auth.c

关系型数据库 Postgresql 6.5.2

 * unnecessarily difficult for legitimate users.  We would not, for example,
 * want to report the password we were expecting to receive...
 * But it seems useful to report the username and authorization method
 * in use, and these are items that must be presumed known to an attacker
 * anyway.
 * Note that many sorts of failure report additional information in the
 * postmaster log, which we hope is only readable by good guys.
 */

static void
auth_failed(Port *port)
{
	char		buffer[512];
	const char *authmethod = "Unknown auth method:";

	switch (port->auth_method)
	{
		case uaReject:
			authmethod = "Rejected host:";
			break;
		case uaKrb4:
			authmethod = "Kerberos4";
			break;
		case uaKrb5:
			authmethod = "Kerberos5";
			break;
		case uaTrust:
			authmethod = "Trusted";
			break;
		case uaIdent:
			authmethod = "IDENT";
			break;
		case uaPassword:
			authmethod = "Password";
			break;
		case uaCrypt:
			authmethod = "Password";
			break;
	}

	sprintf(buffer, "%s authentication failed for user '%s'",
			authmethod, port->user);

	PacketSendError(&port->pktInfo, buffer);
}


/*
 * be_recvauth -- server demux routine for incoming authentication information
 */
void
be_recvauth(Port *port)
{

	/*
	 * Get the authentication method to use for this frontend/database
	 * combination.  Note: a failure return indicates a problem with the
	 * hba config file, not with the request.  hba.c should have dropped
	 * an error message into the postmaster logfile if it failed.
	 */

	if (hba_getauthmethod(&port->raddr, port->user, port->database,
						port->auth_arg, &port->auth_method) != STATUS_OK)
		PacketSendError(&port->pktInfo,
						"Missing or erroneous pg_hba.conf file, see postmaster log for details");

	else if (PG_PROTOCOL_MAJOR(port->proto) == 0)
	{
		/* Handle old style authentication. */

		if (old_be_recvauth(port) != STATUS_OK)
			auth_failed(port);
	}
	else
	{
		/* Handle new style authentication. */

		AuthRequest areq = AUTH_REQ_OK;
		PacketDoneProc auth_handler = NULL;

		switch (port->auth_method)
		{
			case uaReject:

				/*
				 * This could have come from an explicit "reject" entry in
				 * pg_hba.conf, but more likely it means there was no
				 * matching entry.	Take pity on the poor user and issue a
				 * helpful error message.  NOTE: this is not a security
				 * breach, because all the info reported here is known at
				 * the frontend and must be assumed known to bad guys.
				 * We're merely helping out the less clueful good guys.
				 * NOTE 2: libpq-be.h defines the maximum error message
				 * length as 99 characters.  It probably wouldn't hurt
				 * anything to increase it, but there might be some client
				 * out there that will fail.  So, be terse.
				 */
				{
					char		buffer[512];
					const char *hostinfo = "localhost";

					if (port->raddr.sa.sa_family == AF_INET)
						hostinfo = inet_ntoa(port->raddr.in.sin_addr);
					sprintf(buffer,
							"No pg_hba.conf entry for host %s, user %s, database %s",
							hostinfo, port->user, port->database);
					PacketSendError(&port->pktInfo, buffer);
					return;
				}
				break;

			case uaKrb4:
				areq = AUTH_REQ_KRB4;
				auth_handler = handle_krb4_auth;
				break;

			case uaKrb5:
				areq = AUTH_REQ_KRB5;
				auth_handler = handle_krb5_auth;
				break;

			case uaTrust:
				areq = AUTH_REQ_OK;
				auth_handler = handle_done_auth;
				break;

			case uaIdent:
				if (authident(&port->raddr.in, &port->laddr.in,
							  port->user, port->auth_arg) == STATUS_OK)
				{
					areq = AUTH_REQ_OK;
					auth_handler = handle_done_auth;
				}

				break;

			case uaPassword:
				areq = AUTH_REQ_PASSWORD;
				auth_handler = handle_password_auth;
				break;

			case uaCrypt:
				areq = AUTH_REQ_CRYPT;
				auth_handler = handle_password_auth;
				break;
		}

		/* Tell the frontend what we want next. */

		if (auth_handler != NULL)
			sendAuthRequest(port, areq, auth_handler);
		else
			auth_failed(port);
	}
}


/*
 * Send an authentication request packet to the frontend.
 */

static void
sendAuthRequest(Port *port, AuthRequest areq, PacketDoneProc handler)
{
	char	   *dp,
			   *sp;
	int			i;
	uint32		net_areq;

	/* Convert to a byte stream. */

	net_areq = htonl(areq);

	dp = port->pktInfo.pkt.ar.data;
	sp = (char *) &net_areq;

	*dp++ = 'R';

	for (i = 1; i <= 4; ++i)
		*dp++ = *sp++;

	/* Add the salt for encrypted passwords. */

	if (areq == AUTH_REQ_CRYPT)
	{
		*dp++ = port->salt[0];
		*dp++ = port->salt[1];
		i += 2;
	}

	PacketSendSetup(&port->pktInfo, i, handler, (void *) port);
}


/*
 * Called when we have told the front end that it is authorised.
 */

static int
handle_done_auth(void *arg, PacketLen len, void *pkt)
{

	/*
	 * Don't generate any more traffic.  This will cause the backend to
	 * start.
	 */

	return STATUS_OK;
}


/*
 * Called when we have told the front end that it should use Kerberos V4
 * authentication.
 */

static int
handle_krb4_auth(void *arg, PacketLen len, void *pkt)
{
	Port	   *port = (Port *) arg;

	if (pg_krb4_recvauth(port) != STATUS_OK)
		auth_failed(port);
	else
		sendAuthRequest(port, AUTH_REQ_OK, handle_done_auth);

	return STATUS_OK;
}


/*
 * Called when we have told the front end that it should use Kerberos V5
 * authentication.
 */

static int
handle_krb5_auth(void *arg, PacketLen len, void *pkt)
{
	Port	   *port = (Port *) arg;

	if (pg_krb5_recvauth(port) != STATUS_OK)
		auth_failed(port);
	else
		sendAuthRequest(port, AUTH_REQ_OK, handle_done_auth);

	return STATUS_OK;
}


/*
 * Called when we have told the front end that it should use password
 * authentication.
 */

static int
handle_password_auth(void *arg, PacketLen len, void *pkt)
{
	Port	   *port = (Port *) arg;

	/* Set up the read of the password packet. */

	PacketReceiveSetup(&port->pktInfo, readPasswordPacket, (void *) port);

	return STATUS_OK;
}


/*
 * Called when we have received the password packet.
 */

static int
readPasswordPacket(void *arg, PacketLen len, void *pkt)
{
	char		password[sizeof(PasswordPacket) + 1];
	Port	   *port = (Port *) arg;

	/* Silently truncate a password that is too big. */

	if (len > sizeof(PasswordPacket))
		len = sizeof(PasswordPacket);

	StrNCpy(password, ((PasswordPacket *) pkt)->passwd, len);

	if (checkPassword(port, port->user, password) != STATUS_OK)
		auth_failed(port);
	else
		sendAuthRequest(port, AUTH_REQ_OK, handle_done_auth);

	return STATUS_OK;			/* don't close the connection yet */
}


/*
 * Use the local flat password file if clear passwords are used and the file is
 * specified.  Otherwise use the password in the pg_shadow table, encrypted or
 * not.
 */

static int
checkPassword(Port *port, char *user, char *password)
{
	if (port->auth_method == uaPassword && port->auth_arg[0] != '\0')
		return verify_password(port->auth_arg, user, password);

	return crypt_verify(port, user, password);
}


/*
 * Server demux routine for incoming authentication information for protocol
 * version 0.
 */
static int
old_be_recvauth(Port *port)
{
	int			status;
	MsgType		msgtype = (MsgType) port->proto;

	/* Handle the authentication that's offered. */

	switch (msgtype)
	{
		case STARTUP_KRB4_MSG:
			status = map_old_to_new(port, uaKrb4, pg_krb4_recvauth(port));
			break;

		case STARTUP_KRB5_MSG:
			status = map_old_to_new(port, uaKrb5, pg_krb5_recvauth(port));
			break;

		case STARTUP_MSG:
			status = map_old_to_new(port, uaTrust, STATUS_OK);
			break;

		case STARTUP_PASSWORD_MSG:
			PacketReceiveSetup(&port->pktInfo, pg_passwordv0_recvauth,
							   (void *) port);

			return STATUS_OK;

		default:
			fprintf(stderr, "Invalid startup message type: %u\n", msgtype);

			return STATUS_OK;
	}

	return status;
}


/*
 * The old style authentication has been done.	Modify the result of this (eg.
 * allow the connection anyway, disallow it anyway, or use the result)
 * depending on what authentication we really want to use.
 */

static int
map_old_to_new(Port *port, UserAuth old, int status)
{
	switch (port->auth_method)
	{
			case uaCrypt:
			case uaReject:
			status = STATUS_ERROR;
			break;

		case uaKrb4:
			if (old != uaKrb4)
				status = STATUS_ERROR;
			break;

		case uaKrb5:
			if (old != uaKrb5)
				status = STATUS_ERROR;
			break;

		case uaTrust:
			status = STATUS_OK;
			break;

		case uaIdent:
			status = authident(&port->raddr.in, &port->laddr.in,
							   port->user, port->auth_arg);
			break;

		case uaPassword:
			if (old != uaPassword)
				status = STATUS_ERROR;

			break;
	}

	return status;
}