path: root/ssh.h

/*
 * 
 * ssh.h
 * 
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * 
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * 
 * Created: Fri Mar 17 17:09:37 1995 ylo
 * 
 * Generic header file for ssh.
 * 
 */

/* RCSID("$Id: ssh.h,v 1.26 2000/02/07 02:20:26 damien Exp $"); */

#ifndef SSH_H
#define SSH_H

#include <netinet/in.h> /* For struct sockaddr_in */
#include <pwd.h> /* For struct pw */
#include <stdarg.h> /* For va_list */
#include <sys/socket.h> /* For struct sockaddr_storage */
#include "fake-socket.h" /* For struct sockaddr_storage */
#ifdef HAVE_SYS_SELECT_H
# include <sys/select.h>
#endif
#include "rsa.h"
#include "cipher.h"

/*
 * The default cipher used if IDEA is not supported by the remote host. It is
 * recommended that this be one of the mandatory ciphers (DES, 3DES), though
 * that is not required.
 */
#define SSH_FALLBACK_CIPHER	SSH_CIPHER_3DES

/* Cipher used for encrypting authentication files. */
#define SSH_AUTHFILE_CIPHER	SSH_CIPHER_3DES

/* Default port number. */
#define SSH_DEFAULT_PORT	22

/* Maximum number of TCP/IP ports forwarded per direction. */
#define SSH_MAX_FORWARDS_PER_DIRECTION	100

/*
 * Maximum number of RSA authentication identity files that can be specified
 * in configuration files or on the command line.
 */
#define SSH_MAX_IDENTITY_FILES		100

/*
 * Major protocol version.  Different version indicates major incompatiblity
 * that prevents communication.
 */
#define PROTOCOL_MAJOR		1

/*
 * Minor protocol version.  Different version indicates minor incompatibility
 * that does not prevent interoperation.
 */
#define PROTOCOL_MINOR		5

/*
 * Name for the service.  The port named by this service overrides the
 * default port if present.
 */
#define SSH_SERVICE_NAME	"ssh"

#ifndef ETCDIR
#define ETCDIR			"/etc"
#endif /* ETCDIR */

#ifndef PIDDIR
#define PIDDIR			"/var/run"
#endif /* PIDDIR */

/*
 * System-wide file containing host keys of known hosts.  This file should be
 * world-readable.
 */
#define SSH_SYSTEM_HOSTFILE	ETCDIR "/ssh_known_hosts"

/*
 * Of these, ssh_host_key must be readable only by root, whereas ssh_config
 * should be world-readable.
 */
#define HOST_KEY_FILE		ETCDIR "/ssh_host_key"
#define SERVER_CONFIG_FILE	ETCDIR "/sshd_config"
#define HOST_CONFIG_FILE	ETCDIR "/ssh_config"

#ifndef SSH_PROGRAM
#define SSH_PROGRAM			"/usr/bin/ssh"
#endif /* SSH_PROGRAM */

#ifndef LOGIN_PROGRAM
#define LOGIN_PROGRAM		"/usr/bin/login"
#endif /* LOGIN_PROGRAM */

#ifndef ASKPASS_PROGRAM
#define ASKPASS_PROGRAM		"/usr/lib/ssh/ssh-askpass"
#endif /* ASKPASS_PROGRAM */

/*
 * The process id of the daemon listening for connections is saved here to
 * make it easier to kill the correct daemon when necessary.
 */
#define SSH_DAEMON_PID_FILE	PIDDIR "/sshd.pid"

/*
 * The directory in user\'s home directory in which the files reside. The
 * directory should be world-readable (though not all files are).
 */
#define SSH_USER_DIR		".ssh"

/*
 * Per-user file containing host keys of known hosts.  This file need not be
 * readable by anyone except the user him/herself, though this does not
 * contain anything particularly secret.
 */
#define SSH_USER_HOSTFILE	"~/.ssh/known_hosts"

/*
 * Name of the default file containing client-side authentication key. This
 * file should only be readable by the user him/herself.
 */
#define SSH_CLIENT_IDENTITY	".ssh/identity"

/*
 * Configuration file in user\'s home directory.  This file need not be
 * readable by anyone but the user him/herself, but does not contain anything
 * particularly secret.  If the user\'s home directory resides on an NFS
 * volume where root is mapped to nobody, this may need to be world-readable.
 */
#define SSH_USER_CONFFILE	".ssh/config"

/*
 * File containing a list of those rsa keys that permit logging in as this
 * user.  This file need not be readable by anyone but the user him/herself,
 * but does not contain anything particularly secret.  If the user\'s home
 * directory resides on an NFS volume where root is mapped to nobody, this
 * may need to be world-readable.  (This file is read by the daemon which is
 * running as root.)
 */
#define SSH_USER_PERMITTED_KEYS	".ssh/authorized_keys"

/*
 * Per-user and system-wide ssh "rc" files.  These files are executed with
 * /bin/sh before starting the shell or command if they exist.  They will be
 * passed "proto cookie" as arguments if X11 forwarding with spoofing is in
 * use.  xauth will be run if neither of these exists.
 */
#define SSH_USER_RC		".ssh/rc"
#define SSH_SYSTEM_RC		ETCDIR "/sshrc"

/*
 * Ssh-only version of /etc/hosts.equiv.  Additionally, the daemon may use
 * ~/.rhosts and /etc/hosts.equiv if rhosts authentication is enabled.
 */
#define SSH_HOSTS_EQUIV		ETCDIR "/shosts.equiv"

/*
 * Name of the environment variable containing the pathname of the
 * authentication socket.
 */
#define SSH_AUTHSOCKET_ENV_NAME	"SSH_AUTH_SOCK"

/*
 * Name of the environment variable containing the pathname of the
 * authentication socket.
 */
#define SSH_AGENTPID_ENV_NAME	"SSH_AGENT_PID"

/*
 * Default path to ssh-askpass used by ssh-add,
 * environment variable for overwriting the default location
 */
#ifndef SSH_ASKPASS_DEFAULT
# define SSH_ASKPASS_DEFAULT	"/usr/X11R6/bin/ssh-askpass"
#endif
#define SSH_ASKPASS_ENV		"SSH_ASKPASS"

/*
 * Force host key length and server key length to differ by at least this
 * many bits.  This is to make double encryption with rsaref work.
 */
#define SSH_KEY_BITS_RESERVED		128

/*
 * Length of the session key in bytes.  (Specified as 256 bits in the
 * protocol.)
 */
#define SSH_SESSION_KEY_LENGTH		32

/* Name of Kerberos service for SSH to use. */
#define KRB4_SERVICE_NAME		"rcmd"

/*
 * Authentication methods.  New types can be added, but old types should not
 * be removed for compatibility.  The maximum allowed value is 31.
 */
#define SSH_AUTH_RHOSTS		1
#define SSH_AUTH_RSA		2
#define SSH_AUTH_PASSWORD	3
#define SSH_AUTH_RHOSTS_RSA	4
#define SSH_AUTH_TIS		5
#define SSH_AUTH_KERBEROS	6
#define SSH_PASS_KERBEROS_TGT	7
				/* 8 to 15 are reserved */
#define SSH_PASS_AFS_TOKEN	21

/* Protocol flags.  These are bit masks. */
#define SSH_PROTOFLAG_SCREEN_NUMBER	1	/* X11 forwarding includes screen */
#define SSH_PROTOFLAG_HOST_IN_FWD_OPEN	2	/* forwarding opens contain host */

/*
 * Definition of message types.  New values can be added, but old values
 * should not be removed or without careful consideration of the consequences
 * for compatibility.  The maximum value is 254; value 255 is reserved for
 * future extension.
 */
/* Message name */			/* msg code */	/* arguments */
#define SSH_MSG_NONE				0	/* no message */
#define SSH_MSG_DISCONNECT			1	/* cause (string) */
#define SSH_SMSG_PUBLIC_KEY			2	/* ck,msk,srvk,hostk */
#define SSH_CMSG_SESSION_KEY			3	/* key (BIGNUM) */
#define SSH_CMSG_USER				4	/* user (string) */
#define SSH_CMSG_AUTH_RHOSTS			5	/* user (string) */
#define SSH_CMSG_AUTH_RSA			6	/* modulus (BIGNUM) */
#define SSH_SMSG_AUTH_RSA_CHALLENGE		7	/* int (BIGNUM) */
#define SSH_CMSG_AUTH_RSA_RESPONSE		8	/* int (BIGNUM) */
#define SSH_CMSG_AUTH_PASSWORD			9	/* pass (string) */
#define SSH_CMSG_REQUEST_PTY		        10	/* TERM, tty modes */
#define SSH_CMSG_WINDOW_SIZE		        11	/* row,col,xpix,ypix */
#define SSH_CMSG_EXEC_SHELL			12	/* */
#define SSH_CMSG_EXEC_CMD			13	/* cmd (string) */
#define SSH_SMSG_SUCCESS			14	/* */
#define SSH_SMSG_FAILURE			15	/* */
#define SSH_CMSG_STDIN_DATA			16	/* data (string) */
#define SSH_SMSG_STDOUT_DATA			17	/* data (string) */
#define SSH_SMSG_STDERR_DATA			18	/* data (string) */
#define SSH_CMSG_EOF				19	/* */
#define SSH_SMSG_EXITSTATUS			20	/* status (int) */
#define SSH_MSG_CHANNEL_OPEN_CONFIRMATION	21	/* channel (int) */
#define SSH_MSG_CHANNEL_OPEN_FAILURE		22	/* channel (int) */
#define SSH_MSG_CHANNEL_DATA			23	/* ch,data (int,str) */
#define SSH_MSG_CHANNEL_CLOSE			24	/* channel (int) */
#define SSH_MSG_CHANNEL_CLOSE_CONFIRMATION	25	/* channel (int) */
/*      SSH_CMSG_X11_REQUEST_FORWARDING         26         OBSOLETE */
#define SSH_SMSG_X11_OPEN			27	/* channel (int) */
#define SSH_CMSG_PORT_FORWARD_REQUEST		28	/* p,host,hp (i,s,i) */
#define SSH_MSG_PORT_OPEN			29	/* ch,h,p (i,s,i) */
#define SSH_CMSG_AGENT_REQUEST_FORWARDING	30	/* */
#define SSH_SMSG_AGENT_OPEN			31	/* port (int) */
#define SSH_MSG_IGNORE				32	/* string */
#define SSH_CMSG_EXIT_CONFIRMATION		33	/* */
#define SSH_CMSG_X11_REQUEST_FORWARDING		34	/* proto,data (s,s) */
#define SSH_CMSG_AUTH_RHOSTS_RSA		35	/* user,mod (s,mpi) */
#define SSH_MSG_DEBUG				36	/* string */
#define SSH_CMSG_REQUEST_COMPRESSION		37	/* level 1-9 (int) */
#define SSH_CMSG_MAX_PACKET_SIZE		38	/* size 4k-1024k (int) */
#define SSH_CMSG_AUTH_TIS			39	/* we use this for s/key */
#define SSH_SMSG_AUTH_TIS_CHALLENGE		40	/* challenge (string) */
#define SSH_CMSG_AUTH_TIS_RESPONSE		41	/* response (string) */
#define SSH_CMSG_AUTH_KERBEROS			42	/* (KTEXT) */
#define SSH_SMSG_AUTH_KERBEROS_RESPONSE		43	/* (KTEXT) */
#define SSH_CMSG_HAVE_KERBEROS_TGT		44	/* credentials (s) */
#define SSH_CMSG_HAVE_AFS_TOKEN			65	/* token (s) */

/*------------ definitions for login.c -------------*/

/*
 * Returns the time when the user last logged in.  Returns 0 if the
 * information is not available.  This must be called before record_login.
 * The host from which the user logged in is stored in buf.
 */
unsigned long 
get_last_login_time(uid_t uid, const char *logname,
    char *buf, unsigned int bufsize);

/*
 * Records that the user has logged in.  This does many things normally done
 * by login(1).
 */
void 
record_login(int pid, const char *ttyname, const char *user, uid_t uid,
    const char *host, struct sockaddr *addr);

/*
 * Records that the user has logged out.  This does many thigs normally done
 * by login(1) or init.
 */
void    record_logout(int pid, const char *ttyname);

/*------------ definitions for sshconnect.c ----------*/

/*
 * Opens a TCP/IP connection to the remote server on the given host.  If port
 * is 0, the default port will be used.  If anonymous is zero, a privileged
 * port will be allocated to make the connection. This requires super-user
 * privileges if anonymous is false. Connection_attempts specifies the
 * maximum number of tries, one per second.  This returns true on success,
 * and zero on failure.  If the connection is successful, this calls
 * packet_set_connection for the connection.
 */
int 
ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
    u_short port, int connection_attempts,
    int anonymous, uid_t original_real_uid,
    const char *proxy_command);

/*
 * Starts a dialog with the server, and authenticates the current user on the
 * server.  This does not need any extra privileges.  The basic connection to
 * the server must already have been established before this is called. If
 * login fails, this function prints an error and never returns. This
 * initializes the random state, and leaves it initialized (it will also have
 * references from the packet module).
 */

void 
ssh_login(int host_key_valid, RSA * host_key, const char *host,
    struct sockaddr * hostaddr, uid_t original_real_uid);

/*------------ Definitions for various authentication methods. -------*/

/*
 * Tries to authenticate the user using the .rhosts file.  Returns true if
 * authentication succeeds.  If ignore_rhosts is non-zero, this will not
 * consider .rhosts and .shosts (/etc/hosts.equiv will still be used).
 */
int     auth_rhosts(struct passwd * pw, const char *client_user);

/*
 * Tries to authenticate the user using the .rhosts file and the host using
 * its host key.  Returns true if authentication succeeds.
 */
int 
auth_rhosts_rsa(struct passwd * pw, const char *client_user,
    BIGNUM * client_host_key_e, BIGNUM * client_host_key_n);

/*
 * Tries to authenticate the user using password.  Returns true if
 * authentication succeeds.
 */
int     auth_password(struct passwd * pw, const char *password);

/*
 * Performs the RSA authentication dialog with the client.  This returns 0 if
 * the client could not be authenticated, and 1 if authentication was
 * successful.  This may exit if there is a serious protocol violation.
 */
int     auth_rsa(struct passwd * pw, BIGNUM * client_n);

/*
 * Parses an RSA key (number of bits, e, n) from a string.  Moves the pointer
 * over the key.  Skips any whitespace at the beginning and at end.
 */
int     auth_rsa_read_key(char **cpp, unsigned int *bitsp, BIGNUM * e, BIGNUM * n);

/*
 * Returns the name of the machine at the other end of the socket.  The
 * returned string should be freed by the caller.
 */
char   *get_remote_hostname(int socket);

/*
 * Return the canonical name of the host in the other side of the current
 * connection (as returned by packet_get_connection).  The host name is
 * cached, so it is efficient to call this several times.
 */
const char *get_canonical_hostname(void);

/*
 * Returns the remote IP address as an ascii string.  The value need not be
 * freed by the caller.
 */
const char *get_remote_ipaddr(void);

/* Returns the port number of the peer of the socket. */
int     get_peer_port(int sock);

/* Returns the port number of the remote/local host. */
int     get_remote_port(void);
int	get_local_port(void);


/*
 * Tries to match the host name (which must be in all lowercase) against the
 * comma-separated sequence of subpatterns (each possibly preceded by ! to
 * indicate negation).  Returns true if there is a positive match; zero
 * otherwise.
 */
int     match_hostname(const char *host, const char *pattern, unsigned int len);

/*
 * Checks whether the given host is already in the list of our known hosts.
 * Returns HOST_OK if the host is known and has the specified key, HOST_NEW
 * if the host is not known, and HOST_CHANGED if the host is known but used
 * to have a different host key.  The host must be in all lowercase.
 */
typedef enum {
	HOST_OK, HOST_NEW, HOST_CHANGED
}       HostStatus;
HostStatus 
check_host_in_hostfile(const char *filename, const char *host,
    BIGNUM * e, BIGNUM * n, BIGNUM * ke, BIGNUM * kn);

/*
 * Appends an entry to the host file.  Returns false if the entry could not
 * be appended.
 */
int 
add_host_to_hostfile(const char *filename, const char *host,
    BIGNUM * e, BIGNUM * n);

/*
 * Performs the RSA authentication challenge-response dialog with the client,
 * and returns true (non-zero) if the client gave the correct answer to our
 * challenge; returns zero if the client gives a wrong answer.
 */
int     auth_rsa_challenge_dialog(BIGNUM * e, BIGNUM * n);

/*
 * Reads a passphrase from /dev/tty with echo turned off.  Returns the
 * passphrase (allocated with xmalloc).  Exits if EOF is encountered. If
 * from_stdin is true, the passphrase will be read from stdin instead.
 */
char   *read_passphrase(const char *prompt, int from_stdin);

/*
 * Saves the authentication (private) key in a file, encrypting it with
 * passphrase.  The identification of the file (lowest 64 bits of n) will
 * precede the key to provide identification of the key without needing a
 * passphrase.
 */
int 
save_private_key(const char *filename, const char *passphrase,
    RSA * private_key, const char *comment);

/*
 * Loads the public part of the key file (public key and comment). Returns 0
 * if an error occurred; zero if the public key was successfully read.  The
 * comment of the key is returned in comment_return if it is non-NULL; the
 * caller must free the value with xfree.
 */
int 
load_public_key(const char *filename, RSA * pub,
    char **comment_return);

/*
 * Loads the private key from the file.  Returns 0 if an error is encountered
 * (file does not exist or is not readable, or passphrase is bad). This
 * initializes the private key.  The comment of the key is returned in
 * comment_return if it is non-NULL; the caller must free the value with
 * xfree.
 */
int 
load_private_key(const char *filename, const char *passphrase,
    RSA * private_key, char **comment_return);

/*------------ Definitions for logging. -----------------------*/

/* Supported syslog facilities and levels. */
typedef enum {
	SYSLOG_FACILITY_DAEMON,
	SYSLOG_FACILITY_USER,
	SYSLOG_FACILITY_AUTH,
	SYSLOG_FACILITY_LOCAL0,
	SYSLOG_FACILITY_LOCAL1,
	SYSLOG_FACILITY_LOCAL2,
	SYSLOG_FACILITY_LOCAL3,
	SYSLOG_FACILITY_LOCAL4,
	SYSLOG_FACILITY_LOCAL5,
	SYSLOG_FACILITY_LOCAL6,
	SYSLOG_FACILITY_LOCAL7
}       SyslogFacility;

typedef enum {
	SYSLOG_LEVEL_QUIET,
	SYSLOG_LEVEL_FATAL,
	SYSLOG_LEVEL_ERROR,
	SYSLOG_LEVEL_INFO,
	SYSLOG_LEVEL_VERBOSE,
	SYSLOG_LEVEL_DEBUG
}       LogLevel;
/* Initializes logging. */
void    log_init(char *av0, LogLevel level, SyslogFacility facility, int on_stderr);

/* Logging implementation, depending on server or client */
void    do_log(LogLevel level, const char *fmt, va_list args);

/* name to facility/level */
SyslogFacility log_facility_number(char *name);
LogLevel log_level_number(char *name);

/* Output a message to syslog or stderr */
void    fatal(const char *fmt,...) __attribute__((format(printf, 1, 2)));
void    error(const char *fmt,...) __attribute__((format(printf, 1, 2)));
void    log(const char *fmt,...) __attribute__((format(printf, 1, 2)));
void    verbose(const char *fmt,...) __attribute__((format(printf, 1, 2)));
void    debug(const char *fmt,...) __attribute__((format(printf, 1, 2)));

/* same as fatal() but w/o logging */
void    fatal_cleanup(void);

/*
 * Registers a cleanup function to be called by fatal()/fatal_cleanup()
 * before exiting. It is permissible to call fatal_remove_cleanup for the
 * function itself from the function.
 */
void    fatal_add_cleanup(void (*proc) (void *context), void *context);

/* Removes a cleanup function to be called at fatal(). */
void    fatal_remove_cleanup(void (*proc) (void *context), void *context);

/*---------------- definitions for channels ------------------*/

/* Sets specific protocol options. */
void    channel_set_options(int hostname_in_open);

/*
 * Allocate a new channel object and set its type and socket.  Remote_name
 * must have been allocated with xmalloc; this will free it when the channel
 * is freed.
 */
int     channel_allocate(int type, int sock, char *remote_name);

/* Free the channel and close its socket. */
void    channel_free(int channel);

/* Add any bits relevant to channels in select bitmasks. */
void    channel_prepare_select(fd_set * readset, fd_set * writeset);

/*
 * After select, perform any appropriate operations for channels which have
 * events pending.
 */
void    channel_after_select(fd_set * readset, fd_set * writeset);

/* If there is data to send to the connection, send some of it now. */
void    channel_output_poll(void);

/*
 * This is called when a packet of type CHANNEL_DATA has just been received.
 * The message type has already been consumed, but channel number and data is
 * still there.
 */
void    channel_input_data(int payload_len);

/* Returns true if no channel has too much buffered data. */
int     channel_not_very_much_buffered_data(void);

/* This is called after receiving CHANNEL_CLOSE. */
void    channel_input_close(void);

/* This is called after receiving CHANNEL_CLOSE_CONFIRMATION. */
void    channel_input_close_confirmation(void);

/* This is called after receiving CHANNEL_OPEN_CONFIRMATION. */
void    channel_input_open_confirmation(void);

/* This is called after receiving CHANNEL_OPEN_FAILURE from the other side. */
void    channel_input_open_failure(void);

/* This closes any sockets that are listening for connections; this removes
   any unix domain sockets. */
void    channel_stop_listening(void);

/*
 * Closes the sockets of all channels.  This is used to close extra file
 * descriptors after a fork.
 */
void    channel_close_all(void);

/* Returns the maximum file descriptor number used by the channels. */
int     channel_max_fd(void);

/* Returns true if there is still an open channel over the connection. */
int     channel_still_open(void);

/*
 * Returns a string containing a list of all open channels.  The list is
 * suitable for displaying to the user.  It uses crlf instead of newlines.
 * The caller should free the string with xfree.
 */
char   *channel_open_message(void);

/*
 * Initiate forwarding of connections to local port "port" through the secure
 * channel to host:port from remote side.  This never returns if there was an
 * error.
 */
void 
channel_request_local_forwarding(u_short port, const char *host,
    u_short remote_port, int gateway_ports);

/*
 * Initiate forwarding of connections to port "port" on remote host through
 * the secure channel to host:port from local side.  This never returns if
 * there was an error.  This registers that open requests for that port are
 * permitted.
 */
void 
channel_request_remote_forwarding(u_short port, const char *host,
    u_short remote_port);

/*
 * Permits opening to any host/port in SSH_MSG_PORT_OPEN.  This is usually
 * called by the server, because the user could connect to any port anyway,
 * and the server has no way to know but to trust the client anyway.
 */
void    channel_permit_all_opens(void);

/*
 * This is called after receiving CHANNEL_FORWARDING_REQUEST.  This initates
 * listening for the port, and sends back a success reply (or disconnect
 * message if there was an error).  This never returns if there was an error.
 */
void    channel_input_port_forward_request(int is_root);

/*
 * This is called after receiving PORT_OPEN message.  This attempts to
 * connect to the given host:port, and sends back CHANNEL_OPEN_CONFIRMATION
 * or CHANNEL_OPEN_FAILURE.
 */
void    channel_input_port_open(int payload_len);

/*
 * Creates a port for X11 connections, and starts listening for it. Returns
 * the display name, or NULL if an error was encountered.
 */
char   *x11_create_display(int screen);

/*
 * Creates an internet domain socket for listening for X11 connections.
 * Returns a suitable value for the DISPLAY variable, or NULL if an error
 * occurs.
 */
char   *x11_create_display_inet(int screen, int x11_display_offset);

/*
 * This is called when SSH_SMSG_X11_OPEN is received.  The packet contains
 * the remote channel number.  We should do whatever we want, and respond
 * with either SSH_MSG_OPEN_CONFIRMATION or SSH_MSG_OPEN_FAILURE.
 */
void    x11_input_open(int payload_len);

/*
 * Requests forwarding of X11 connections.  This should be called on the
 * client only.
 */
void    x11_request_forwarding(void);

/*
 * Requests forwarding for X11 connections, with authentication spoofing.
 * This should be called in the client only.
 */
void    x11_request_forwarding_with_spoofing(const char *proto, const char *data);

/* Sends a message to the server to request authentication fd forwarding. */
void    auth_request_forwarding(void);

/*
 * Returns the name of the forwarded authentication socket.  Returns NULL if
 * there is no forwarded authentication socket.  The returned value points to
 * a static buffer.
 */
char   *auth_get_socket_name(void);

/*
 * This if called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
 * This starts forwarding authentication requests.
 */
void    auth_input_request_forwarding(struct passwd * pw);

/* This is called to process an SSH_SMSG_AGENT_OPEN message. */
void    auth_input_open_request(void);

/*
 * Returns true if the given string matches the pattern (which may contain ?
 * and * as wildcards), and zero if it does not match.
 */
int     match_pattern(const char *s, const char *pattern);

/*
 * Expands tildes in the file name.  Returns data allocated by xmalloc.
 * Warning: this calls getpw*.
 */
char   *tilde_expand_filename(const char *filename, uid_t my_uid);

/*
 * Performs the interactive session.  This handles data transmission between
 * the client and the program.  Note that the notion of stdin, stdout, and
 * stderr in this function is sort of reversed: this function writes to stdin
 * (of the child program), and reads from stdout and stderr (of the child
 * program).
 */
void    server_loop(int pid, int fdin, int fdout, int fderr);

/* Client side main loop for the interactive session. */
int     client_loop(int have_pty, int escape_char);

/* Linked list of custom environment strings (see auth-rsa.c). */
struct envstring {
	struct envstring *next;
	char   *s;
};

/*
 * Ensure all of data on socket comes through. f==read || f==write
 */
int	atomicio(int (*f)(), int fd, void *s, size_t n);

#ifdef KRB4
#include <krb.h>
/*
 * Performs Kerberos v4 mutual authentication with the client. This returns 0
 * if the client could not be authenticated, and 1 if authentication was
 * successful.  This may exit if there is a serious protocol violation.
 */
int     auth_krb4(const char *server_user, KTEXT auth, char **client);
int     krb4_init(uid_t uid);
void    krb4_cleanup_proc(void *ignore);
int	auth_krb4_password(struct passwd * pw, const char *password);

#ifdef AFS
#include <kafs.h>

/* Accept passed Kerberos v4 ticket-granting ticket and AFS tokens. */
int     auth_kerberos_tgt(struct passwd * pw, const char *string);
int     auth_afs_token(struct passwd * pw, const char *token_string);

int     creds_to_radix(CREDENTIALS * creds, unsigned char *buf);
int     radix_to_creds(const char *buf, CREDENTIALS * creds);
#endif				/* AFS */

#endif				/* KRB4 */

#ifdef SKEY
#include <skey.h>
char   *skey_fake_keyinfo(char *username);
int	auth_skey_password(struct passwd * pw, const char *password);
#endif				/* SKEY */

/* AF_UNSPEC or AF_INET or AF_INET6 */
extern int IPv4or6;

#ifdef USE_PAM
#include "auth-pam.h"
#endif /* USE_PAM */

#endif				/* SSH_H */