sftp.c

一个支持FTP,SFTP的客户端程序

{
    struct sftp_request *req = sftp_alloc_request();
    struct sftp_packet *pktout;

    pktout = sftp_pkt_init(SSH_FXP_READDIR);
    sftp_pkt_adduint32(pktout, req->id);
    sftp_pkt_addstring_start(pktout);
    sftp_pkt_addstring_data(pktout, handle->hstring, handle->hlen);
    sftp_send(pktout);

    return req;
}

struct fxp_names *fxp_readdir_recv(struct sftp_packet *pktin,
				   struct sftp_request *req)
{
    sfree(req);
    if (pktin->type == SSH_FXP_NAME) {
	struct fxp_names *ret;
	unsigned long i;

	/*
	 * Sanity-check the number of names. Minimum is obviously
	 * zero. Maximum is the remaining space in the packet
	 * divided by the very minimum length of a name, which is
	 * 12 bytes (4 for an empty filename, 4 for an empty
	 * longname, 4 for a set of attribute flags indicating that
	 * no other attributes are supplied).
	 */
	if (!sftp_pkt_getuint32(pktin, &i) ||
	    i > (pktin->length-pktin->savedpos)/12) {
	    fxp_internal_error("malformed FXP_NAME packet");
	    sftp_pkt_free(pktin);
	    return NULL;
	}

	/*
	 * Ensure the implicit multiplication in the snewn() call
	 * doesn't suffer integer overflow and cause us to malloc
	 * too little space.
	 */
	if (i > INT_MAX / sizeof(struct fxp_name)) {
	    fxp_internal_error("unreasonably large FXP_NAME packet");
	    sftp_pkt_free(pktin);
	    return NULL;
	}

	ret = snew(struct fxp_names);
	ret->nnames = i;
	ret->names = snewn(ret->nnames, struct fxp_name);
	for (i = 0; i < ret->nnames; i++) {
	    char *str1, *str2;
	    int len1, len2;
	    if (!sftp_pkt_getstring(pktin, &str1, &len1) ||
		!sftp_pkt_getstring(pktin, &str2, &len2) ||
		!sftp_pkt_getattrs(pktin, &ret->names[i].attrs)) {
		fxp_internal_error("malformed FXP_NAME packet");
		while (i--) {
		    sfree(ret->names[i].filename);
		    sfree(ret->names[i].longname);
		}
		sfree(ret->names);
		sfree(ret);
		sfree(pktin);
		return NULL;
	    }
	    ret->names[i].filename = mkstr(str1, len1);
	    ret->names[i].longname = mkstr(str2, len2);
	}
        sftp_pkt_free(pktin);
	return ret;
    } else {
	fxp_got_status(pktin);
        sftp_pkt_free(pktin);
	return NULL;
    }
}

/*
 * Write to a file. Returns 0 on error, 1 on OK.
 */
struct sftp_request *fxp_write_send(struct fxp_handle *handle,
				    char *buffer, uint64 offset, int len)
{
    struct sftp_request *req = sftp_alloc_request();
    struct sftp_packet *pktout;

    pktout = sftp_pkt_init(SSH_FXP_WRITE);
    sftp_pkt_adduint32(pktout, req->id);
    sftp_pkt_addstring_start(pktout);
    sftp_pkt_addstring_data(pktout, handle->hstring, handle->hlen);
    sftp_pkt_adduint64(pktout, offset);
    sftp_pkt_addstring_start(pktout);
    sftp_pkt_addstring_data(pktout, buffer, len);
    sftp_send(pktout);

    return req;
}

int fxp_write_recv(struct sftp_packet *pktin, struct sftp_request *req)
{
    sfree(req);
    fxp_got_status(pktin);
    sftp_pkt_free(pktin);
    return fxp_errtype == SSH_FX_OK;
}

/*
 * Free up an fxp_names structure.
 */
void fxp_free_names(struct fxp_names *names)
{
    int i;

    for (i = 0; i < names->nnames; i++) {
	sfree(names->names[i].filename);
	sfree(names->names[i].longname);
    }
    sfree(names->names);
    sfree(names);
}

/*
 * Duplicate an fxp_name structure.
 */
struct fxp_name *fxp_dup_name(struct fxp_name *name)
{
    struct fxp_name *ret;
    ret = snew(struct fxp_name);
    ret->filename = dupstr(name->filename);
    ret->longname = dupstr(name->longname);
    ret->attrs = name->attrs;	       /* structure copy */
    return ret;
}

/*
 * Free up an fxp_name structure.
 */
void fxp_free_name(struct fxp_name *name)
{
    sfree(name->filename);
    sfree(name->longname);
    sfree(name);
}

/*
 * Store user data in an sftp_request structure.
 */
void *fxp_get_userdata(struct sftp_request *req)
{
    return req->userdata;
}

void fxp_set_userdata(struct sftp_request *req, void *data)
{
    req->userdata = data;
}

/*
 * A wrapper to go round fxp_read_* and fxp_write_*, which manages
 * the queueing of multiple read/write requests.
 */

struct req {
    char *buffer;
    int len, retlen, complete;
    uint64 offset;
    struct req *next, *prev;
};

struct fxp_xfer {
    uint64 offset, furthestdata, filesize;
    int req_totalsize, req_maxsize, eof, err;
    struct fxp_handle *fh;
    struct req *head, *tail;
};

static struct fxp_xfer *xfer_init(struct fxp_handle *fh, uint64 offset)
{
    struct fxp_xfer *xfer = snew(struct fxp_xfer);

    xfer->fh = fh;
    xfer->offset = offset;
    xfer->head = xfer->tail = NULL;
    xfer->req_totalsize = 0;
    xfer->req_maxsize = 16384;
    xfer->err = 0;
    xfer->filesize = uint64_make(ULONG_MAX, ULONG_MAX);
    xfer->furthestdata = uint64_make(0, 0);

    return xfer;
}

int xfer_done(struct fxp_xfer *xfer)
{
    /*
     * We're finished if we've seen EOF _and_ there are no
     * outstanding requests.
     */
    return (xfer->eof || xfer->err) && !xfer->head;
}

void xfer_download_queue(struct fxp_xfer *xfer)
{
    while (xfer->req_totalsize < xfer->req_maxsize &&
	   !xfer->eof && !xfer->err) {
	/*
	 * Queue a new read request.
	 */
	struct req *rr;
	struct sftp_request *req;

	rr = snew(struct req);
	rr->offset = xfer->offset;
	rr->complete = 0;
	if (xfer->tail) {
	    xfer->tail->next = rr;
	    rr->prev = xfer->tail;
	} else {
	    xfer->head = rr;
	    rr->prev = NULL;
	}
	xfer->tail = rr;
	rr->next = NULL;

	rr->len = 4096;
	rr->buffer = snewn(rr->len, char);
	sftp_register(req = fxp_read_send(xfer->fh, rr->offset, rr->len));
	fxp_set_userdata(req, rr);

	xfer->offset = uint64_add32(xfer->offset, rr->len);
	xfer->req_totalsize += rr->len;

#ifdef DEBUG_DOWNLOAD
	{ char buf[40]; uint64_decimal(rr->offset, buf); printf("queueing read request %p at %s\n", rr, buf); }
#endif
    }
}

struct fxp_xfer *xfer_download_init(struct fxp_handle *fh, uint64 offset)
{
    struct fxp_xfer *xfer = xfer_init(fh, offset);

    xfer->eof = FALSE;
    xfer_download_queue(xfer);

    return xfer;
}

int xfer_download_gotpkt(struct fxp_xfer *xfer, struct sftp_packet *pktin)
{
    struct sftp_request *rreq;
    struct req *rr;

    rreq = sftp_find_request(pktin);
    rr = (struct req *)fxp_get_userdata(rreq);
    if (!rr)
	return 0;		       /* this packet isn't ours */
    rr->retlen = fxp_read_recv(pktin, rreq, rr->buffer, rr->len);
#ifdef DEBUG_DOWNLOAD
    printf("read request %p has returned [%d]\n", rr, rr->retlen);
#endif

    if ((rr->retlen < 0 && fxp_error_type()==SSH_FX_EOF) || rr->retlen == 0) {
	xfer->eof = TRUE;
	rr->complete = -1;
#ifdef DEBUG_DOWNLOAD
	printf("setting eof\n");
#endif
    } else if (rr->retlen < 0) {
	/* some error other than EOF; signal it back to caller */
	xfer_set_error(xfer);
	rr->complete = -1;
	return -1;
    }

    rr->complete = 1;

    /*
     * Special case: if we have received fewer bytes than we
     * actually read, we should do something. For the moment I'll
     * just throw an ersatz FXP error to signal this; the SFTP
     * draft I've got says that it can't happen except on special
     * files, in which case seeking probably has very little
     * meaning and so queueing an additional read request to fill
     * up the gap sounds like the wrong answer. I'm not sure what I
     * should be doing here - if it _was_ a special file, I suspect
     * I simply shouldn't have been queueing multiple requests in
     * the first place...
     */
    if (rr->retlen > 0 && uint64_compare(xfer->furthestdata, rr->offset) < 0) {
	xfer->furthestdata = rr->offset;
#ifdef DEBUG_DOWNLOAD
	{ char buf[40];
	uint64_decimal(xfer->furthestdata, buf);
	printf("setting furthestdata = %s\n", buf); }
#endif
    }

    if (rr->retlen < rr->len) {
	uint64 filesize = uint64_add32(rr->offset,
				       (rr->retlen < 0 ? 0 : rr->retlen));
#ifdef DEBUG_DOWNLOAD
	{ char buf[40];
	uint64_decimal(filesize, buf);
	printf("short block! trying filesize = %s\n", buf); }
#endif
	if (uint64_compare(xfer->filesize, filesize) > 0) {
	    xfer->filesize = filesize;
#ifdef DEBUG_DOWNLOAD
	    printf("actually changing filesize\n");
#endif	    
	}
    }

    if (uint64_compare(xfer->furthestdata, xfer->filesize) > 0) {
	fxp_error_message = "received a short buffer from FXP_READ, but not"
	    " at EOF";
	fxp_errtype = -1;
	xfer_set_error(xfer);
	return -1;
    }

    return 1;
}

void xfer_set_error(struct fxp_xfer *xfer)
{
    xfer->err = 1;
}

int xfer_download_data(struct fxp_xfer *xfer, void **buf, int *len)
{
    void *retbuf = NULL;
    int retlen = 0;

    /*
     * Discard anything at the head of the rr queue with complete <
     * 0; return the first thing with complete > 0.
     */
    while (xfer->head && xfer->head->complete && !retbuf) {
	struct req *rr = xfer->head;

	if (rr->complete > 0) {
	    retbuf = rr->buffer;
	    retlen = rr->retlen;
#ifdef DEBUG_DOWNLOAD
	    printf("handing back data from read request %p\n", rr);
#endif
	}
#ifdef DEBUG_DOWNLOAD
	else
	    printf("skipping failed read request %p\n", rr);
#endif

	xfer->head = xfer->head->next;
	if (xfer->head)
	    xfer->head->prev = NULL;
	else
	    xfer->tail = NULL;
	xfer->req_totalsize -= rr->len;
	sfree(rr);
    }

    if (retbuf) {
	*buf = retbuf;
	*len = retlen;
	return 1;
    } else
	return 0;
}

struct fxp_xfer *xfer_upload_init(struct fxp_handle *fh, uint64 offset)
{
    struct fxp_xfer *xfer = xfer_init(fh, offset);

    /*
     * We set `eof' to 1 because this will cause xfer_done() to
     * return true iff there are no outstanding requests. During an
     * upload, our caller will be responsible for working out
     * whether all the data has been sent, so all it needs to know
     * from us is whether the outstanding requests have been
     * handled once that's done.
     */
    xfer->eof = 1;

    return xfer;
}

int xfer_upload_ready(struct fxp_xfer *xfer)
{
    if (xfer->req_totalsize < xfer->req_maxsize)
	return 1;
    else
	return 0;
}

void xfer_upload_data(struct fxp_xfer *xfer, char *buffer, int len)
{
    struct req *rr;
    struct sftp_request *req;

    rr = snew(struct req);
    rr->offset = xfer->offset;
    rr->complete = 0;
    if (xfer->tail) {
	xfer->tail->next = rr;
	rr->prev = xfer->tail;
    } else {
	xfer->head = rr;
	rr->prev = NULL;
    }
    xfer->tail = rr;
    rr->next = NULL;

    rr->len = len;
    rr->buffer = NULL;
    sftp_register(req = fxp_write_send(xfer->fh, buffer, rr->offset, len));
    fxp_set_userdata(req, rr);

    xfer->offset = uint64_add32(xfer->offset, rr->len);
    xfer->req_totalsize += rr->len;

#ifdef DEBUG_UPLOAD
    { char buf[40]; uint64_decimal(rr->offset, buf); printf("queueing write request %p at %s [len %d]\n", rr, buf, len); }
#endif
}

int xfer_upload_gotpkt(struct fxp_xfer *xfer, struct sftp_packet *pktin)
{
    struct sftp_request *rreq;
    struct req *rr, *prev, *next;
    int ret;

    rreq = sftp_find_request(pktin);
    rr = (struct req *)fxp_get_userdata(rreq);
    if (!rr)
	return 0;		       /* this packet isn't ours */
    ret = fxp_write_recv(pktin, rreq);
#ifdef DEBUG_UPLOAD
    printf("write request %p has returned [%d]\n", rr, ret);
#endif

    /*
     * Remove this one from the queue.
     */
    prev = rr->prev;
    next = rr->next;
    if (prev)
	prev->next = next;
    else
	xfer->head = next;
    if (next)
	next->prev = prev;
    else
	xfer->tail = prev;
    xfer->req_totalsize -= rr->len;
    sfree(rr);

    if (!ret)
	return -1;

    return 1;
}

void xfer_cleanup(struct fxp_xfer *xfer)
{
    struct req *rr;
    while (xfer->head) {
	rr = xfer->head;
	xfer->head = xfer->head->next;
	sfree(rr->buffer);
	sfree(rr);
    }
    sfree(xfer);
}