Attachment 3494 Details for Bug 2948 – sftp server copy-data extension v2

[patch] sftp server copy-data extension v2

0001-sftp-server-support-copy-data-request.patch (text/plain), 6.86 KB, created by Mike Frysinger on 2021-04-05 00:57:55 AEST

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Creator: Mike Frysinger

Created: 2021-04-05 00:57:55 AEST

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patch

obsolete

>From b0be085aa727dad8b806e41217f4a319a5a24ff9 Mon Sep 17 00:00:00 2001
>From: Mike Frysinger <vapier@chromium.org>
>Date: Wed, 24 Oct 2018 23:20:34 -0400
>Subject: [PATCH 1/2] sftp-server: support copy-data request
>
>Add support to the sftp-server for the copy-data extension defined in
>[1].  This provides for efficient copying on the server side otherwise
>clients have to emulate it by downloading the file before uploading it
>to the new path.  For large files or slow networks, this can be
>prohibitively slow. Now doing a file copy is limited only by the server
>I/O.
>
>For clients that provide virtual file systems on top of SFTP, this can
>provide significant performance gains.
>
>[1] https://tools.ietf.org/html/draft-ietf-secsh-filexfer-extensions-00#section-7
>---
> PROTOCOL      | 39 +++++++++++++++++++++-
> sftp-server.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 130 insertions(+), 1 deletion(-)
>
>diff --git a/PROTOCOL b/PROTOCOL
>index 0b2ea60a74ba..47b69078cc64 100644
>--- a/PROTOCOL
>+++ b/PROTOCOL
>@@ -460,7 +460,7 @@ This request asks the server to call fsync(2) on an open file handle.
> 	string		"fsync@openssh.com"
> 	string		handle
> 
>-One receiving this request, a server will call fsync(handle_fd) and will
>+On receiving this request, a server will call fsync(handle_fd) and will
> respond with a SSH_FXP_STATUS message.
> 
> This extension is advertised in the SSH_FXP_VERSION hello with version
>@@ -525,6 +525,43 @@ limits.
> This extension is advertised in the SSH_FXP_VERSION hello with version
> "1".
> 
>+3.8. sftp: Extension request "copy-data"
>+
>+This request asks the server to copy data from one open file handle and
>+write it to a different open file handle.  This avoids needing to transfer
>+the data across the network twice (a download followed by an upload).
>+
>+	byte		SSH_FXP_EXTENDED
>+	uint32		id
>+	string		"copy-data"
>+	string		read-from-handle
>+	uint64		read-from-offset
>+	uint64		read-data-length
>+	string		write-to-handle
>+	uint64		write-to-offset
>+
>+The server will copy read-data-length bytes starting from
>+read-from-offset from the read-from-handle and write them to
>+write-to-handle starting from write-to-offset, and then respond with a
>+SSH_FXP_STATUS message.
>+
>+It's equivalent to issuing a series of SSH_FXP_READ requests on
>+read-from-handle and a series of requests of SSH_FXP_WRITE on
>+write-to-handle.
>+
>+If read-from-handle and write-to-handle are the same, the server will
>+fail the request and respond with a SSH_FX_INVALID_PARAMETER message.
>+
>+If read-data-length is 0, then the server will read data from the
>+read-from-handle until EOF is reached.
>+
>+This extension is advertised in the SSH_FXP_VERSION hello with version
>+"1".
>+
>+This request is identical to the "copy-data" request documented in:
>+
>+https://tools.ietf.org/html/draft-ietf-secsh-filexfer-extensions-00#section-7
>+
> 4. Miscellaneous changes
> 
> 4.1 Public key format
>diff --git a/sftp-server.c b/sftp-server.c
>index cce52dbc2f11..06e10a23a8e7 100644
>--- a/sftp-server.c
>+++ b/sftp-server.c
>@@ -41,6 +41,7 @@
> #include <unistd.h>
> #include <stdarg.h>
> 
>+#include "atomicio.h"
> #include "xmalloc.h"
> #include "sshbuf.h"
> #include "ssherr.h"
>@@ -115,6 +116,7 @@ static void process_extended_hardlink(u_int32_t id);
> static void process_extended_fsync(u_int32_t id);
> static void process_extended_lsetstat(u_int32_t id);
> static void process_extended_limits(u_int32_t id);
>+static void process_extended_copy_data(u_int32_t id);
> static void process_extended(u_int32_t id);
> 
> struct sftp_handler {
>@@ -158,6 +160,7 @@ static const struct sftp_handler extended_handlers[] = {
> 	{ "fsync", "fsync@openssh.com", 0, process_extended_fsync, 1 },
> 	{ "lsetstat", "lsetstat@openssh.com", 0, process_extended_lsetstat, 1 },
> 	{ "limits", "limits@openssh.com", 0, process_extended_limits, 1 },
>+	{ "copy-data", "copy-data", 0, process_extended_copy_data, 1 },
> 	{ NULL, NULL, 0, NULL, 0 }
> };
> 
>@@ -706,6 +709,7 @@ process_init(void)
> 	compose_extension(msg, "fsync@openssh.com", "1");
> 	compose_extension(msg, "lsetstat@openssh.com", "1");
> 	compose_extension(msg, "limits@openssh.com", "1");
>+	compose_extension(msg, "copy-data", "1");
> 
> 	send_msg(msg);
> 	sshbuf_free(msg);
>@@ -1515,6 +1519,94 @@ process_extended_limits(u_int32_t id)
> 	sshbuf_free(msg);
> }
> 
>+static void
>+process_extended_copy_data(u_int32_t id)
>+{
>+	u_char buf[64*1024];
>+	int read_handle, read_fd, write_handle, write_fd;
>+	u_int64_t len, read_off, read_len, write_off;
>+	int r, copy_until_eof, status = SSH2_FX_OP_UNSUPPORTED;
>+	size_t ret;
>+
>+	if ((r = get_handle(iqueue, &read_handle)) != 0 ||
>+	    (r = sshbuf_get_u64(iqueue, &read_off)) != 0 ||
>+	    (r = sshbuf_get_u64(iqueue, &read_len)) != 0 ||
>+	    (r = get_handle(iqueue, &write_handle)) != 0 ||
>+	    (r = sshbuf_get_u64(iqueue, &write_off)) != 0)
>+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
>+
>+	debug("request %u: copy-data from \"%s\" (handle %d) off %llu len %llu "
>+	    "to \"%s\" (handle %d) off %llu",
>+	    id, handle_to_name(read_handle), read_handle,
>+	    (unsigned long long)read_off, (unsigned long long)read_len,
>+	    handle_to_name(write_handle), write_handle,
>+	    (unsigned long long)write_off);
>+
>+	/* For read length of 0, we read until EOF. */
>+	if (read_len == 0) {
>+		read_len = (u_int64_t)-1 - read_off;
>+		copy_until_eof = 1;
>+	} else
>+		copy_until_eof = 0;
>+
>+	read_fd = handle_to_fd(read_handle);
>+	write_fd = handle_to_fd(write_handle);
>+
>+	/* Disallow reading & writing to the same handle or same path or dirs */
>+	if (read_handle == write_handle || read_fd < 0 || write_fd < 0 ||
>+	    !strcmp(handle_to_name(read_handle), handle_to_name(write_handle))) {
>+		status = SSH2_FX_FAILURE;
>+		goto out;
>+	}
>+
>+	if (lseek(read_fd, read_off, SEEK_SET) < 0) {
>+		status = errno_to_portable(errno);
>+		error("%s: read_seek failed", __func__);
>+		goto out;
>+	}
>+
>+	if (!(handle_to_flags(write_handle) & O_APPEND) &&
>+			lseek(write_fd, write_off, SEEK_SET) < 0) {
>+		status = errno_to_portable(errno);
>+		error("%s: write_seek failed", __func__);
>+		goto out;
>+	}
>+
>+	/* Process the request in chunks. */
>+	while (read_len > 0 || copy_until_eof) {
>+		len = MINIMUM(sizeof(buf), read_len);
>+		read_len -= len;
>+
>+		ret = atomicio(read, read_fd, buf, len);
>+		if (ret == 0 && errno == EPIPE) {
>+			status = copy_until_eof ? SSH2_FX_OK : SSH2_FX_EOF;
>+			break;
>+		} else if (ret == 0) {
>+			status = errno_to_portable(errno);
>+			error("%s: read failed: %s", __func__, strerror(errno));
>+			break;
>+		}
>+		len = ret;
>+		handle_update_read(read_handle, len);
>+
>+		ret = atomicio(vwrite, write_fd, buf, len);
>+		if (ret != len) {
>+			status = errno_to_portable(errno);
>+			error("%s: write failed: %llu != %llu: %s", __func__,
>+			      (unsigned long long)ret, (unsigned long long)len,
>+			      strerror(errno));
>+			break;
>+		}
>+		handle_update_write(write_handle, len);
>+	}
>+
>+	if (read_len == 0)
>+		status = SSH2_FX_OK;
>+
>+ out:
>+	send_status(id, status);
>+}
>+
> static void
> process_extended(u_int32_t id)
> {
>-- 
>2.30.2
>

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