Re: [PATCH] Adds support for SSH_FXP_LINK request to sftp-server and

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On Tue, May 08, 2007 at 06:09:22PM +0100, Peter Collingbourne wrote:
> On Tue, May 08, 2007 at 05:13:39PM +0200, Daniele Calore wrote:
> > - Solutions:
> > 1- Upgrade define SSH2_FILEXFER_VERSION to 4 ???
> > (and also update the check)
>
> If we do this then perhaps it should go to 7 (I assume the version
> numbers correspond to drafts?) But then we may not be completely
> compliant with 7 yet. Of course if the check fails we should revert
> to sending a SYMLINK request (if version >=3D 3), but only if sym =3D
> 1. This is because only the hardlink request requires the oldpath to
> be normalised, and sending a normalised oldpath for a symlink request
> would lead to problems.
>=20
> This behaviour would cause compatibility problems if the bare 'ln'
> command is issued to a new client connected to an old server, not
> to mention the fact that the behaviour of ln has changed anyway.
> Perhaps the best course of action would be to change the -s flag to
> an -h flag, with the default being softlinks? Of course this would
> be inconsistent with the ln(1) command.

I am attaching a patch which incorporates some of my above suggestions.
According to draft 7 and all future drafts, the current version of
the filexfer protocol is 6, which is the version number I am using
in my patch. I would like feedback on whether an -s flag or an -h
flag would be best for the ln command of the sftp client.

Thanks,
--=20
Peter

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diff -ur openssh.orig/sftp.1 openssh/sftp.1
--- openssh.orig/sftp.1 2006-01-20 00:31:47.000000000 +0000
+++ openssh/sftp.1 2007-05-14 20:56:49.000000000 +0100
@@ -321,11 +321,17 @@
.It Ic lmkdir Ar path
Create local directory specified by
.Ar path .
-.It Ic ln Ar oldpath Ar newpath
-Create a symbolic link from
+.It Xo Ic ln
+.Op Fl s
+.Ar oldpath Ar newpath
+.Xc
+Create a hard link from
.Ar oldpath
to
-.Ar newpath .
+.Ar newpath ,
+or a symbolic link if the
+.Fl s
+flag is specified.
.It Ic lpwd
Print local working directory.
.It Xo Ic ls
diff -ur openssh.orig/sftp.c openssh/sftp.c
--- openssh.orig/sftp.c 2007-01-05 05:30:41.000000000 +0000
+++ openssh/sftp.c 2007-05-14 20:48:38.000000000 +0100
@@ -122,6 +122,7 @@
#define I_SYMLINK 21
#define I_VERSION 22
#define I_PROGRESS 23
+#define I_LINK 24
=20
struct CMD {
const char *c;
@@ -144,7 +145,7 @@
{ "lchdir", I_LCHDIR },
{ "lls", I_LLS },
{ "lmkdir", I_LMKDIR },
- { "ln", I_SYMLINK },
+ { "ln", I_LINK },
{ "lpwd", I_LPWD },
{ "ls", I_LS },
{ "lumask", I_LUMASK },
@@ -202,7 +203,7 @@
printf("help Display this help text\n");
printf("get remote-path [local-path] Download file\n");
printf("lls [ls-options [path]] Display local directory listing\n");
- printf("ln oldpath newpath Symlink remote file\n");
+ printf("ln [-s] oldpath newpath (Sym)link remote file\n");
printf("lmkdir path Create local directory\n");
printf("lpwd Print local working directory\n");
printf("ls [path] Display remote directory listing\n"=
);
@@ -369,6 +370,29 @@
}
=20
static int
+parse_link_flags(const char **cpp, int *sflag)
+{
+ const char *cp =3D *cpp;
+
+ /* Check for flags */
+ if (cp[0] =3D=3D '-' && cp[1] && strchr(WHITESPACE, cp[2])) {
+ switch (cp[1]) {
+ case 's':
+ case 'S':
+ *sflag =3D 1;
+ break;
+ default:
+ error("Invalid flag -%c", cp[1]);
+ return(-1);
+ }
+ cp +=3D 2;
+ *cpp =3D cp + strspn(cp, WHITESPACE);
+ }
+
+ return(0);
+}
+
+static int
parse_ls_flags(const char **cpp, int *lflag)
{
const char *cp =3D *cpp;
@@ -867,7 +891,7 @@
}
=20
static int
-parse_args(const char **cpp, int *pflag, int *lflag, int *iflag,
+parse_args(const char **cpp, int *pflag, int *lflag, int *sflag, int *ifla=
g,
unsigned long *n_arg, char **path1, char **path2)
{
const char *cmd, *cp =3D *cpp;
@@ -915,7 +939,7 @@
}
=20
/* Get arguments and parse flags */
- *lflag =3D *pflag =3D *n_arg =3D 0;
+ *sflag =3D *lflag =3D *pflag =3D *n_arg =3D 0;
*path1 =3D *path2 =3D NULL;
switch (cmdnum) {
case I_GET:
@@ -934,6 +958,9 @@
if (get_pathname(&cp, path2))
return(-1);
break;
+ case I_LINK:
+ if (parse_link_flags(&cp, sflag))
+ return(-1);
case I_RENAME:
case I_SYMLINK:
if (get_pathname(&cp, path1))
@@ -1027,7 +1054,7 @@
int err_abort)
{
char *path1, *path2, *tmp;
- int pflag, lflag, iflag, cmdnum, i;
+ int pflag, lflag, sflag, iflag, cmdnum, i;
unsigned long n_arg;
Attrib a, *aa;
char path_buf[MAXPATHLEN];
@@ -1035,7 +1062,7 @@
glob_t g;
=20
path1 =3D path2 =3D NULL;
- cmdnum =3D parse_args(&cmd, &pflag, &lflag, &iflag, &n_arg,
+ cmdnum =3D parse_args(&cmd, &pflag, &lflag, &sflag, &iflag, &n_arg,
&path1, &path2);
=20
if (iflag !=3D 0)
@@ -1067,6 +1094,13 @@
path2 =3D make_absolute(path2, *pwd);
err =3D do_symlink(conn, path1, path2);
break;
+ case I_LINK:
+ if (!sflag) {
+ path1 =3D make_absolute(path1, *pwd);
+ }
+ path2 =3D make_absolute(path2, *pwd);
+ err =3D do_link(conn, path1, path2, sflag);
+ break;
case I_RM:
path1 =3D make_absolute(path1, *pwd);
remote_glob(conn, path1, GLOB_NOCHECK, NULL, &g);
diff -ur openssh.orig/sftp-client.c openssh/sftp-client.c
--- openssh.orig/sftp-client.c 2007-02-19 11:13:39.000000000 +0000
+++ openssh/sftp-client.c 2007-05-14 20:48:38.000000000 +0100
@@ -686,6 +686,47 @@
return(status);
}
=20
+int
+do_link(struct sftp_conn *conn, char *oldpath, char *newpath, int sym)
+{
+ Buffer msg;
+ u_int status, id;
+
+ if (conn->version >=3D 3 && conn->version < 6 && sym) {
+ /*
+ * For backwards-compatibility, send a symlink request
+ * if possible and server does not support link request.
+ */
+ return(do_symlink(conn, oldpath, newpath));
+ }
+
+ if (conn->version < 6) {
+ error("This server does not support the link operation");
+ return(SSH2_FX_OP_UNSUPPORTED);
+ }
+
+ buffer_init(&msg);
+
+ /* Send link request */
+ id =3D conn->msg_id++;
+ buffer_put_char(&msg, SSH2_FXP_LINK);
+ buffer_put_int(&msg, id);
+ buffer_put_cstring(&msg, newpath);
+ buffer_put_cstring(&msg, oldpath);
+ buffer_put_char(&msg, sym);
+ send_msg(conn->fd_out, &msg);
+ debug3("Sent message SSH2_FXP_LINK \"%s\" -> \"%s\" (sym=3D%d)", oldpath,
+ newpath, sym);
+ buffer_free(&msg);
+
+ status =3D get_status(conn->fd_in, id);
+ if (status !=3D SSH2_FX_OK)
+ error("Couldn't link file \"%s\" to \"%s\": %s", oldpath,
+ newpath, fx2txt(status));
+
+ return(status);
+}
+
char *
do_readlink(struct sftp_conn *conn, char *path)
{
diff -ur openssh.orig/sftp-client.h openssh/sftp-client.h
--- openssh.orig/sftp-client.h 2005-05-26 03:05:49.000000000 +0100
+++ openssh/sftp-client.h 2007-05-14 20:48:38.000000000 +0100
@@ -76,9 +76,12 @@
/* Rename 'oldpath' to 'newpath' */
int do_rename(struct sftp_conn *, char *, char *);
=20
-/* Rename 'oldpath' to 'newpath' */
+/* Symlink 'oldpath' to 'newpath' */
int do_symlink(struct sftp_conn *, char *, char *);
=20
+/* Link 'oldpath' to 'newpath', with a symlink if 'sflag' is set */
+int do_link(struct sftp_conn *, char *, char *, int);
+
/* Return target of symlink 'path' - caller must free result */
char *do_readlink(struct sftp_conn *, char *);
=20
diff -ur openssh.orig/sftp.h openssh/sftp.h
--- openssh.orig/sftp.h 2006-03-26 04:30:02.000000000 +0100
+++ openssh/sftp.h 2007-05-14 20:48:38.000000000 +0100
@@ -29,7 +29,7 @@
*/
=20
/* version */
-#define SSH2_FILEXFER_VERSION 3
+#define SSH2_FILEXFER_VERSION 6
=20
/* client to server */
#define SSH2_FXP_INIT 1
@@ -52,6 +52,7 @@
#define SSH2_FXP_RENAME 18
#define SSH2_FXP_READLINK 19
#define SSH2_FXP_SYMLINK 20
+#define SSH2_FXP_LINK 21
=20
/* server to client */
#define SSH2_FXP_VERSION 2
diff -ur openssh.orig/sftp-server.c openssh/sftp-server.c
--- openssh.orig/sftp-server.c 2007-01-05 05:31:03.000000000 +0000
+++ openssh/sftp-server.c 2007-05-14 20:53:37.000000000 +0100
@@ -48,6 +48,7 @@
/* helper */
#define get_int64() buffer_get_int64(&iqueue);
#define get_int() buffer_get_int(&iqueue);
+#define get_char() buffer_get_char(&iqueue);
#define get_string(lenp) buffer_get_string(&iqueue, lenp);
=20
/* Our verbosity */
@@ -1070,6 +1071,32 @@
}
=20
static void
+process_link(void)
+{
+ u_int32_t id;
+ char *oldpath, *newpath;
+ u_int sym;
+ int ret, status;
+
+ id =3D get_int();
+ newpath =3D get_string(NULL);
+ oldpath =3D get_string(NULL);
+ sym =3D get_char();
+ debug3("request %u: link", id);
+ logit("link old \"%s\" new \"%s\" sym %u", oldpath, newpath, sym);
+ /* this will fail if 'newpath' exists */
+ if (sym) {
+ ret =3D symlink(oldpath, newpath);
+ } else {
+ ret =3D link(oldpath, newpath);
+ }
+ status =3D (ret =3D=3D -1) ? errno_to_portable(errno) : SSH2_FX_OK;
+ send_status(id, status);
+ xfree(oldpath);
+ xfree(newpath);
+}
+
+static void
process_extended(void)
{
u_int32_t id;
@@ -1165,6 +1192,9 @@
case SSH2_FXP_SYMLINK:
process_symlink();
break;
+ case SSH2_FXP_LINK:
+ process_link();
+ break;
case SSH2_FXP_EXTENDED:
process_extended();
break;

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