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

 /*
  *
  * readconf.c
  *
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  *
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
  *
  * Created: Sat Apr 22 00:03:10 1995 ylo
  *
  * Functions for reading the configuration files.
  *
  */

 #include "includes.h"
 RCSID("$Id: readconf.c,v 1.7 1999/12/06 00:47:29 damien Exp $");

 #include "ssh.h"
 #include "cipher.h"
 #include "readconf.h"
 #include "xmalloc.h"

 /* Format of the configuration file:

    # Configuration data is parsed as follows:
    #  1. command line options
    #  2. user-specific file
    #  3. system-wide file
    # Any configuration value is only changed the first time it is set.
    # Thus, host-specific definitions should be at the beginning of the
    # configuration file, and defaults at the end.

    # Host-specific declarations.  These may override anything above.  A single
    # host may match multiple declarations; these are processed in the order
    # that they are given in.

    Host *.ngs.fi ngs.fi
      FallBackToRsh no

    Host fake.com
      HostName another.host.name.real.org
      User blaah
      Port 34289
      ForwardX11 no
      ForwardAgent no

    Host books.com
      RemoteForward 9999 shadows.cs.hut.fi:9999
      Cipher 3des

    Host fascist.blob.com
      Port 23123
      User tylonen
      RhostsAuthentication no
      PasswordAuthentication no

    Host puukko.hut.fi
      User t35124p
      ProxyCommand ssh-proxy %h %p

    Host *.fr
      UseRsh yes

    Host *.su
      Cipher none
      PasswordAuthentication no

    # Defaults for various options
    Host *
      ForwardAgent no
      ForwardX11 yes
      RhostsAuthentication yes
      PasswordAuthentication yes
      RSAAuthentication yes
      RhostsRSAAuthentication yes
      FallBackToRsh no
      UseRsh no
      StrictHostKeyChecking yes
      KeepAlives no
      IdentityFile ~/.ssh/identity
      Port 22
      EscapeChar ~

 */

 /* Keyword tokens. */

 typedef enum {
 	oBadOption,
 	oForwardAgent, oForwardX11, oGatewayPorts, oRhostsAuthentication,
 	oPasswordAuthentication, oRSAAuthentication, oFallBackToRsh, oUseRsh,
 	oSkeyAuthentication,
 #ifdef KRB4
 	oKerberosAuthentication,
 #endif /* KRB4 */
 #ifdef AFS
 	oKerberosTgtPassing, oAFSTokenPassing,
 #endif
 	oIdentityFile, oHostName, oPort, oCipher, oRemoteForward, oLocalForward,
 	oUser, oHost, oEscapeChar, oRhostsRSAAuthentication, oProxyCommand,
 	oGlobalKnownHostsFile, oUserKnownHostsFile, oConnectionAttempts,
 	oBatchMode, oCheckHostIP, oStrictHostKeyChecking, oCompression,
 	oCompressionLevel, oKeepAlives, oNumberOfPasswordPrompts, oTISAuthentication,
 	oUsePrivilegedPort, oLogLevel
 } OpCodes;

 /* Textual representations of the tokens. */

 static struct {
 	const char *name;
 	OpCodes opcode;
 } keywords[] = {
 	{ "forwardagent", oForwardAgent },
 	{ "forwardx11", oForwardX11 },
 	{ "gatewayports", oGatewayPorts },
 	{ "useprivilegedport", oUsePrivilegedPort },
 	{ "rhostsauthentication", oRhostsAuthentication },
 	{ "passwordauthentication", oPasswordAuthentication },
 	{ "rsaauthentication", oRSAAuthentication },
 	{ "skeyauthentication", oSkeyAuthentication },
 #ifdef KRB4
 	{ "kerberosauthentication", oKerberosAuthentication },
 #endif /* KRB4 */
 #ifdef AFS
 	{ "kerberostgtpassing", oKerberosTgtPassing },
 	{ "afstokenpassing", oAFSTokenPassing },
 #endif
 	{ "fallbacktorsh", oFallBackToRsh },
 	{ "usersh", oUseRsh },
 	{ "identityfile", oIdentityFile },
 	{ "hostname", oHostName },
 	{ "proxycommand", oProxyCommand },
 	{ "port", oPort },
 	{ "cipher", oCipher },
 	{ "remoteforward", oRemoteForward },
 	{ "localforward", oLocalForward },
 	{ "user", oUser },
 	{ "host", oHost },
 	{ "escapechar", oEscapeChar },
 	{ "rhostsrsaauthentication", oRhostsRSAAuthentication },
 	{ "globalknownhostsfile", oGlobalKnownHostsFile },
 	{ "userknownhostsfile", oUserKnownHostsFile },
 	{ "connectionattempts", oConnectionAttempts },
 	{ "batchmode", oBatchMode },
 	{ "checkhostip", oCheckHostIP },
 	{ "stricthostkeychecking", oStrictHostKeyChecking },
 	{ "compression", oCompression },
 	{ "compressionlevel", oCompressionLevel },
 	{ "keepalive", oKeepAlives },
 	{ "numberofpasswordprompts", oNumberOfPasswordPrompts },
 	{ "tisauthentication", oTISAuthentication },
 	{ "loglevel", oLogLevel },
 	{ NULL, 0 }
 };

 /* Characters considered whitespace in strtok calls. */
 #define WHITESPACE " \t\r\n"


 /*
  * Adds a local TCP/IP port forward to options.  Never returns if there is an
  * error.
  */

 void
 add_local_forward(Options *options, u_short port, const char *host,
 		  u_short host_port)
 {
 	Forward *fwd;
 	extern uid_t original_real_uid;
 	if (port < IPPORT_RESERVED && original_real_uid != 0)
 		fatal("Privileged ports can only be forwarded by root.\n");
 	if (options->num_local_forwards >= SSH_MAX_FORWARDS_PER_DIRECTION)
 		fatal("Too many local forwards (max %d).", SSH_MAX_FORWARDS_PER_DIRECTION);
 	fwd = &options->local_forwards[options->num_local_forwards++];
 	fwd->port = port;
 	fwd->host = xstrdup(host);
 	fwd->host_port = host_port;
 }

 /*
  * Adds a remote TCP/IP port forward to options.  Never returns if there is
  * an error.
  */

 void
 add_remote_forward(Options *options, u_short port, const char *host,
 		   u_short host_port)
 {
 	Forward *fwd;
 	if (options->num_remote_forwards >= SSH_MAX_FORWARDS_PER_DIRECTION)
 		fatal("Too many remote forwards (max %d).",
 		      SSH_MAX_FORWARDS_PER_DIRECTION);
 	fwd = &options->remote_forwards[options->num_remote_forwards++];
 	fwd->port = port;
 	fwd->host = xstrdup(host);
 	fwd->host_port = host_port;
 }

 /*
  * Returns the number of the token pointed to by cp of length len. Never
  * returns if the token is not known.
  */

 static OpCodes
 parse_token(const char *cp, const char *filename, int linenum)
 {
 	unsigned int i;

 	for (i = 0; keywords[i].name; i++)
 		if (strcasecmp(cp, keywords[i].name) == 0)
 			return keywords[i].opcode;

 	fprintf(stderr, "%s: line %d: Bad configuration option: %s\n",
 		filename, linenum, cp);
 	return oBadOption;
 }

 /*
  * Processes a single option line as used in the configuration files. This
  * only sets those values that have not already been set.
  */

 int
 process_config_line(Options *options, const char *host,
 		    char *line, const char *filename, int linenum,
 		    int *activep)
 {
 	char buf[256], *cp, *string, **charptr, *cp2;
 	int opcode, *intptr, value;
 	u_short fwd_port, fwd_host_port;

 	/* Skip leading whitespace. */
 	cp = line + strspn(line, WHITESPACE);
 	if (!*cp || *cp == '\n' || *cp == '#')
 		return 0;

 	/* Get the keyword. (Each line is supposed to begin with a keyword). */
 	cp = strtok(cp, WHITESPACE);
 	opcode = parse_token(cp, filename, linenum);

 	switch (opcode) {
 	case oBadOption:
 		/* don't panic, but count bad options */
 		return -1;
 		/* NOTREACHED */
 	case oForwardAgent:
 		intptr = &options->forward_agent;
 parse_flag:
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing yes/no argument.", filename, linenum);
 		value = 0;	/* To avoid compiler warning... */
 		if (strcmp(cp, "yes") == 0 || strcmp(cp, "true") == 0)
 			value = 1;
 		else if (strcmp(cp, "no") == 0 || strcmp(cp, "false") == 0)
 			value = 0;
 		else
 			fatal("%.200s line %d: Bad yes/no argument.", filename, linenum);
 		if (*activep && *intptr == -1)
 			*intptr = value;
 		break;

 	case oForwardX11:
 		intptr = &options->forward_x11;
 		goto parse_flag;

 	case oGatewayPorts:
 		intptr = &options->gateway_ports;
 		goto parse_flag;

 	case oUsePrivilegedPort:
 		intptr = &options->use_privileged_port;
 		goto parse_flag;

 	case oRhostsAuthentication:
 		intptr = &options->rhosts_authentication;
 		goto parse_flag;

 	case oPasswordAuthentication:
 		intptr = &options->password_authentication;
 		goto parse_flag;

 	case oRSAAuthentication:
 		intptr = &options->rsa_authentication;
 		goto parse_flag;

 	case oRhostsRSAAuthentication:
 		intptr = &options->rhosts_rsa_authentication;
 		goto parse_flag;

 	case oTISAuthentication:
 		/* fallthrough, there is no difference on the client side */
 	case oSkeyAuthentication:
 		intptr = &options->skey_authentication;
 		goto parse_flag;

 #ifdef KRB4
 	case oKerberosAuthentication:
 		intptr = &options->kerberos_authentication;
 		goto parse_flag;
 #endif /* KRB4 */

 #ifdef AFS
 	case oKerberosTgtPassing:
 		intptr = &options->kerberos_tgt_passing;
 		goto parse_flag;

 	case oAFSTokenPassing:
 		intptr = &options->afs_token_passing;
 		goto parse_flag;
 #endif

 	case oFallBackToRsh:
 		intptr = &options->fallback_to_rsh;
 		goto parse_flag;

 	case oUseRsh:
 		intptr = &options->use_rsh;
 		goto parse_flag;

 	case oBatchMode:
 		intptr = &options->batch_mode;
 		goto parse_flag;

 	case oCheckHostIP:
 		intptr = &options->check_host_ip;
 		goto parse_flag;

 	case oStrictHostKeyChecking:
 		intptr = &options->strict_host_key_checking;
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing yes/no argument.",
 			      filename, linenum);
 		value = 0;	/* To avoid compiler warning... */
 		if (strcmp(cp, "yes") == 0 || strcmp(cp, "true") == 0)
 			value = 1;
 		else if (strcmp(cp, "no") == 0 || strcmp(cp, "false") == 0)
 			value = 0;
 		else if (strcmp(cp, "ask") == 0)
 			value = 2;
 		else
 			fatal("%.200s line %d: Bad yes/no/ask argument.", filename, linenum);
 		if (*activep && *intptr == -1)
 			*intptr = value;
 		break;

 	case oCompression:
 		intptr = &options->compression;
 		goto parse_flag;

 	case oKeepAlives:
 		intptr = &options->keepalives;
 		goto parse_flag;

 	case oNumberOfPasswordPrompts:
 		intptr = &options->number_of_password_prompts;
 		goto parse_int;

 	case oCompressionLevel:
 		intptr = &options->compression_level;
 		goto parse_int;

 	case oIdentityFile:
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing argument.", filename, linenum);
 		if (*activep) {
 			if (options->num_identity_files >= SSH_MAX_IDENTITY_FILES)
 				fatal("%.200s line %d: Too many identity files specified (max %d).",
 				      filename, linenum, SSH_MAX_IDENTITY_FILES);
 			options->identity_files[options->num_identity_files++] = xstrdup(cp);
 		}
 		break;

 	case oUser:
 		charptr = &options->user;
 parse_string:
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing argument.", filename, linenum);
 		if (*activep && *charptr == NULL)
 			*charptr = xstrdup(cp);
 		break;

 	case oGlobalKnownHostsFile:
 		charptr = &options->system_hostfile;
 		goto parse_string;

 	case oUserKnownHostsFile:
 		charptr = &options->user_hostfile;
 		goto parse_string;

 	case oHostName:
 		charptr = &options->hostname;
 		goto parse_string;

 	case oProxyCommand:
 		charptr = &options->proxy_command;
 		string = xstrdup("");
 		while ((cp = strtok(NULL, WHITESPACE)) != NULL) {
 			string = xrealloc(string, strlen(string) + strlen(cp) + 2);
 			strcat(string, " ");
 			strcat(string, cp);
 		}
 		if (*activep && *charptr == NULL)
 			*charptr = string;
 		else
 			xfree(string);
 		return 0;

 	case oPort:
 		intptr = &options->port;
 parse_int:
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing argument.", filename, linenum);
 		if (cp[0] < '0' || cp[0] > '9')
 			fatal("%.200s line %d: Bad number.", filename, linenum);

 		/* Octal, decimal, or hex format? */
 		value = strtol(cp, &cp2, 0);
 		if (cp == cp2)
 			fatal("%.200s line %d: Bad number.", filename, linenum);
 		if (*activep && *intptr == -1)
 			*intptr = value;
 		break;

 	case oConnectionAttempts:
 		intptr = &options->connection_attempts;
 		goto parse_int;

 	case oCipher:
 		intptr = &options->cipher;
 		cp = strtok(NULL, WHITESPACE);
 		value = cipher_number(cp);
 		if (value == -1)
 			fatal("%.200s line %d: Bad cipher '%s'.",
 			      filename, linenum, cp ? cp : "<NONE>");
 		if (*activep && *intptr == -1)
 			*intptr = value;
 		break;

 	case oLogLevel:
 		intptr = (int *) &options->log_level;
 		cp = strtok(NULL, WHITESPACE);
 		value = log_level_number(cp);
 		if (value == (LogLevel) - 1)
 			fatal("%.200s line %d: unsupported log level '%s'\n",
 			      filename, linenum, cp ? cp : "<NONE>");
 		if (*activep && (LogLevel) * intptr == -1)
 			*intptr = (LogLevel) value;
 		break;

 	case oRemoteForward:
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing argument.", filename, linenum);
 		if (cp[0] < '0' || cp[0] > '9')
 			fatal("%.200s line %d: Badly formatted port number.",
 			      filename, linenum);
 		fwd_port = atoi(cp);
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing second argument.",
 			      filename, linenum);
 		if (sscanf(cp, "%255[^:]:%hu", buf, &fwd_host_port) != 2)
 			fatal("%.200s line %d: Badly formatted host:port.",
 			      filename, linenum);
 		if (*activep)
 			add_remote_forward(options, fwd_port, buf, fwd_host_port);
 		break;

 	case oLocalForward:
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing argument.", filename, linenum);
 		if (cp[0] < '0' || cp[0] > '9')
 			fatal("%.200s line %d: Badly formatted port number.",
 			      filename, linenum);
 		fwd_port = atoi(cp);
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing second argument.",
 			      filename, linenum);
 		if (sscanf(cp, "%255[^:]:%hu", buf, &fwd_host_port) != 2)
 			fatal("%.200s line %d: Badly formatted host:port.",
 			      filename, linenum);
 		if (*activep)
 			add_local_forward(options, fwd_port, buf, fwd_host_port);
 		break;

 	case oHost:
 		*activep = 0;
 		while ((cp = strtok(NULL, WHITESPACE)) != NULL)
 			if (match_pattern(host, cp)) {
 				debug("Applying options for %.100s", cp);
 				*activep = 1;
 				break;
 			}
 		/* Avoid garbage check below, as strtok already returned NULL. */
 		return 0;

 	case oEscapeChar:
 		intptr = &options->escape_char;
 		cp = strtok(NULL, WHITESPACE);
 		if (!cp)
 			fatal("%.200s line %d: Missing argument.", filename, linenum);
 		if (cp[0] == '^' && cp[2] == 0 &&
 		    (unsigned char) cp[1] >= 64 && (unsigned char) cp[1] < 128)
 			value = (unsigned char) cp[1] & 31;
 		else if (strlen(cp) == 1)
 			value = (unsigned char) cp[0];
 		else if (strcmp(cp, "none") == 0)
 			value = -2;
 		else {
 			fatal("%.200s line %d: Bad escape character.",
 			      filename, linenum);
 			/* NOTREACHED */
 			value = 0;	/* Avoid compiler warning. */
 		}
 		if (*activep && *intptr == -1)
 			*intptr = value;
 		break;

 	default:
 		fatal("process_config_line: Unimplemented opcode %d", opcode);
 	}

 	/* Check that there is no garbage at end of line. */
 	if (strtok(NULL, WHITESPACE) != NULL)
 		fatal("%.200s line %d: garbage at end of line.",
 		      filename, linenum);
 	return 0;
 }


 /*
  * Reads the config file and modifies the options accordingly.  Options
  * should already be initialized before this call.  This never returns if
  * there is an error.  If the file does not exist, this returns immediately.
  */

 void
 read_config_file(const char *filename, const char *host, Options *options)
 {
 	FILE *f;
 	char line[1024];
 	int active, linenum;
 	int bad_options = 0;

 	/* Open the file. */
 	f = fopen(filename, "r");
 	if (!f)
 		return;

 	debug("Reading configuration data %.200s", filename);

 	/*
 	 * Mark that we are now processing the options.  This flag is turned
 	 * on/off by Host specifications.
 	 */
 	active = 1;
 	linenum = 0;
 	while (fgets(line, sizeof(line), f)) {
 		/* Update line number counter. */
 		linenum++;
 		if (process_config_line(options, host, line, filename, linenum, &active) != 0)
 			bad_options++;
 	}
 	fclose(f);
 	if (bad_options > 0)
 		fatal("%s: terminating, %d bad configuration options\n",
 		      filename, bad_options);
 }

 /*
  * Initializes options to special values that indicate that they have not yet
  * been set.  Read_config_file will only set options with this value. Options
  * are processed in the following order: command line, user config file,
  * system config file.  Last, fill_default_options is called.
  */

 void
 initialize_options(Options * options)
 {
 	memset(options, 'X', sizeof(*options));
 	options->forward_agent = -1;
 	options->forward_x11 = -1;
 	options->gateway_ports = -1;
 	options->use_privileged_port = -1;
 	options->rhosts_authentication = -1;
 	options->rsa_authentication = -1;
 	options->skey_authentication = -1;
 #ifdef KRB4
 	options->kerberos_authentication = -1;
 #endif
 #ifdef AFS
 	options->kerberos_tgt_passing = -1;
 	options->afs_token_passing = -1;
 #endif
 	options->password_authentication = -1;
 	options->rhosts_rsa_authentication = -1;
 	options->fallback_to_rsh = -1;
 	options->use_rsh = -1;
 	options->batch_mode = -1;
 	options->check_host_ip = -1;
 	options->strict_host_key_checking = -1;
 	options->compression = -1;
 	options->keepalives = -1;
 	options->compression_level = -1;
 	options->port = -1;
 	options->connection_attempts = -1;
 	options->number_of_password_prompts = -1;
 	options->cipher = -1;
 	options->num_identity_files = 0;
 	options->hostname = NULL;
 	options->proxy_command = NULL;
 	options->user = NULL;
 	options->escape_char = -1;
 	options->system_hostfile = NULL;
 	options->user_hostfile = NULL;
 	options->num_local_forwards = 0;
 	options->num_remote_forwards = 0;
 	options->log_level = (LogLevel) - 1;
 }

 /*
  * Called after processing other sources of option data, this fills those
  * options for which no value has been specified with their default values.
  */

 void
 fill_default_options(Options * options)
 {
 	if (options->forward_agent == -1)
 		options->forward_agent = 1;
 	if (options->forward_x11 == -1)
 		options->forward_x11 = 1;
 	if (options->gateway_ports == -1)
 		options->gateway_ports = 0;
 	if (options->use_privileged_port == -1)
 		options->use_privileged_port = 1;
 	if (options->rhosts_authentication == -1)
 		options->rhosts_authentication = 1;
 	if (options->rsa_authentication == -1)
 		options->rsa_authentication = 1;
 	if (options->skey_authentication == -1)
 		options->skey_authentication = 0;
 #ifdef KRB4
 	if (options->kerberos_authentication == -1)
 		options->kerberos_authentication = 1;
 #endif /* KRB4 */
 #ifdef AFS
 	if (options->kerberos_tgt_passing == -1)
 		options->kerberos_tgt_passing = 1;
 	if (options->afs_token_passing == -1)
 		options->afs_token_passing = 1;
 #endif /* AFS */
 	if (options->password_authentication == -1)
 		options->password_authentication = 1;
 	if (options->rhosts_rsa_authentication == -1)
 		options->rhosts_rsa_authentication = 1;
 	if (options->fallback_to_rsh == -1)
 		options->fallback_to_rsh = 1;
 	if (options->use_rsh == -1)
 		options->use_rsh = 0;
 	if (options->batch_mode == -1)
 		options->batch_mode = 0;
 	if (options->check_host_ip == -1)
 		options->check_host_ip = 1;
 	if (options->strict_host_key_checking == -1)
 		options->strict_host_key_checking = 2;	/* 2 is default */
 	if (options->compression == -1)
 		options->compression = 0;
 	if (options->keepalives == -1)
 		options->keepalives = 1;
 	if (options->compression_level == -1)
 		options->compression_level = 6;
 	if (options->port == -1)
 		options->port = 0;	/* Filled in ssh_connect. */
 	if (options->connection_attempts == -1)
 		options->connection_attempts = 4;
 	if (options->number_of_password_prompts == -1)
 		options->number_of_password_prompts = 3;
 	/* Selected in ssh_login(). */
 	if (options->cipher == -1)
 		options->cipher = SSH_CIPHER_NOT_SET;
 	if (options->num_identity_files == 0) {
 		options->identity_files[0] =
 			xmalloc(2 + strlen(SSH_CLIENT_IDENTITY) + 1);
 		sprintf(options->identity_files[0], "~/%.100s", SSH_CLIENT_IDENTITY);
 		options->num_identity_files = 1;
 	}
 	if (options->escape_char == -1)
 		options->escape_char = '~';
 	if (options->system_hostfile == NULL)
 		options->system_hostfile = SSH_SYSTEM_HOSTFILE;
 	if (options->user_hostfile == NULL)
 		options->user_hostfile = SSH_USER_HOSTFILE;
 	if (options->log_level == (LogLevel) - 1)
 		options->log_level = SYSLOG_LEVEL_INFO;
 	/* options->proxy_command should not be set by default */
 	/* options->user will be set in the main program if appropriate */
 	/* options->hostname will be set in the main program if appropriate */
 }
	/*
	*
	* readconf.c
	*
	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	*
	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	* All rights reserved
	*
	* Created: Sat Apr 22 00:03:10 1995 ylo
	*
	* Functions for reading the configuration files.
	*
	*/

	#include "includes.h"
	RCSID("$Id: readconf.c,v 1.7 1999/12/06 00:47:29 damien Exp $");

	#include "ssh.h"
	#include "cipher.h"
	#include "readconf.h"
	#include "xmalloc.h"

	/* Format of the configuration file:

	# Configuration data is parsed as follows:
	# 1. command line options
	# 2. user-specific file
	# 3. system-wide file
	# Any configuration value is only changed the first time it is set.
	# Thus, host-specific definitions should be at the beginning of the
	# configuration file, and defaults at the end.

	# Host-specific declarations. These may override anything above. A single
	# host may match multiple declarations; these are processed in the order
	# that they are given in.

	Host *.ngs.fi ngs.fi
	FallBackToRsh no

	Host fake.com
	HostName another.host.name.real.org
	User blaah
	Port 34289
	ForwardX11 no
	ForwardAgent no

	Host books.com
	RemoteForward 9999 shadows.cs.hut.fi:9999
	Cipher 3des

	Host fascist.blob.com
	Port 23123
	User tylonen
	RhostsAuthentication no
	PasswordAuthentication no

	Host puukko.hut.fi
	User t35124p
	ProxyCommand ssh-proxy %h %p

	Host *.fr
	UseRsh yes

	Host *.su
	Cipher none
	PasswordAuthentication no

	# Defaults for various options
	Host *
	ForwardAgent no
	ForwardX11 yes
	RhostsAuthentication yes
	PasswordAuthentication yes
	RSAAuthentication yes
	RhostsRSAAuthentication yes
	FallBackToRsh no
	UseRsh no
	StrictHostKeyChecking yes
	KeepAlives no
	IdentityFile ~/.ssh/identity
	Port 22
	EscapeChar ~

	*/

	/* Keyword tokens. */

	typedef enum {
	oBadOption,
	oForwardAgent, oForwardX11, oGatewayPorts, oRhostsAuthentication,
	oPasswordAuthentication, oRSAAuthentication, oFallBackToRsh, oUseRsh,
	oSkeyAuthentication,
	#ifdef KRB4
	oKerberosAuthentication,
	#endif /* KRB4 */
	#ifdef AFS
	oKerberosTgtPassing, oAFSTokenPassing,
	#endif
	oIdentityFile, oHostName, oPort, oCipher, oRemoteForward, oLocalForward,
	oUser, oHost, oEscapeChar, oRhostsRSAAuthentication, oProxyCommand,
	oGlobalKnownHostsFile, oUserKnownHostsFile, oConnectionAttempts,
	oBatchMode, oCheckHostIP, oStrictHostKeyChecking, oCompression,
	oCompressionLevel, oKeepAlives, oNumberOfPasswordPrompts, oTISAuthentication,
	oUsePrivilegedPort, oLogLevel
	} OpCodes;

	/* Textual representations of the tokens. */

	static struct {
	const char *name;
	OpCodes opcode;
	} keywords[] = {
	{ "forwardagent", oForwardAgent },
	{ "forwardx11", oForwardX11 },
	{ "gatewayports", oGatewayPorts },
	{ "useprivilegedport", oUsePrivilegedPort },
	{ "rhostsauthentication", oRhostsAuthentication },
	{ "passwordauthentication", oPasswordAuthentication },
	{ "rsaauthentication", oRSAAuthentication },
	{ "skeyauthentication", oSkeyAuthentication },
	#ifdef KRB4
	{ "kerberosauthentication", oKerberosAuthentication },
	#endif /* KRB4 */
	#ifdef AFS
	{ "kerberostgtpassing", oKerberosTgtPassing },
	{ "afstokenpassing", oAFSTokenPassing },
	#endif
	{ "fallbacktorsh", oFallBackToRsh },
	{ "usersh", oUseRsh },
	{ "identityfile", oIdentityFile },
	{ "hostname", oHostName },
	{ "proxycommand", oProxyCommand },
	{ "port", oPort },
	{ "cipher", oCipher },
	{ "remoteforward", oRemoteForward },
	{ "localforward", oLocalForward },
	{ "user", oUser },
	{ "host", oHost },
	{ "escapechar", oEscapeChar },
	{ "rhostsrsaauthentication", oRhostsRSAAuthentication },
	{ "globalknownhostsfile", oGlobalKnownHostsFile },
	{ "userknownhostsfile", oUserKnownHostsFile },
	{ "connectionattempts", oConnectionAttempts },
	{ "batchmode", oBatchMode },
	{ "checkhostip", oCheckHostIP },
	{ "stricthostkeychecking", oStrictHostKeyChecking },
	{ "compression", oCompression },
	{ "compressionlevel", oCompressionLevel },
	{ "keepalive", oKeepAlives },
	{ "numberofpasswordprompts", oNumberOfPasswordPrompts },
	{ "tisauthentication", oTISAuthentication },
	{ "loglevel", oLogLevel },
	{ NULL, 0 }
	};

	/* Characters considered whitespace in strtok calls. */
	#define WHITESPACE " \t\r\n"


	/*
	* Adds a local TCP/IP port forward to options. Never returns if there is an
	* error.
	*/

	void
	add_local_forward(Options options, u_short port, const char host,
	u_short host_port)
	{
	Forward *fwd;
	extern uid_t original_real_uid;
	if (port < IPPORT_RESERVED && original_real_uid != 0)
	fatal("Privileged ports can only be forwarded by root.\n");
	if (options->num_local_forwards >= SSH_MAX_FORWARDS_PER_DIRECTION)
	fatal("Too many local forwards (max %d).", SSH_MAX_FORWARDS_PER_DIRECTION);
	fwd = &options->local_forwards[options->num_local_forwards++];
	fwd->port = port;
	fwd->host = xstrdup(host);
	fwd->host_port = host_port;
	}

	/*
	* Adds a remote TCP/IP port forward to options. Never returns if there is
	* an error.
	*/

	void
	add_remote_forward(Options options, u_short port, const char host,
	u_short host_port)
	{
	Forward *fwd;
	if (options->num_remote_forwards >= SSH_MAX_FORWARDS_PER_DIRECTION)
	fatal("Too many remote forwards (max %d).",
	SSH_MAX_FORWARDS_PER_DIRECTION);
	fwd = &options->remote_forwards[options->num_remote_forwards++];
	fwd->port = port;
	fwd->host = xstrdup(host);
	fwd->host_port = host_port;
	}

	/*
	* Returns the number of the token pointed to by cp of length len. Never
	* returns if the token is not known.
	*/

	static OpCodes
	parse_token(const char cp, const char filename, int linenum)
	{
	unsigned int i;

	for (i = 0; keywords[i].name; i++)
	if (strcasecmp(cp, keywords[i].name) == 0)
	return keywords[i].opcode;

	fprintf(stderr, "%s: line %d: Bad configuration option: %s\n",
	filename, linenum, cp);
	return oBadOption;
	}

	/*
	* Processes a single option line as used in the configuration files. This
	* only sets those values that have not already been set.
	*/

	int
	process_config_line(Options options, const char host,
	char line, const char filename, int linenum,
	int *activep)
	{
	char buf[256], cp, string, *charptr, cp2;
	int opcode, *intptr, value;
	u_short fwd_port, fwd_host_port;

	/* Skip leading whitespace. */
	cp = line + strspn(line, WHITESPACE);
	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	return 0;

	/* Get the keyword. (Each line is supposed to begin with a keyword). */
	cp = strtok(cp, WHITESPACE);
	opcode = parse_token(cp, filename, linenum);

	switch (opcode) {
	case oBadOption:
	/* don't panic, but count bad options */
	return -1;
	/* NOTREACHED */
	case oForwardAgent:
	intptr = &options->forward_agent;
	parse_flag:
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing yes/no argument.", filename, linenum);
	value = 0; /* To avoid compiler warning... */
	if (strcmp(cp, "yes") == 0 \|\| strcmp(cp, "true") == 0)
	value = 1;
	else if (strcmp(cp, "no") == 0 \|\| strcmp(cp, "false") == 0)
	value = 0;
	else
	fatal("%.200s line %d: Bad yes/no argument.", filename, linenum);
	if (activep && intptr == -1)
	*intptr = value;
	break;

	case oForwardX11:
	intptr = &options->forward_x11;
	goto parse_flag;

	case oGatewayPorts:
	intptr = &options->gateway_ports;
	goto parse_flag;

	case oUsePrivilegedPort:
	intptr = &options->use_privileged_port;
	goto parse_flag;

	case oRhostsAuthentication:
	intptr = &options->rhosts_authentication;
	goto parse_flag;

	case oPasswordAuthentication:
	intptr = &options->password_authentication;
	goto parse_flag;

	case oRSAAuthentication:
	intptr = &options->rsa_authentication;
	goto parse_flag;

	case oRhostsRSAAuthentication:
	intptr = &options->rhosts_rsa_authentication;
	goto parse_flag;

	case oTISAuthentication:
	/* fallthrough, there is no difference on the client side */
	case oSkeyAuthentication:
	intptr = &options->skey_authentication;
	goto parse_flag;

	#ifdef KRB4
	case oKerberosAuthentication:
	intptr = &options->kerberos_authentication;
	goto parse_flag;
	#endif /* KRB4 */

	#ifdef AFS
	case oKerberosTgtPassing:
	intptr = &options->kerberos_tgt_passing;
	goto parse_flag;

	case oAFSTokenPassing:
	intptr = &options->afs_token_passing;
	goto parse_flag;
	#endif

	case oFallBackToRsh:
	intptr = &options->fallback_to_rsh;
	goto parse_flag;

	case oUseRsh:
	intptr = &options->use_rsh;
	goto parse_flag;

	case oBatchMode:
	intptr = &options->batch_mode;
	goto parse_flag;

	case oCheckHostIP:
	intptr = &options->check_host_ip;
	goto parse_flag;

	case oStrictHostKeyChecking:
	intptr = &options->strict_host_key_checking;
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing yes/no argument.",
	filename, linenum);
	value = 0; /* To avoid compiler warning... */
	if (strcmp(cp, "yes") == 0 \|\| strcmp(cp, "true") == 0)
	value = 1;
	else if (strcmp(cp, "no") == 0 \|\| strcmp(cp, "false") == 0)
	value = 0;
	else if (strcmp(cp, "ask") == 0)
	value = 2;
	else
	fatal("%.200s line %d: Bad yes/no/ask argument.", filename, linenum);
	if (activep && intptr == -1)
	*intptr = value;
	break;

	case oCompression:
	intptr = &options->compression;
	goto parse_flag;

	case oKeepAlives:
	intptr = &options->keepalives;
	goto parse_flag;

	case oNumberOfPasswordPrompts:
	intptr = &options->number_of_password_prompts;
	goto parse_int;

	case oCompressionLevel:
	intptr = &options->compression_level;
	goto parse_int;

	case oIdentityFile:
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing argument.", filename, linenum);
	if (*activep) {
	if (options->num_identity_files >= SSH_MAX_IDENTITY_FILES)
	fatal("%.200s line %d: Too many identity files specified (max %d).",
	filename, linenum, SSH_MAX_IDENTITY_FILES);
	options->identity_files[options->num_identity_files++] = xstrdup(cp);
	}
	break;

	case oUser:
	charptr = &options->user;
	parse_string:
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing argument.", filename, linenum);
	if (activep && charptr == NULL)
	*charptr = xstrdup(cp);
	break;

	case oGlobalKnownHostsFile:
	charptr = &options->system_hostfile;
	goto parse_string;

	case oUserKnownHostsFile:
	charptr = &options->user_hostfile;
	goto parse_string;

	case oHostName:
	charptr = &options->hostname;
	goto parse_string;

	case oProxyCommand:
	charptr = &options->proxy_command;
	string = xstrdup("");
	while ((cp = strtok(NULL, WHITESPACE)) != NULL) {
	string = xrealloc(string, strlen(string) + strlen(cp) + 2);
	strcat(string, " ");
	strcat(string, cp);
	}
	if (activep && charptr == NULL)
	*charptr = string;
	else
	xfree(string);
	return 0;

	case oPort:
	intptr = &options->port;
	parse_int:
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing argument.", filename, linenum);
	if (cp[0] < '0' \|\| cp[0] > '9')
	fatal("%.200s line %d: Bad number.", filename, linenum);

	/* Octal, decimal, or hex format? */
	value = strtol(cp, &cp2, 0);
	if (cp == cp2)
	fatal("%.200s line %d: Bad number.", filename, linenum);
	if (activep && intptr == -1)
	*intptr = value;
	break;

	case oConnectionAttempts:
	intptr = &options->connection_attempts;
	goto parse_int;

	case oCipher:
	intptr = &options->cipher;
	cp = strtok(NULL, WHITESPACE);
	value = cipher_number(cp);
	if (value == -1)
	fatal("%.200s line %d: Bad cipher '%s'.",
	filename, linenum, cp ? cp : "<NONE>");
	if (activep && intptr == -1)
	*intptr = value;
	break;

	case oLogLevel:
	intptr = (int *) &options->log_level;
	cp = strtok(NULL, WHITESPACE);
	value = log_level_number(cp);
	if (value == (LogLevel) - 1)
	fatal("%.200s line %d: unsupported log level '%s'\n",
	filename, linenum, cp ? cp : "<NONE>");
	if (activep && (LogLevel) intptr == -1)
	*intptr = (LogLevel) value;
	break;

	case oRemoteForward:
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing argument.", filename, linenum);
	if (cp[0] < '0' \|\| cp[0] > '9')
	fatal("%.200s line %d: Badly formatted port number.",
	filename, linenum);
	fwd_port = atoi(cp);
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing second argument.",
	filename, linenum);
	if (sscanf(cp, "%255[^:]:%hu", buf, &fwd_host_port) != 2)
	fatal("%.200s line %d: Badly formatted host:port.",
	filename, linenum);
	if (*activep)
	add_remote_forward(options, fwd_port, buf, fwd_host_port);
	break;

	case oLocalForward:
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing argument.", filename, linenum);
	if (cp[0] < '0' \|\| cp[0] > '9')
	fatal("%.200s line %d: Badly formatted port number.",
	filename, linenum);
	fwd_port = atoi(cp);
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing second argument.",
	filename, linenum);
	if (sscanf(cp, "%255[^:]:%hu", buf, &fwd_host_port) != 2)
	fatal("%.200s line %d: Badly formatted host:port.",
	filename, linenum);
	if (*activep)
	add_local_forward(options, fwd_port, buf, fwd_host_port);
	break;

	case oHost:
	*activep = 0;
	while ((cp = strtok(NULL, WHITESPACE)) != NULL)
	if (match_pattern(host, cp)) {
	debug("Applying options for %.100s", cp);
	*activep = 1;
	break;
	}
	/* Avoid garbage check below, as strtok already returned NULL. */
	return 0;

	case oEscapeChar:
	intptr = &options->escape_char;
	cp = strtok(NULL, WHITESPACE);
	if (!cp)
	fatal("%.200s line %d: Missing argument.", filename, linenum);
	if (cp[0] == '^' && cp[2] == 0 &&
	(unsigned char) cp[1] >= 64 && (unsigned char) cp[1] < 128)
	value = (unsigned char) cp[1] & 31;
	else if (strlen(cp) == 1)
	value = (unsigned char) cp[0];
	else if (strcmp(cp, "none") == 0)
	value = -2;
	else {
	fatal("%.200s line %d: Bad escape character.",
	filename, linenum);
	/* NOTREACHED */
	value = 0; /* Avoid compiler warning. */
	}
	if (activep && intptr == -1)
	*intptr = value;
	break;

	default:
	fatal("process_config_line: Unimplemented opcode %d", opcode);
	}

	/* Check that there is no garbage at end of line. */
	if (strtok(NULL, WHITESPACE) != NULL)
	fatal("%.200s line %d: garbage at end of line.",
	filename, linenum);
	return 0;
	}


	/*
	* Reads the config file and modifies the options accordingly. Options
	* should already be initialized before this call. This never returns if
	* there is an error. If the file does not exist, this returns immediately.
	*/

	void
	read_config_file(const char filename, const char host, Options *options)
	{
	FILE *f;
	char line[1024];
	int active, linenum;
	int bad_options = 0;

	/* Open the file. */
	f = fopen(filename, "r");
	if (!f)
	return;

	debug("Reading configuration data %.200s", filename);

	/*
	* Mark that we are now processing the options. This flag is turned
	* on/off by Host specifications.
	*/
	active = 1;
	linenum = 0;
	while (fgets(line, sizeof(line), f)) {
	/* Update line number counter. */
	linenum++;
	if (process_config_line(options, host, line, filename, linenum, &active) != 0)
	bad_options++;
	}
	fclose(f);
	if (bad_options > 0)
	fatal("%s: terminating, %d bad configuration options\n",
	filename, bad_options);
	}

	/*
	* Initializes options to special values that indicate that they have not yet
	* been set. Read_config_file will only set options with this value. Options
	* are processed in the following order: command line, user config file,
	* system config file. Last, fill_default_options is called.
	*/

	void
	initialize_options(Options * options)
	{
	memset(options, 'X', sizeof(*options));
	options->forward_agent = -1;
	options->forward_x11 = -1;
	options->gateway_ports = -1;
	options->use_privileged_port = -1;
	options->rhosts_authentication = -1;
	options->rsa_authentication = -1;
	options->skey_authentication = -1;
	#ifdef KRB4
	options->kerberos_authentication = -1;
	#endif
	#ifdef AFS
	options->kerberos_tgt_passing = -1;
	options->afs_token_passing = -1;
	#endif
	options->password_authentication = -1;
	options->rhosts_rsa_authentication = -1;
	options->fallback_to_rsh = -1;
	options->use_rsh = -1;
	options->batch_mode = -1;
	options->check_host_ip = -1;
	options->strict_host_key_checking = -1;
	options->compression = -1;
	options->keepalives = -1;
	options->compression_level = -1;
	options->port = -1;
	options->connection_attempts = -1;
	options->number_of_password_prompts = -1;
	options->cipher = -1;
	options->num_identity_files = 0;
	options->hostname = NULL;
	options->proxy_command = NULL;
	options->user = NULL;
	options->escape_char = -1;
	options->system_hostfile = NULL;
	options->user_hostfile = NULL;
	options->num_local_forwards = 0;
	options->num_remote_forwards = 0;
	options->log_level = (LogLevel) - 1;
	}

	/*
	* Called after processing other sources of option data, this fills those
	* options for which no value has been specified with their default values.
	*/

	void
	fill_default_options(Options * options)
	{
	if (options->forward_agent == -1)
	options->forward_agent = 1;
	if (options->forward_x11 == -1)
	options->forward_x11 = 1;
	if (options->gateway_ports == -1)
	options->gateway_ports = 0;
	if (options->use_privileged_port == -1)
	options->use_privileged_port = 1;
	if (options->rhosts_authentication == -1)
	options->rhosts_authentication = 1;
	if (options->rsa_authentication == -1)
	options->rsa_authentication = 1;
	if (options->skey_authentication == -1)
	options->skey_authentication = 0;
	#ifdef KRB4
	if (options->kerberos_authentication == -1)
	options->kerberos_authentication = 1;
	#endif /* KRB4 */
	#ifdef AFS
	if (options->kerberos_tgt_passing == -1)
	options->kerberos_tgt_passing = 1;
	if (options->afs_token_passing == -1)
	options->afs_token_passing = 1;
	#endif /* AFS */
	if (options->password_authentication == -1)
	options->password_authentication = 1;
	if (options->rhosts_rsa_authentication == -1)
	options->rhosts_rsa_authentication = 1;
	if (options->fallback_to_rsh == -1)
	options->fallback_to_rsh = 1;
	if (options->use_rsh == -1)
	options->use_rsh = 0;
	if (options->batch_mode == -1)
	options->batch_mode = 0;
	if (options->check_host_ip == -1)
	options->check_host_ip = 1;
	if (options->strict_host_key_checking == -1)
	options->strict_host_key_checking = 2; /* 2 is default */
	if (options->compression == -1)
	options->compression = 0;
	if (options->keepalives == -1)
	options->keepalives = 1;
	if (options->compression_level == -1)
	options->compression_level = 6;
	if (options->port == -1)
	options->port = 0; /* Filled in ssh_connect. */
	if (options->connection_attempts == -1)
	options->connection_attempts = 4;
	if (options->number_of_password_prompts == -1)
	options->number_of_password_prompts = 3;
	/* Selected in ssh_login(). */
	if (options->cipher == -1)
	options->cipher = SSH_CIPHER_NOT_SET;
	if (options->num_identity_files == 0) {
	options->identity_files[0] =
	xmalloc(2 + strlen(SSH_CLIENT_IDENTITY) + 1);
	sprintf(options->identity_files[0], "~/%.100s", SSH_CLIENT_IDENTITY);
	options->num_identity_files = 1;
	}
	if (options->escape_char == -1)
	options->escape_char = '~';
	if (options->system_hostfile == NULL)
	options->system_hostfile = SSH_SYSTEM_HOSTFILE;
	if (options->user_hostfile == NULL)
	options->user_hostfile = SSH_USER_HOSTFILE;
	if (options->log_level == (LogLevel) - 1)
	options->log_level = SYSLOG_LEVEL_INFO;
	/* options->proxy_command should not be set by default */
	/* options->user will be set in the main program if appropriate */
	/* options->hostname will be set in the main program if appropriate */
	}