readconf.c

/*
 * 
 * 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 1.8 2000/03/09 10:27:51 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 = 0;
	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 */
}