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ssh.c
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ssh.c
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/*
* SSH backend.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <assert.h>
#include <limits.h>
#include <signal.h>
#include "putty.h"
#include "pageant.h" /* for AGENT_MAX_MSGLEN */
#include "tree234.h"
#include "storage.h"
#include "marshal.h"
#include "ssh.h"
#ifndef NO_GSSAPI
#include "sshgssc.h"
#include "sshgss.h"
#define MIN_CTXT_LIFETIME 5 /* Avoid rekey with short lifetime (seconds) */
#define GSS_KEX_CAPABLE (1<<0) /* Can do GSS KEX */
#define GSS_CRED_UPDATED (1<<1) /* Cred updated since previous delegation */
#define GSS_CTXT_EXPIRES (1<<2) /* Context expires before next timer */
#define GSS_CTXT_MAYFAIL (1<<3) /* Context may expire during handshake */
#endif
/*
* Packet type contexts, so that ssh2_pkt_type can correctly decode
* the ambiguous type numbers back into the correct type strings.
*/
typedef enum {
SSH2_PKTCTX_NOKEX,
SSH2_PKTCTX_DHGROUP,
SSH2_PKTCTX_DHGEX,
SSH2_PKTCTX_ECDHKEX,
SSH2_PKTCTX_GSSKEX,
SSH2_PKTCTX_RSAKEX
} Pkt_KCtx;
typedef enum {
SSH2_PKTCTX_NOAUTH,
SSH2_PKTCTX_PUBLICKEY,
SSH2_PKTCTX_PASSWORD,
SSH2_PKTCTX_GSSAPI,
SSH2_PKTCTX_KBDINTER
} Pkt_ACtx;
static const char *const ssh2_disconnect_reasons[] = {
NULL,
"host not allowed to connect",
"protocol error",
"key exchange failed",
"host authentication failed",
"MAC error",
"compression error",
"service not available",
"protocol version not supported",
"host key not verifiable",
"connection lost",
"by application",
"too many connections",
"auth cancelled by user",
"no more auth methods available",
"illegal user name",
};
/*
* Various remote-bug flags.
*/
#define BUG_CHOKES_ON_SSH1_IGNORE 1
#define BUG_SSH2_HMAC 2
#define BUG_NEEDS_SSH1_PLAIN_PASSWORD 4
#define BUG_CHOKES_ON_RSA 8
#define BUG_SSH2_RSA_PADDING 16
#define BUG_SSH2_DERIVEKEY 32
#define BUG_SSH2_REKEY 64
#define BUG_SSH2_PK_SESSIONID 128
#define BUG_SSH2_MAXPKT 256
#define BUG_CHOKES_ON_SSH2_IGNORE 512
#define BUG_CHOKES_ON_WINADJ 1024
#define BUG_SENDS_LATE_REQUEST_REPLY 2048
#define BUG_SSH2_OLDGEX 4096
#define DH_MIN_SIZE 1024
#define DH_MAX_SIZE 8192
/*
* Codes for terminal modes.
* Most of these are the same in SSH-1 and SSH-2.
* This list is derived from RFC 4254 and
* SSH-1 RFC-1.2.31.
*/
static const struct ssh_ttymode {
const char* const mode;
int opcode;
enum { TTY_OP_CHAR, TTY_OP_BOOL } type;
} ssh_ttymodes[] = {
/* "V" prefix discarded for special characters relative to SSH specs */
{ "INTR", 1, TTY_OP_CHAR },
{ "QUIT", 2, TTY_OP_CHAR },
{ "ERASE", 3, TTY_OP_CHAR },
{ "KILL", 4, TTY_OP_CHAR },
{ "EOF", 5, TTY_OP_CHAR },
{ "EOL", 6, TTY_OP_CHAR },
{ "EOL2", 7, TTY_OP_CHAR },
{ "START", 8, TTY_OP_CHAR },
{ "STOP", 9, TTY_OP_CHAR },
{ "SUSP", 10, TTY_OP_CHAR },
{ "DSUSP", 11, TTY_OP_CHAR },
{ "REPRINT", 12, TTY_OP_CHAR },
{ "WERASE", 13, TTY_OP_CHAR },
{ "LNEXT", 14, TTY_OP_CHAR },
{ "FLUSH", 15, TTY_OP_CHAR },
{ "SWTCH", 16, TTY_OP_CHAR },
{ "STATUS", 17, TTY_OP_CHAR },
{ "DISCARD", 18, TTY_OP_CHAR },
{ "IGNPAR", 30, TTY_OP_BOOL },
{ "PARMRK", 31, TTY_OP_BOOL },
{ "INPCK", 32, TTY_OP_BOOL },
{ "ISTRIP", 33, TTY_OP_BOOL },
{ "INLCR", 34, TTY_OP_BOOL },
{ "IGNCR", 35, TTY_OP_BOOL },
{ "ICRNL", 36, TTY_OP_BOOL },
{ "IUCLC", 37, TTY_OP_BOOL },
{ "IXON", 38, TTY_OP_BOOL },
{ "IXANY", 39, TTY_OP_BOOL },
{ "IXOFF", 40, TTY_OP_BOOL },
{ "IMAXBEL", 41, TTY_OP_BOOL },
{ "IUTF8", 42, TTY_OP_BOOL },
{ "ISIG", 50, TTY_OP_BOOL },
{ "ICANON", 51, TTY_OP_BOOL },
{ "XCASE", 52, TTY_OP_BOOL },
{ "ECHO", 53, TTY_OP_BOOL },
{ "ECHOE", 54, TTY_OP_BOOL },
{ "ECHOK", 55, TTY_OP_BOOL },
{ "ECHONL", 56, TTY_OP_BOOL },
{ "NOFLSH", 57, TTY_OP_BOOL },
{ "TOSTOP", 58, TTY_OP_BOOL },
{ "IEXTEN", 59, TTY_OP_BOOL },
{ "ECHOCTL", 60, TTY_OP_BOOL },
{ "ECHOKE", 61, TTY_OP_BOOL },
{ "PENDIN", 62, TTY_OP_BOOL }, /* XXX is this a real mode? */
{ "OPOST", 70, TTY_OP_BOOL },
{ "OLCUC", 71, TTY_OP_BOOL },
{ "ONLCR", 72, TTY_OP_BOOL },
{ "OCRNL", 73, TTY_OP_BOOL },
{ "ONOCR", 74, TTY_OP_BOOL },
{ "ONLRET", 75, TTY_OP_BOOL },
{ "CS7", 90, TTY_OP_BOOL },
{ "CS8", 91, TTY_OP_BOOL },
{ "PARENB", 92, TTY_OP_BOOL },
{ "PARODD", 93, TTY_OP_BOOL }
};
/* Miscellaneous other tty-related constants. */
#define SSH_TTY_OP_END 0
/* The opcodes for ISPEED/OSPEED differ between SSH-1 and SSH-2. */
#define SSH1_TTY_OP_ISPEED 192
#define SSH1_TTY_OP_OSPEED 193
#define SSH2_TTY_OP_ISPEED 128
#define SSH2_TTY_OP_OSPEED 129
/* Helper functions for parsing tty-related config. */
static unsigned int ssh_tty_parse_specchar(char *s)
{
unsigned int ret;
if (*s) {
char *next = NULL;
ret = ctrlparse(s, &next);
if (!next) ret = s[0];
} else {
ret = 255; /* special value meaning "don't set" */
}
return ret;
}
static unsigned int ssh_tty_parse_boolean(char *s)
{
if (stricmp(s, "yes") == 0 ||
stricmp(s, "on") == 0 ||
stricmp(s, "true") == 0 ||
stricmp(s, "+") == 0)
return 1; /* true */
else if (stricmp(s, "no") == 0 ||
stricmp(s, "off") == 0 ||
stricmp(s, "false") == 0 ||
stricmp(s, "-") == 0)
return 0; /* false */
else
return (atoi(s) != 0);
}
/* Safely convert rekey_time to unsigned long minutes */
static unsigned long rekey_mins(int rekey_time, unsigned long def)
{
if (rekey_time < 0 || rekey_time > MAX_TICK_MINS)
rekey_time = def;
return (unsigned long)rekey_time;
}
#define translate(x) if (type == x) return #x
#define translatek(x,ctx) if (type == x && (pkt_kctx == ctx)) return #x
#define translatea(x,ctx) if (type == x && (pkt_actx == ctx)) return #x
static const char *ssh1_pkt_type(int type)
{
translate(SSH1_MSG_DISCONNECT);
translate(SSH1_SMSG_PUBLIC_KEY);
translate(SSH1_CMSG_SESSION_KEY);
translate(SSH1_CMSG_USER);
translate(SSH1_CMSG_AUTH_RSA);
translate(SSH1_SMSG_AUTH_RSA_CHALLENGE);
translate(SSH1_CMSG_AUTH_RSA_RESPONSE);
translate(SSH1_CMSG_AUTH_PASSWORD);
translate(SSH1_CMSG_REQUEST_PTY);
translate(SSH1_CMSG_WINDOW_SIZE);
translate(SSH1_CMSG_EXEC_SHELL);
translate(SSH1_CMSG_EXEC_CMD);
translate(SSH1_SMSG_SUCCESS);
translate(SSH1_SMSG_FAILURE);
translate(SSH1_CMSG_STDIN_DATA);
translate(SSH1_SMSG_STDOUT_DATA);
translate(SSH1_SMSG_STDERR_DATA);
translate(SSH1_CMSG_EOF);
translate(SSH1_SMSG_EXIT_STATUS);
translate(SSH1_MSG_CHANNEL_OPEN_CONFIRMATION);
translate(SSH1_MSG_CHANNEL_OPEN_FAILURE);
translate(SSH1_MSG_CHANNEL_DATA);
translate(SSH1_MSG_CHANNEL_CLOSE);
translate(SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION);
translate(SSH1_SMSG_X11_OPEN);
translate(SSH1_CMSG_PORT_FORWARD_REQUEST);
translate(SSH1_MSG_PORT_OPEN);
translate(SSH1_CMSG_AGENT_REQUEST_FORWARDING);
translate(SSH1_SMSG_AGENT_OPEN);
translate(SSH1_MSG_IGNORE);
translate(SSH1_CMSG_EXIT_CONFIRMATION);
translate(SSH1_CMSG_X11_REQUEST_FORWARDING);
translate(SSH1_CMSG_AUTH_RHOSTS_RSA);
translate(SSH1_MSG_DEBUG);
translate(SSH1_CMSG_REQUEST_COMPRESSION);
translate(SSH1_CMSG_AUTH_TIS);
translate(SSH1_SMSG_AUTH_TIS_CHALLENGE);
translate(SSH1_CMSG_AUTH_TIS_RESPONSE);
translate(SSH1_CMSG_AUTH_CCARD);
translate(SSH1_SMSG_AUTH_CCARD_CHALLENGE);
translate(SSH1_CMSG_AUTH_CCARD_RESPONSE);
return "unknown";
}
static const char *ssh2_pkt_type(Pkt_KCtx pkt_kctx, Pkt_ACtx pkt_actx,
int type)
{
translatea(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE,SSH2_PKTCTX_GSSAPI);
translatea(SSH2_MSG_USERAUTH_GSSAPI_TOKEN,SSH2_PKTCTX_GSSAPI);
translatea(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,SSH2_PKTCTX_GSSAPI);
translatea(SSH2_MSG_USERAUTH_GSSAPI_ERROR,SSH2_PKTCTX_GSSAPI);
translatea(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK,SSH2_PKTCTX_GSSAPI);
translatea(SSH2_MSG_USERAUTH_GSSAPI_MIC, SSH2_PKTCTX_GSSAPI);
translate(SSH2_MSG_DISCONNECT);
translate(SSH2_MSG_IGNORE);
translate(SSH2_MSG_UNIMPLEMENTED);
translate(SSH2_MSG_DEBUG);
translate(SSH2_MSG_SERVICE_REQUEST);
translate(SSH2_MSG_SERVICE_ACCEPT);
translate(SSH2_MSG_KEXINIT);
translate(SSH2_MSG_NEWKEYS);
translatek(SSH2_MSG_KEXDH_INIT, SSH2_PKTCTX_DHGROUP);
translatek(SSH2_MSG_KEXDH_REPLY, SSH2_PKTCTX_DHGROUP);
translatek(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD, SSH2_PKTCTX_DHGEX);
translatek(SSH2_MSG_KEX_DH_GEX_REQUEST, SSH2_PKTCTX_DHGEX);
translatek(SSH2_MSG_KEX_DH_GEX_GROUP, SSH2_PKTCTX_DHGEX);
translatek(SSH2_MSG_KEX_DH_GEX_INIT, SSH2_PKTCTX_DHGEX);
translatek(SSH2_MSG_KEX_DH_GEX_REPLY, SSH2_PKTCTX_DHGEX);
translatek(SSH2_MSG_KEXRSA_PUBKEY, SSH2_PKTCTX_RSAKEX);
translatek(SSH2_MSG_KEXRSA_SECRET, SSH2_PKTCTX_RSAKEX);
translatek(SSH2_MSG_KEXRSA_DONE, SSH2_PKTCTX_RSAKEX);
translatek(SSH2_MSG_KEX_ECDH_INIT, SSH2_PKTCTX_ECDHKEX);
translatek(SSH2_MSG_KEX_ECDH_REPLY, SSH2_PKTCTX_ECDHKEX);
translatek(SSH2_MSG_KEXGSS_INIT, SSH2_PKTCTX_GSSKEX);
translatek(SSH2_MSG_KEXGSS_CONTINUE, SSH2_PKTCTX_GSSKEX);
translatek(SSH2_MSG_KEXGSS_COMPLETE, SSH2_PKTCTX_GSSKEX);
translatek(SSH2_MSG_KEXGSS_HOSTKEY, SSH2_PKTCTX_GSSKEX);
translatek(SSH2_MSG_KEXGSS_ERROR, SSH2_PKTCTX_GSSKEX);
translatek(SSH2_MSG_KEXGSS_GROUPREQ, SSH2_PKTCTX_GSSKEX);
translatek(SSH2_MSG_KEXGSS_GROUP, SSH2_PKTCTX_GSSKEX);
translate(SSH2_MSG_USERAUTH_REQUEST);
translate(SSH2_MSG_USERAUTH_FAILURE);
translate(SSH2_MSG_USERAUTH_SUCCESS);
translate(SSH2_MSG_USERAUTH_BANNER);
translatea(SSH2_MSG_USERAUTH_PK_OK, SSH2_PKTCTX_PUBLICKEY);
translatea(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ, SSH2_PKTCTX_PASSWORD);
translatea(SSH2_MSG_USERAUTH_INFO_REQUEST, SSH2_PKTCTX_KBDINTER);
translatea(SSH2_MSG_USERAUTH_INFO_RESPONSE, SSH2_PKTCTX_KBDINTER);
translate(SSH2_MSG_GLOBAL_REQUEST);
translate(SSH2_MSG_REQUEST_SUCCESS);
translate(SSH2_MSG_REQUEST_FAILURE);
translate(SSH2_MSG_CHANNEL_OPEN);
translate(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
translate(SSH2_MSG_CHANNEL_OPEN_FAILURE);
translate(SSH2_MSG_CHANNEL_WINDOW_ADJUST);
translate(SSH2_MSG_CHANNEL_DATA);
translate(SSH2_MSG_CHANNEL_EXTENDED_DATA);
translate(SSH2_MSG_CHANNEL_EOF);
translate(SSH2_MSG_CHANNEL_CLOSE);
translate(SSH2_MSG_CHANNEL_REQUEST);
translate(SSH2_MSG_CHANNEL_SUCCESS);
translate(SSH2_MSG_CHANNEL_FAILURE);
return "unknown";
}
#undef translate
#undef translatec
/* Enumeration values for fields in SSH-1 packets */
enum {
PKT_END, PKT_INT, PKT_CHAR, PKT_DATA, PKT_STR, PKT_BIGNUM,
};
/*
* Coroutine mechanics for the sillier bits of the code. If these
* macros look impenetrable to you, you might find it helpful to
* read
*
* https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html
*
* which explains the theory behind these macros.
*
* In particular, if you are getting `case expression not constant'
* errors when building with MS Visual Studio, this is because MS's
* Edit and Continue debugging feature causes their compiler to
* violate ANSI C. To disable Edit and Continue debugging:
*
* - right-click ssh.c in the FileView
* - click Settings
* - select the C/C++ tab and the General category
* - under `Debug info:', select anything _other_ than `Program
* Database for Edit and Continue'.
*/
#define crBegin(v) { int *crLine = &v; switch(v) { case 0:;
#define crBeginState crBegin(s->crLine)
#define crStateP(t, v) \
struct t *s; \
if (!(v)) { s = (v) = snew(struct t); s->crLine = 0; } \
s = (v);
#define crState(t) crStateP(t, ssh->t)
#define crFinish(z) } *crLine = 0; return (z); }
#define crFinishV } *crLine = 0; return; }
#define crFinishFree(z) } sfree(s); return (z); }
#define crFinishFreeV } sfree(s); return; }
#define crReturn(z) \
do {\
*crLine =__LINE__; return (z); case __LINE__:;\
} while (0)
#define crReturnV \
do {\
*crLine=__LINE__; return; case __LINE__:;\
} while (0)
#define crStop(z) do{ *crLine = 0; return (z); }while(0)
#define crStopV do{ *crLine = 0; return; }while(0)
#define crWaitUntil(c) do { crReturn(0); } while (!(c))
#define crWaitUntilV(c) do { crReturnV; } while (!(c))
#define crMaybeWaitUntil(c) do { while (!(c)) crReturn(0); } while (0)
#define crMaybeWaitUntilV(c) do { while (!(c)) crReturnV; } while (0)
typedef struct PktIn PktIn;
typedef struct PktOut PktOut;
static struct PktOut *ssh1_pkt_init(int pkt_type);
static struct PktOut *ssh2_pkt_init(int pkt_type);
static void ssh_pkt_ensure(struct PktOut *, int length);
static void ssh_pkt_adddata(struct PktOut *, const void *data, int len);
static ptrlen ssh2_pkt_construct(Ssh, struct PktOut *);
static void ssh2_pkt_send(Ssh, struct PktOut *);
static void ssh2_pkt_send_noqueue(Ssh, struct PktOut *);
static void do_ssh1_login(void *vctx);
static void do_ssh2_userauth(void *vctx);
static void ssh2_connection_setup(Ssh ssh);
static void do_ssh2_connection(void *vctx);
static void ssh_channel_init(struct ssh_channel *c);
static struct ssh_channel *ssh_channel_msg(Ssh ssh, PktIn *pktin);
static void ssh_channel_got_eof(struct ssh_channel *c);
static void ssh2_channel_check_close(struct ssh_channel *c);
static void ssh_channel_close_local(struct ssh_channel *c, char const *reason);
static void ssh_channel_destroy(struct ssh_channel *c);
static void ssh_channel_unthrottle(struct ssh_channel *c, int bufsize);
static void ssh2_msg_something_unimplemented(Ssh ssh, PktIn *pktin);
static void ssh2_general_packet_processing(Ssh ssh, PktIn *pktin);
static void ssh1_login_input(Ssh ssh);
static void ssh2_userauth_input(Ssh ssh);
static void ssh2_connection_input(Ssh ssh);
/*
* Buffer management constants. There are several of these for
* various different purposes:
*
* - SSH1_BUFFER_LIMIT is the amount of backlog that must build up
* on a local data stream before we throttle the whole SSH
* connection (in SSH-1 only). Throttling the whole connection is
* pretty drastic so we set this high in the hope it won't
* happen very often.
*
* - SSH_MAX_BACKLOG is the amount of backlog that must build up
* on the SSH connection itself before we defensively throttle
* _all_ local data streams. This is pretty drastic too (though
* thankfully unlikely in SSH-2 since the window mechanism should
* ensure that the server never has any need to throttle its end
* of the connection), so we set this high as well.
*
* - OUR_V2_WINSIZE is the default window size we present on SSH-2
* channels.
*
* - OUR_V2_BIGWIN is the window size we advertise for the only
* channel in a simple connection. It must be <= INT_MAX.
*
* - OUR_V2_MAXPKT is the official "maximum packet size" we send
* to the remote side. This actually has nothing to do with the
* size of the _packet_, but is instead a limit on the amount
* of data we're willing to receive in a single SSH2 channel
* data message.
*
* - OUR_V2_PACKETLIMIT is actually the maximum size of SSH
* _packet_ we're prepared to cope with. It must be a multiple
* of the cipher block size, and must be at least 35000.
*/
#define SSH1_BUFFER_LIMIT 32768
#define SSH_MAX_BACKLOG 32768
#define OUR_V2_WINSIZE 16384
#define OUR_V2_BIGWIN 0x7fffffff
#define OUR_V2_MAXPKT 0x4000UL
#define OUR_V2_PACKETLIMIT 0x9000UL
struct ssh_signkey_with_user_pref_id {
const ssh_keyalg *alg;
int id;
};
const static struct ssh_signkey_with_user_pref_id hostkey_algs[] = {
{ &ssh_ecdsa_ed25519, HK_ED25519 },
{ &ssh_ecdsa_nistp256, HK_ECDSA },
{ &ssh_ecdsa_nistp384, HK_ECDSA },
{ &ssh_ecdsa_nistp521, HK_ECDSA },
{ &ssh_dss, HK_DSA },
{ &ssh_rsa, HK_RSA },
};
const static struct ssh_mac *const macs[] = {
&ssh_hmac_sha256, &ssh_hmac_sha1, &ssh_hmac_sha1_96, &ssh_hmac_md5
};
const static struct ssh_mac *const buggymacs[] = {
&ssh_hmac_sha1_buggy, &ssh_hmac_sha1_96_buggy, &ssh_hmac_md5
};
static void *ssh_comp_none_init(void)
{
return NULL;
}
static void ssh_comp_none_cleanup(void *handle)
{
}
static int ssh_comp_none_block(void *handle, unsigned char *block, int len,
unsigned char **outblock, int *outlen)
{
return 0;
}
static int ssh_comp_none_disable(void *handle)
{
return 0;
}
const static struct ssh_compress ssh_comp_none = {
"none", NULL,
ssh_comp_none_init, ssh_comp_none_cleanup, ssh_comp_none_block,
ssh_comp_none_init, ssh_comp_none_cleanup, ssh_comp_none_block,
ssh_comp_none_disable, NULL
};
extern const struct ssh_compress ssh_zlib;
const static struct ssh_compress *const compressions[] = {
&ssh_zlib, &ssh_comp_none
};
enum { /* channel types */
CHAN_MAINSESSION,
CHAN_X11,
CHAN_AGENT,
CHAN_SOCKDATA,
/*
* CHAN_SHARING indicates a channel which is tracked here on
* behalf of a connection-sharing downstream. We do almost nothing
* with these channels ourselves: all messages relating to them
* get thrown straight to sshshare.c and passed on almost
* unmodified to downstream.
*/
CHAN_SHARING,
/*
* CHAN_ZOMBIE is used to indicate a channel for which we've
* already destroyed the local data source: for instance, if a
* forwarded port experiences a socket error on the local side, we
* immediately destroy its local socket and turn the SSH channel
* into CHAN_ZOMBIE.
*/
CHAN_ZOMBIE
};
typedef void (*handler_fn_t)(Ssh ssh, PktIn *pktin);
typedef void (*chandler_fn_t)(Ssh ssh, PktIn *pktin, void *ctx);
typedef void (*cchandler_fn_t)(struct ssh_channel *, PktIn *, void *);
/*
* Each channel has a queue of outstanding CHANNEL_REQUESTS and their
* handlers.
*/
struct outstanding_channel_request {
cchandler_fn_t handler;
void *ctx;
struct outstanding_channel_request *next;
};
/*
* 2-3-4 tree storing channels.
*/
struct ssh_channel {
Ssh ssh; /* pointer back to main context */
unsigned remoteid, localid;
int type;
/* True if we opened this channel but server hasn't confirmed. */
int halfopen;
/*
* In SSH-1, this value contains four bits:
*
* 1 We have sent SSH1_MSG_CHANNEL_CLOSE.
* 2 We have sent SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION.
* 4 We have received SSH1_MSG_CHANNEL_CLOSE.
* 8 We have received SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION.
*
* A channel is completely finished with when all four bits are set.
*
* In SSH-2, the four bits mean:
*
* 1 We have sent SSH2_MSG_CHANNEL_EOF.
* 2 We have sent SSH2_MSG_CHANNEL_CLOSE.
* 4 We have received SSH2_MSG_CHANNEL_EOF.
* 8 We have received SSH2_MSG_CHANNEL_CLOSE.
*
* A channel is completely finished with when we have both sent
* and received CLOSE.
*
* The symbolic constants below use the SSH-2 terminology, which
* is a bit confusing in SSH-1, but we have to use _something_.
*/
#define CLOSES_SENT_EOF 1
#define CLOSES_SENT_CLOSE 2
#define CLOSES_RCVD_EOF 4
#define CLOSES_RCVD_CLOSE 8
int closes;
/*
* This flag indicates that an EOF is pending on the outgoing side
* of the channel: that is, wherever we're getting the data for
* this channel has sent us some data followed by EOF. We can't
* actually send the EOF until we've finished sending the data, so
* we set this flag instead to remind us to do so once our buffer
* is clear.
*/
int pending_eof;
/*
* True if this channel is causing the underlying connection to be
* throttled.
*/
int throttling_conn;
union {
struct ssh2_data_channel {
bufchain outbuffer;
unsigned remwindow, remmaxpkt;
/* locwindow is signed so we can cope with excess data. */
int locwindow, locmaxwin;
/*
* remlocwin is the amount of local window that we think
* the remote end had available to it after it sent the
* last data packet or window adjust ack.
*/
int remlocwin;
/*
* These store the list of channel requests that haven't
* been acked.
*/
struct outstanding_channel_request *chanreq_head, *chanreq_tail;
enum { THROTTLED, UNTHROTTLING, UNTHROTTLED } throttle_state;
} v2;
} v;
union {
struct ssh_agent_channel {
bufchain inbuffer;
agent_pending_query *pending;
} a;
struct ssh_x11_channel {
struct X11Connection *xconn;
int initial;
} x11;
struct ssh_pfd_channel {
struct PortForwarding *pf;
} pfd;
struct ssh_sharing_channel {
void *ctx;
} sharing;
} u;
};
/*
* 2-3-4 tree storing remote->local port forwardings. SSH-1 and SSH-2
* use this structure in different ways, reflecting SSH-2's
* altogether saner approach to port forwarding.
*
* In SSH-1, you arrange a remote forwarding by sending the server
* the remote port number, and the local destination host:port.
* When a connection comes in, the server sends you back that
* host:port pair, and you connect to it. This is a ready-made
* security hole if you're not on the ball: a malicious server
* could send you back _any_ host:port pair, so if you trustingly
* connect to the address it gives you then you've just opened the
* entire inside of your corporate network just by connecting
* through it to a dodgy SSH server. Hence, we must store a list of
* host:port pairs we _are_ trying to forward to, and reject a
* connection request from the server if it's not in the list.
*
* In SSH-2, each side of the connection minds its own business and
* doesn't send unnecessary information to the other. You arrange a
* remote forwarding by sending the server just the remote port
* number. When a connection comes in, the server tells you which
* of its ports was connected to; and _you_ have to remember what
* local host:port pair went with that port number.
*
* Hence, in SSH-1 this structure is indexed by destination
* host:port pair, whereas in SSH-2 it is indexed by source port.
*/
struct ssh_portfwd; /* forward declaration */
struct ssh_rportfwd {
unsigned sport, dport;
char *shost, *dhost;
char *sportdesc;
void *share_ctx;
struct ssh_portfwd *pfrec;
};
static void free_rportfwd(struct ssh_rportfwd *pf)
{
if (pf) {
sfree(pf->sportdesc);
sfree(pf->shost);
sfree(pf->dhost);
sfree(pf);
}
}
/*
* Separately to the rportfwd tree (which is for looking up port
* open requests from the server), a tree of _these_ structures is
* used to keep track of all the currently open port forwardings,
* so that we can reconfigure in mid-session if the user requests
* it.
*/
struct ssh_portfwd {
enum { DESTROY, KEEP, CREATE } status;
int type;
unsigned sport, dport;
char *saddr, *daddr;
char *sserv, *dserv;
struct ssh_rportfwd *remote;
int addressfamily;
struct PortListener *local;
};
#define free_portfwd(pf) ( \
((pf) ? (sfree((pf)->saddr), sfree((pf)->daddr), \
sfree((pf)->sserv), sfree((pf)->dserv)) : (void)0 ), sfree(pf) )
typedef struct PacketQueueNode PacketQueueNode;
struct PacketQueueNode {
PacketQueueNode *next, *prev;
};
struct PktIn {
int refcount;
int type;
unsigned long sequence; /* SSH-2 incoming sequence number */
long encrypted_len; /* for SSH-2 total-size counting */
PacketQueueNode qnode; /* for linking this packet on to a queue */
BinarySource_IMPLEMENTATION;
};
struct PktOut {
long prefix; /* bytes up to and including type field */
long length; /* total bytes, including prefix */
int type;
long forcepad; /* SSH-2: force padding to at least this length */
unsigned char *data; /* allocated storage */
long maxlen; /* amount of storage allocated for `data' */
long encrypted_len; /* for SSH-2 total-size counting */
/* Extra metadata used in SSH packet logging mode, allowing us to
* log in the packet header line that the packet came from a
* connection-sharing downstream and what if anything unusual was
* done to it. The additional_log_text field is expected to be a
* static string - it will not be freed. */
unsigned downstream_id;
const char *additional_log_text;
BinarySink_IMPLEMENTATION;
};
static void ssh1_protocol_setup(Ssh ssh);
static void ssh2_protocol_setup(Ssh ssh);
static void ssh2_bare_connection_protocol_setup(Ssh ssh);
static void ssh_size(void *handle, int width, int height);
static void ssh_special(void *handle, Telnet_Special);
static int ssh2_try_send(struct ssh_channel *c);
static int ssh_send_channel_data(struct ssh_channel *c,
const char *buf, int len);
static void ssh_throttle_all(Ssh ssh, int enable, int bufsize);
static void ssh2_set_window(struct ssh_channel *c, int newwin);
static int ssh_sendbuffer(void *handle);
static int ssh_do_close(Ssh ssh, int notify_exit);
static void ssh2_timer(void *ctx, unsigned long now);
static int ssh2_timer_update(Ssh ssh, unsigned long rekey_time);
#ifndef NO_GSSAPI
static void ssh2_gss_update(Ssh ssh, int definitely_rekeying);
static PktOut *ssh2_gss_authpacket(Ssh ssh, Ssh_gss_ctx gss_ctx,
const char *authtype);
#endif
static void ssh2_msg_unexpected(Ssh ssh, PktIn *pktin);
static void ssh_unref_packet(PktIn *pkt);
struct PacketQueue {
PacketQueueNode end;
};
static void pq_init(struct PacketQueue *pq)
{
pq->end.next = pq->end.prev = &pq->end;
}
static void pq_push(struct PacketQueue *pq, PktIn *pkt)
{
PacketQueueNode *node = &pkt->qnode;
assert(!node->next);
assert(!node->prev);
node->next = &pq->end;
node->prev = pq->end.prev;
node->next->prev = node;
node->prev->next = node;
}
static void pq_push_front(struct PacketQueue *pq, PktIn *pkt)
{
PacketQueueNode *node = &pkt->qnode;
assert(!node->next);
assert(!node->prev);
node->prev = &pq->end;
node->next = pq->end.next;
node->next->prev = node;
node->prev->next = node;
}
static PktIn *pq_peek(struct PacketQueue *pq)
{
if (pq->end.next == &pq->end)
return NULL;
return FROMFIELD(pq->end.next, PktIn, qnode);
}
static PktIn *pq_pop(struct PacketQueue *pq)
{
PacketQueueNode *node = pq->end.next;
if (node == &pq->end)
return NULL;
node->next->prev = node->prev;
node->prev->next = node->next;
node->prev = node->next = NULL;
return FROMFIELD(node, PktIn, qnode);
}
static void pq_clear(struct PacketQueue *pq)
{
PktIn *pkt;
while ((pkt = pq_pop(pq)) != NULL)
ssh_unref_packet(pkt);
}
static int pq_empty_on_to_front_of(struct PacketQueue *src,
struct PacketQueue *dest)
{
struct PacketQueueNode *srcfirst, *srclast;
if (src->end.next == &src->end)
return FALSE;
srcfirst = src->end.next;
srclast = src->end.prev;
srcfirst->prev = &dest->end;
srclast->next = dest->end.next;
srcfirst->prev->next = srcfirst;
srclast->next->prev = srclast;
src->end.next = src->end.prev = &src->end;
return TRUE;
}
struct rdpkt1_state_tag {
long len, pad, biglen, length, maxlen;
unsigned char *data;
unsigned long realcrc, gotcrc;
int chunk;
PktIn *pktin;
};
struct rdpkt2_state_tag {
long len, pad, payload, packetlen, maclen, length, maxlen;
unsigned char *buf;
size_t bufsize;
unsigned char *data;
int cipherblk;
unsigned long incoming_sequence;
PktIn *pktin;
};
struct rdpkt2_bare_state_tag {
long packetlen, maxlen;
unsigned char *data;
unsigned long incoming_sequence;
PktIn *pktin;
};
struct queued_handler;
struct queued_handler {
int msg1, msg2;
chandler_fn_t handler;
void *ctx;
struct queued_handler *next;
};
/*
* Enumeration of high-level classes of reason why we might need to do
* a repeat key exchange. The full detailed reason in human-readable
* form for the Event Log is kept in ssh->rekey_reason, but
* ssh->rekey_class is a variable with this enum type which is used to
* discriminate between classes of reason that the code needs to treat
* differently.
*
* RK_NONE == 0 is the value indicating that no rekey is currently
* needed at all. RK_INITIAL indicates that we haven't even done the
* _first_ key exchange yet. RK_NORMAL is the usual case.
* RK_GSS_UPDATE indicates that we're rekeying because we've just got
* new GSSAPI credentials (hence there's no point in doing a
* preliminary check for new GSS creds, because we already know the
* answer); RK_POST_USERAUTH indicates that _if_ we're going to need a
* post-userauth immediate rekey for any reason, this is the moment to
* do it.
*
* So RK_POST_USERAUTH only tells the transport layer to _consider_
* rekeying, not to definitely do it. Also, that one enum value is
* special in that do_ssh2_transport fills in the reason text after it
* decides whether it needs a rekey at all. In the other cases,
* rekey_reason is set up at the same time as rekey_class.
*/
enum RekeyClass {
RK_NONE = 0,
RK_INITIAL,
RK_NORMAL,
RK_POST_USERAUTH,
RK_GSS_UPDATE
};
struct ssh_tag {
char *v_c, *v_s;
void *exhash;
BinarySink *exhash_bs;
Socket s;
const Plug_vtable *plugvt;
void *ldisc;
void *logctx;
unsigned char session_key[32];
int v1_compressing;
int v1_remote_protoflags;
int v1_local_protoflags;
int agentfwd_enabled;
int X11_fwd_enabled;
int remote_bugs;
const struct ssh_cipher *cipher;
void *v1_cipher_ctx;
void *crcda_ctx;
const struct ssh2_cipher *cscipher, *sccipher;
void *cs_cipher_ctx, *sc_cipher_ctx;
const struct ssh_mac *csmac, *scmac;
int csmac_etm, scmac_etm;
void *cs_mac_ctx, *sc_mac_ctx;
BinarySink *sc_mac_bs;
const struct ssh_compress *cscomp, *sccomp;
void *cs_comp_ctx, *sc_comp_ctx;
const struct ssh_kex *kex;
const ssh_keyalg *hostkey_alg;
char *hostkey_str; /* string representation, for easy checking in rekeys */
unsigned char v2_session_id[SSH2_KEX_MAX_HASH_LEN];
int v2_session_id_len;
void *kex_ctx;
int bare_connection;
int attempting_connshare;
void *connshare;
char *savedhost;
int savedport;
int send_ok;
int echoing, editing;
int session_started;
void *frontend;
int ospeed, ispeed; /* temporaries */
int term_width, term_height;
tree234 *channels; /* indexed by local id */
struct ssh_channel *mainchan; /* primary session channel */
int ncmode; /* is primary channel direct-tcpip? */
int exitcode;
int close_expected;
int clean_exit;
int disconnect_message_seen;
tree234 *rportfwds, *portfwds;
enum {
SSH_STATE_PREPACKET,
SSH_STATE_BEFORE_SIZE,
SSH_STATE_INTERMED,
SSH_STATE_SESSION,
SSH_STATE_CLOSED
} state;
int size_needed, eof_needed;
int sent_console_eof;
int got_pty; /* affects EOF behaviour on main channel */
PktOut **queue;
int queuelen, queuesize;
int queueing;
unsigned char *deferred_send_data;
int deferred_len, deferred_size;
/*
* Gross hack: pscp will try to start SFTP but fall back to
* scp1 if that fails. This variable is the means by which
* scp.c can reach into the SSH code and find out which one it
* got.
*/
int fallback_cmd;
bufchain banner; /* accumulates banners during do_ssh2_userauth */
Pkt_KCtx pkt_kctx;
Pkt_ACtx pkt_actx;
struct X11Display *x11disp;
struct X11FakeAuth *x11auth;
tree234 *x11authtree;
int version;
int conn_throttle_count;
int overall_bufsize;
int throttled_all;
int v1_stdout_throttling;
unsigned long v2_outgoing_sequence;
int ssh1_rdpkt_crstate;
int ssh2_rdpkt_crstate;
int ssh2_bare_rdpkt_crstate;
int do_ssh1_connection_crstate;
void *do_ssh_init_state;
void *do_ssh1_login_state;
void *do_ssh2_transport_state;
void *do_ssh2_userauth_state;
void *do_ssh2_connection_state;
void *do_ssh_connection_init_state;
bufchain incoming_data;
struct IdempotentCallback incoming_data_consumer;
int incoming_data_seen_eof;
char *incoming_data_eof_message;
struct PacketQueue pq_full;
struct IdempotentCallback pq_full_consumer;
struct PacketQueue pq_ssh1_login;
struct IdempotentCallback ssh1_login_icb;
struct PacketQueue pq_ssh1_connection;
struct IdempotentCallback ssh1_connection_icb;