ssh.c

大名鼎鼎的远程登录软件putty的Symbian版源码

 * 2-3-4 tree storing channels.
 */
struct ssh_channel {
    Ssh ssh;			       /* pointer back to main context */
    unsigned remoteid, localid;
    int type;
    /*
     * In SSH1, 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.
     */
    int closes;
    union {
	struct ssh1_data_channel {
	    int throttling;
	} v1;
	struct ssh2_data_channel {
	    bufchain outbuffer;
	    unsigned remwindow, remmaxpkt;
	    unsigned locwindow;
	} v2;
    } v;
    union {
	struct ssh_agent_channel {
	    unsigned char *message;
	    unsigned char msglen[4];
	    unsigned lensofar, totallen;
	} a;
	struct ssh_x11_channel {
	    Socket s;
	} x11;
	struct ssh_pfd_channel {
	    Socket s;
	} pfd;
    } 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 stores host:port pairs we intend
 * to allow connections to, and is indexed by those host:port
 * pairs. In SSH 2 it stores a mapping from source port to
 * destination host:port pair, and is indexed by source port.
 */
struct ssh_rportfwd {
    unsigned sport, dport;
    char dhost[256];
};

struct Packet {
    long length;
    int type;
    unsigned char *data;
    unsigned char *body;
    long savedpos;
    long maxlen;
};

static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt);
static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt);
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 void ssh2_add_channel_data(struct ssh_channel *c, char *buf, int len);
static void ssh_throttle_all(Ssh ssh, int enable, int bufsize);
static void ssh2_set_window(struct ssh_channel *c, unsigned newwin);
static int ssh_sendbuffer(void *handle);
static void ssh_do_close(Ssh ssh);
static unsigned long ssh_pkt_getuint32(Ssh ssh);
static int ssh2_pkt_getbool(Ssh ssh);
static void ssh_pkt_getstring(Ssh ssh, char **p, int *length);

struct rdpkt1_state_tag {
    long len, pad, biglen, to_read;
    unsigned long realcrc, gotcrc;
    unsigned char *p;
    int i;
    int chunk;
};

struct rdpkt2_state_tag {
    long len, pad, payload, packetlen, maclen;
    int i;
    int cipherblk;
    unsigned long incoming_sequence;
};

struct ssh_tag {
    const struct plug_function_table *fn;
    /* the above field _must_ be first in the structure */

    SHA_State exhash, exhashbase;

    Socket s;

    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;
    void *cs_mac_ctx, *sc_mac_ctx;
    const struct ssh_compress *cscomp, *sccomp;
    void *cs_comp_ctx, *sc_comp_ctx;
    const struct ssh_kex *kex;
    const struct ssh_signkey *hostkey;
    unsigned char v2_session_id[20];
    void *kex_ctx;

    char *savedhost;
    int savedport;
    int send_ok;
    int echoing, editing;

    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 exitcode;

    tree234 *rportfwds;

    enum {
	SSH_STATE_PREPACKET,
	SSH_STATE_BEFORE_SIZE,
	SSH_STATE_INTERMED,
	SSH_STATE_SESSION,
	SSH_STATE_CLOSED
    } state;

    int size_needed, eof_needed;

    struct Packet pktin;
    struct Packet pktout;
    unsigned char *deferred_send_data;
    int deferred_len, deferred_size;

    /*
     * State associated with packet logging
     */
    int pktout_logmode;
    int pktout_nblanks;
    struct logblank_t *pktout_blanks;

    /*
     * 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;

    /*
     * Used for username and password input.
     */
    char *userpass_input_buffer;
    int userpass_input_buflen;
    int userpass_input_bufpos;
    int userpass_input_echo;

    char *portfwd_strptr;
    int pkt_ctx;

    void *x11auth;

    int version;
    int v1_throttle_count;
    int overall_bufsize;
    int throttled_all;
    int v1_stdout_throttling;
    int v2_outgoing_sequence;

    int ssh1_rdpkt_crstate;
    int ssh2_rdpkt_crstate;
    int do_ssh_init_crstate;
    int ssh_gotdata_crstate;
    int ssh1_protocol_crstate;
    int do_ssh1_login_crstate;
    int do_ssh2_transport_crstate;
    int do_ssh2_authconn_crstate;

    void *do_ssh_init_state;
    void *do_ssh1_login_state;
    void *do_ssh2_transport_state;
    void *do_ssh2_authconn_state;

    struct rdpkt1_state_tag rdpkt1_state;
    struct rdpkt2_state_tag rdpkt2_state;

    void (*protocol) (Ssh ssh, unsigned char *in, int inlen, int ispkt);
    int (*s_rdpkt) (Ssh ssh, unsigned char **data, int *datalen);

    /*
     * We maintain a full _copy_ of a Config structure here, not
     * merely a pointer to it. That way, when we're passed a new
     * one for reconfiguration, we can check the differences and
     * potentially reconfigure port forwardings etc in mid-session.
     */
    Config cfg;

    /*
     * Used to transfer data back from async agent callbacks.
     */
    void *agent_response;
    int agent_response_len;

    /*
     * Text manipulation buffers for port forwarding. These are kept
     * here to simplify the state machine code in the protocol
     * funtions. We can't put these to stack under Symbian OS (too
     * big), and using local variables for the heap allocated buffers
     * would be cumbersome since we'd need to free and reallocate them
     * around every coroutine call. "One of the PuTTY source files
     * contains possibly the worst piece of C preprocessor hackery
     * I've ever seen in production code." indeed.
     */
    char *sports;
    char *dports;
    char *saddr;
    char *host;

    /*
     * Special code list to be returned from ssh_get_specials(). Placing it
     * here avoids makiung it writable static data.
     */
    struct telnet_special *specials;
};

#define logevent(s) logevent(ssh->frontend, s)

/* logevent, only printf-formatted. */
static void logeventf(Ssh ssh, const char *fmt, ...)
{
    va_list ap;
    char *buf;

    va_start(ap, fmt);
    buf = dupvprintf(fmt, ap);
    va_end(ap);
    logevent(buf);
    sfree(buf);
}

#define bombout(msg) \
    do { \
        char *text = dupprintf msg; \
	ssh_do_close(ssh); \
        logevent(text); \
        connection_fatal(ssh->frontend, "%s", text); \
        sfree(text); \
    } while (0)

/* Functions to leave bits out of the SSH packet log file. */

static void dont_log_password(Ssh ssh, int blanktype)
{
    if (ssh->cfg.logomitpass)
	ssh->pktout_logmode = blanktype;
}

static void dont_log_data(Ssh ssh, int blanktype)
{
    if (ssh->cfg.logomitdata)
	ssh->pktout_logmode = blanktype;
}

static void end_log_omission(Ssh ssh)
{
    ssh->pktout_logmode = PKTLOG_EMIT;
}

static int ssh_channelcmp(void *av, void *bv)
{
    struct ssh_channel *a = (struct ssh_channel *) av;
    struct ssh_channel *b = (struct ssh_channel *) bv;
    if (a->localid < b->localid)
	return -1;
    if (a->localid > b->localid)
	return +1;
    return 0;
}
static int ssh_channelfind(void *av, void *bv)
{
    unsigned *a = (unsigned *) av;
    struct ssh_channel *b = (struct ssh_channel *) bv;
    if (*a < b->localid)
	return -1;
    if (*a > b->localid)
	return +1;
    return 0;
}

static int ssh_rportcmp_ssh1(void *av, void *bv)
{
    struct ssh_rportfwd *a = (struct ssh_rportfwd *) av;
    struct ssh_rportfwd *b = (struct ssh_rportfwd *) bv;
    int i;
    if ( (i = strcmp(a->dhost, b->dhost)) != 0)
	return i < 0 ? -1 : +1;
    if (a->dport > b->dport)
	return +1;
    if (a->dport < b->dport)
	return -1;
    return 0;
}

static int ssh_rportcmp_ssh2(void *av, void *bv)
{
    struct ssh_rportfwd *a = (struct ssh_rportfwd *) av;
    struct ssh_rportfwd *b = (struct ssh_rportfwd *) bv;

    if (a->sport > b->sport)
	return +1;
    if (a->sport < b->sport)
	return -1;
    return 0;
}

static int alloc_channel_id(Ssh ssh)
{
    const unsigned CHANNEL_NUMBER_OFFSET = 256;
    unsigned low, high, mid;
    int tsize;
    struct ssh_channel *c;

    /*
     * First-fit allocation of channel numbers: always pick the
     * lowest unused one. To do this, binary-search using the
     * counted B-tree to find the largest channel ID which is in a
     * contiguous sequence from the beginning. (Precisely
     * everything in that sequence must have ID equal to its tree
     * index plus CHANNEL_NUMBER_OFFSET.)
     */
    tsize = count234(ssh->channels);

    low = UINT_MAX;
    high = tsize;
    while (high - low > 1) {
	mid = (high + low) / 2;
	c = index234(ssh->channels, mid);
	if (c->localid == mid + CHANNEL_NUMBER_OFFSET)
	    low = mid;		       /* this one is fine */
	else
	    high = mid;		       /* this one is past it */
    }
    /*
     * Now low points to either -1, or the tree index of the
     * largest ID in the initial sequence.
     */
    {
	unsigned i = low + 1 + CHANNEL_NUMBER_OFFSET;
	assert(NULL == find234(ssh->channels, &i, ssh_channelfind));
    }
    return low + 1 + CHANNEL_NUMBER_OFFSET;
}

static void c_write(Ssh ssh, const char *buf, int len)
{
    if ((statics()->flags & FLAG_STDERR)) {
	int i;
	for (i = 0; i < len; i++)
	    if (buf[i] != '\r')
		fputc(buf[i], stderr);
	return;
    }
    from_backend(ssh->frontend, 1, buf, len);
}

static void c_write_untrusted(Ssh ssh, const char *buf, int len)
{
    int i;
    for (i = 0; i < len; i++) {
	if (buf[i] == '\n')
	    c_write(ssh, "\r\n", 2);
	else if ((buf[i] & 0x60) || (buf[i] == '\r'))
	    c_write(ssh, buf + i, 1);
    }
}

static void c_write_str(Ssh ssh, const char *buf)
{
    c_write(ssh, buf, strlen(buf));
}

/*
 * Collect incoming data in the incoming packet buffer.
 * Decipher and verify the packet when it is completely read.
 * Drop SSH1_MSG_DEBUG and SSH1_MSG_IGNORE packets.
 * Update the *data and *datalen variables.
 * Return the additional nr of bytes needed, or 0 when
 * a complete packet is available.
 */