path: root/src/backend/libpq/auth.c

/*-------------------------------------------------------------------------
 *
 * auth.c
 *	  Routines to handle network authentication
 *
 * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/backend/libpq/auth.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <pwd.h>
#include <unistd.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif

#include "commands/user.h"
#include "common/ip.h"
#include "common/md5.h"
#include "libpq/auth.h"
#include "libpq/crypt.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "libpq/sasl.h"
#include "libpq/scram.h"
#include "miscadmin.h"
#include "port/pg_bswap.h"
#include "postmaster/postmaster.h"
#include "replication/walsender.h"
#include "storage/ipc.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "utils/timestamp.h"

/*----------------------------------------------------------------
 * Global authentication functions
 *----------------------------------------------------------------
 */
static void auth_failed(Port *port, int status, const char *logdetail);
static char *recv_password_packet(Port *port);
static void set_authn_id(Port *port, const char *id);


/*----------------------------------------------------------------
 * Password-based authentication methods (password, md5, and scram-sha-256)
 *----------------------------------------------------------------
 */
static int	CheckPasswordAuth(Port *port, const char **logdetail);
static int	CheckPWChallengeAuth(Port *port, const char **logdetail);

static int	CheckMD5Auth(Port *port, char *shadow_pass,
						 const char **logdetail);


/*----------------------------------------------------------------
 * Ident authentication
 *----------------------------------------------------------------
 */
/* Max size of username ident server can return (per RFC 1413) */
#define IDENT_USERNAME_MAX 512

/* Standard TCP port number for Ident service.  Assigned by IANA */
#define IDENT_PORT 113

static int	ident_inet(hbaPort *port);


/*----------------------------------------------------------------
 * Peer authentication
 *----------------------------------------------------------------
 */
static int	auth_peer(hbaPort *port);


/*----------------------------------------------------------------
 * PAM authentication
 *----------------------------------------------------------------
 */
#ifdef USE_PAM
#ifdef HAVE_PAM_PAM_APPL_H
#include <pam/pam_appl.h>
#endif
#ifdef HAVE_SECURITY_PAM_APPL_H
#include <security/pam_appl.h>
#endif

#define PGSQL_PAM_SERVICE "postgresql"	/* Service name passed to PAM */

static int	CheckPAMAuth(Port *port, const char *user, const char *password);
static int	pam_passwd_conv_proc(int num_msg, const struct pam_message **msg,
								 struct pam_response **resp, void *appdata_ptr);

static struct pam_conv pam_passw_conv = {
	&pam_passwd_conv_proc,
	NULL
};

static const char *pam_passwd = NULL;	/* Workaround for Solaris 2.6
										 * brokenness */
static Port *pam_port_cludge;	/* Workaround for passing "Port *port" into
								 * pam_passwd_conv_proc */
static bool pam_no_password;	/* For detecting no-password-given */
#endif							/* USE_PAM */


/*----------------------------------------------------------------
 * BSD authentication
 *----------------------------------------------------------------
 */
#ifdef USE_BSD_AUTH
#include <bsd_auth.h>

static int	CheckBSDAuth(Port *port, char *user);
#endif							/* USE_BSD_AUTH */


/*----------------------------------------------------------------
 * LDAP authentication
 *----------------------------------------------------------------
 */
#ifdef USE_LDAP
#ifndef WIN32
/* We use a deprecated function to keep the codepath the same as win32. */
#define LDAP_DEPRECATED 1
#include <ldap.h>
#else
#include <winldap.h>

/* Correct header from the Platform SDK */
typedef
ULONG		(*__ldap_start_tls_sA) (IN PLDAP ExternalHandle,
									OUT PULONG ServerReturnValue,
									OUT LDAPMessage **result,
									IN PLDAPControlA * ServerControls,
									IN PLDAPControlA * ClientControls
);
#endif

static int	CheckLDAPAuth(Port *port);

/* LDAP_OPT_DIAGNOSTIC_MESSAGE is the newer spelling */
#ifndef LDAP_OPT_DIAGNOSTIC_MESSAGE
#define LDAP_OPT_DIAGNOSTIC_MESSAGE LDAP_OPT_ERROR_STRING
#endif

#endif							/* USE_LDAP */

/*----------------------------------------------------------------
 * Cert authentication
 *----------------------------------------------------------------
 */
#ifdef USE_SSL
static int	CheckCertAuth(Port *port);
#endif


/*----------------------------------------------------------------
 * Kerberos and GSSAPI GUCs
 *----------------------------------------------------------------
 */
char	   *pg_krb_server_keyfile;
bool		pg_krb_caseins_users;


/*----------------------------------------------------------------
 * GSSAPI Authentication
 *----------------------------------------------------------------
 */
#ifdef ENABLE_GSS
#include "libpq/be-gssapi-common.h"

static int	pg_GSS_checkauth(Port *port);
static int	pg_GSS_recvauth(Port *port);
#endif							/* ENABLE_GSS */


/*----------------------------------------------------------------
 * SSPI Authentication
 *----------------------------------------------------------------
 */
#ifdef ENABLE_SSPI
typedef SECURITY_STATUS
			(WINAPI * QUERY_SECURITY_CONTEXT_TOKEN_FN) (PCtxtHandle, void **);
static int	pg_SSPI_recvauth(Port *port);
static int	pg_SSPI_make_upn(char *accountname,
							 size_t accountnamesize,
							 char *domainname,
							 size_t domainnamesize,
							 bool update_accountname);
#endif

/*----------------------------------------------------------------
 * RADIUS Authentication
 *----------------------------------------------------------------
 */
static int	CheckRADIUSAuth(Port *port);
static int	PerformRadiusTransaction(const char *server, const char *secret, const char *portstr, const char *identifier, const char *user_name, const char *passwd);


/*
 * Maximum accepted size of GSS and SSPI authentication tokens.
 * We also use this as a limit on ordinary password packet lengths.
 *
 * Kerberos tickets are usually quite small, but the TGTs issued by Windows
 * domain controllers include an authorization field known as the Privilege
 * Attribute Certificate (PAC), which contains the user's Windows permissions
 * (group memberships etc.). The PAC is copied into all tickets obtained on
 * the basis of this TGT (even those issued by Unix realms which the Windows
 * realm trusts), and can be several kB in size. The maximum token size
 * accepted by Windows systems is determined by the MaxAuthToken Windows
 * registry setting. Microsoft recommends that it is not set higher than
 * 65535 bytes, so that seems like a reasonable limit for us as well.
 */
#define PG_MAX_AUTH_TOKEN_LENGTH	65535

/*----------------------------------------------------------------
 * Global authentication functions
 *----------------------------------------------------------------
 */

/*
 * This hook allows plugins to get control following client authentication,
 * but before the user has been informed about the results.  It could be used
 * to record login events, insert a delay after failed authentication, etc.
 */
ClientAuthentication_hook_type ClientAuthentication_hook = NULL;

/*
 * Tell the user the authentication failed, but not (much about) why.
 *
 * There is a tradeoff here between security concerns and making life
 * 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.  In
 * particular, if logdetail isn't NULL, we send that string to the log.
 */
static void
auth_failed(Port *port, int status, const char *logdetail)
{
	const char *errstr;
	char	   *cdetail;
	int			errcode_return = ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION;

	/*
	 * If we failed due to EOF from client, just quit; there's no point in
	 * trying to send a message to the client, and not much point in logging
	 * the failure in the postmaster log.  (Logging the failure might be
	 * desirable, were it not for the fact that libpq closes the connection
	 * unceremoniously if challenged for a password when it hasn't got one to
	 * send.  We'll get a useless log entry for every psql connection under
	 * password auth, even if it's perfectly successful, if we log STATUS_EOF
	 * events.)
	 */
	if (status == STATUS_EOF)
		proc_exit(0);

	switch (port->hba->auth_method)
	{
		case uaReject:
		case uaImplicitReject:
			errstr = gettext_noop("authentication failed for user \"%s\": host rejected");
			break;
		case uaTrust:
			errstr = gettext_noop("\"trust\" authentication failed for user \"%s\"");
			break;
		case uaIdent:
			errstr = gettext_noop("Ident authentication failed for user \"%s\"");
			break;
		case uaPeer:
			errstr = gettext_noop("Peer authentication failed for user \"%s\"");
			break;
		case uaPassword:
		case uaMD5:
		case uaSCRAM:
			errstr = gettext_noop("password authentication failed for user \"%s\"");
			/* We use it to indicate if a .pgpass password failed. */
			errcode_return = ERRCODE_INVALID_PASSWORD;
			break;
		case uaGSS:
			errstr = gettext_noop("GSSAPI authentication failed for user \"%s\"");
			break;
		case uaSSPI:
			errstr = gettext_noop("SSPI authentication failed for user \"%s\"");
			break;
		case uaPAM:
			errstr = gettext_noop("PAM authentication failed for user \"%s\"");
			break;
		case uaBSD:
			errstr = gettext_noop("BSD authentication failed for user \"%s\"");
			break;
		case uaLDAP:
			errstr = gettext_noop("LDAP authentication failed for user \"%s\"");
			break;
		case uaCert:
			errstr = gettext_noop("certificate authentication failed for user \"%s\"");
			break;
		case uaRADIUS:
			errstr = gettext_noop("RADIUS authentication failed for user \"%s\"");
			break;
		default:
			errstr = gettext_noop("authentication failed for user \"%s\": invalid authentication method");
			break;
	}

	cdetail = psprintf(_("Connection matched pg_hba.conf line %d: \"%s\""),
					   port->hba->linenumber, port->hba->rawline);
	if (logdetail)
		logdetail = psprintf("%s\n%s", logdetail, cdetail);
	else
		logdetail = cdetail;

	ereport(FATAL,
			(errcode(errcode_return),
			 errmsg(errstr, port->user_name),
			 logdetail ? errdetail_log("%s", logdetail) : 0));

	/* doesn't return */
}


/*
 * Sets the authenticated identity for the current user.  The provided string
 * will be copied into the TopMemoryContext.  The ID will be logged if
 * log_connections is enabled.
 *
 * Auth methods should call this routine exactly once, as soon as the user is
 * successfully authenticated, even if they have reasons to know that
 * authorization will fail later.
 *
 * The provided string will be copied into TopMemoryContext, to match the
 * lifetime of the Port, so it is safe to pass a string that is managed by an
 * external library.
 */
static void
set_authn_id(Port *port, const char *id)
{
	Assert(id);

	if (port->authn_id)
	{
		/*
		 * An existing authn_id should never be overwritten; that means two
		 * authentication providers are fighting (or one is fighting itself).
		 * Don't leak any authn details to the client, but don't let the
		 * connection continue, either.
		 */
		ereport(FATAL,
				(errmsg("authentication identifier set more than once"),
				 errdetail_log("previous identifier: \"%s\"; new identifier: \"%s\"",
							   port->authn_id, id)));
	}

	port->authn_id = MemoryContextStrdup(TopMemoryContext, id);

	if (Log_connections)
	{
		ereport(LOG,
				errmsg("connection authenticated: identity=\"%s\" method=%s "
					   "(%s:%d)",
					   port->authn_id, hba_authname(port->hba->auth_method), HbaFileName,
					   port->hba->linenumber));
	}
}


/*
 * Client authentication starts here.  If there is an error, this
 * function does not return and the backend process is terminated.
 */
void
ClientAuthentication(Port *port)
{
	int			status = STATUS_ERROR;
	const char *logdetail = NULL;

	/*
	 * Get the authentication method to use for this frontend/database
	 * combination.  Note: we do not parse the file at this point; this has
	 * already been done elsewhere.  hba.c dropped an error message into the
	 * server logfile if parsing the hba config file failed.
	 */
	hba_getauthmethod(port);

	CHECK_FOR_INTERRUPTS();

	/*
	 * This is the first point where we have access to the hba record for the
	 * current connection, so perform any verifications based on the hba
	 * options field that should be done *before* the authentication here.
	 */
	if (port->hba->clientcert != clientCertOff)
	{
		/* If we haven't loaded a root certificate store, fail */
		if (!secure_loaded_verify_locations())
			ereport(FATAL,
					(errcode(ERRCODE_CONFIG_FILE_ERROR),
					 errmsg("client certificates can only be checked if a root certificate store is available")));

		/*
		 * If we loaded a root certificate store, and if a certificate is
		 * present on the client, then it has been verified against our root
		 * certificate store, and the connection would have been aborted
		 * already if it didn't verify ok.
		 */
		if (!port->peer_cert_valid)
			ereport(FATAL,
					(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
					 errmsg("connection requires a valid client certificate")));
	}

	/*
	 * Now proceed to do the actual authentication check
	 */
	switch (port->hba->auth_method)
	{
		case uaReject:

			/*
			 * An explicit "reject" entry in pg_hba.conf.  This report exposes
			 * the fact that there's an explicit reject entry, which is
			 * perhaps not so desirable from a security standpoint; but the
			 * message for an implicit reject could confuse the DBA a lot when
			 * the true situation is a match to an explicit reject.  And we
			 * don't want to change the message for an implicit reject.  As
			 * noted below, the additional information shown here doesn't
			 * expose anything not known to an attacker.
			 */
			{
				char		hostinfo[NI_MAXHOST];
				const char *encryption_state;

				pg_getnameinfo_all(&port->raddr.addr, port->raddr.salen,
								   hostinfo, sizeof(hostinfo),
								   NULL, 0,
								   NI_NUMERICHOST);

				encryption_state =
#ifdef ENABLE_GSS
					(port->gss && port->gss->enc) ? _("GSS encryption") :
#endif
#ifdef USE_SSL
					port->ssl_in_use ? _("SSL encryption") :
#endif
					_("no encryption");

				if (am_walsender && !am_db_walsender)
					ereport(FATAL,
							(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
					/* translator: last %s describes encryption state */
							 errmsg("pg_hba.conf rejects replication connection for host \"%s\", user \"%s\", %s",
									hostinfo, port->user_name,
									encryption_state)));
				else
					ereport(FATAL,
							(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
					/* translator: last %s describes encryption state */
							 errmsg("pg_hba.conf rejects connection for host \"%s\", user \"%s\", database \"%s\", %s",
									hostinfo, port->user_name,
									port->database_name,
									encryption_state)));
				break;
			}

		case uaImplicitReject:

			/*
			 * No matching entry, so tell the user we fell through.
			 *
			 * NOTE: the extra info reported here is not a security breach,
			 * because all that info is known at the frontend and must be
			 * assumed known to bad guys.  We're merely helping out the less
			 * clueful good guys.
			 */
			{
				char		hostinfo[NI_MAXHOST];
				const char *encryption_state;

				pg_getnameinfo_all(&port->raddr.addr, port->raddr.salen,
								   hostinfo, sizeof(hostinfo),
								   NULL, 0,
								   NI_NUMERICHOST);

				encryption_state =
#ifdef ENABLE_GSS
					(port->gss && port->gss->enc) ? _("GSS encryption") :
#endif
#ifdef USE_SSL
					port->ssl_in_use ? _("SSL encryption") :
#endif
					_("no encryption");

#define HOSTNAME_LOOKUP_DETAIL(port) \
				(port->remote_hostname ? \
				 (port->remote_hostname_resolv == +1 ? \
				  errdetail_log("Client IP address resolved to \"%s\", forward lookup matches.", \
								port->remote_hostname) : \
				  port->remote_hostname_resolv == 0 ? \
				  errdetail_log("Client IP address resolved to \"%s\", forward lookup not checked.", \
								port->remote_hostname) : \
				  port->remote_hostname_resolv == -1 ? \
				  errdetail_log("Client IP address resolved to \"%s\", forward lookup does not match.", \
								port->remote_hostname) : \
				  port->remote_hostname_resolv == -2 ? \
				  errdetail_log("Could not translate client host name \"%s\" to IP address: %s.", \
								port->remote_hostname, \
								gai_strerror(port->remote_hostname_errcode)) : \
				  0) \
				 : (port->remote_hostname_resolv == -2 ? \
					errdetail_log("Could not resolve client IP address to a host name: %s.", \
								  gai_strerror(port->remote_hostname_errcode)) : \
					0))

				if (am_walsender && !am_db_walsender)
					ereport(FATAL,
							(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
					/* translator: last %s describes encryption state */
							 errmsg("no pg_hba.conf entry for replication connection from host \"%s\", user \"%s\", %s",
									hostinfo, port->user_name,
									encryption_state),
							 HOSTNAME_LOOKUP_DETAIL(port)));
				else
					ereport(FATAL,
							(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
					/* translator: last %s describes encryption state */
							 errmsg("no pg_hba.conf entry for host \"%s\", user \"%s\", database \"%s\", %s",
									hostinfo, port->user_name,
									port->database_name,
									encryption_state),
							 HOSTNAME_LOOKUP_DETAIL(port)));
				break;
			}

		case uaGSS:
#ifdef ENABLE_GSS
			/* We might or might not have the gss workspace already */
			if (port->gss == NULL)
				port->gss = (pg_gssinfo *)
					MemoryContextAllocZero(TopMemoryContext,
										   sizeof(pg_gssinfo));
			port->gss->auth = true;

			/*
			 * If GSS state was set up while enabling encryption, we can just
			 * check the client's principal.  Otherwise, ask for it.
			 */
			if (port->gss->enc)
				status = pg_GSS_checkauth(port);
			else
			{
				sendAuthRequest(port, AUTH_REQ_GSS, NULL, 0);
				status = pg_GSS_recvauth(port);
			}
#else
			Assert(false);
#endif
			break;

		case uaSSPI:
#ifdef ENABLE_SSPI
			if (port->gss == NULL)
				port->gss = (pg_gssinfo *)
					MemoryContextAllocZero(TopMemoryContext,
										   sizeof(pg_gssinfo));
			sendAuthRequest(port, AUTH_REQ_SSPI, NULL, 0);
			status = pg_SSPI_recvauth(port);
#else
			Assert(false);
#endif
			break;

		case uaPeer:
			status = auth_peer(port);
			break;

		case uaIdent:
			status = ident_inet(port);
			break;

		case uaMD5:
		case uaSCRAM:
			status = CheckPWChallengeAuth(port, &logdetail);
			break;

		case uaPassword:
			status = CheckPasswordAuth(port, &logdetail);
			break;

		case uaPAM:
#ifdef USE_PAM
			status = CheckPAMAuth(port, port->user_name, "");
#else
			Assert(false);
#endif							/* USE_PAM */
			break;

		case uaBSD:
#ifdef USE_BSD_AUTH
			status = CheckBSDAuth(port, port->user_name);
#else
			Assert(false);
#endif							/* USE_BSD_AUTH */
			break;

		case uaLDAP:
#ifdef USE_LDAP
			status = CheckLDAPAuth(port);
#else
			Assert(false);
#endif
			break;
		case uaRADIUS:
			status = CheckRADIUSAuth(port);
			break;
		case uaCert:
			/* uaCert will be treated as if clientcert=verify-full (uaTrust) */
		case uaTrust:
			status = STATUS_OK;
			break;
	}

	if ((status == STATUS_OK && port->hba->clientcert == clientCertFull)
		|| port->hba->auth_method == uaCert)
	{
		/*
		 * Make sure we only check the certificate if we use the cert method
		 * or verify-full option.
		 */
#ifdef USE_SSL
		status = CheckCertAuth(port);
#else
		Assert(false);
#endif
	}

	if (ClientAuthentication_hook)
		(*ClientAuthentication_hook) (port, status);

	if (status == STATUS_OK)
		sendAuthRequest(port, AUTH_REQ_OK, NULL, 0);
	else
		auth_failed(port, status, logdetail);
}


/*
 * Send an authentication request packet to the frontend.
 */
void
sendAuthRequest(Port *port, AuthRequest areq, const char *extradata, int extralen)
{
	StringInfoData buf;

	CHECK_FOR_INTERRUPTS();

	pq_beginmessage(&buf, 'R');
	pq_sendint32(&buf, (int32) areq);
	if (extralen > 0)
		pq_sendbytes(&buf, extradata, extralen);

	pq_endmessage(&buf);

	/*
	 * Flush message so client will see it, except for AUTH_REQ_OK and
	 * AUTH_REQ_SASL_FIN, which need not be sent until we are ready for
	 * queries.
	 */
	if (areq != AUTH_REQ_OK && areq != AUTH_REQ_SASL_FIN)
		pq_flush();

	CHECK_FOR_INTERRUPTS();
}

/*
 * Collect password response packet from frontend.
 *
 * Returns NULL if couldn't get password, else palloc'd string.
 */
static char *
recv_password_packet(Port *port)
{
	StringInfoData buf;
	int			mtype;

	pq_startmsgread();

	/* Expect 'p' message type */
	mtype = pq_getbyte();
	if (mtype != 'p')
	{
		/*
		 * If the client just disconnects without offering a password, don't
		 * make a log entry.  This is legal per protocol spec and in fact
		 * commonly done by psql, so complaining just clutters the log.
		 */
		if (mtype != EOF)
			ereport(ERROR,
					(errcode(ERRCODE_PROTOCOL_VIOLATION),
					 errmsg("expected password response, got message type %d",
							mtype)));
		return NULL;			/* EOF or bad message type */
	}

	initStringInfo(&buf);
	if (pq_getmessage(&buf, PG_MAX_AUTH_TOKEN_LENGTH))	/* receive password */
	{
		/* EOF - pq_getmessage already logged a suitable message */
		pfree(buf.data);
		return NULL;
	}

	/*
	 * Apply sanity check: password packet length should agree with length of
	 * contained string.  Note it is safe to use strlen here because
	 * StringInfo is guaranteed to have an appended '\0'.
	 */
	if (strlen(buf.data) + 1 != buf.len)
		ereport(ERROR,
				(errcode(ERRCODE_PROTOCOL_VIOLATION),
				 errmsg("invalid password packet size")));

	/*
	 * Don't allow an empty password. Libpq treats an empty password the same
	 * as no password at all, and won't even try to authenticate. But other
	 * clients might, so allowing it would be confusing.
	 *
	 * Note that this only catches an empty password sent by the client in
	 * plaintext. There's also a check in CREATE/ALTER USER that prevents an
	 * empty string from being stored as a user's password in the first place.
	 * We rely on that for MD5 and SCRAM authentication, but we still need
	 * this check here, to prevent an empty password from being used with
	 * authentication methods that check the password against an external
	 * system, like PAM, LDAP and RADIUS.
	 */
	if (buf.len == 1)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PASSWORD),
				 errmsg("empty password returned by client")));

	/* Do not echo password to logs, for security. */
	elog(DEBUG5, "received password packet");

	/*
	 * Return the received string.  Note we do not attempt to do any
	 * character-set conversion on it; since we don't yet know the client's
	 * encoding, there wouldn't be much point.
	 */
	return buf.data;
}


/*----------------------------------------------------------------
 * Password-based authentication mechanisms
 *----------------------------------------------------------------
 */

/*
 * Plaintext password authentication.
 */
static int
CheckPasswordAuth(Port *port, const char **logdetail)
{
	char	   *passwd;
	int			result;
	char	   *shadow_pass;

	sendAuthRequest(port, AUTH_REQ_PASSWORD, NULL, 0);

	passwd = recv_password_packet(port);
	if (passwd == NULL)
		return STATUS_EOF;		/* client wouldn't send password */

	shadow_pass = get_role_password(port->user_name, logdetail);
	if (shadow_pass)
	{
		result = plain_crypt_verify(port->user_name, shadow_pass, passwd,
									logdetail);
	}
	else
		result = STATUS_ERROR;

	if (shadow_pass)
		pfree(shadow_pass);
	pfree(passwd);

	if (result == STATUS_OK)
		set_authn_id(port, port->user_name);

	return result;
}

/*
 * MD5 and SCRAM authentication.
 */
static int
CheckPWChallengeAuth(Port *port, const char **logdetail)
{
	int			auth_result;
	char	   *shadow_pass;
	PasswordType pwtype;

	Assert(port->hba->auth_method == uaSCRAM ||
		   port->hba->auth_method == uaMD5);

	/* First look up the user's password. */
	shadow_pass = get_role_password(port->user_name, logdetail);

	/*
	 * If the user does not exist, or has no password or it's expired, we
	 * still go through the motions of authentication, to avoid revealing to
	 * the client that the user didn't exist.  If 'md5' is allowed, we choose
	 * whether to use 'md5' or 'scram-sha-256' authentication based on current
	 * password_encryption setting.  The idea is that most genuine users
	 * probably have a password of that type, and if we pretend that this user
	 * had a password of that type, too, it "blends in" best.
	 */
	if (!shadow_pass)
		pwtype = Password_encryption;
	else
		pwtype = get_password_type(shadow_pass);

	/*
	 * If 'md5' authentication is allowed, decide whether to perform 'md5' or
	 * 'scram-sha-256' authentication based on the type of password the user
	 * has.  If it's an MD5 hash, we must do MD5 authentication, and if it's a
	 * SCRAM secret, we must do SCRAM authentication.
	 *
	 * If MD5 authentication is not allowed, always use SCRAM.  If the user
	 * had an MD5 password, CheckSASLAuth() with the SCRAM mechanism will
	 * fail.
	 */
	if (port->hba->auth_method == uaMD5 && pwtype == PASSWORD_TYPE_MD5)
		auth_result = CheckMD5Auth(port, shadow_pass, logdetail);
	else
		auth_result = CheckSASLAuth(&pg_be_scram_mech, port, shadow_pass,
									logdetail);

	if (shadow_pass)
		pfree(shadow_pass);
	else
	{
		/*
		 * If get_role_password() returned error, authentication better not
		 * have succeeded.
		 */
		Assert(auth_result != STATUS_OK);
	}

	if (auth_result == STATUS_OK)
		set_authn_id(port, port->user_name);

	return auth_result;
}

static int
CheckMD5Auth(Port *port, char *shadow_pass, const char **logdetail)
{
	char		md5Salt[4];		/* Password salt */
	char	   *passwd;
	int			result;

	if (Db_user_namespace)
		ereport(FATAL,
				(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
				 errmsg("MD5 authentication is not supported when \"db_user_namespace\" is enabled")));

	/* include the salt to use for computing the response */
	if (!pg_strong_random(md5Salt, 4))
	{
		ereport(LOG,
				(errmsg("could not generate random MD5 salt")));
		return STATUS_ERROR;
	}

	sendAuthRequest(port, AUTH_REQ_MD5, md5Salt, 4);

	passwd = recv_password_packet(port);
	if (passwd == NULL)
		return STATUS_EOF;		/* client wouldn't send password */

	if (shadow_pass)
		result = md5_crypt_verify(port->user_name, shadow_pass, passwd,
								  md5Salt, 4, logdetail);
	else
		result = STATUS_ERROR;

	pfree(passwd);

	return result;
}


/*----------------------------------------------------------------
 * GSSAPI authentication system
 *----------------------------------------------------------------
 */
#ifdef ENABLE_GSS
static int
pg_GSS_recvauth(Port *port)
{
	OM_uint32	maj_stat,
				min_stat,
				lmin_s,
				gflags;
	int			mtype;
	StringInfoData buf;
	gss_buffer_desc gbuf;

	/*
	 * Use the configured keytab, if there is one.  Unfortunately, Heimdal
	 * doesn't support the cred store extensions, so use the env var.
	 */
	if (pg_krb_server_keyfile != NULL && pg_krb_server_keyfile[0] != '\0')
	{
		if (setenv("KRB5_KTNAME", pg_krb_server_keyfile, 1) != 0)
		{
			/* The only likely failure cause is OOM, so use that errcode */
			ereport(FATAL,
					(errcode(ERRCODE_OUT_OF_MEMORY),
					 errmsg("could not set environment: %m")));
		}
	}

	/*
	 * We accept any service principal that's present in our keytab. This
	 * increases interoperability between kerberos implementations that see
	 * for example case sensitivity differently, while not really opening up
	 * any vector of attack.
	 */
	port->gss->cred = GSS_C_NO_CREDENTIAL;

	/*
	 * Initialize sequence with an empty context
	 */
	port->gss->ctx = GSS_C_NO_CONTEXT;

	/*
	 * Loop through GSSAPI message exchange. This exchange can consist of
	 * multiple messages sent in both directions. First message is always from
	 * the client. All messages from client to server are password packets
	 * (type 'p').
	 */
	do
	{
		pq_startmsgread();

		CHECK_FOR_INTERRUPTS();

		mtype = pq_getbyte();
		if (mtype != 'p')
		{
			/* Only log error if client didn't disconnect. */
			if (mtype != EOF)
				ereport(ERROR,
						(errcode(ERRCODE_PROTOCOL_VIOLATION),
						 errmsg("expected GSS response, got message type %d",
								mtype)));
			return STATUS_ERROR;
		}

		/* Get the actual GSS token */
		initStringInfo(&buf);
		if (pq_getmessage(&buf, PG_MAX_AUTH_TOKEN_LENGTH))
		{
			/* EOF - pq_getmessage already logged error */
			pfree(buf.data);
			return STATUS_ERROR;
		}

		/* Map to GSSAPI style buffer */
		gbuf.length = buf.len;
		gbuf.value = buf.data;

		elog(DEBUG4, "processing received GSS token of length %u",
			 (unsigned int) gbuf.length);

		maj_stat = gss_accept_sec_context(&min_stat,
										  &port->gss->ctx,
										  port->gss->cred,
										  &gbuf,
										  GSS_C_NO_CHANNEL_BINDINGS,
										  &port->gss->name,
										  NULL,
										  &port->gss->outbuf,
										  &gflags,
										  NULL,
										  NULL);

		/* gbuf no longer used */
		pfree(buf.data);

		elog(DEBUG5, "gss_accept_sec_context major: %u, "
			 "minor: %u, outlen: %u, outflags: %x",
			 maj_stat, min_stat,
			 (unsigned int) port->gss->outbuf.length, gflags);

		CHECK_FOR_INTERRUPTS();

		if (port->gss->outbuf.length != 0)
		{
			/*
			 * Negotiation generated data to be sent to the client.
			 */
			elog(DEBUG4, "sending GSS response token of length %u",
				 (unsigned int) port->gss->outbuf.length);

			sendAuthRequest(port, AUTH_REQ_GSS_CONT,
							port->gss->outbuf.value, port->gss->outbuf.length);

			gss_release_buffer(&lmin_s, &port->gss->outbuf);
		}

		if (maj_stat != GSS_S_COMPLETE && maj_stat != GSS_S_CONTINUE_NEEDED)
		{
			gss_delete_sec_context(&lmin_s, &port->gss->ctx, GSS_C_NO_BUFFER);
			pg_GSS_error(_("accepting GSS security context failed"),
						 maj_stat, min_stat);
			return STATUS_ERROR;
		}

		if (maj_stat == GSS_S_CONTINUE_NEEDED)
			elog(DEBUG4, "GSS continue needed");

	} while (maj_stat == GSS_S_CONTINUE_NEEDED);

	if (port->gss->cred != GSS_C_NO_CREDENTIAL)
	{
		/*
		 * Release service principal credentials
		 */
		gss_release_cred(&min_stat, &port->gss->cred);
	}
	return pg_GSS_checkauth(port);
}

/*
 * Check whether the GSSAPI-authenticated user is allowed to connect as the
 * claimed username.
 */
static int
pg_GSS_checkauth(Port *port)
{
	int			ret;
	OM_uint32	maj_stat,
				min_stat,
				lmin_s;
	gss_buffer_desc gbuf;
	char	   *princ;

	/*
	 * Get the name of the user that authenticated, and compare it to the pg
	 * username that was specified for the connection.
	 */
	maj_stat = gss_display_name(&min_stat, port->gss->name, &gbuf, NULL);
	if (maj_stat != GSS_S_COMPLETE)
	{
		pg_GSS_error(_("retrieving GSS user name failed"),
					 maj_stat, min_stat);
		return STATUS_ERROR;
	}

	/*
	 * gbuf.value might not be null-terminated, so turn it into a regular
	 * null-terminated string.
	 */
	princ = palloc(gbuf.length + 1);
	memcpy(princ, gbuf.value, gbuf.length);
	princ[gbuf.length] = '\0';
	gss_release_buffer(&lmin_s, &gbuf);

	/*
	 * Copy the original name of the authenticated principal into our backend
	 * memory for display later.
	 *
	 * This is also our authenticated identity.  Set it now, rather than
	 * waiting for the usermap check below, because authentication has already
	 * succeeded and we want the log file to reflect that.
	 */
	port->gss->princ = MemoryContextStrdup(TopMemoryContext, princ);
	set_authn_id(port, princ);

	/*
	 * Split the username at the realm separator
	 */
	if (strchr(princ, '@'))
	{
		char	   *cp = strchr(princ, '@');

		/*
		 * If we are not going to include the realm in the username that is
		 * passed to the ident map, destructively modify it here to remove the
		 * realm. Then advance past the separator to check the realm.
		 */
		if (!port->hba->include_realm)
			*cp = '\0';
		cp++;

		if (port->hba->krb_realm != NULL && strlen(port->hba->krb_realm))
		{
			/*
			 * Match the realm part of the name first
			 */
			if (pg_krb_caseins_users)
				ret = pg_strcasecmp(port->hba->krb_realm, cp);
			else
				ret = strcmp(port->hba->krb_realm, cp);

			if (ret)
			{
				/* GSS realm does not match */
				elog(DEBUG2,
					 "GSSAPI realm (%s) and configured realm (%s) don't match",
					 cp, port->hba->krb_realm);
				pfree(princ);
				return STATUS_ERROR;
			}
		}
	}
	else if (port->hba->krb_realm && strlen(port->hba->krb_realm))
	{
		elog(DEBUG2,
			 "GSSAPI did not return realm but realm matching was requested");
		pfree(princ);
		return STATUS_ERROR;
	}

	ret = check_usermap(port->hba->usermap, port->user_name, princ,
						pg_krb_caseins_users);

	pfree(princ);

	return ret;
}
#endif							/* ENABLE_GSS */


/*----------------------------------------------------------------
 * SSPI authentication system
 *----------------------------------------------------------------
 */
#ifdef ENABLE_SSPI

/*
 * Generate an error for SSPI authentication.  The caller should apply
 * _() to errmsg to make it translatable.
 */
static void
pg_SSPI_error(int severity, const char *errmsg, SECURITY_STATUS r)
{
	char		sysmsg[256];

	if (FormatMessage(FORMAT_MESSAGE_IGNORE_INSERTS |
					  FORMAT_MESSAGE_FROM_SYSTEM,
					  NULL, r, 0,
					  sysmsg, sizeof(sysmsg), NULL) == 0)
		ereport(severity,
				(errmsg_internal("%s", errmsg),
				 errdetail_internal("SSPI error %x", (unsigned int) r)));
	else
		ereport(severity,
				(errmsg_internal("%s", errmsg),
				 errdetail_internal("%s (%x)", sysmsg, (unsigned int) r)));
}

static int
pg_SSPI_recvauth(Port *port)
{
	int			mtype;
	StringInfoData buf;
	SECURITY_STATUS r;
	CredHandle	sspicred;
	CtxtHandle *sspictx = NULL,
				newctx;
	TimeStamp	expiry;
	ULONG		contextattr;
	SecBufferDesc inbuf;
	SecBufferDesc outbuf;
	SecBuffer	OutBuffers[1];
	SecBuffer	InBuffers[1];
	HANDLE		token;
	TOKEN_USER *tokenuser;
	DWORD		retlen;
	char		accountname[MAXPGPATH];
	char		domainname[MAXPGPATH];
	DWORD		accountnamesize = sizeof(accountname);
	DWORD		domainnamesize = sizeof(domainname);
	SID_NAME_USE accountnameuse;
	HMODULE		secur32;
	char	   *authn_id;

	QUERY_SECURITY_CONTEXT_TOKEN_FN _QuerySecurityContextToken;

	/*
	 * Acquire a handle to the server credentials.
	 */
	r = AcquireCredentialsHandle(NULL,
								 "negotiate",
								 SECPKG_CRED_INBOUND,
								 NULL,
								 NULL,
								 NULL,
								 NULL,
								 &sspicred,
								 &expiry);
	if (r != SEC_E_OK)
		pg_SSPI_error(ERROR, _("could not acquire SSPI credentials"), r);

	/*
	 * Loop through SSPI message exchange. This exchange can consist of
	 * multiple messages sent in both directions. First message is always from
	 * the client. All messages from client to server are password packets
	 * (type 'p').
	 */
	do
	{
		pq_startmsgread();
		mtype = pq_getbyte();
		if (mtype != 'p')
		{
			if (sspictx != NULL)
			{
				DeleteSecurityContext(sspictx);
				free(sspictx);
			}
			FreeCredentialsHandle(&sspicred);

			/* Only log error if client didn't disconnect. */
			if (mtype != EOF)
				ereport(ERROR,
						(errcode(ERRCODE_PROTOCOL_VIOLATION),
						 errmsg("expected SSPI response, got message type %d",
								mtype)));
			return STATUS_ERROR;
		}

		/* Get the actual SSPI token */
		initStringInfo(&buf);
		if (pq_getmessage(&buf, PG_MAX_AUTH_TOKEN_LENGTH))
		{
			/* EOF - pq_getmessage already logged error */
			pfree(buf.data);
			if (sspictx != NULL)
			{
				DeleteSecurityContext(sspictx);
				free(sspictx);
			}
			FreeCredentialsHandle(&sspicred);
			return STATUS_ERROR;
		}

		/* Map to SSPI style buffer */
		inbuf.ulVersion = SECBUFFER_VERSION;
		inbuf.cBuffers = 1;
		inbuf.pBuffers = InBuffers;
		InBuffers[0].pvBuffer = buf.data;
		InBuffers[0].cbBuffer = buf.len;
		InBuffers[0].BufferType = SECBUFFER_TOKEN;

		/* Prepare output buffer */
		OutBuffers[0].pvBuffer = NULL;
		OutBuffers[0].BufferType = SECBUFFER_TOKEN;
		OutBuffers[0].cbBuffer = 0;
		outbuf.cBuffers = 1;
		outbuf.pBuffers = OutBuffers;
		outbuf.ulVersion = SECBUFFER_VERSION;

		elog(DEBUG4, "processing received SSPI token of length %u",
			 (unsigned int) buf.len);

		r = AcceptSecurityContext(&sspicred,
								  sspictx,
								  &inbuf,
								  ASC_REQ_ALLOCATE_MEMORY,
								  SECURITY_NETWORK_DREP,
								  &newctx,
								  &outbuf,
								  &contextattr,
								  NULL);

		/* input buffer no longer used */
		pfree(buf.data);

		if (outbuf.cBuffers > 0 && outbuf.pBuffers[0].cbBuffer > 0)
		{
			/*
			 * Negotiation generated data to be sent to the client.
			 */
			elog(DEBUG4, "sending SSPI response token of length %u",
				 (unsigned int) outbuf.pBuffers[0].cbBuffer);

			port->gss->outbuf.length = outbuf.pBuffers[0].cbBuffer;
			port->gss->outbuf.value = outbuf.pBuffers[0].pvBuffer;

			sendAuthRequest(port, AUTH_REQ_GSS_CONT,
							port->gss->outbuf.value, port->gss->outbuf.length);

			FreeContextBuffer(outbuf.pBuffers[0].pvBuffer);
		}

		if (r != SEC_E_OK && r != SEC_I_CONTINUE_NEEDED)
		{
			if (sspictx != NULL)
			{
				DeleteSecurityContext(sspictx);
				free(sspictx);
			}
			FreeCredentialsHandle(&sspicred);
			pg_SSPI_error(ERROR,
						  _("could not accept SSPI security context"), r);
		}

		/*
		 * Overwrite the current context with the one we just received. If
		 * sspictx is NULL it was the first loop and we need to allocate a
		 * buffer for it. On subsequent runs, we can just overwrite the buffer
		 * contents since the size does not change.
		 */
		if (sspictx == NULL)
		{
			sspictx = malloc(sizeof(CtxtHandle));
			if (sspictx == NULL)
				ereport(ERROR,
						(errmsg("out of memory")));
		}

		memcpy(sspictx, &newctx, sizeof(CtxtHandle));

		if (r == SEC_I_CONTINUE_NEEDED)
			elog(DEBUG4, "SSPI continue needed");

	} while (r == SEC_I_CONTINUE_NEEDED);


	/*
	 * Release service principal credentials
	 */
	FreeCredentialsHandle(&sspicred);


	/*
	 * SEC_E_OK indicates that authentication is now complete.
	 *
	 * Get the name of the user that authenticated, and compare it to the pg
	 * username that was specified for the connection.
	 *
	 * MingW is missing the export for QuerySecurityContextToken in the
	 * secur32 library, so we have to load it dynamically.
	 */

	secur32 = LoadLibrary("SECUR32.DLL");
	if (secur32 == NULL)
		ereport(ERROR,
				(errmsg("could not load library \"%s\": error code %lu",
						"SECUR32.DLL", GetLastError())));

	_QuerySecurityContextToken = (QUERY_SECURITY_CONTEXT_TOKEN_FN) (pg_funcptr_t)
		GetProcAddress(secur32, "QuerySecurityContextToken");
	if (_QuerySecurityContextToken == NULL)
	{
		FreeLibrary(secur32);
		ereport(ERROR,
				(errmsg_internal("could not locate QuerySecurityContextToken in secur32.dll: error code %lu",
								 GetLastError())));
	}

	r = (_QuerySecurityContextToken) (sspictx, &token);
	if (r != SEC_E_OK)
	{
		FreeLibrary(secur32);
		pg_SSPI_error(ERROR,
					  _("could not get token from SSPI security context"), r);
	}

	FreeLibrary(secur32);

	/*
	 * No longer need the security context, everything from here on uses the
	 * token instead.
	 */
	DeleteSecurityContext(sspictx);
	free(sspictx);

	if (!GetTokenInformation(token, TokenUser, NULL, 0, &retlen) && GetLastError() != 122)
		ereport(ERROR,
				(errmsg_internal("could not get token information buffer size: error code %lu",
								 GetLastError())));

	tokenuser = malloc(retlen);
	if (tokenuser == NULL)
		ereport(ERROR,
				(errmsg("out of memory")));

	if (!GetTokenInformation(token, TokenUser, tokenuser, retlen, &retlen))
		ereport(ERROR,
				(errmsg_internal("could not get token information: error code %lu",
								 GetLastError())));

	CloseHandle(token);

	if (!LookupAccountSid(NULL, tokenuser->User.Sid, accountname, &accountnamesize,
						  domainname, &domainnamesize, &accountnameuse))
		ereport(ERROR,
				(errmsg_internal("could not look up account SID: error code %lu",
								 GetLastError())));

	free(tokenuser);

	if (!port->hba->compat_realm)
	{
		int			status = pg_SSPI_make_upn(accountname, sizeof(accountname),
											  domainname, sizeof(domainname),
											  port->hba->upn_username);

		if (status != STATUS_OK)
			/* Error already reported from pg_SSPI_make_upn */
			return status;
	}

	/*
	 * We have all of the information necessary to construct the authenticated
	 * identity.  Set it now, rather than waiting for check_usermap below,
	 * because authentication has already succeeded and we want the log file
	 * to reflect that.
	 */
	if (port->hba->compat_realm)
	{
		/* SAM-compatible format. */
		authn_id = psprintf("%s\\%s", domainname, accountname);
	}
	else
	{
		/* Kerberos principal format. */
		authn_id = psprintf("%s@%s", accountname, domainname);
	}

	set_authn_id(port, authn_id);
	pfree(authn_id);

	/*
	 * Compare realm/domain if requested. In SSPI, always compare case
	 * insensitive.
	 */
	if (port->hba->krb_realm && strlen(port->hba->krb_realm))
	{
		if (pg_strcasecmp(port->hba->krb_realm, domainname) != 0)
		{
			elog(DEBUG2,
				 "SSPI domain (%s) and configured domain (%s) don't match",
				 domainname, port->hba->krb_realm);

			return STATUS_ERROR;
		}
	}

	/*
	 * We have the username (without domain/realm) in accountname, compare to
	 * the supplied value. In SSPI, always compare case insensitive.
	 *
	 * If set to include realm, append it in <username>@<realm> format.
	 */
	if (port->hba->include_realm)
	{
		char	   *namebuf;
		int			retval;

		namebuf = psprintf("%s@%s", accountname, domainname);
		retval = check_usermap(port->hba->usermap, port->user_name, namebuf, true);
		pfree(namebuf);
		return retval;
	}
	else
		return check_usermap(port->hba->usermap, port->user_name, accountname, true);
}

/*
 * Replaces the domainname with the Kerberos realm name,
 * and optionally the accountname with the Kerberos user name.
 */
static int
pg_SSPI_make_upn(char *accountname,
				 size_t accountnamesize,
				 char *domainname,
				 size_t domainnamesize,
				 bool update_accountname)
{
	char	   *samname;
	char	   *upname = NULL;
	char	   *p = NULL;
	ULONG		upnamesize = 0;
	size_t		upnamerealmsize;
	BOOLEAN		res;

	/*
	 * Build SAM name (DOMAIN\user), then translate to UPN
	 * (user@kerberos.realm). The realm name is returned in lower case, but
	 * that is fine because in SSPI auth, string comparisons are always
	 * case-insensitive.
	 */

	samname = psprintf("%s\\%s", domainname, accountname);
	res = TranslateName(samname, NameSamCompatible, NameUserPrincipal,
						NULL, &upnamesize);

	if ((!res && GetLastError() != ERROR_INSUFFICIENT_BUFFER)
		|| upnamesize == 0)
	{
		pfree(samname);
		ereport(LOG,
				(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
				 errmsg("could not translate name")));
		return STATUS_ERROR;
	}

	/* upnamesize includes the terminating NUL. */
	upname = palloc(upnamesize);

	res = TranslateName(samname, NameSamCompatible, NameUserPrincipal,
						upname, &upnamesize);

	pfree(samname);
	if (res)
		p = strchr(upname, '@');

	if (!res || p == NULL)
	{
		pfree(upname);
		ereport(LOG,
				(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
				 errmsg("could not translate name")));
		return STATUS_ERROR;
	}

	/* Length of realm name after the '@', including the NUL. */
	upnamerealmsize = upnamesize - (p - upname + 1);

	/* Replace domainname with realm name. */
	if (upnamerealmsize > domainnamesize)
	{
		pfree(upname);
		ereport(LOG,
				(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
				 errmsg("realm name too long")));
		return STATUS_ERROR;
	}

	/* Length is now safe. */
	strcpy(domainname, p + 1);

	/* Replace account name as well (in case UPN != SAM)? */
	if (update_accountname)
	{
		if ((p - upname + 1) > accountnamesize)
		{
			pfree(upname);
			ereport(LOG,
					(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
					 errmsg("translated account name too long")));
			return STATUS_ERROR;
		}

		*p = 0;
		strcpy(accountname, upname);
	}

	pfree(upname);
	return STATUS_OK;
}
#endif							/* ENABLE_SSPI */



/*----------------------------------------------------------------
 * Ident authentication system
 *----------------------------------------------------------------
 */

/*
 *	Parse the string "*ident_response" as a response from a query to an Ident
 *	server.  If it's a normal response indicating a user name, return true
 *	and store the user name at *ident_user. If it's anything else,
 *	return false.
 */
static bool
interpret_ident_response(const char *ident_response,
						 char *ident_user)
{
	const char *cursor = ident_response;	/* Cursor into *ident_response */

	/*
	 * Ident's response, in the telnet tradition, should end in crlf (\r\n).
	 */
	if (strlen(ident_response) < 2)
		return false;
	else if (ident_response[strlen(ident_response) - 2] != '\r')
		return false;
	else
	{
		while (*cursor != ':' && *cursor != '\r')
			cursor++;			/* skip port field */

		if (*cursor != ':')
			return false;
		else
		{
			/* We're positioned to colon before response type field */
			char		response_type[80];
			int			i;		/* Index into *response_type */

			cursor++;			/* Go over colon */
			while (pg_isblank(*cursor))
				cursor++;		/* skip blanks */
			i = 0;
			while (*cursor != ':' && *cursor != '\r' && !pg_isblank(*cursor) &&
				   i < (int) (sizeof(response_type) - 1))
				response_type[i++] = *cursor++;
			response_type[i] = '\0';
			while (pg_isblank(*cursor))
				cursor++;		/* skip blanks */
			if (strcmp(response_type, "USERID") != 0)
				return false;
			else
			{
				/*
				 * It's a USERID response.  Good.  "cursor" should be pointing
				 * to the colon that precedes the operating system type.
				 */
				if (*cursor != ':')
					return false;
				else
				{
					cursor++;	/* Go over colon */
					/* Skip over operating system field. */
					while (*cursor != ':' && *cursor != '\r')
						cursor++;
					if (*cursor != ':')
						return false;
					else
					{
						int			i;	/* Index into *ident_user */

						cursor++;	/* Go over colon */
						while (pg_isblank(*cursor))
							cursor++;	/* skip blanks */
						/* Rest of line is user name.  Copy it over. */
						i = 0;
						while (*cursor != '\r' && i < IDENT_USERNAME_MAX)
							ident_user[i++] = *cursor++;
						ident_user[i] = '\0';
						return true;
					}
				}
			}
		}
	}
}


/*
 *	Talk to the ident server on "remote_addr" and find out who
 *	owns the tcp connection to "local_addr"
 *	If the username is successfully retrieved, check the usermap.
 *
 *	XXX: Using WaitLatchOrSocket() and doing a CHECK_FOR_INTERRUPTS() if the
 *	latch was set would improve the responsiveness to timeouts/cancellations.
 */
static int
ident_inet(hbaPort *port)
{
	const SockAddr remote_addr = port->raddr;
	const SockAddr local_addr = port->laddr;
	char		ident_user[IDENT_USERNAME_MAX + 1];
	pgsocket	sock_fd = PGINVALID_SOCKET; /* for talking to Ident server */
	int			rc;				/* Return code from a locally called function */
	bool		ident_return;
	char		remote_addr_s[NI_MAXHOST];
	char		remote_port[NI_MAXSERV];
	char		local_addr_s[NI_MAXHOST];
	char		local_port[NI_MAXSERV];
	char		ident_port[NI_MAXSERV];
	char		ident_query[80];
	char		ident_response[80 + IDENT_USERNAME_MAX];
	struct addrinfo *ident_serv = NULL,
			   *la = NULL,
				hints;

	/*
	 * Might look a little weird to first convert it to text and then back to
	 * sockaddr, but it's protocol independent.
	 */
	pg_getnameinfo_all(&remote_addr.addr, remote_addr.salen,
					   remote_addr_s, sizeof(remote_addr_s),
					   remote_port, sizeof(remote_port),
					   NI_NUMERICHOST | NI_NUMERICSERV);
	pg_getnameinfo_all(&local_addr.addr, local_addr.salen,
					   local_addr_s, sizeof(local_addr_s),
					   local_port, sizeof(local_port),
					   NI_NUMERICHOST | NI_NUMERICSERV);

	snprintf(ident_port, sizeof(ident_port), "%d", IDENT_PORT);
	hints.ai_flags = AI_NUMERICHOST;
	hints.ai_family = remote_addr.addr.ss_family;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_protocol = 0;
	hints.ai_addrlen = 0;
	hints.ai_canonname = NULL;
	hints.ai_addr = NULL;
	hints.ai_next = NULL;
	rc = pg_getaddrinfo_all(remote_addr_s, ident_port, &hints, &ident_serv);
	if (rc || !ident_serv)
	{
		/* we don't expect this to happen */
		ident_return = false;
		goto ident_inet_done;
	}

	hints.ai_flags = AI_NUMERICHOST;
	hints.ai_family = local_addr.addr.ss_family;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_protocol = 0;
	hints.ai_addrlen = 0;
	hints.ai_canonname = NULL;
	hints.ai_addr = NULL;
	hints.ai_next = NULL;
	rc = pg_getaddrinfo_all(local_addr_s, NULL, &hints, &la);
	if (rc || !la)
	{
		/* we don't expect this to happen */
		ident_return = false;
		goto ident_inet_done;
	}

	sock_fd = socket(ident_serv->ai_family, ident_serv->ai_socktype,
					 ident_serv->ai_protocol);
	if (sock_fd == PGINVALID_SOCKET)
	{
		ereport(LOG,
				(errcode_for_socket_access(),
				 errmsg("could not create socket for Ident connection: %m")));
		ident_return = false;
		goto ident_inet_done;
	}

	/*
	 * Bind to the address which the client originally contacted, otherwise
	 * the ident server won't be able to match up the right connection. This
	 * is necessary if the PostgreSQL server is running on an IP alias.
	 */
	rc = bind(sock_fd, la->ai_addr, la->ai_addrlen);
	if (rc != 0)
	{
		ereport(LOG,
				(errcode_for_socket_access(),
				 errmsg("could not bind to local address \"%s\": %m",
						local_addr_s)));
		ident_return = false;
		goto ident_inet_done;
	}

	rc = connect(sock_fd, ident_serv->ai_addr,
				 ident_serv->ai_addrlen);
	if (rc != 0)
	{
		ereport(LOG,
				(errcode_for_socket_access(),
				 errmsg("could not connect to Ident server at address \"%s\", port %s: %m",
						remote_addr_s, ident_port)));
		ident_return = false;
		goto ident_inet_done;
	}

	/* The query we send to the Ident server */
	snprintf(ident_query, sizeof(ident_query), "%s,%s\r\n",
			 remote_port, local_port);

	/* loop in case send is interrupted */
	do
	{
		CHECK_FOR_INTERRUPTS();

		rc = send(sock_fd, ident_query, strlen(ident_query), 0);
	} while (rc < 0 && errno == EINTR);

	if (rc < 0)
	{
		ereport(LOG,
				(errcode_for_socket_access(),
				 errmsg("could not send query to Ident server at address \"%s\", port %s: %m",
						remote_addr_s, ident_port)));
		ident_return = false;
		goto ident_inet_done;
	}

	do
	{
		CHECK_FOR_INTERRUPTS();

		rc = recv(sock_fd, ident_response, sizeof(ident_response) - 1, 0);
	} while (rc < 0 && errno == EINTR);

	if (rc < 0)
	{
		ereport(LOG,
				(errcode_for_socket_access(),
				 errmsg("could not receive response from Ident server at address \"%s\", port %s: %m",
						remote_addr_s, ident_port)));
		ident_return = false;
		goto ident_inet_done;
	}

	ident_response[rc] = '\0';
	ident_return = interpret_ident_response(ident_response, ident_user);
	if (!ident_return)
		ereport(LOG,
				(errmsg("invalidly formatted response from Ident server: \"%s\"",
						ident_response)));

ident_inet_done:
	if (sock_fd != PGINVALID_SOCKET)
		closesocket(sock_fd);
	if (ident_serv)
		pg_freeaddrinfo_all(remote_addr.addr.ss_family, ident_serv);
	if (la)
		pg_freeaddrinfo_all(local_addr.addr.ss_family, la);

	if (ident_return)
	{
		/*
		 * Success!  Store the identity, then check the usermap. Note that
		 * setting the authenticated identity is done before checking the
		 * usermap, because at this point authentication has succeeded.
		 */
		set_authn_id(port, ident_user);
		return check_usermap(port->hba->usermap, port->user_name, ident_user, false);
	}
	return STATUS_ERROR;
}


/*----------------------------------------------------------------
 * Peer authentication system
 *----------------------------------------------------------------
 */

/*
 *	Ask kernel about the credentials of the connecting process,
 *	determine the symbolic name of the corresponding user, and check
 *	if valid per the usermap.
 *
 *	Iff authorized, return STATUS_OK, otherwise return STATUS_ERROR.
 */
static int
auth_peer(hbaPort *port)
{
	uid_t		uid;
	gid_t		gid;
#ifndef WIN32
	struct passwd *pw;
	int			ret;
#endif

	if (getpeereid(port->sock, &uid, &gid) != 0)
	{
		/* Provide special error message if getpeereid is a stub */
		if (errno == ENOSYS)
			ereport(LOG,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("peer authentication is not supported on this platform")));
		else
			ereport(LOG,
					(errcode_for_socket_access(),
					 errmsg("could not get peer credentials: %m")));
		return STATUS_ERROR;
	}

#ifndef WIN32
	errno = 0;					/* clear errno before call */
	pw = getpwuid(uid);
	if (!pw)
	{
		int			save_errno = errno;

		ereport(LOG,
				(errmsg("could not look up local user ID %ld: %s",
						(long) uid,
						save_errno ? strerror(save_errno) : _("user does not exist"))));
		return STATUS_ERROR;
	}

	/*
	 * Make a copy of static getpw*() result area; this is our authenticated
	 * identity.  Set it before calling check_usermap, because authentication
	 * has already succeeded and we want the log file to reflect that.
	 */
	set_authn_id(port, pw->pw_name);

	ret = check_usermap(port->hba->usermap, port->user_name, port->authn_id, false);

	return ret;
#else
	/* should have failed with ENOSYS above */
	Assert(false);
	return STATUS_ERROR;
#endif
}


/*----------------------------------------------------------------
 * PAM authentication system
 *----------------------------------------------------------------
 */
#ifdef USE_PAM

/*
 * PAM conversation function
 */

static int
pam_passwd_conv_proc(int num_msg, const struct pam_message **msg,
					 struct pam_response **resp, void *appdata_ptr)
{
	const char *passwd;
	struct pam_response *reply;
	int			i;

	if (appdata_ptr)
		passwd = (char *) appdata_ptr;
	else
	{
		/*
		 * Workaround for Solaris 2.6 where the PAM library is broken and does
		 * not pass appdata_ptr to the conversation routine
		 */
		passwd = pam_passwd;
	}

	*resp = NULL;				/* in case of error exit */

	if (num_msg <= 0 || num_msg > PAM_MAX_NUM_MSG)
		return PAM_CONV_ERR;

	/*
	 * Explicitly not using palloc here - PAM will free this memory in
	 * pam_end()
	 */
	if ((reply = calloc(num_msg, sizeof(struct pam_response))) == NULL)
	{
		ereport(LOG,
				(errcode(ERRCODE_OUT_OF_MEMORY),
				 errmsg("out of memory")));
		return PAM_CONV_ERR;
	}

	for (i = 0; i < num_msg; i++)
	{
		switch (msg[i]->msg_style)
		{
			case PAM_PROMPT_ECHO_OFF:
				if (strlen(passwd) == 0)
				{
					/*
					 * Password wasn't passed to PAM the first time around -
					 * let's go ask the client to send a password, which we
					 * then stuff into PAM.
					 */
					sendAuthRequest(pam_port_cludge, AUTH_REQ_PASSWORD, NULL, 0);
					passwd = recv_password_packet(pam_port_cludge);
					if (passwd == NULL)
					{
						/*
						 * Client didn't want to send password.  We
						 * intentionally do not log anything about this,
						 * either here or at higher levels.
						 */
						pam_no_password = true;
						goto fail;
					}
				}
				if ((reply[i].resp = strdup(passwd)) == NULL)
					goto fail;
				reply[i].resp_retcode = PAM_SUCCESS;
				break;
			case PAM_ERROR_MSG:
				ereport(LOG,
						(errmsg("error from underlying PAM layer: %s",
								msg[i]->msg)));
				/* FALL THROUGH */
			case PAM_TEXT_INFO:
				/* we don't bother to log TEXT_INFO messages */
				if ((reply[i].resp = strdup("")) == NULL)
					goto fail;
				reply[i].resp_retcode = PAM_SUCCESS;
				break;
			default:
				ereport(LOG,
						(errmsg("unsupported PAM conversation %d/\"%s\"",
								msg[i]->msg_style,
								msg[i]->msg ? msg[i]->msg : "(none)")));
				goto fail;
		}
	}

	*resp = reply;
	return PAM_SUCCESS;

fail:
	/* free up whatever we allocated */
	for (i = 0; i < num_msg; i++)
	{
		if (reply[i].resp != NULL)
			free(reply[i].resp);
	}
	free(reply);

	return PAM_CONV_ERR;
}


/*
 * Check authentication against PAM.
 */
static int
CheckPAMAuth(Port *port, const char *user, const char *password)
{
	int			retval;
	pam_handle_t *pamh = NULL;

	/*
	 * We can't entirely rely on PAM to pass through appdata --- it appears
	 * not to work on at least Solaris 2.6.  So use these ugly static
	 * variables instead.
	 */
	pam_passwd = password;
	pam_port_cludge = port;
	pam_no_password = false;

	/*
	 * Set the application data portion of the conversation struct.  This is
	 * later used inside the PAM conversation to pass the password to the
	 * authentication module.
	 */
	pam_passw_conv.appdata_ptr = unconstify(char *, password);	/* from password above,
																 * not allocated */

	/* Optionally, one can set the service name in pg_hba.conf */
	if (port->hba->pamservice && port->hba->pamservice[0] != '\0')
		retval = pam_start(port->hba->pamservice, "pgsql@",
						   &pam_passw_conv, &pamh);
	else
		retval = pam_start(PGSQL_PAM_SERVICE, "pgsql@",
						   &pam_passw_conv, &pamh);

	if (retval != PAM_SUCCESS)
	{
		ereport(LOG,
				(errmsg("could not create PAM authenticator: %s",
						pam_strerror(pamh, retval))));
		pam_passwd = NULL;		/* Unset pam_passwd */
		return STATUS_ERROR;
	}

	retval = pam_set_item(pamh, PAM_USER, user);

	if (retval != PAM_SUCCESS)
	{
		ereport(LOG,
				(errmsg("pam_set_item(PAM_USER) failed: %s",
						pam_strerror(pamh, retval))));
		pam_passwd = NULL;		/* Unset pam_passwd */
		return STATUS_ERROR;
	}

	if (port->hba->conntype != ctLocal)
	{
		char		hostinfo[NI_MAXHOST];
		int			flags;

		if (port->hba->pam_use_hostname)
			flags = 0;
		else
			flags = NI_NUMERICHOST | NI_NUMERICSERV;

		retval = pg_getnameinfo_all(&port->raddr.addr, port->raddr.salen,
									hostinfo, sizeof(hostinfo), NULL, 0,
									flags);
		if (retval != 0)
		{
			ereport(WARNING,
					(errmsg_internal("pg_getnameinfo_all() failed: %s",
									 gai_strerror(retval))));
			return STATUS_ERROR;
		}

		retval = pam_set_item(pamh, PAM_RHOST, hostinfo);

		if (retval != PAM_SUCCESS)
		{
			ereport(LOG,
					(errmsg("pam_set_item(PAM_RHOST) failed: %s",
							pam_strerror(pamh, retval))));
			pam_passwd = NULL;
			return STATUS_ERROR;
		}
	}

	retval = pam_set_item(pamh, PAM_CONV, &pam_passw_conv);

	if (retval != PAM_SUCCESS)
	{
		ereport(LOG,
				(errmsg("pam_set_item(PAM_CONV) failed: %s",
						pam_strerror(pamh, retval))));
		pam_passwd = NULL;		/* Unset pam_passwd */
		return STATUS_ERROR;
	}

	retval = pam_authenticate(pamh, 0);

	if (retval != PAM_SUCCESS)
	{
		/* If pam_passwd_conv_proc saw EOF, don't log anything */
		if (!pam_no_password)
			ereport(LOG,
					(errmsg("pam_authenticate failed: %s",
							pam_strerror(pamh, retval))));
		pam_passwd = NULL;		/* Unset pam_passwd */
		return pam_no_password ? STATUS_EOF : STATUS_ERROR;
	}

	retval = pam_acct_mgmt(pamh, 0);

	if (retval != PAM_SUCCESS)
	{
		/* If pam_passwd_conv_proc saw EOF, don't log anything */
		if (!pam_no_password)
			ereport(LOG,
					(errmsg("pam_acct_mgmt failed: %s",
							pam_strerror(pamh, retval))));
		pam_passwd = NULL;		/* Unset pam_passwd */
		return pam_no_password ? STATUS_EOF : STATUS_ERROR;
	}

	retval = pam_end(pamh, retval);

	if (retval != PAM_SUCCESS)
	{
		ereport(LOG,
				(errmsg("could not release PAM authenticator: %s",
						pam_strerror(pamh, retval))));
	}

	pam_passwd = NULL;			/* Unset pam_passwd */

	if (retval == PAM_SUCCESS)
		set_authn_id(port, user);

	return (retval == PAM_SUCCESS ? STATUS_OK : STATUS_ERROR);
}
#endif							/* USE_PAM */


/*----------------------------------------------------------------
 * BSD authentication system
 *----------------------------------------------------------------
 */
#ifdef USE_BSD_AUTH
static int
CheckBSDAuth(Port *port, char *user)
{
	char	   *passwd;
	int			retval;

	/* Send regular password request to client, and get the response */
	sendAuthRequest(port, AUTH_REQ_PASSWORD, NULL, 0);

	passwd = recv_password_packet(port);
	if (passwd == NULL)
		return STATUS_EOF;

	/*
	 * Ask the BSD auth system to verify password.  Note that auth_userokay
	 * will overwrite the password string with zeroes, but it's just a
	 * temporary string so we don't care.
	 */
	retval = auth_userokay(user, NULL, "auth-postgresql", passwd);

	pfree(passwd);

	if (!retval)
		return STATUS_ERROR;

	set_authn_id(port, user);
	return STATUS_OK;
}
#endif							/* USE_BSD_AUTH */


/*----------------------------------------------------------------
 * LDAP authentication system
 *----------------------------------------------------------------
 */
#ifdef USE_LDAP

static int	errdetail_for_ldap(LDAP *ldap);

/*
 * Initialize a connection to the LDAP server, including setting up
 * TLS if requested.
 */
static int
InitializeLDAPConnection(Port *port, LDAP **ldap)
{
	const char *scheme;
	int			ldapversion = LDAP_VERSION3;
	int			r;

	scheme = port->hba->ldapscheme;
	if (scheme == NULL)
		scheme = "ldap";
#ifdef WIN32
	if (strcmp(scheme, "ldaps") == 0)
		*ldap = ldap_sslinit(port->hba->ldapserver, port->hba->ldapport, 1);
	else
		*ldap = ldap_init(port->hba->ldapserver, port->hba->ldapport);
	if (!*ldap)
	{
		ereport(LOG,
				(errmsg("could not initialize LDAP: error code %d",
						(int) LdapGetLastError())));

		return STATUS_ERROR;
	}
#else
#ifdef HAVE_LDAP_INITIALIZE

	/*
	 * OpenLDAP provides a non-standard extension ldap_initialize() that takes
	 * a list of URIs, allowing us to request "ldaps" instead of "ldap".  It
	 * also provides ldap_domain2hostlist() to find LDAP servers automatically
	 * using DNS SRV.  They were introduced in the same version, so for now we
	 * don't have an extra configure check for the latter.
	 */
	{
		StringInfoData uris;
		char	   *hostlist = NULL;
		char	   *p;
		bool		append_port;

		/* We'll build a space-separated scheme://hostname:port list here */
		initStringInfo(&uris);

		/*
		 * If pg_hba.conf provided no hostnames, we can ask OpenLDAP to try to
		 * find some by extracting a domain name from the base DN and looking
		 * up DSN SRV records for _ldap._tcp.<domain>.
		 */
		if (!port->hba->ldapserver || port->hba->ldapserver[0] == '\0')
		{
			char	   *domain;

			/* ou=blah,dc=foo,dc=bar -> foo.bar */
			if (ldap_dn2domain(port->hba->ldapbasedn, &domain))
			{
				ereport(LOG,
						(errmsg("could not extract domain name from ldapbasedn")));
				return STATUS_ERROR;
			}

			/* Look up a list of LDAP server hosts and port numbers */
			if (ldap_domain2hostlist(domain, &hostlist))
			{
				ereport(LOG,
						(errmsg("LDAP authentication could not find DNS SRV records for \"%s\"",
								domain),
						 (errhint("Set an LDAP server name explicitly."))));
				ldap_memfree(domain);
				return STATUS_ERROR;
			}
			ldap_memfree(domain);

			/* We have a space-separated list of host:port entries */
			p = hostlist;
			append_port = false;
		}
		else
		{
			/* We have a space-separated list of hosts from pg_hba.conf */
			p = port->hba->ldapserver;
			append_port = true;
		}

		/* Convert the list of host[:port] entries to full URIs */
		do
		{
			size_t		size;

			/* Find the span of the next entry */
			size = strcspn(p, " ");

			/* Append a space separator if this isn't the first URI */
			if (uris.len > 0)
				appendStringInfoChar(&uris, ' ');

			/* Append scheme://host:port */
			appendStringInfoString(&uris, scheme);
			appendStringInfoString(&uris, "://");
			appendBinaryStringInfo(&uris, p, size);
			if (append_port)
				appendStringInfo(&uris, ":%d", port->hba->ldapport);

			/* Step over this entry and any number of trailing spaces */
			p += size;
			while (*p == ' ')
				++p;
		} while (*p);

		/* Free memory from OpenLDAP if we looked up SRV records */
		if (hostlist)
			ldap_memfree(hostlist);

		/* Finally, try to connect using the URI list */
		r = ldap_initialize(ldap, uris.data);
		pfree(uris.data);
		if (r != LDAP_SUCCESS)
		{
			ereport(LOG,
					(errmsg("could not initialize LDAP: %s",
							ldap_err2string(r))));

			return STATUS_ERROR;
		}
	}
#else
	if (strcmp(scheme, "ldaps") == 0)
	{
		ereport(LOG,
				(errmsg("ldaps not supported with this LDAP library")));

		return STATUS_ERROR;
	}
	*ldap = ldap_init(port->hba->ldapserver, port->hba->ldapport);
	if (!*ldap)
	{
		ereport(LOG,
				(errmsg("could not initialize LDAP: %m")));

		return STATUS_ERROR;
	}
#endif
#endif

	if ((r = ldap_set_option(*ldap, LDAP_OPT_PROTOCOL_VERSION, &ldapversion)) != LDAP_SUCCESS)
	{
		ereport(LOG,
				(errmsg("could not set LDAP protocol version: %s",
						ldap_err2string(r)),
				 errdetail_for_ldap(*ldap)));
		ldap_unbind(*ldap);
		return STATUS_ERROR;
	}

	if (port->hba->ldaptls)
	{
#ifndef WIN32
		if ((r = ldap_start_tls_s(*ldap, NULL, NULL)) != LDAP_SUCCESS)
#else
		static __ldap_start_tls_sA _ldap_start_tls_sA = NULL;

		if (_ldap_start_tls_sA == NULL)
		{
			/*
			 * Need to load this function dynamically because it may not exist
			 * on Windows, and causes a load error for the whole exe if
			 * referenced.
			 */
			HANDLE		ldaphandle;

			ldaphandle = LoadLibrary("WLDAP32.DLL");
			if (ldaphandle == NULL)
			{
				/*
				 * should never happen since we import other files from
				 * wldap32, but check anyway
				 */
				ereport(LOG,
						(errmsg("could not load library \"%s\": error code %lu",
								"WLDAP32.DLL", GetLastError())));
				ldap_unbind(*ldap);
				return STATUS_ERROR;
			}
			_ldap_start_tls_sA = (__ldap_start_tls_sA) (pg_funcptr_t) GetProcAddress(ldaphandle, "ldap_start_tls_sA");
			if (_ldap_start_tls_sA == NULL)
			{
				ereport(LOG,
						(errmsg("could not load function _ldap_start_tls_sA in wldap32.dll"),
						 errdetail("LDAP over SSL is not supported on this platform.")));
				ldap_unbind(*ldap);
				FreeLibrary(ldaphandle);
				return STATUS_ERROR;
			}

			/*
			 * Leak LDAP handle on purpose, because we need the library to
			 * stay open. This is ok because it will only ever be leaked once
			 * per process and is automatically cleaned up on process exit.
			 */
		}
		if ((r = _ldap_start_tls_sA(*ldap, NULL, NULL, NULL, NULL)) != LDAP_SUCCESS)
#endif
		{
			ereport(LOG,
					(errmsg("could not start LDAP TLS session: %s",
							ldap_err2string(r)),
					 errdetail_for_ldap(*ldap)));
			ldap_unbind(*ldap);
			return STATUS_ERROR;
		}
	}

	return STATUS_OK;
}

/* Placeholders recognized by FormatSearchFilter.  For now just one. */
#define LPH_USERNAME "$username"
#define LPH_USERNAME_LEN (sizeof(LPH_USERNAME) - 1)

/* Not all LDAP implementations define this. */
#ifndef LDAP_NO_ATTRS
#define LDAP_NO_ATTRS "1.1"
#endif

/* Not all LDAP implementations define this. */
#ifndef LDAPS_PORT
#define LDAPS_PORT 636
#endif

/*
 * Return a newly allocated C string copied from "pattern" with all
 * occurrences of the placeholder "$username" replaced with "user_name".
 */
static char *
FormatSearchFilter(const char *pattern, const char *user_name)
{
	StringInfoData output;

	initStringInfo(&output);
	while (*pattern != '\0')
	{
		if (strncmp(pattern, LPH_USERNAME, LPH_USERNAME_LEN) == 0)
		{
			appendStringInfoString(&output, user_name);
			pattern += LPH_USERNAME_LEN;
		}
		else
			appendStringInfoChar(&output, *pattern++);
	}

	return output.data;
}

/*
 * Perform LDAP authentication
 */
static int
CheckLDAPAuth(Port *port)
{
	char	   *passwd;
	LDAP	   *ldap;
	int			r;
	char	   *fulluser;
	const char *server_name;

#ifdef HAVE_LDAP_INITIALIZE

	/*
	 * For OpenLDAP, allow empty hostname if we have a basedn.  We'll look for
	 * servers with DNS SRV records via OpenLDAP library facilities.
	 */
	if ((!port->hba->ldapserver || port->hba->ldapserver[0] == '\0') &&
		(!port->hba->ldapbasedn || port->hba->ldapbasedn[0] == '\0'))
	{
		ereport(LOG,
				(errmsg("LDAP server not specified, and no ldapbasedn")));
		return STATUS_ERROR;
	}
#else
	if (!port->hba->ldapserver || port->hba->ldapserver[0] == '\0')
	{
		ereport(LOG,
				(errmsg("LDAP server not specified")));
		return STATUS_ERROR;
	}
#endif

	/*
	 * If we're using SRV records, we don't have a server name so we'll just
	 * show an empty string in error messages.
	 */
	server_name = port->hba->ldapserver ? port->hba->ldapserver : "";

	if (port->hba->ldapport == 0)
	{
		if (port->hba->ldapscheme != NULL &&
			strcmp(port->hba->ldapscheme, "ldaps") == 0)
			port->hba->ldapport = LDAPS_PORT;
		else
			port->hba->ldapport = LDAP_PORT;
	}

	sendAuthRequest(port, AUTH_REQ_PASSWORD, NULL, 0);

	passwd = recv_password_packet(port);
	if (passwd == NULL)
		return STATUS_EOF;		/* client wouldn't send password */

	if (InitializeLDAPConnection(port, &ldap) == STATUS_ERROR)
	{
		/* Error message already sent */
		pfree(passwd);
		return STATUS_ERROR;
	}

	if (port->hba->ldapbasedn)
	{
		/*
		 * First perform an LDAP search to find the DN for the user we are
		 * trying to log in as.
		 */
		char	   *filter;
		LDAPMessage *search_message;
		LDAPMessage *entry;
		char	   *attributes[] = {LDAP_NO_ATTRS, NULL};
		char	   *dn;
		char	   *c;
		int			count;

		/*
		 * Disallow any characters that we would otherwise need to escape,
		 * since they aren't really reasonable in a username anyway. Allowing
		 * them would make it possible to inject any kind of custom filters in
		 * the LDAP filter.
		 */
		for (c = port->user_name; *c; c++)
		{
			if (*c == '*' ||
				*c == '(' ||
				*c == ')' ||
				*c == '\\' ||
				*c == '/')
			{
				ereport(LOG,
						(errmsg("invalid character in user name for LDAP authentication")));
				ldap_unbind(ldap);
				pfree(passwd);
				return STATUS_ERROR;
			}
		}

		/*
		 * Bind with a pre-defined username/password (if available) for
		 * searching. If none is specified, this turns into an anonymous bind.
		 */
		r = ldap_simple_bind_s(ldap,
							   port->hba->ldapbinddn ? port->hba->ldapbinddn : "",
							   port->hba->ldapbindpasswd ? port->hba->ldapbindpasswd : "");
		if (r != LDAP_SUCCESS)
		{
			ereport(LOG,
					(errmsg("could not perform initial LDAP bind for ldapbinddn \"%s\" on server \"%s\": %s",
							port->hba->ldapbinddn ? port->hba->ldapbinddn : "",
							server_name,
							ldap_err2string(r)),
					 errdetail_for_ldap(ldap)));
			ldap_unbind(ldap);
			pfree(passwd);
			return STATUS_ERROR;
		}

		/* Build a custom filter or a single attribute filter? */
		if (port->hba->ldapsearchfilter)
			filter = FormatSearchFilter(port->hba->ldapsearchfilter, port->user_name);
		else if (port->hba->ldapsearchattribute)
			filter = psprintf("(%s=%s)", port->hba->ldapsearchattribute, port->user_name);
		else
			filter = psprintf("(uid=%s)", port->user_name);

		r = ldap_search_s(ldap,
						  port->hba->ldapbasedn,
						  port->hba->ldapscope,
						  filter,
						  attributes,
						  0,
						  &search_message);

		if (r != LDAP_SUCCESS)
		{
			ereport(LOG,
					(errmsg("could not search LDAP for filter \"%s\" on server \"%s\": %s",
							filter, server_name, ldap_err2string(r)),
					 errdetail_for_ldap(ldap)));
			ldap_unbind(ldap);
			pfree(passwd);
			pfree(filter);
			return STATUS_ERROR;
		}

		count = ldap_count_entries(ldap, search_message);
		if (count != 1)
		{
			if (count == 0)
				ereport(LOG,
						(errmsg("LDAP user \"%s\" does not exist", port->user_name),
						 errdetail("LDAP search for filter \"%s\" on server \"%s\" returned no entries.",
								   filter, server_name)));
			else
				ereport(LOG,
						(errmsg("LDAP user \"%s\" is not unique", port->user_name),
						 errdetail_plural("LDAP search for filter \"%s\" on server \"%s\" returned %d entry.",
										  "LDAP search for filter \"%s\" on server \"%s\" returned %d entries.",
										  count,
										  filter, server_name, count)));

			ldap_unbind(ldap);
			pfree(passwd);
			pfree(filter);
			ldap_msgfree(search_message);
			return STATUS_ERROR;
		}

		entry = ldap_first_entry(ldap, search_message);
		dn = ldap_get_dn(ldap, entry);
		if (dn == NULL)
		{
			int			error;

			(void) ldap_get_option(ldap, LDAP_OPT_ERROR_NUMBER, &error);
			ereport(LOG,
					(errmsg("could not get dn for the first entry matching \"%s\" on server \"%s\": %s",
							filter, server_name,
							ldap_err2string(error)),
					 errdetail_for_ldap(ldap)));
			ldap_unbind(ldap);
			pfree(passwd);
			pfree(filter);
			ldap_msgfree(search_message);
			return STATUS_ERROR;
		}
		fulluser = pstrdup(dn);

		pfree(filter);
		ldap_memfree(dn);
		ldap_msgfree(search_message);

		/* Unbind and disconnect from the LDAP server */
		r = ldap_unbind_s(ldap);
		if (r != LDAP_SUCCESS)
		{
			ereport(LOG,
					(errmsg("could not unbind after searching for user \"%s\" on server \"%s\"",
							fulluser, server_name)));
			pfree(passwd);
			pfree(fulluser);
			return STATUS_ERROR;
		}

		/*
		 * Need to re-initialize the LDAP connection, so that we can bind to
		 * it with a different username.
		 */
		if (InitializeLDAPConnection(port, &ldap) == STATUS_ERROR)
		{
			pfree(passwd);
			pfree(fulluser);

			/* Error message already sent */
			return STATUS_ERROR;
		}
	}
	else
		fulluser = psprintf("%s%s%s",
							port->hba->ldapprefix ? port->hba->ldapprefix : "",
							port->user_name,
							port->hba->ldapsuffix ? port->hba->ldapsuffix : "");

	r = ldap_simple_bind_s(ldap, fulluser, passwd);

	if (r != LDAP_SUCCESS)
	{
		ereport(LOG,
				(errmsg("LDAP login failed for user \"%s\" on server \"%s\": %s",
						fulluser, server_name, ldap_err2string(r)),
				 errdetail_for_ldap(ldap)));
		ldap_unbind(ldap);
		pfree(passwd);
		pfree(fulluser);
		return STATUS_ERROR;
	}

	/* Save the original bind DN as the authenticated identity. */
	set_authn_id(port, fulluser);

	ldap_unbind(ldap);
	pfree(passwd);
	pfree(fulluser);

	return STATUS_OK;
}

/*
 * Add a detail error message text to the current error if one can be
 * constructed from the LDAP 'diagnostic message'.
 */
static int
errdetail_for_ldap(LDAP *ldap)
{
	char	   *message;
	int			rc;

	rc = ldap_get_option(ldap, LDAP_OPT_DIAGNOSTIC_MESSAGE, &message);
	if (rc == LDAP_SUCCESS && message != NULL)
	{
		errdetail("LDAP diagnostics: %s", message);
		ldap_memfree(message);
	}

	return 0;
}

#endif							/* USE_LDAP */


/*----------------------------------------------------------------
 * SSL client certificate authentication
 *----------------------------------------------------------------
 */
#ifdef USE_SSL
static int
CheckCertAuth(Port *port)
{
	int			status_check_usermap = STATUS_ERROR;
	char	   *peer_username = NULL;

	Assert(port->ssl);

	/* select the correct field to compare */
	switch (port->hba->clientcertname)
	{
		case clientCertDN:
			peer_username = port->peer_dn;
			break;
		case clientCertCN:
			peer_username = port->peer_cn;
	}

	/* Make sure we have received a username in the certificate */
	if (peer_username == NULL ||
		strlen(peer_username) <= 0)
	{
		ereport(LOG,
				(errmsg("certificate authentication failed for user \"%s\": client certificate contains no user name",
						port->user_name)));
		return STATUS_ERROR;
	}

	if (port->hba->auth_method == uaCert)
	{
		/*
		 * For cert auth, the client's Subject DN is always our authenticated
		 * identity, even if we're only using its CN for authorization.  Set
		 * it now, rather than waiting for check_usermap() below, because
		 * authentication has already succeeded and we want the log file to
		 * reflect that.
		 */
		if (!port->peer_dn)
		{
			/*
			 * This should not happen as both peer_dn and peer_cn should be
			 * set in this context.
			 */
			ereport(LOG,
					(errmsg("certificate authentication failed for user \"%s\": unable to retrieve subject DN",
							port->user_name)));
			return STATUS_ERROR;
		}

		set_authn_id(port, port->peer_dn);
	}

	/* Just pass the certificate cn/dn to the usermap check */
	status_check_usermap = check_usermap(port->hba->usermap, port->user_name, peer_username, false);
	if (status_check_usermap != STATUS_OK)
	{
		/*
		 * If clientcert=verify-full was specified and the authentication
		 * method is other than uaCert, log the reason for rejecting the
		 * authentication.
		 */
		if (port->hba->clientcert == clientCertFull && port->hba->auth_method != uaCert)
		{
			switch (port->hba->clientcertname)
			{
				case clientCertDN:
					ereport(LOG,
							(errmsg("certificate validation (clientcert=verify-full) failed for user \"%s\": DN mismatch",
									port->user_name)));
					break;
				case clientCertCN:
					ereport(LOG,
							(errmsg("certificate validation (clientcert=verify-full) failed for user \"%s\": CN mismatch",
									port->user_name)));
			}
		}
	}
	return status_check_usermap;
}
#endif


/*----------------------------------------------------------------
 * RADIUS authentication
 *----------------------------------------------------------------
 */

/*
 * RADIUS authentication is described in RFC2865 (and several others).
 */

#define RADIUS_VECTOR_LENGTH 16
#define RADIUS_HEADER_LENGTH 20
#define RADIUS_MAX_PASSWORD_LENGTH 128

/* Maximum size of a RADIUS packet we will create or accept */
#define RADIUS_BUFFER_SIZE 1024

typedef struct
{
	uint8		attribute;
	uint8		length;
	uint8		data[FLEXIBLE_ARRAY_MEMBER];
} radius_attribute;

typedef struct
{
	uint8		code;
	uint8		id;
	uint16		length;
	uint8		vector[RADIUS_VECTOR_LENGTH];
	/* this is a bit longer than strictly necessary: */
	char		pad[RADIUS_BUFFER_SIZE - RADIUS_VECTOR_LENGTH];
} radius_packet;

/* RADIUS packet types */
#define RADIUS_ACCESS_REQUEST	1
#define RADIUS_ACCESS_ACCEPT	2
#define RADIUS_ACCESS_REJECT	3

/* RADIUS attributes */
#define RADIUS_USER_NAME		1
#define RADIUS_PASSWORD			2
#define RADIUS_SERVICE_TYPE		6
#define RADIUS_NAS_IDENTIFIER	32

/* RADIUS service types */
#define RADIUS_AUTHENTICATE_ONLY	8

/* Seconds to wait - XXX: should be in a config variable! */
#define RADIUS_TIMEOUT 3

static void
radius_add_attribute(radius_packet *packet, uint8 type, const unsigned char *data, int len)
{
	radius_attribute *attr;

	if (packet->length + len > RADIUS_BUFFER_SIZE)
	{
		/*
		 * With remotely realistic data, this can never happen. But catch it
		 * just to make sure we don't overrun a buffer. We'll just skip adding
		 * the broken attribute, which will in the end cause authentication to
		 * fail.
		 */
		elog(WARNING,
			 "adding attribute code %d with length %d to radius packet would create oversize packet, ignoring",
			 type, len);
		return;
	}

	attr = (radius_attribute *) ((unsigned char *) packet + packet->length);
	attr->attribute = type;
	attr->length = len + 2;		/* total size includes type and length */
	memcpy(attr->data, data, len);
	packet->length += attr->length;
}

static int
CheckRADIUSAuth(Port *port)
{
	char	   *passwd;
	ListCell   *server,
			   *secrets,
			   *radiusports,
			   *identifiers;

	/* Make sure struct alignment is correct */
	Assert(offsetof(radius_packet, vector) == 4);

	/* Verify parameters */
	if (list_length(port->hba->radiusservers) < 1)
	{
		ereport(LOG,
				(errmsg("RADIUS server not specified")));
		return STATUS_ERROR;
	}

	if (list_length(port->hba->radiussecrets) < 1)
	{
		ereport(LOG,
				(errmsg("RADIUS secret not specified")));
		return STATUS_ERROR;
	}

	/* Send regular password request to client, and get the response */
	sendAuthRequest(port, AUTH_REQ_PASSWORD, NULL, 0);

	passwd = recv_password_packet(port);
	if (passwd == NULL)
		return STATUS_EOF;		/* client wouldn't send password */

	if (strlen(passwd) > RADIUS_MAX_PASSWORD_LENGTH)
	{
		ereport(LOG,
				(errmsg("RADIUS authentication does not support passwords longer than %d characters", RADIUS_MAX_PASSWORD_LENGTH)));
		pfree(passwd);
		return STATUS_ERROR;
	}

	/*
	 * Loop over and try each server in order.
	 */
	secrets = list_head(port->hba->radiussecrets);
	radiusports = list_head(port->hba->radiusports);
	identifiers = list_head(port->hba->radiusidentifiers);
	foreach(server, port->hba->radiusservers)
	{
		int			ret = PerformRadiusTransaction(lfirst(server),
												   lfirst(secrets),
												   radiusports ? lfirst(radiusports) : NULL,
												   identifiers ? lfirst(identifiers) : NULL,
												   port->user_name,
												   passwd);

		/*------
		 * STATUS_OK = Login OK
		 * STATUS_ERROR = Login not OK, but try next server
		 * STATUS_EOF = Login not OK, and don't try next server
		 *------
		 */
		if (ret == STATUS_OK)
		{
			set_authn_id(port, port->user_name);

			pfree(passwd);
			return STATUS_OK;
		}
		else if (ret == STATUS_EOF)
		{
			pfree(passwd);
			return STATUS_ERROR;
		}

		/*
		 * secret, port and identifiers either have length 0 (use default),
		 * length 1 (use the same everywhere) or the same length as servers.
		 * So if the length is >1, we advance one step. In other cases, we
		 * don't and will then reuse the correct value.
		 */
		if (list_length(port->hba->radiussecrets) > 1)
			secrets = lnext(port->hba->radiussecrets, secrets);
		if (list_length(port->hba->radiusports) > 1)
			radiusports = lnext(port->hba->radiusports, radiusports);
		if (list_length(port->hba->radiusidentifiers) > 1)
			identifiers = lnext(port->hba->radiusidentifiers, identifiers);
	}

	/* No servers left to try, so give up */
	pfree(passwd);
	return STATUS_ERROR;
}

static int
PerformRadiusTransaction(const char *server, const char *secret, const char *portstr, const char *identifier, const char *user_name, const char *passwd)
{
	radius_packet radius_send_pack;
	radius_packet radius_recv_pack;
	radius_packet *packet = &radius_send_pack;
	radius_packet *receivepacket = &radius_recv_pack;
	char	   *radius_buffer = (char *) &radius_send_pack;
	char	   *receive_buffer = (char *) &radius_recv_pack;
	int32		service = pg_hton32(RADIUS_AUTHENTICATE_ONLY);
	uint8	   *cryptvector;
	int			encryptedpasswordlen;
	uint8		encryptedpassword[RADIUS_MAX_PASSWORD_LENGTH];
	uint8	   *md5trailer;
	int			packetlength;
	pgsocket	sock;

#ifdef HAVE_IPV6
	struct sockaddr_in6 localaddr;
	struct sockaddr_in6 remoteaddr;
#else
	struct sockaddr_in localaddr;
	struct sockaddr_in remoteaddr;
#endif
	struct addrinfo hint;
	struct addrinfo *serveraddrs;
	int			port;
	socklen_t	addrsize;
	fd_set		fdset;
	struct timeval endtime;
	int			i,
				j,
				r;

	/* Assign default values */
	if (portstr == NULL)
		portstr = "1812";
	if (identifier == NULL)
		identifier = "postgresql";

	MemSet(&hint, 0, sizeof(hint));
	hint.ai_socktype = SOCK_DGRAM;
	hint.ai_family = AF_UNSPEC;
	port = atoi(portstr);

	r = pg_getaddrinfo_all(server, portstr, &hint, &serveraddrs);
	if (r || !serveraddrs)
	{
		ereport(LOG,
				(errmsg("could not translate RADIUS server name \"%s\" to address: %s",
						server, gai_strerror(r))));
		if (serveraddrs)
			pg_freeaddrinfo_all(hint.ai_family, serveraddrs);
		return STATUS_ERROR;
	}
	/* XXX: add support for multiple returned addresses? */

	/* Construct RADIUS packet */
	packet->code = RADIUS_ACCESS_REQUEST;
	packet->length = RADIUS_HEADER_LENGTH;
	if (!pg_strong_random(packet->vector, RADIUS_VECTOR_LENGTH))
	{
		ereport(LOG,
				(errmsg("could not generate random encryption vector")));
		pg_freeaddrinfo_all(hint.ai_family, serveraddrs);
		return STATUS_ERROR;
	}
	packet->id = packet->vector[0];
	radius_add_attribute(packet, RADIUS_SERVICE_TYPE, (const unsigned char *) &service, sizeof(service));
	radius_add_attribute(packet, RADIUS_USER_NAME, (const unsigned char *) user_name, strlen(user_name));
	radius_add_attribute(packet, RADIUS_NAS_IDENTIFIER, (const unsigned char *) identifier, strlen(identifier));

	/*
	 * RADIUS password attributes are calculated as: e[0] = p[0] XOR
	 * MD5(secret + Request Authenticator) for the first group of 16 octets,
	 * and then: e[i] = p[i] XOR MD5(secret + e[i-1]) for the following ones
	 * (if necessary)
	 */
	encryptedpasswordlen = ((strlen(passwd) + RADIUS_VECTOR_LENGTH - 1) / RADIUS_VECTOR_LENGTH) * RADIUS_VECTOR_LENGTH;
	cryptvector = palloc(strlen(secret) + RADIUS_VECTOR_LENGTH);
	memcpy(cryptvector, secret, strlen(secret));

	/* for the first iteration, we use the Request Authenticator vector */
	md5trailer = packet->vector;
	for (i = 0; i < encryptedpasswordlen; i += RADIUS_VECTOR_LENGTH)
	{
		const char *errstr = NULL;

		memcpy(cryptvector + strlen(secret), md5trailer, RADIUS_VECTOR_LENGTH);

		/*
		 * .. and for subsequent iterations the result of the previous XOR
		 * (calculated below)
		 */
		md5trailer = encryptedpassword + i;

		if (!pg_md5_binary(cryptvector, strlen(secret) + RADIUS_VECTOR_LENGTH,
						   encryptedpassword + i, &errstr))
		{
			ereport(LOG,
					(errmsg("could not perform MD5 encryption of password: %s",
							errstr)));
			pfree(cryptvector);
			pg_freeaddrinfo_all(hint.ai_family, serveraddrs);
			return STATUS_ERROR;
		}

		for (j = i; j < i + RADIUS_VECTOR_LENGTH; j++)
		{
			if (j < strlen(passwd))
				encryptedpassword[j] = passwd[j] ^ encryptedpassword[j];
			else
				encryptedpassword[j] = '\0' ^ encryptedpassword[j];
		}
	}
	pfree(cryptvector);

	radius_add_attribute(packet, RADIUS_PASSWORD, encryptedpassword, encryptedpasswordlen);

	/* Length needs to be in network order on the wire */
	packetlength = packet->length;
	packet->length = pg_hton16(packet->length);

	sock = socket(serveraddrs[0].ai_family, SOCK_DGRAM, 0);
	if (sock == PGINVALID_SOCKET)
	{
		ereport(LOG,
				(errmsg("could not create RADIUS socket: %m")));
		pg_freeaddrinfo_all(hint.ai_family, serveraddrs);
		return STATUS_ERROR;
	}

	memset(&localaddr, 0, sizeof(localaddr));
#ifdef HAVE_IPV6
	localaddr.sin6_family = serveraddrs[0].ai_family;
	localaddr.sin6_addr = in6addr_any;
	if (localaddr.sin6_family == AF_INET6)
		addrsize = sizeof(struct sockaddr_in6);
	else
		addrsize = sizeof(struct sockaddr_in);
#else
	localaddr.sin_family = serveraddrs[0].ai_family;
	localaddr.sin_addr.s_addr = INADDR_ANY;
	addrsize = sizeof(struct sockaddr_in);
#endif

	if (bind(sock, (struct sockaddr *) &localaddr, addrsize))
	{
		ereport(LOG,
				(errmsg("could not bind local RADIUS socket: %m")));
		closesocket(sock);
		pg_freeaddrinfo_all(hint.ai_family, serveraddrs);
		return STATUS_ERROR;
	}

	if (sendto(sock, radius_buffer, packetlength, 0,
			   serveraddrs[0].ai_addr, serveraddrs[0].ai_addrlen) < 0)
	{
		ereport(LOG,
				(errmsg("could not send RADIUS packet: %m")));
		closesocket(sock);
		pg_freeaddrinfo_all(hint.ai_family, serveraddrs);
		return STATUS_ERROR;
	}

	/* Don't need the server address anymore */
	pg_freeaddrinfo_all(hint.ai_family, serveraddrs);

	/*
	 * Figure out at what time we should time out. We can't just use a single
	 * call to select() with a timeout, since somebody can be sending invalid
	 * packets to our port thus causing us to retry in a loop and never time
	 * out.
	 *
	 * XXX: Using WaitLatchOrSocket() and doing a CHECK_FOR_INTERRUPTS() if
	 * the latch was set would improve the responsiveness to
	 * timeouts/cancellations.
	 */
	gettimeofday(&endtime, NULL);
	endtime.tv_sec += RADIUS_TIMEOUT;

	while (true)
	{
		struct timeval timeout;
		struct timeval now;
		int64		timeoutval;
		const char *errstr = NULL;

		gettimeofday(&now, NULL);
		timeoutval = (endtime.tv_sec * 1000000 + endtime.tv_usec) - (now.tv_sec * 1000000 + now.tv_usec);
		if (timeoutval <= 0)
		{
			ereport(LOG,
					(errmsg("timeout waiting for RADIUS response from %s",
							server)));
			closesocket(sock);
			return STATUS_ERROR;
		}
		timeout.tv_sec = timeoutval / 1000000;
		timeout.tv_usec = timeoutval % 1000000;

		FD_ZERO(&fdset);
		FD_SET(sock, &fdset);

		r = select(sock + 1, &fdset, NULL, NULL, &timeout);
		if (r < 0)
		{
			if (errno == EINTR)
				continue;

			/* Anything else is an actual error */
			ereport(LOG,
					(errmsg("could not check status on RADIUS socket: %m")));
			closesocket(sock);
			return STATUS_ERROR;
		}
		if (r == 0)
		{
			ereport(LOG,
					(errmsg("timeout waiting for RADIUS response from %s",
							server)));
			closesocket(sock);
			return STATUS_ERROR;
		}

		/*
		 * Attempt to read the response packet, and verify the contents.
		 *
		 * Any packet that's not actually a RADIUS packet, or otherwise does
		 * not validate as an explicit reject, is just ignored and we retry
		 * for another packet (until we reach the timeout). This is to avoid
		 * the possibility to denial-of-service the login by flooding the
		 * server with invalid packets on the port that we're expecting the
		 * RADIUS response on.
		 */

		addrsize = sizeof(remoteaddr);
		packetlength = recvfrom(sock, receive_buffer, RADIUS_BUFFER_SIZE, 0,
								(struct sockaddr *) &remoteaddr, &addrsize);
		if (packetlength < 0)
		{
			ereport(LOG,
					(errmsg("could not read RADIUS response: %m")));
			closesocket(sock);
			return STATUS_ERROR;
		}

#ifdef HAVE_IPV6
		if (remoteaddr.sin6_port != pg_hton16(port))
#else
		if (remoteaddr.sin_port != pg_hton16(port))
#endif
		{
#ifdef HAVE_IPV6
			ereport(LOG,
					(errmsg("RADIUS response from %s was sent from incorrect port: %d",
							server, pg_ntoh16(remoteaddr.sin6_port))));
#else
			ereport(LOG,
					(errmsg("RADIUS response from %s was sent from incorrect port: %d",
							server, pg_ntoh16(remoteaddr.sin_port))));
#endif
			continue;
		}

		if (packetlength < RADIUS_HEADER_LENGTH)
		{
			ereport(LOG,
					(errmsg("RADIUS response from %s too short: %d", server, packetlength)));
			continue;
		}

		if (packetlength != pg_ntoh16(receivepacket->length))
		{
			ereport(LOG,
					(errmsg("RADIUS response from %s has corrupt length: %d (actual length %d)",
							server, pg_ntoh16(receivepacket->length), packetlength)));
			continue;
		}

		if (packet->id != receivepacket->id)
		{
			ereport(LOG,
					(errmsg("RADIUS response from %s is to a different request: %d (should be %d)",
							server, receivepacket->id, packet->id)));
			continue;
		}

		/*
		 * Verify the response authenticator, which is calculated as
		 * MD5(Code+ID+Length+RequestAuthenticator+Attributes+Secret)
		 */
		cryptvector = palloc(packetlength + strlen(secret));

		memcpy(cryptvector, receivepacket, 4);	/* code+id+length */
		memcpy(cryptvector + 4, packet->vector, RADIUS_VECTOR_LENGTH);	/* request
																		 * authenticator, from
																		 * original packet */
		if (packetlength > RADIUS_HEADER_LENGTH)	/* there may be no
													 * attributes at all */
			memcpy(cryptvector + RADIUS_HEADER_LENGTH, receive_buffer + RADIUS_HEADER_LENGTH, packetlength - RADIUS_HEADER_LENGTH);
		memcpy(cryptvector + packetlength, secret, strlen(secret));

		if (!pg_md5_binary(cryptvector,
						   packetlength + strlen(secret),
						   encryptedpassword, &errstr))
		{
			ereport(LOG,
					(errmsg("could not perform MD5 encryption of received packet: %s",
							errstr)));
			pfree(cryptvector);
			continue;
		}
		pfree(cryptvector);

		if (memcmp(receivepacket->vector, encryptedpassword, RADIUS_VECTOR_LENGTH) != 0)
		{
			ereport(LOG,
					(errmsg("RADIUS response from %s has incorrect MD5 signature",
							server)));
			continue;
		}

		if (receivepacket->code == RADIUS_ACCESS_ACCEPT)
		{
			closesocket(sock);
			return STATUS_OK;
		}
		else if (receivepacket->code == RADIUS_ACCESS_REJECT)
		{
			closesocket(sock);
			return STATUS_EOF;
		}
		else
		{
			ereport(LOG,
					(errmsg("RADIUS response from %s has invalid code (%d) for user \"%s\"",
							server, receivepacket->code, user_name)));
			continue;
		}
	}							/* while (true) */
}