putty-source/unix/uxagentc.c

/*
 * SSH agent client code.
 */

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>

#include "putty.h"
#include "misc.h"
#include "tree234.h"
#include "puttymem.h"

#define GET_32BIT(cp) \
    (((unsigned long)(unsigned char)(cp)[0] << 24) | \
    ((unsigned long)(unsigned char)(cp)[1] << 16) | \
    ((unsigned long)(unsigned char)(cp)[2] << 8) | \
    ((unsigned long)(unsigned char)(cp)[3]))

int agent_exists(void)
{
    if (getenv("SSH_AUTH_SOCK") != NULL)
	return TRUE;
    return FALSE;
}

static tree234 *agent_connections;
struct agent_connection {
    int fd;
    char *retbuf;
    char sizebuf[4];
    int retsize, retlen;
    void (*callback)(void *, void *, int);
    void *callback_ctx;
};
static int agent_conncmp(void *av, void *bv)
{
    struct agent_connection *a = (struct agent_connection *) av;
    struct agent_connection *b = (struct agent_connection *) bv;
    if (a->fd < b->fd)
	return -1;
    if (a->fd > b->fd)
	return +1;
    return 0;
}
static int agent_connfind(void *av, void *bv)
{
    int afd = *(int *) av;
    struct agent_connection *b = (struct agent_connection *) bv;
    if (afd < b->fd)
	return -1;
    if (afd > b->fd)
	return +1;
    return 0;
}

static int agent_select_result(int fd, int event)
{
    int ret;
    struct agent_connection *conn;

    assert(event == 1);		       /* not selecting for anything but R */

    conn = find234(agent_connections, &fd, agent_connfind);
    if (!conn) {
	uxsel_del(fd);
	return 1;
    }

    ret = read(fd, conn->retbuf+conn->retlen, conn->retsize-conn->retlen);
    if (ret <= 0) {
	if (conn->retbuf != conn->sizebuf) sfree(conn->retbuf);
	conn->retbuf = NULL;
	conn->retlen = 0;
	goto done;
    }
    conn->retlen += ret;
    if (conn->retsize == 4 && conn->retlen == 4) {
	conn->retsize = GET_32BIT(conn->retbuf);
	if (conn->retsize <= 0) {
	    conn->retbuf = NULL;
	    conn->retlen = 0;
	    goto done;
	}
	conn->retsize += 4;
	assert(conn->retbuf == conn->sizebuf);
	conn->retbuf = snewn(conn->retsize, char);
	memcpy(conn->retbuf, conn->sizebuf, 4);
    }

    if (conn->retlen < conn->retsize)
	return 0;		       /* more data to come */

    done:
    /*
     * We have now completed the agent query. Do the callback, and
     * clean up. (Of course we don't free retbuf, since ownership
     * of that passes to the callback.)
     */
    conn->callback(conn->callback_ctx, conn->retbuf, conn->retlen);
    uxsel_del(fd);
    close(fd);
    del234(agent_connections, conn);
    sfree(conn);
    return 0;
}

int agent_query(void *in, int inlen, void **out, int *outlen,
		void (*callback)(void *, void *, int), void *callback_ctx)
{
    char *name;
    int sock;
    struct sockaddr_un addr;
    int done;
    struct agent_connection *conn;

    name = getenv("SSH_AUTH_SOCK");
    if (!name)
	goto failure;

    sock = socket(PF_UNIX, SOCK_STREAM, 0);
    if (sock < 0) {
	perror("socket(PF_UNIX)");
	exit(1);
    }

    addr.sun_family = AF_UNIX;
    strncpy(addr.sun_path, name, sizeof(addr.sun_path));
    if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
	close(sock);
	goto failure;
    }

    for (done = 0; done < inlen ;) {
	int ret = write(sock, (char *)in + done, inlen - done);
	if (ret <= 0) {
	    close(sock);
	    goto failure;
	}
	done += ret;
    }

    if (!agent_connections)
	agent_connections = newtree234(agent_conncmp);

    conn = snew(struct agent_connection);
    conn->fd = sock;
    conn->retbuf = conn->sizebuf;
    conn->retsize = 4;
    conn->retlen = 0;
    conn->callback = callback;
    conn->callback_ctx = callback_ctx;
    add234(agent_connections, conn);

    uxsel_set(sock, 1, agent_select_result);
    return 0;

    failure:
    *out = NULL;
    *outlen = 0;
    return 1;
}