char *blob, *signature;
 	int bloblen, slen;
 	int skip = 0;
 	int ret = -1;

 	dsa_make_key_blob(k, &blob, &bloblen);

 	/* data to be signed */
 	buffer_init(&b);
 	if (datafellows & SSH_COMPAT_SESSIONID_ENCODING) {
 		buffer_put_string(&b, session_id2, session_id2_len);
 		skip = buffer_len(&b);
 	} else {
 		buffer_append(&b, session_id2, session_id2_len);
 		skip = session_id2_len;
 	}
 	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 	buffer_put_cstring(&b, authctxt->server_user);
 	buffer_put_cstring(&b,
 	    datafellows & SSH_BUG_PUBKEYAUTH ?
 	    "ssh-userauth" :
 	    authctxt->service);
 	buffer_put_cstring(&b, "publickey");
 	buffer_put_char(&b, 1);
 	buffer_put_cstring(&b, KEX_DSS);
 	buffer_put_string(&b, blob, bloblen);

 	/* generate signature */
 	ret = (*sign_callback)(authctxt, k, &signature, &slen, buffer_ptr(&b), buffer_len(&b));
 	if (ret == -1) {
 		xfree(blob);
 		buffer_free(&b);
 		return 0;
 	}
 #ifdef DEBUG_DSS
 	buffer_dump(&b);
 #endif
 	if (datafellows & SSH_BUG_PUBKEYAUTH) {
 		buffer_clear(&b);
 		buffer_append(&b, session_id2, session_id2_len);
 		buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 		buffer_put_cstring(&b, authctxt->server_user);
 		buffer_put_cstring(&b, authctxt->service);
 		buffer_put_cstring(&b, "publickey");
 		buffer_put_char(&b, 1);
 		buffer_put_cstring(&b, KEX_DSS);
 		buffer_put_string(&b, blob, bloblen);
 	}
 	xfree(blob);
 	/* append signature */
 	buffer_put_string(&b, signature, slen);
 	xfree(signature);

 	/* skip session id and packet type */
 	if (buffer_len(&b) < skip + 1)
 		fatal("userauth_pubkey: internal error");
 	buffer_consume(&b, skip + 1);

 	/* put remaining data from buffer into packet */
 	packet_start(SSH2_MSG_USERAUTH_REQUEST);
 	packet_put_raw(buffer_ptr(&b), buffer_len(&b));
 	buffer_free(&b);

 	/* send */
 	packet_send();
 	packet_write_wait();

 	return 1;
 }

 /* sign callback */
 int dsa_sign_cb(Authctxt *authctxt, Key *key, unsigned char **sigp, int *lenp,
     unsigned char *data, int datalen)
 {
 	return dsa_sign(key, sigp, lenp, data, datalen);
 }

 int
 userauth_pubkey_identity(Authctxt *authctxt, char *filename)
 {
 	Key *k;
 	int i, ret, try_next;
 	struct stat st;

 	if (stat(filename, &st) != 0) {
 		debug("key does not exist: %s", filename);
 		return 0;
 	}
 	debug("try pubkey: %s", filename);

 	k = key_new(KEY_DSA);
 	if (!load_private_key(filename, "", k, NULL)) {
 		int success = 0;
 		char *passphrase;
 		char prompt[300];
 		snprintf(prompt, sizeof prompt,
 		     "Enter passphrase for DSA key '%.100s': ",
 		     filename);
 		for (i = 0; i < options.number_of_password_prompts; i++) {
 			passphrase = read_passphrase(prompt, 0);
 			if (strcmp(passphrase, "") != 0) {
 				success = load_private_key(filename, passphrase, k, NULL);
 				try_next = 0;
 			} else {
 				debug2("no passphrase given, try next key");
 				try_next = 1;
 			}
 			memset(passphrase, 0, strlen(passphrase));
 			xfree(passphrase);
 			if (success || try_next)
 				break;
 			debug2("bad passphrase given, try again...");
 		}
 		if (!success) {
 			key_free(k);
 			return 0;
 		}
 	}
 	ret = sign_and_send_pubkey(authctxt, k, dsa_sign_cb);
 	key_free(k);
 	return ret;
 }

 /* sign callback */
 int agent_sign_cb(Authctxt *authctxt, Key *key, unsigned char **sigp, int *lenp,
     unsigned char *data, int datalen)
 {
 	return ssh_agent_sign(authctxt->agent, key, sigp, lenp, data, datalen);
 }

 int
 userauth_pubkey_agent(Authctxt *authctxt)
 {
 	static int called = 0;
 	char *comment;
 	Key *k;
 	int ret;

 	if (called == 0) {
 		k = ssh_get_first_identity(authctxt->agent, &comment, 2);
 		called = 1;
 	} else {
 		k = ssh_get_next_identity(authctxt->agent, &comment, 2);
 	}
 	if (k == NULL) {
 		debug2("no more DSA keys from agent");
 		return 0;
 	}
 	debug("trying DSA agent key %s", comment);
 	xfree(comment);
 	ret = sign_and_send_pubkey(authctxt, k, agent_sign_cb);
 	key_free(k);
 	return ret;
 }

 int
 userauth_pubkey(Authctxt *authctxt)
 {
 	static int idx = 0;
 	int sent = 0;

 	if (authctxt->agent != NULL)
 		sent = userauth_pubkey_agent(authctxt);
 	while (sent == 0 && idx < options.num_identity_files2)
 		sent = userauth_pubkey_identity(authctxt, options.identity_files2[idx++]);
 	return sent;
 }


 /* find auth method */

 #define	DELIM	","

 static char *def_authlist = "publickey,password";
 static char *authlist_current = NULL;	 /* clean copy used for comparison */
 static char *authname_current = NULL;	 /* last used auth method */
 static char *authlist_working = NULL;	 /* copy that gets modified by strtok_r() */
 static char *authlist_state = NULL;	 /* state variable for strtok_r() */

 /*
  * Before starting to use a new authentication method list sent by the
  * server, reset internal variables.  This should also be called when
  * finished processing server list to free resources.
  */
 void
 authmethod_clear()
 {
 	if (authlist_current != NULL) {
 		xfree(authlist_current);
 		authlist_current = NULL;
 	}
 	if (authlist_working != NULL) {
 		xfree(authlist_working);
 		authlist_working = NULL;
 	}
 	if (authname_current != NULL) {
 		xfree(authname_current);
 		authlist_state = NULL;
 	}
 	if (authlist_state != NULL)
 		authlist_state = NULL;
 	return;
 }

 /*
  * given auth method name, if configurable options permit this method fill
  * in auth_ident field and return true, otherwise return false.
  */
 int
 authmethod_is_enabled(Authmethod *method)
 {
 	if (method == NULL)
 		return 0;
 	/* return false if options indicate this method is disabled */
 	if  (method->enabled == NULL || *method->enabled == 0)
 		return 0;
 	/* return false if batch mode is enabled but method needs interactive mode */
 	if  (method->batch_flag != NULL && *method->batch_flag != 0)
 		return 0;
 	return 1;
 }

 Authmethod *
 authmethod_lookup(const char *name)
 {
 	Authmethod *method = NULL;
 	if (name != NULL)
 		for (method = authmethods; method->name != NULL; method++)
 			if (strcmp(name, method->name) == 0)
 				return method;
 	debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
 	return NULL;
 }

 /*
  * Given the authentication method list sent by the server, return the
  * next method we should try.  If the server initially sends a nil list,
  * use a built-in default list.  If the server sends a nil list after
  * previously sending a valid list, continue using the list originally
  * sent.
  */

 Authmethod *
 authmethod_get(char *authlist)
 {
 	char *name = NULL;
 	Authmethod *method = NULL;

 	/* Use a suitable default if we're passed a nil list.  */
 	if (authlist == NULL || strlen(authlist) == 0)
 		authlist = def_authlist;

 	if (authlist_current == NULL || strcmp(authlist, authlist_current) != 0) {
 		/* start over if passed a different list */
 		authmethod_clear();
 		authlist_current = xstrdup(authlist);
 		authlist_working = xstrdup(authlist);
 		name = strtok_r(authlist_working, DELIM, &authlist_state);
 	} else {
 		/*
 		 * try to use previously used authentication method
 		 * or continue to use previously passed list
 		 */
 		name = (authname_current != NULL) ?
 		    authname_current : strtok_r(NULL, DELIM, &authlist_state);
 	}

 	while (name != NULL) {
 		method = authmethod_lookup(name);
 		if (method != NULL && authmethod_is_enabled(method))
 			break;
 		name = strtok_r(NULL, DELIM, &authlist_state);
 	}

 	if (authname_current != NULL)
 		xfree(authname_current);

 	if (name != NULL) {
 		debug("next auth method to try is %s", name);
 		authname_current = xstrdup(name);
 		return method;
 	} else {
 		debug("no more auth methods to try");
 		authname_current = NULL;
 		return NULL;
 	}
 }
	/*
	* 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: sshconnect2.c,v 1.20 2000/09/21 11:25:07 markus Exp $");

	#include <openssl/bn.h>
	#include <openssl/rsa.h>
	#include <openssl/dsa.h>
	#include <openssl/md5.h>
	#include <openssl/dh.h>
	#include <openssl/hmac.h>

	#include "ssh.h"
	#include "xmalloc.h"
	#include "rsa.h"
	#include "buffer.h"
	#include "packet.h"
	#include "cipher.h"
	#include "uidswap.h"
	#include "compat.h"
	#include "readconf.h"
	#include "bufaux.h"
	#include "ssh2.h"
	#include "kex.h"
	#include "myproposal.h"
	#include "key.h"
	#include "dsa.h"
	#include "sshconnect.h"
	#include "authfile.h"
	#include "dispatch.h"
	#include "authfd.h"

	/* import */
	extern char *client_version_string;
	extern char *server_version_string;
	extern Options options;

	/*
	* SSH2 key exchange
	*/

	unsigned char *session_id2 = NULL;
	int session_id2_len = 0;

	void
	ssh_kex_dh(Kex kex, char host, struct sockaddr *hostaddr,
	Buffer client_kexinit, Buffer server_kexinit)
	{
	#ifdef DEBUG_KEXDH
	int i;
	#endif
	int plen, dlen;
	unsigned int klen, kout;
	char *signature = NULL;
	unsigned int slen;
	char *server_host_key_blob = NULL;
	Key *server_host_key;
	unsigned int sbloblen;
	DH *dh;
	BIGNUM *dh_server_pub = 0;
	BIGNUM *shared_secret = 0;
	unsigned char *kbuf;
	unsigned char *hash;

	debug("Sending SSH2_MSG_KEXDH_INIT.");
	/* generate and send 'e', client DH public key */
	dh = dh_new_group1();
	packet_start(SSH2_MSG_KEXDH_INIT);
	packet_put_bignum2(dh->pub_key);
	packet_send();
	packet_write_wait();

	#ifdef DEBUG_KEXDH
	fprintf(stderr, "\np= ");
	BN_print_fp(stderr, dh->p);
	fprintf(stderr, "\ng= ");
	BN_print_fp(stderr, dh->g);
	fprintf(stderr, "\npub= ");
	BN_print_fp(stderr, dh->pub_key);
	fprintf(stderr, "\n");
	DHparams_print_fp(stderr, dh);
	#endif

	debug("Wait SSH2_MSG_KEXDH_REPLY.");

	packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);

	debug("Got SSH2_MSG_KEXDH_REPLY.");

	/* key, cert */
	server_host_key_blob = packet_get_string(&sbloblen);
	server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen);
	if (server_host_key == NULL)
	fatal("cannot decode server_host_key_blob");

	check_host_key(host, hostaddr, server_host_key,
	options.user_hostfile2, options.system_hostfile2);

	/* DH paramter f, server public DH key */
	dh_server_pub = BN_new();
	if (dh_server_pub == NULL)
	fatal("dh_server_pub == NULL");
	packet_get_bignum2(dh_server_pub, &dlen);

	#ifdef DEBUG_KEXDH
	fprintf(stderr, "\ndh_server_pub= ");
	BN_print_fp(stderr, dh_server_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_server_pub));
	#endif

	/* signed H */
	signature = packet_get_string(&slen);
	packet_done();

	if (!dh_pub_is_valid(dh, dh_server_pub))
	packet_disconnect("bad server public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	kout = DH_compute_key(kbuf, dh_server_pub, dh);
	#ifdef DEBUG_KEXDH
	debug("shared secret: len %d/%d", klen, kout);
	fprintf(stderr, "shared secret == ");
	for (i = 0; i< kout; i++)
	fprintf(stderr, "%02x", (kbuf[i])&0xff);
	fprintf(stderr, "\n");
	#endif
	shared_secret = BN_new();

	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	/* calc and verify H */
	hash = kex_hash(
	client_version_string,
	server_version_string,
	buffer_ptr(client_kexinit), buffer_len(client_kexinit),
	buffer_ptr(server_kexinit), buffer_len(server_kexinit),
	server_host_key_blob, sbloblen,
	dh->pub_key,
	dh_server_pub,
	shared_secret
	);
	xfree(server_host_key_blob);
	DH_free(dh);
	#ifdef DEBUG_KEXDH
	fprintf(stderr, "hash == ");
	for (i = 0; i< 20; i++)
	fprintf(stderr, "%02x", (hash[i])&0xff);
	fprintf(stderr, "\n");
	#endif
	if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1)
	fatal("dsa_verify failed for server_host_key");
	key_free(server_host_key);

	kex_derive_keys(kex, hash, shared_secret);
	packet_set_kex(kex);

	/* save session id */
	session_id2_len = 20;
	session_id2 = xmalloc(session_id2_len);
	memcpy(session_id2, hash, session_id2_len);
	}

	void
	ssh_kex2(char host, struct sockaddr hostaddr)
	{
	int i, plen;
	Kex *kex;
	Buffer client_kexinit, server_kexinit;
	char *sprop[PROPOSAL_MAX];

	if (options.ciphers != NULL) {
	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
	myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
	} else if (options.cipher == SSH_CIPHER_3DES) {
	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
	myproposal[PROPOSAL_ENC_ALGS_STOC] =
	(char *) cipher_name(SSH_CIPHER_3DES_CBC);
	} else if (options.cipher == SSH_CIPHER_BLOWFISH) {
	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
	myproposal[PROPOSAL_ENC_ALGS_STOC] =
	(char *) cipher_name(SSH_CIPHER_BLOWFISH_CBC);
	}
	if (options.compression) {
	myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib";
	myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
	} else {
	myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none";
	myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
	}

	/* buffers with raw kexinit messages */
	server_kexinit = xmalloc(sizeof(*server_kexinit));
	buffer_init(server_kexinit);
	client_kexinit = kex_init(myproposal);

	/* algorithm negotiation */
	kex_exchange_kexinit(client_kexinit, server_kexinit, sprop);
	kex = kex_choose_conf(myproposal, sprop, 0);
	for (i = 0; i < PROPOSAL_MAX; i++)
	xfree(sprop[i]);

	/* server authentication and session key agreement */
	ssh_kex_dh(kex, host, hostaddr, client_kexinit, server_kexinit);

	buffer_free(client_kexinit);
	buffer_free(server_kexinit);
	xfree(client_kexinit);
	xfree(server_kexinit);

	debug("Wait SSH2_MSG_NEWKEYS.");
	packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
	packet_done();
	debug("GOT SSH2_MSG_NEWKEYS.");

	debug("send SSH2_MSG_NEWKEYS.");
	packet_start(SSH2_MSG_NEWKEYS);
	packet_send();
	packet_write_wait();
	debug("done: send SSH2_MSG_NEWKEYS.");

	#ifdef DEBUG_KEXDH
	/* send 1st encrypted/maced/compressed message */
	packet_start(SSH2_MSG_IGNORE);
	packet_put_cstring("markus");
	packet_send();
	packet_write_wait();
	#endif
	debug("done: KEX2.");
	}

	/*
	* Authenticate user
	*/

	typedef struct Authctxt Authctxt;
	typedef struct Authmethod Authmethod;

	typedef int sign_cb_fn(
	Authctxt authctxt, Key key,
	unsigned char *sigp, int lenp, unsigned char *data, int datalen);

	struct Authctxt {
	const char *server_user;
	const char *host;
	const char *service;
	AuthenticationConnection *agent;
	int success;
	Authmethod *method;
	};
	struct Authmethod {
	char name; / string to compare against server's list */
	int (userauth)(Authctxt authctxt);
	int enabled; / flag in option struct that enables method */
	int batch_flag; / flag in option struct that disables method */
	};

	void input_userauth_success(int type, int plen, void *ctxt);
	void input_userauth_failure(int type, int plen, void *ctxt);
	void input_userauth_error(int type, int plen, void *ctxt);
	int userauth_pubkey(Authctxt *authctxt);
	int userauth_passwd(Authctxt *authctxt);

	void authmethod_clear();
	Authmethod authmethod_get(char auth_list);

	Authmethod authmethods[] = {
	{"publickey",
	userauth_pubkey,
	&options.dsa_authentication,
	NULL},
	{"password",
	userauth_passwd,
	&options.password_authentication,
	&options.batch_mode},
	{NULL, NULL, NULL, NULL}
	};

	void
	ssh_userauth2(const char server_user, char host)
	{
	Authctxt authctxt;
	int type;
	int plen;

	debug("send SSH2_MSG_SERVICE_REQUEST");
	packet_start(SSH2_MSG_SERVICE_REQUEST);
	packet_put_cstring("ssh-userauth");
	packet_send();
	packet_write_wait();
	type = packet_read(&plen);
	if (type != SSH2_MSG_SERVICE_ACCEPT) {
	fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
	}
	if (packet_remaining() > 0) {
	char *reply = packet_get_string(&plen);
	debug("service_accept: %s", reply);
	xfree(reply);
	packet_done();
	} else {
	debug("buggy server: service_accept w/o service");
	}
	packet_done();
	debug("got SSH2_MSG_SERVICE_ACCEPT");

	/* setup authentication context */
	authctxt.agent = ssh_get_authentication_connection();
	authctxt.server_user = server_user;
	authctxt.host = host;
	authctxt.service = "ssh-connection"; /* service name */
	authctxt.success = 0;
	authctxt.method = NULL;

	/* initial userauth request */
	packet_start(SSH2_MSG_USERAUTH_REQUEST);
	packet_put_cstring(authctxt.server_user);
	packet_put_cstring(authctxt.service);
	packet_put_cstring("none");
	packet_send();
	packet_write_wait();

	authmethod_clear();

	dispatch_init(&input_userauth_error);
	dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
	dispatch_set(SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
	dispatch_run(DISPATCH_BLOCK, &authctxt.success, &authctxt); /* loop until success */

	if (authctxt.agent != NULL)
	ssh_close_authentication_connection(authctxt.agent);

	debug("ssh-userauth2 successfull");
	}
	void
	input_userauth_error(int type, int plen, void *ctxt)
	{
	fatal("input_userauth_error: bad message during authentication");
	}
	void
	input_userauth_success(int type, int plen, void *ctxt)
	{
	Authctxt *authctxt = ctxt;
	if (authctxt == NULL)
	fatal("input_userauth_success: no authentication context");
	authctxt->success = 1; /* break out */
	}
	void
	input_userauth_failure(int type, int plen, void *ctxt)
	{
	Authmethod *method = NULL;
	Authctxt *authctxt = ctxt;
	char *authlist = NULL;
	int partial;
	int dlen;

	if (authctxt == NULL)
	fatal("input_userauth_failure: no authentication context");

	authlist = packet_get_string(&dlen);
	partial = packet_get_char();
	packet_done();

	if (partial != 0)
	debug("partial success");
	debug("authentications that can continue: %s", authlist);

	for (;;) {
	/* try old method or get next method */
	method = authmethod_get(authlist);
	if (method == NULL)
	fatal("Unable to find an authentication method");
	if (method->userauth(authctxt) != 0) {
	debug2("we sent a packet, wait for reply");
	break;
	} else {
	debug2("we did not send a packet, disable method");
	method->enabled = NULL;
	}
	}
	xfree(authlist);
	}

	int
	userauth_passwd(Authctxt *authctxt)
	{
	static int attempt = 0;
	char prompt[80];
	char *password;

	if (attempt++ >= options.number_of_password_prompts)
	return 0;

	if(attempt != 1)
	error("Permission denied, please try again.");

	snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
	authctxt->server_user, authctxt->host);
	password = read_passphrase(prompt, 0);
	packet_start(SSH2_MSG_USERAUTH_REQUEST);
	packet_put_cstring(authctxt->server_user);
	packet_put_cstring(authctxt->service);
	packet_put_cstring("password");
	packet_put_char(0);
	packet_put_cstring(password);
	memset(password, 0, strlen(password));
	xfree(password);
	packet_send();
	packet_write_wait();
	return 1;
	}

	int
	sign_and_send_pubkey(Authctxt authctxt, Key k, sign_cb_fn *sign_callback)
	{
	Buffer b;
	unsigned char blob, signature;
	int bloblen, slen;
	int skip = 0;
	int ret = -1;

	dsa_make_key_blob(k, &blob, &bloblen);

	/* data to be signed */
	buffer_init(&b);
	if (datafellows & SSH_COMPAT_SESSIONID_ENCODING) {
	buffer_put_string(&b, session_id2, session_id2_len);
	skip = buffer_len(&b);
	} else {
	buffer_append(&b, session_id2, session_id2_len);
	skip = session_id2_len;
	}
	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	buffer_put_cstring(&b, authctxt->server_user);
	buffer_put_cstring(&b,
	datafellows & SSH_BUG_PUBKEYAUTH ?
	"ssh-userauth" :
	authctxt->service);
	buffer_put_cstring(&b, "publickey");
	buffer_put_char(&b, 1);
	buffer_put_cstring(&b, KEX_DSS);
	buffer_put_string(&b, blob, bloblen);

	/* generate signature */
	ret = (*sign_callback)(authctxt, k, &signature, &slen, buffer_ptr(&b), buffer_len(&b));
	if (ret == -1) {
	xfree(blob);
	buffer_free(&b);
	return 0;
	}
	#ifdef DEBUG_DSS
	buffer_dump(&b);
	#endif
	if (datafellows & SSH_BUG_PUBKEYAUTH) {
	buffer_clear(&b);
	buffer_append(&b, session_id2, session_id2_len);
	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	buffer_put_cstring(&b, authctxt->server_user);
	buffer_put_cstring(&b, authctxt->service);
	buffer_put_cstring(&b, "publickey");
	buffer_put_char(&b, 1);
	buffer_put_cstring(&b, KEX_DSS);
	buffer_put_string(&b, blob, bloblen);
	}
	xfree(blob);
	/* append signature */
	buffer_put_string(&b, signature, slen);
	xfree(signature);

	/* skip session id and packet type */
	if (buffer_len(&b) < skip + 1)
	fatal("userauth_pubkey: internal error");
	buffer_consume(&b, skip + 1);

	/* put remaining data from buffer into packet */
	packet_start(SSH2_MSG_USERAUTH_REQUEST);
	packet_put_raw(buffer_ptr(&b), buffer_len(&b));
	buffer_free(&b);

	/* send */
	packet_send();
	packet_write_wait();

	return 1;
	}

	/* sign callback */
	int dsa_sign_cb(Authctxt authctxt, Key key, unsigned char *sigp, int lenp,
	unsigned char *data, int datalen)
	{
	return dsa_sign(key, sigp, lenp, data, datalen);
	}

	int
	userauth_pubkey_identity(Authctxt authctxt, char filename)
	{
	Key *k;
	int i, ret, try_next;
	struct stat st;

	if (stat(filename, &st) != 0) {
	debug("key does not exist: %s", filename);
	return 0;
	}
	debug("try pubkey: %s", filename);

	k = key_new(KEY_DSA);
	if (!load_private_key(filename, "", k, NULL)) {
	int success = 0;
	char *passphrase;
	char prompt[300];
	snprintf(prompt, sizeof prompt,
	"Enter passphrase for DSA key '%.100s': ",
	filename);
	for (i = 0; i < options.number_of_password_prompts; i++) {
	passphrase = read_passphrase(prompt, 0);
	if (strcmp(passphrase, "") != 0) {
	success = load_private_key(filename, passphrase, k, NULL);
	try_next = 0;
	} else {
	debug2("no passphrase given, try next key");
	try_next = 1;
	}
	memset(passphrase, 0, strlen(passphrase));
	xfree(passphrase);
	if (success \|\| try_next)
	break;
	debug2("bad passphrase given, try again...");
	}
	if (!success) {
	key_free(k);
	return 0;
	}
	}
	ret = sign_and_send_pubkey(authctxt, k, dsa_sign_cb);
	key_free(k);
	return ret;
	}

	/* sign callback */
	int agent_sign_cb(Authctxt authctxt, Key key, unsigned char *sigp, int lenp,
	unsigned char *data, int datalen)
	{
	return ssh_agent_sign(authctxt->agent, key, sigp, lenp, data, datalen);
	}

	int
	userauth_pubkey_agent(Authctxt *authctxt)
	{
	static int called = 0;
	char *comment;
	Key *k;
	int ret;

	if (called == 0) {
	k = ssh_get_first_identity(authctxt->agent, &comment, 2);
	called = 1;
	} else {
	k = ssh_get_next_identity(authctxt->agent, &comment, 2);
	}
	if (k == NULL) {
	debug2("no more DSA keys from agent");
	return 0;
	}
	debug("trying DSA agent key %s", comment);
	xfree(comment);
	ret = sign_and_send_pubkey(authctxt, k, agent_sign_cb);
	key_free(k);
	return ret;
	}

	int
	userauth_pubkey(Authctxt *authctxt)
	{
	static int idx = 0;
	int sent = 0;

	if (authctxt->agent != NULL)
	sent = userauth_pubkey_agent(authctxt);
	while (sent == 0 && idx < options.num_identity_files2)
	sent = userauth_pubkey_identity(authctxt, options.identity_files2[idx++]);
	return sent;
	}


	/* find auth method */

	#define DELIM ","

	static char *def_authlist = "publickey,password";
	static char authlist_current = NULL; / clean copy used for comparison */
	static char authname_current = NULL; / last used auth method */
	static char authlist_working = NULL; / copy that gets modified by strtok_r() */
	static char authlist_state = NULL; / state variable for strtok_r() */

	/*
	* Before starting to use a new authentication method list sent by the
	* server, reset internal variables. This should also be called when
	* finished processing server list to free resources.
	*/
	void
	authmethod_clear()
	{
	if (authlist_current != NULL) {
	xfree(authlist_current);
	authlist_current = NULL;
	}
	if (authlist_working != NULL) {
	xfree(authlist_working);
	authlist_working = NULL;
	}
	if (authname_current != NULL) {
	xfree(authname_current);
	authlist_state = NULL;
	}
	if (authlist_state != NULL)
	authlist_state = NULL;
	return;
	}

	/*
	* given auth method name, if configurable options permit this method fill
	* in auth_ident field and return true, otherwise return false.
	*/
	int
	authmethod_is_enabled(Authmethod *method)
	{
	if (method == NULL)
	return 0;
	/* return false if options indicate this method is disabled */
	if (method->enabled == NULL \|\| *method->enabled == 0)
	return 0;
	/* return false if batch mode is enabled but method needs interactive mode */
	if (method->batch_flag != NULL && *method->batch_flag != 0)
	return 0;
	return 1;
	}

	Authmethod *
	authmethod_lookup(const char *name)
	{
	Authmethod *method = NULL;
	if (name != NULL)
	for (method = authmethods; method->name != NULL; method++)
	if (strcmp(name, method->name) == 0)
	return method;
	debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
	return NULL;
	}

	/*
	* Given the authentication method list sent by the server, return the
	* next method we should try. If the server initially sends a nil list,
	* use a built-in default list. If the server sends a nil list after
	* previously sending a valid list, continue using the list originally
	* sent.
	*/

	Authmethod *
	authmethod_get(char *authlist)
	{
	char *name = NULL;
	Authmethod *method = NULL;

	/* Use a suitable default if we're passed a nil list. */
	if (authlist == NULL \|\| strlen(authlist) == 0)
	authlist = def_authlist;

	if (authlist_current == NULL \|\| strcmp(authlist, authlist_current) != 0) {
	/* start over if passed a different list */
	authmethod_clear();
	authlist_current = xstrdup(authlist);
	authlist_working = xstrdup(authlist);
	name = strtok_r(authlist_working, DELIM, &authlist_state);
	} else {
	/*
	* try to use previously used authentication method
	* or continue to use previously passed list
	*/
	name = (authname_current != NULL) ?
	authname_current : strtok_r(NULL, DELIM, &authlist_state);
	}

	while (name != NULL) {
	method = authmethod_lookup(name);
	if (method != NULL && authmethod_is_enabled(method))
	break;
	name = strtok_r(NULL, DELIM, &authlist_state);
	}

	if (authname_current != NULL)
	xfree(authname_current);

	if (name != NULL) {
	debug("next auth method to try is %s", name);
	authname_current = xstrdup(name);
	return method;
	} else {
	debug("no more auth methods to try");
	authname_current = NULL;
	return NULL;
	}
	}