Mailing List Archive

Add support to the sftp-server for the home-directory extension defined
in [1]. This overlaps a bit with the existing expand-path@openssh.com,
but uses a more official protocol name, and so is a bit more likely to
be implemented by clients.

I wrote this before expand-path@openssh.com existed, so posting it if
only to not be totally wasted effort. I'd understand if people would
prefer not to implement this at all, but if there is interest, I can
see about unifying the two functions a bit.

[1] https://tools.ietf.org/html/draft-ietf-secsh-filexfer-extensions-00#section-7
---
PROTOCOL | 20 ++++++++++++++++++++
sftp-server.c | 29 +++++++++++++++++++++++++++++
2 files changed, 49 insertions(+)

diff --git a/PROTOCOL b/PROTOCOL
index 2d50b5cb0528..7a035994489b 100644
--- a/PROTOCOL
+++ b/PROTOCOL
@@ -613,6 +613,26 @@ This request is identical to the "copy-data" request documented in:

https://tools.ietf.org/html/draft-ietf-secsh-filexfer-extensions-00#section-7

+4.11. sftp: Extension request "home-directory"
+
+This request asks the server to expand the specified user's home directory.
+An empty username implies the current user. This can be used by the client
+to expand ~/ type paths locally.
+
+ byte SSH_FXP_EXTENDED
+ uint32 id
+ string "home-directory"
+ string username
+
+This extension is advertised in the SSH_FXP_VERSION hello with version
+"1".
+
+This provides similar information as the "expand-path@openssh.com" extension.
+
+This request is identical to the "home-directory" request documented in:
+
+https://datatracker.ietf.org/doc/html/draft-ietf-secsh-filexfer-extensions-00#section-5
+
5. Miscellaneous changes

5.1 Public key format
diff --git a/sftp-server.c b/sftp-server.c
index 3dd19d4c81db..3aea751a9d67 100644
--- a/sftp-server.c
+++ b/sftp-server.c
@@ -121,6 +121,7 @@ static void process_extended_lsetstat(u_int32_t id);
static void process_extended_limits(u_int32_t id);
static void process_extended_expand(u_int32_t id);
static void process_extended_copy_data(u_int32_t id);
+static void process_extended_home_directory(u_int32_t id);
static void process_extended(u_int32_t id);

struct sftp_handler {
@@ -167,6 +168,8 @@ static const struct sftp_handler extended_handlers[] = {
{ "expand-path", "expand-path@openssh.com", 0,
process_extended_expand, 0 },
{ "copy-data", "copy-data", 0, process_extended_copy_data, 1 },
+ { "home-directory", "home-directory", 0,
+ process_extended_home_directory, 0 },
{ NULL, NULL, 0, NULL, 0 }
};

@@ -724,6 +727,7 @@ process_init(void)
compose_extension(msg, "limits@openssh.com", "1");
compose_extension(msg, "expand-path@openssh.com", "1");
compose_extension(msg, "copy-data", "1");
+ compose_extension(msg, "home-directory", "1");

send_msg(msg);
sshbuf_free(msg);
@@ -1684,6 +1688,31 @@ process_extended_copy_data(u_int32_t id)
send_status(id, status);
}

+static void
+process_extended_home_directory(u_int32_t id)
+{
+ char *username;
+ struct passwd *user_pw;
+ int r;
+ Stat s;
+
+ if ((r = sshbuf_get_cstring(iqueue, &username, NULL)) != 0)
+ fatal_fr(r, "parse");
+
+ debug3("request %u: home-directory \"%s\"", id, username);
+ if ((user_pw = getpwnam(username)) == NULL) {
+ send_status(id, errno_to_portable(errno));
+ goto out;
+ }
+
+ verbose("home-directory \"%s\"", pw->pw_dir);
+ attrib_clear(&s.attrib);
+ s.name = s.long_name = pw->pw_dir;
+ send_names(id, 1, &s);
+ out:
+ free(username);
+}
+
static void
process_extended(u_int32_t id)
{
--
2.34.1

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