putty-source/unix/uxproxy.c

/*
 * uxproxy.c: Unix implementation of platform_new_connection(),
 * supporting an OpenSSH-like proxy command.
 */

#include <stdio.h>
#include <assert.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>

#include "tree234.h"
#include "putty.h"
#include "network.h"
#include "proxy.h"

typedef struct LocalProxySocket {
    int to_cmd, from_cmd, cmd_err;     /* fds */

    char *error;

    Plug *plug;

    bufchain pending_output_data;
    bufchain pending_input_data;
    bufchain pending_error_data;
    enum { EOF_NO, EOF_PENDING, EOF_SENT } outgoingeof;

    int pending_error;

    Socket sock;
} LocalProxySocket;

static void localproxy_select_result(int fd, int event);

/*
 * Trees to look up the pipe fds in.
 */
static tree234 *localproxy_by_fromfd;
static tree234 *localproxy_by_tofd;
static tree234 *localproxy_by_errfd;
static int localproxy_fromfd_cmp(void *av, void *bv)
{
    LocalProxySocket *a = (LocalProxySocket *)av;
    LocalProxySocket *b = (LocalProxySocket *)bv;
    if (a->from_cmd < b->from_cmd)
	return -1;
    if (a->from_cmd > b->from_cmd)
	return +1;
    return 0;
}
static int localproxy_fromfd_find(void *av, void *bv)
{
    int a = *(int *)av;
    LocalProxySocket *b = (LocalProxySocket *)bv;
    if (a < b->from_cmd)
	return -1;
    if (a > b->from_cmd)
	return +1;
    return 0;
}
static int localproxy_tofd_cmp(void *av, void *bv)
{
    LocalProxySocket *a = (LocalProxySocket *)av;
    LocalProxySocket *b = (LocalProxySocket *)bv;
    if (a->to_cmd < b->to_cmd)
	return -1;
    if (a->to_cmd > b->to_cmd)
	return +1;
    return 0;
}
static int localproxy_tofd_find(void *av, void *bv)
{
    int a = *(int *)av;
    LocalProxySocket *b = (LocalProxySocket *)bv;
    if (a < b->to_cmd)
	return -1;
    if (a > b->to_cmd)
	return +1;
    return 0;
}
static int localproxy_errfd_cmp(void *av, void *bv)
{
    LocalProxySocket *a = (LocalProxySocket *)av;
    LocalProxySocket *b = (LocalProxySocket *)bv;
    if (a->cmd_err < b->cmd_err)
	return -1;
    if (a->cmd_err > b->cmd_err)
	return +1;
    return 0;
}
static int localproxy_errfd_find(void *av, void *bv)
{
    int a = *(int *)av;
    LocalProxySocket *b = (LocalProxySocket *)bv;
    if (a < b->cmd_err)
	return -1;
    if (a > b->cmd_err)
	return +1;
    return 0;
}

/* basic proxy socket functions */

static Plug *sk_localproxy_plug (Socket *s, Plug *p)
{
    LocalProxySocket *ps = FROMFIELD(s, LocalProxySocket, sock);
    Plug *ret = ps->plug;
    if (p)
	ps->plug = p;
    return ret;
}

static void sk_localproxy_close (Socket *s)
{
    LocalProxySocket *ps = FROMFIELD(s, LocalProxySocket, sock);

    if (ps->to_cmd >= 0) {
        del234(localproxy_by_tofd, ps);
        uxsel_del(ps->to_cmd);
        close(ps->to_cmd);
    }

    if (ps->from_cmd >= 0) {
        del234(localproxy_by_fromfd, ps);
        uxsel_del(ps->from_cmd);
        close(ps->from_cmd);
    }

    if (ps->cmd_err >= 0) {
        del234(localproxy_by_errfd, ps);
        uxsel_del(ps->cmd_err);
        close(ps->cmd_err);
    }

    bufchain_clear(&ps->pending_input_data);
    bufchain_clear(&ps->pending_output_data);
    bufchain_clear(&ps->pending_error_data);

    delete_callbacks_for_context(ps);

    sfree(ps);
}

static void localproxy_error_callback(void *vs)
{
    LocalProxySocket *ps = (LocalProxySocket *)vs;

    /*
     * Just in case other socket work has caused this socket to vanish
     * or become somehow non-erroneous before this callback arrived...
     */
    if (!ps->pending_error)
        return;

    /*
     * An error has occurred on this socket. Pass it to the plug.
     */
    plug_closing(ps->plug, strerror(ps->pending_error), ps->pending_error, 0);
}

static int localproxy_try_send(LocalProxySocket *ps)
{
    int sent = 0;

    while (bufchain_size(&ps->pending_output_data) > 0) {
	void *data;
	int len, ret;

	bufchain_prefix(&ps->pending_output_data, &data, &len);
	ret = write(ps->to_cmd, data, len);
	if (ret < 0 && errno != EWOULDBLOCK) {
            if (!ps->pending_error) {
                ps->pending_error = errno;
                queue_toplevel_callback(localproxy_error_callback, ps);
            }
            return 0;
	} else if (ret <= 0) {
	    break;
	} else {
	    bufchain_consume(&ps->pending_output_data, ret);
	    sent += ret;
	}
    }

    if (ps->outgoingeof == EOF_PENDING) {
        del234(localproxy_by_tofd, ps);
        close(ps->to_cmd);
        uxsel_del(ps->to_cmd);
        ps->to_cmd = -1;
        ps->outgoingeof = EOF_SENT;
    }

    if (bufchain_size(&ps->pending_output_data) == 0)
	uxsel_del(ps->to_cmd);
    else
	uxsel_set(ps->to_cmd, 2, localproxy_select_result);

    return sent;
}

static int sk_localproxy_write (Socket *s, const void *data, int len)
{
    LocalProxySocket *ps = FROMFIELD(s, LocalProxySocket, sock);

    assert(ps->outgoingeof == EOF_NO);

    bufchain_add(&ps->pending_output_data, data, len);

    localproxy_try_send(ps);

    return bufchain_size(&ps->pending_output_data);
}

static int sk_localproxy_write_oob (Socket *s, const void *data, int len)
{
    /*
     * oob data is treated as inband; nasty, but nothing really
     * better we can do
     */
    return sk_localproxy_write(s, data, len);
}

static void sk_localproxy_write_eof (Socket *s)
{
    LocalProxySocket *ps = FROMFIELD(s, LocalProxySocket, sock);

    assert(ps->outgoingeof == EOF_NO);
    ps->outgoingeof = EOF_PENDING;

    localproxy_try_send(ps);
}

static void sk_localproxy_flush (Socket *s)
{
    /* LocalProxySocket *ps = FROMFIELD(s, LocalProxySocket, sock); */
    /* do nothing */
}

static void sk_localproxy_set_frozen (Socket *s, int is_frozen)
{
    LocalProxySocket *ps = FROMFIELD(s, LocalProxySocket, sock);

    if (ps->from_cmd < 0)
        return;

    if (is_frozen)
	uxsel_del(ps->from_cmd);
    else
	uxsel_set(ps->from_cmd, 1, localproxy_select_result);
}

static const char * sk_localproxy_socket_error (Socket *s)
{
    LocalProxySocket *ps = FROMFIELD(s, LocalProxySocket, sock);
    return ps->error;
}

static void localproxy_select_result(int fd, int event)
{
    LocalProxySocket *s;
    char buf[20480];
    int ret;

    if (!(s = find234(localproxy_by_fromfd, &fd, localproxy_fromfd_find)) &&
	!(s = find234(localproxy_by_errfd, &fd, localproxy_errfd_find)) &&
	!(s = find234(localproxy_by_tofd, &fd, localproxy_tofd_find)) )
	return;		       /* boggle */

    if (event == 1) {
        if (fd == s->cmd_err) {
            ret = read(fd, buf, sizeof(buf));
            if (ret > 0) {
                log_proxy_stderr(s->plug, &s->pending_error_data, buf, ret);
            } else {
                del234(localproxy_by_errfd, s);
                uxsel_del(s->cmd_err);
                close(s->cmd_err);
                s->cmd_err = -1;
            }
        } else {
            assert(fd == s->from_cmd);
            ret = read(fd, buf, sizeof(buf));
            if (ret > 0) {
                plug_receive(s->plug, 0, buf, ret);
            } else {
                if (ret < 0) {
                    plug_closing(s->plug, strerror(errno), errno, 0);
                } else {
                    plug_closing(s->plug, NULL, 0, 0);
                }
                del234(localproxy_by_fromfd, s);
                uxsel_del(s->from_cmd);
                close(s->from_cmd);
                s->from_cmd = -1;
            }
        }
    } else if (event == 2) {
	assert(fd == s->to_cmd);
	if (localproxy_try_send(s))
	    plug_sent(s->plug, bufchain_size(&s->pending_output_data));
    }
}

static const SocketVtable LocalProxySocket_sockvt = {
    sk_localproxy_plug,
    sk_localproxy_close,
    sk_localproxy_write,
    sk_localproxy_write_oob,
    sk_localproxy_write_eof,
    sk_localproxy_flush,
    sk_localproxy_set_frozen,
    sk_localproxy_socket_error,
    NULL, /* peer_info */
};

Socket *platform_new_connection(SockAddr *addr, const char *hostname,
                                int port, int privport,
                                int oobinline, int nodelay, int keepalive,
                                Plug *plug, Conf *conf)
{
    char *cmd;

    LocalProxySocket *ret;
    int to_cmd_pipe[2], from_cmd_pipe[2], cmd_err_pipe[2], pid, proxytype;

    proxytype = conf_get_int(conf, CONF_proxy_type);
    if (proxytype != PROXY_CMD && proxytype != PROXY_FUZZ)
	return NULL;

    ret = snew(LocalProxySocket);
    ret->sock.vt = &LocalProxySocket_sockvt;
    ret->plug = plug;
    ret->error = NULL;
    ret->outgoingeof = EOF_NO;
    ret->pending_error = 0;

    bufchain_init(&ret->pending_input_data);
    bufchain_init(&ret->pending_output_data);
    bufchain_init(&ret->pending_error_data);

    if (proxytype == PROXY_CMD) {
	cmd = format_telnet_command(addr, port, conf);

        {
            char *logmsg = dupprintf("Starting local proxy command: %s", cmd);
            plug_log(plug, 2, NULL, 0, logmsg, 0);
            sfree(logmsg);
        }

	/*
	 * Create the pipes to the proxy command, and spawn the proxy
	 * command process.
	 */
	if (pipe(to_cmd_pipe) < 0 ||
	    pipe(from_cmd_pipe) < 0 ||
            pipe(cmd_err_pipe) < 0) {
	    ret->error = dupprintf("pipe: %s", strerror(errno));
	    sfree(cmd);
	    return &ret->sock;
	}
	cloexec(to_cmd_pipe[1]);
	cloexec(from_cmd_pipe[0]);
        cloexec(cmd_err_pipe[0]);

	pid = fork();

	if (pid < 0) {
	    ret->error = dupprintf("fork: %s", strerror(errno));
	    sfree(cmd);
	    return &ret->sock;
	} else if (pid == 0) {
	    close(0);
	    close(1);
	    dup2(to_cmd_pipe[0], 0);
	    dup2(from_cmd_pipe[1], 1);
	    close(to_cmd_pipe[0]);
	    close(from_cmd_pipe[1]);
            dup2(cmd_err_pipe[1], 2);
	    noncloexec(0);
	    noncloexec(1);
	    execl("/bin/sh", "sh", "-c", cmd, (void *)NULL);
	    _exit(255);
	}

	sfree(cmd);

	close(to_cmd_pipe[0]);
	close(from_cmd_pipe[1]);
        close(cmd_err_pipe[1]);

	ret->to_cmd = to_cmd_pipe[1];
	ret->from_cmd = from_cmd_pipe[0];
	ret->cmd_err = cmd_err_pipe[0];
    } else {
	cmd = format_telnet_command(addr, port, conf);
	ret->to_cmd = open("/dev/null", O_WRONLY);
	if (ret->to_cmd == -1) {
	    ret->error = dupprintf("/dev/null: %s", strerror(errno));
	    sfree(cmd);
	    return &ret->sock;
	}
	ret->from_cmd = open(cmd, O_RDONLY);
	if (ret->from_cmd == -1) {
	    ret->error = dupprintf("%s: %s", cmd, strerror(errno));
	    sfree(cmd);
	    return &ret->sock;
	}
	sfree(cmd);
	ret->cmd_err = -1;
    }

    if (!localproxy_by_fromfd)
	localproxy_by_fromfd = newtree234(localproxy_fromfd_cmp);
    if (!localproxy_by_tofd)
	localproxy_by_tofd = newtree234(localproxy_tofd_cmp);
    if (!localproxy_by_errfd)
	localproxy_by_errfd = newtree234(localproxy_errfd_cmp);

    add234(localproxy_by_fromfd, ret);
    add234(localproxy_by_tofd, ret);
    if (ret->cmd_err >= 0)
        add234(localproxy_by_errfd, ret);

    uxsel_set(ret->from_cmd, 1, localproxy_select_result);
    if (ret->cmd_err >= 0)
        uxsel_set(ret->cmd_err, 1, localproxy_select_result);

    /* We are responsible for this and don't need it any more */
    sk_addr_free(addr);

    return &ret->sock;
}