cli-auth.c

/*
 * Dropbear SSH
 * 
 * Copyright (c) 2002,2003 Matt Johnston
 * Copyright (c) 2004 by Mihnea Stoenescu
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE. */

#include "includes.h"
#include "session.h"
#include "auth.h"
#include "dbutil.h"
#include "buffer.h"
#include "ssh.h"
#include "packet.h"
#include "runopts.h"

/* Send a "none" auth request to get available methods */
void cli_auth_getmethods() {
	TRACE(("enter cli_auth_getmethods"))
	CHECKCLEARTOWRITE();
	buf_putbyte(ses.writepayload, SSH_MSG_USERAUTH_REQUEST);
	buf_putstring(ses.writepayload, cli_opts.username,
			strlen(cli_opts.username));
	buf_putstring(ses.writepayload, SSH_SERVICE_CONNECTION,
			SSH_SERVICE_CONNECTION_LEN);
	buf_putstring(ses.writepayload, "none", 4); /* 'none' method */

	encrypt_packet();

#if DROPBEAR_CLI_IMMEDIATE_AUTH
	/* We can't haven't two auth requests in-flight with delayed zlib mode
	since if the first one succeeds then the remote side will 
	expect the second one to be compressed. 
	Race described at
	http://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/zlib-openssh.html
	*/
	if (ses.keys->trans.algo_comp != DROPBEAR_COMP_ZLIB_DELAY) {
		ses.authstate.authtypes = AUTH_TYPE_PUBKEY;
#if DROPBEAR_USE_PASSWORD_ENV
		if (getenv(DROPBEAR_PASSWORD_ENV)) {
			ses.authstate.authtypes |= AUTH_TYPE_PASSWORD | AUTH_TYPE_INTERACT;
		}
#endif
		if (cli_auth_try() == DROPBEAR_SUCCESS) {
			TRACE(("skipped initial none auth query"))
			/* Note that there will be two auth responses in-flight */
			cli_ses.ignore_next_auth_response = 1;
		}
	}
#endif
	TRACE(("leave cli_auth_getmethods"))
}

void recv_msg_userauth_banner() {

	char* banner = NULL;
	unsigned int bannerlen;
	unsigned int i, linecount;
	int truncated = 0;

	TRACE(("enter recv_msg_userauth_banner"))
	if (ses.authstate.authdone) {
		TRACE(("leave recv_msg_userauth_banner: banner after auth done"))
		return;
	}

	if (cli_opts.quiet) {
		TRACE(("not showing banner"))
		return;
	}

	banner = buf_getstring(ses.payload, &bannerlen);
	buf_eatstring(ses.payload); /* The language string */

	if (bannerlen > MAX_BANNER_SIZE) {
		TRACE(("recv_msg_userauth_banner: bannerlen too long: %d", bannerlen))
		truncated = 1;
	} else {
		cleantext(banner);

		/* Limit to 24 lines */
		linecount = 1;
		for (i = 0; i < bannerlen; i++) {
			if (banner[i] == '\n') {
				if (linecount >= MAX_BANNER_LINES) {
					banner[i] = '\0';
					truncated = 1;
					break;
				}
				linecount++;
			}
		}
		fprintf(stderr, "%s\n", banner);
	}

	if (truncated) {
		fprintf(stderr, "[Banner from the server is too long]\n");
	}

	m_free(banner);
	TRACE(("leave recv_msg_userauth_banner"))
}

/* This handles the message-specific types which
 * all have a value of 60. These are
 * SSH_MSG_USERAUTH_PASSWD_CHANGEREQ,
 * SSH_MSG_USERAUTH_PK_OK, &
 * SSH_MSG_USERAUTH_INFO_REQUEST. */
void recv_msg_userauth_specific_60() {

#if DROPBEAR_CLI_PUBKEY_AUTH
	if (cli_ses.lastauthtype == AUTH_TYPE_PUBKEY) {
		recv_msg_userauth_pk_ok();
		return;
	}
#endif

#if DROPBEAR_CLI_INTERACT_AUTH
	if (cli_ses.lastauthtype == AUTH_TYPE_INTERACT) {
		recv_msg_userauth_info_request();
		return;
	}
#endif

#if DROPBEAR_CLI_PASSWORD_AUTH
	if (cli_ses.lastauthtype == AUTH_TYPE_PASSWORD) {
		/* Eventually there could be proper password-changing
		 * support. However currently few servers seem to
		 * implement it, and password auth is last-resort
		 * regardless - keyboard-interactive is more likely
		 * to be used anyway. */
		dropbear_close("Your password has expired.");
	}
#endif

	dropbear_exit("Unexpected userauth packet");
}

void recv_msg_userauth_failure() {

	char * methods = NULL;
	char * tok = NULL;
	unsigned int methlen = 0;
	unsigned int partial = 0;
	unsigned int i = 0;

	TRACE(("<- MSG_USERAUTH_FAILURE"))
	TRACE(("enter recv_msg_userauth_failure"))

	if (ses.authstate.authdone) {
		TRACE(("leave recv_msg_userauth_failure, already authdone."))
		return;
	}

	if (cli_ses.state != USERAUTH_REQ_SENT) {
		/* Perhaps we should be more fatal? */
		dropbear_exit("Unexpected userauth failure");
	}

	/* When DROPBEAR_CLI_IMMEDIATE_AUTH is set there will be an initial response for 
	the "none" auth request, and then a response to the immediate auth request. 
	We need to be careful handling them. */
	if (cli_ses.ignore_next_auth_response) {
		cli_ses.state = USERAUTH_REQ_SENT;
		cli_ses.ignore_next_auth_response = 0;
		TRACE(("leave recv_msg_userauth_failure, ignored response, state set to USERAUTH_REQ_SENT"));
		return;
	} else  {
#if DROPBEAR_CLI_PUBKEY_AUTH
		/* If it was a pubkey auth request, we should cross that key 
		 * off the list. */
		if (cli_ses.lastauthtype == AUTH_TYPE_PUBKEY) {
			cli_pubkeyfail();
		}
#endif

#if DROPBEAR_CLI_INTERACT_AUTH
		/* If we get a failure message for keyboard interactive without
		 * receiving any request info packet, then we don't bother trying
		 * keyboard interactive again */
		if (cli_ses.lastauthtype == AUTH_TYPE_INTERACT
				&& !cli_ses.interact_request_received) {
			TRACE(("setting auth_interact_failed = 1"))
			cli_ses.auth_interact_failed = 1;
		}
#endif
		cli_ses.state = USERAUTH_FAIL_RCVD;
		cli_ses.lastauthtype = AUTH_TYPE_NONE;
	}

	methods = buf_getstring(ses.payload, &methlen);

	partial = buf_getbool(ses.payload);

	if (partial) {
		dropbear_log(LOG_INFO, "Authentication partially succeeded, more attempts required");
	} else {
		ses.authstate.failcount++;
	}

	TRACE(("Methods (len %d): '%s'", methlen, methods))

	ses.authstate.authdone=0;
	ses.authstate.authtypes=0;

	/* Split with nulls rather than commas */
	for (i = 0; i < methlen; i++) {
		if (methods[i] == ',') {
			methods[i] = '\0';
		}
	}

	tok = methods; /* tok stores the next method we'll compare */
	for (i = 0; i <= methlen; i++) {
		if (methods[i] == '\0') {
			TRACE(("auth method '%s'", tok))
#if DROPBEAR_CLI_PUBKEY_AUTH
			if (strncmp(AUTH_METHOD_PUBKEY, tok,
				AUTH_METHOD_PUBKEY_LEN) == 0) {
				ses.authstate.authtypes |= AUTH_TYPE_PUBKEY;
			}
#endif
#if DROPBEAR_CLI_INTERACT_AUTH
			if (strncmp(AUTH_METHOD_INTERACT, tok,
				AUTH_METHOD_INTERACT_LEN) == 0) {
				ses.authstate.authtypes |= AUTH_TYPE_INTERACT;
			}
#endif
#if DROPBEAR_CLI_PASSWORD_AUTH
			if (strncmp(AUTH_METHOD_PASSWORD, tok,
				AUTH_METHOD_PASSWORD_LEN) == 0) {
				ses.authstate.authtypes |= AUTH_TYPE_PASSWORD;
			}
#endif
			tok = &methods[i+1]; /* Must make sure we don't use it after the
									last loop, since it'll point to something
									undefined */
		}
	}

	m_free(methods);
		
	TRACE(("leave recv_msg_userauth_failure"))
}

void recv_msg_userauth_success() {
	/* This function can validly get called multiple times
	if DROPBEAR_CLI_IMMEDIATE_AUTH is set */

	DEBUG1(("received msg_userauth_success"))
	if (cli_opts.disable_trivial_auth && cli_ses.is_trivial_auth) {
		dropbear_exit("trivial authentication not allowed");
	}
	/* Note: in delayed-zlib mode, setting authdone here 
	 * will enable compression in the transport layer */
	ses.authstate.authdone = 1;
	cli_ses.state = USERAUTH_SUCCESS_RCVD;
	cli_ses.lastauthtype = AUTH_TYPE_NONE;

#if DROPBEAR_CLI_PUBKEY_AUTH
	cli_auth_pubkey_cleanup();
#endif
}

int cli_auth_try() {

	int finished = 0;
	TRACE(("enter cli_auth_try"))

	CHECKCLEARTOWRITE();
	
	/* Order to try is pubkey, interactive, password.
	 * As soon as "finished" is set for one, we don't do any more. */
#if DROPBEAR_CLI_PUBKEY_AUTH
	if (ses.authstate.authtypes & AUTH_TYPE_PUBKEY) {
		finished = cli_auth_pubkey();
		cli_ses.lastauthtype = AUTH_TYPE_PUBKEY;
	}
#endif

#if DROPBEAR_CLI_INTERACT_AUTH
	if (!finished && (ses.authstate.authtypes & AUTH_TYPE_INTERACT)) {
		if (ses.keys->trans.algo_crypt->cipherdesc == NULL) {
			fprintf(stderr, "Sorry, I won't let you use interactive auth unencrypted.\n");
		} else {
			if (!cli_ses.auth_interact_failed) {
				cli_auth_interactive();
				cli_ses.lastauthtype = AUTH_TYPE_INTERACT;
				finished = 1;
			}
		}
	}
#endif

#if DROPBEAR_CLI_PASSWORD_AUTH
	if (!finished && (ses.authstate.authtypes & AUTH_TYPE_PASSWORD)) {
		if (ses.keys->trans.algo_crypt->cipherdesc == NULL) {
			fprintf(stderr, "Sorry, I won't let you use password auth unencrypted.\n");
		} else {
			cli_auth_password();
			finished = 1;
			cli_ses.lastauthtype = AUTH_TYPE_PASSWORD;
		}
	}
#endif

	TRACE(("cli_auth_try lastauthtype %d", cli_ses.lastauthtype))

	if (finished) {
		TRACE(("leave cli_auth_try success"))
		return DROPBEAR_SUCCESS;
	}
	TRACE(("leave cli_auth_try failure"))
	return DROPBEAR_FAILURE;
}

#if DROPBEAR_CLI_PASSWORD_AUTH || DROPBEAR_CLI_INTERACT_AUTH
/* A helper for getpass() that exits if the user cancels. The returned
 * password is statically allocated by getpass() */
char* getpass_or_cancel(const char* prompt)
{
	char* password = NULL;
	
#if DROPBEAR_USE_PASSWORD_ENV
	/* Password provided in an environment var */
	password = getenv(DROPBEAR_PASSWORD_ENV);
	if (password)
	{
		return password;
	}
#endif

	password = getpass(prompt);

	/* 0x03 is a ctrl-c character in the buffer. */
	if (password == NULL || strchr(password, '\3') != NULL) {
		dropbear_close("Interrupted.");
	}
	return password;
}
#endif