readconf.c

OpenSSH 是 SSH （Secure SHell） 协议的免费开源实现。它用安全、加密的网络连接工具代替了 telnet、ftp、 rlogin、rsh 和 rcp 工具。OpenSSH 支持

/*
 * Author: Tatu Ylonen <[e-mail]>
 * Copyright (c) 1995 Tatu Ylonen <[e-mail]>, Espoo, Finland
 *                    All rights reserved
 * Functions for reading the configuration files.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */

#include "includes.h"
RCSID("$OpenBSD: readconf.c,v 1.137 2005/03/04 08:48:06 djm Exp $");

#include "ssh.h"
#include "xmalloc.h"
#include "compat.h"
#include "cipher.h"
#include "pathnames.h"
#include "log.h"
#include "readconf.h"
#include "match.h"
#include "misc.h"
#include "kex.h"
#include "mac.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
     User foo

   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
     PasswordAuthentication no

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

   Host *.fr
     PublicKeyAuthentication no

   Host *.su
     Cipher none
     PasswordAuthentication no

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

*/

/* Keyword tokens. */

typedef enum {
	oBadOption,
	oForwardAgent, oForwardX11, oForwardX11Trusted, oGatewayPorts,
	oPasswordAuthentication, oRSAAuthentication,
	oChallengeResponseAuthentication, oXAuthLocation,
	oIdentityFile, oHostName, oPort, oCipher, oRemoteForward, oLocalForward,
	oUser, oHost, oEscapeChar, oRhostsRSAAuthentication, oProxyCommand,
	oGlobalKnownHostsFile, oUserKnownHostsFile, oConnectionAttempts,
	oBatchMode, oCheckHostIP, oStrictHostKeyChecking, oCompression,
	oCompressionLevel, oTCPKeepAlive, oNumberOfPasswordPrompts,
	oUsePrivilegedPort, oLogLevel, oCiphers, oProtocol, oMacs,
	oGlobalKnownHostsFile2, oUserKnownHostsFile2, oPubkeyAuthentication,
	oKbdInteractiveAuthentication, oKbdInteractiveDevices, oHostKeyAlias,
	oDynamicForward, oPreferredAuthentications, oHostbasedAuthentication,
	oHostKeyAlgorithms, oBindAddress, oSmartcardDevice,
	oClearAllForwardings, oNoHostAuthenticationForLocalhost,
	oEnableSSHKeysign, oRekeyLimit, oVerifyHostKeyDNS, oConnectTimeout,
	oAddressFamily, oGssAuthentication, oGssDelegateCreds,
	oServerAliveInterval, oServerAliveCountMax, oIdentitiesOnly,
	oSendEnv, oControlPath, oControlMaster, oHashKnownHosts,
	oDeprecated, oUnsupported
} OpCodes;

/* Textual representations of the tokens. */

static struct {
	const char *name;
	OpCodes opcode;
} keywords[] = {
	{ "forwardagent", oForwardAgent },
	{ "forwardx11", oForwardX11 },
	{ "forwardx11trusted", oForwardX11Trusted },
	{ "xauthlocation", oXAuthLocation },
	{ "gatewayports", oGatewayPorts },
	{ "useprivilegedport", oUsePrivilegedPort },
	{ "rhostsauthentication", oDeprecated },
	{ "passwordauthentication", oPasswordAuthentication },
	{ "kbdinteractiveauthentication", oKbdInteractiveAuthentication },
	{ "kbdinteractivedevices", oKbdInteractiveDevices },
	{ "rsaauthentication", oRSAAuthentication },
	{ "pubkeyauthentication", oPubkeyAuthentication },
	{ "dsaauthentication", oPubkeyAuthentication },		    /* alias */
	{ "rhostsrsaauthentication", oRhostsRSAAuthentication },
	{ "hostbasedauthentication", oHostbasedAuthentication },
	{ "challengeresponseauthentication", oChallengeResponseAuthentication },
	{ "skeyauthentication", oChallengeResponseAuthentication }, /* alias */
	{ "tisauthentication", oChallengeResponseAuthentication },  /* alias */
	{ "kerberosauthentication", oUnsupported },
	{ "kerberostgtpassing", oUnsupported },
	{ "afstokenpassing", oUnsupported },
#if defined(GSSAPI)
	{ "gssapiauthentication", oGssAuthentication },
	{ "gssapidelegatecredentials", oGssDelegateCreds },
#else
	{ "gssapiauthentication", oUnsupported },
	{ "gssapidelegatecredentials", oUnsupported },
#endif
	{ "fallbacktorsh", oDeprecated },
	{ "usersh", oDeprecated },
	{ "identityfile", oIdentityFile },
	{ "identityfile2", oIdentityFile },			/* alias */
	{ "identitiesonly", oIdentitiesOnly },
	{ "hostname", oHostName },
	{ "hostkeyalias", oHostKeyAlias },
	{ "proxycommand", oProxyCommand },
	{ "port", oPort },
	{ "cipher", oCipher },
	{ "ciphers", oCiphers },
	{ "macs", oMacs },
	{ "protocol", oProtocol },
	{ "remoteforward", oRemoteForward },
	{ "localforward", oLocalForward },
	{ "user", oUser },
	{ "host", oHost },
	{ "escapechar", oEscapeChar },
	{ "globalknownhostsfile", oGlobalKnownHostsFile },
	{ "userknownhostsfile", oUserKnownHostsFile },		/* obsolete */
	{ "globalknownhostsfile2", oGlobalKnownHostsFile2 },
	{ "userknownhostsfile2", oUserKnownHostsFile2 },	/* obsolete */
	{ "connectionattempts", oConnectionAttempts },
	{ "batchmode", oBatchMode },
	{ "checkhostip", oCheckHostIP },
	{ "stricthostkeychecking", oStrictHostKeyChecking },
	{ "compression", oCompression },
	{ "compressionlevel", oCompressionLevel },
	{ "tcpkeepalive", oTCPKeepAlive },
	{ "keepalive", oTCPKeepAlive },				/* obsolete */
	{ "numberofpasswordprompts", oNumberOfPasswordPrompts },
	{ "loglevel", oLogLevel },
	{ "dynamicforward", oDynamicForward },
	{ "preferredauthentications", oPreferredAuthentications },
	{ "hostkeyalgorithms", oHostKeyAlgorithms },
	{ "bindaddress", oBindAddress },
#ifdef SMARTCARD
	{ "smartcarddevice", oSmartcardDevice },
#else
	{ "smartcarddevice", oUnsupported },
#endif
	{ "clearallforwardings", oClearAllForwardings },
	{ "enablesshkeysign", oEnableSSHKeysign },
	{ "verifyhostkeydns", oVerifyHostKeyDNS },
	{ "nohostauthenticationforlocalhost", oNoHostAuthenticationForLocalhost },
	{ "rekeylimit", oRekeyLimit },
	{ "connecttimeout", oConnectTimeout },
	{ "addressfamily", oAddressFamily },
	{ "serveraliveinterval", oServerAliveInterval },
	{ "serveralivecountmax", oServerAliveCountMax },
	{ "sendenv", oSendEnv },
	{ "controlpath", oControlPath },
	{ "controlmaster", oControlMaster },
	{ "hashknownhosts", oHashKnownHosts },
	{ NULL, oBadOption }
};

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

void
add_local_forward(Options *options, const Forward *newfwd)
{
	Forward *fwd;
#ifndef NO_IPPORT_RESERVED_CONCEPT
	extern uid_t original_real_uid;
	if (newfwd->listen_port < IPPORT_RESERVED && original_real_uid != 0)
		fatal("Privileged ports can only be forwarded by root.");
#endif
	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->listen_host = (newfwd->listen_host == NULL) ?
	    NULL : xstrdup(newfwd->listen_host);
	fwd->listen_port = newfwd->listen_port;
	fwd->connect_host = xstrdup(newfwd->connect_host);
	fwd->connect_port = newfwd->connect_port;
}

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

void
add_remote_forward(Options *options, const Forward *newfwd)
{
	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->listen_host = (newfwd->listen_host == NULL) ?
	    NULL : xstrdup(newfwd->listen_host);
	fwd->listen_port = newfwd->listen_port;
	fwd->connect_host = xstrdup(newfwd->connect_host);
	fwd->connect_port = newfwd->connect_port;
}

static void
clear_forwardings(Options *options)
{
	int i;

	for (i = 0; i < options->num_local_forwards; i++) {
		xfree(options->local_forwards[i].listen_host);
		xfree(options->local_forwards[i].connect_host);
	}
	options->num_local_forwards = 0;
	for (i = 0; i < options->num_remote_forwards; i++) {
		xfree(options->remote_forwards[i].listen_host);
		xfree(options->remote_forwards[i].connect_host);
	}
	options->num_remote_forwards = 0;
}

/*
 * Returns the number of the token pointed to by cp or oBadOption.
 */

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

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

	error("%s: line %d: Bad configuration option: %s",
	    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.
 */
#define WHITESPACE " \t\r\n"

int
process_config_line(Options *options, const char *host,
		    char *line, const char *filename, int linenum,
		    int *activep)
{
	char *s, **charptr, *endofnumber, *keyword, *arg, *arg2, fwdarg[256];
	int opcode, *intptr, value;
	size_t len;
	Forward fwd;

	/* Strip trailing whitespace */
	for(len = strlen(line) - 1; len > 0; len--) {
		if (strchr(WHITESPACE, line[len]) == NULL)
			break;
		line[len] = '\0';
	}

	s = line;
	/* Get the keyword. (Each line is supposed to begin with a keyword). */
	keyword = strdelim(&s);
	/* Ignore leading whitespace. */
	if (*keyword == '\0')
		keyword = strdelim(&s);
	if (keyword == NULL || !*keyword || *keyword == '\n' || *keyword == '#')
		return 0;

	opcode = parse_token(keyword, filename, linenum);

	switch (opcode) {
	case oBadOption:
		/* don't panic, but count bad options */
		return -1;
		/* NOTREACHED */
	case oConnectTimeout:
		intptr = &options->connection_timeout;
parse_time:
		arg = strdelim(&s);
		if (!arg || *arg == '\0')
			fatal("%s line %d: missing time value.",
			    filename, linenum);
		if ((value = convtime(arg)) == -1)
			fatal("%s line %d: invalid time value.",
			    filename, linenum);
		if (*intptr == -1)
			*intptr = value;
		break;

	case oForwardAgent:
		intptr = &options->forward_agent;
parse_flag:
		arg = strdelim(&s);
		if (!arg || *arg == '\0')
			fatal("%.200s line %d: Missing yes/no argument.", filename, linenum);
		value = 0;	/* To avoid compiler warning... */
		if (strcmp(arg, "yes") == 0 || strcmp(arg, "true") == 0)
			value = 1;
		else if (strcmp(arg, "no") == 0 || strcmp(arg, "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 oForwardX11Trusted:
		intptr = &options->forward_x11_trusted;
		goto parse_flag;

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

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

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

	case oKbdInteractiveAuthentication:
		intptr = &options->kbd_interactive_authentication;
		goto parse_flag;

	case oKbdInteractiveDevices:
		charptr = &options->kbd_interactive_devices;