From 6988fa317478435eceb92efae5a7c51123421cb5 Mon Sep 17 00:00:00 2001 From: Daniel Kobras Date: Mon, 26 Sep 2022 10:27:19 +0200 Subject: [PATCH 1/2] s3: smbd: Consistently map EAs to user namespace Samba has always been mapping Windows EAs to the 'user' namespace on the POSIX side. However, in the opposite direction, the mapping would also map other user-readable POSIX EA namespaces to Windows EAs, only stripping the 'user' namespace prefix, and passing all other EA names verbatim. This means any POSIX EA 'other.foo' collides with 'user.other.foo' on the Windows side, hence the mapping of non-user namespaces is unreliable. Also, copy operations via Windows would rename an existing POSIX EA 'other.foo' in the source file to 'user.other.foo' in the destination. The 'user' namespace, however, may not be enabled on the underlying filesystem, leading to subtle failure modes like the ones reported in eg. Fix the issues by restricting the mapping to the 'user' POSIX EA namespace consistently for either direction. Link: https://lists.samba.org/archive/samba-technical/2022-September/137634.html BUG: https://bugzilla.samba.org/show_bug.cgi?id=15186 Signed-off-by: Daniel Kobras Reviewed-by: Michael Weiser Tested-by: Michael Weiser Reviewed-by: Jeremy Allison Reviewed-by: Volker Lendecke (cherry picked from commit 34c6db64c2ff62673f8df218487cda4139c10843) --- source3/smbd/smb2_trans2.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/source3/smbd/smb2_trans2.c b/source3/smbd/smb2_trans2.c index b2a0cc4140a..8d1e31df1f3 100644 --- a/source3/smbd/smb2_trans2.c +++ b/source3/smbd/smb2_trans2.c @@ -454,7 +454,19 @@ static NTSTATUS get_ea_list_from_fsp(TALLOC_CTX *mem_ctx, struct ea_list *listp; fstring dos_ea_name; - if (strnequal(names[i], "system.", 7) + /* + * POSIX EA names are divided into several namespaces by + * means of string prefixes. Usually, the system controls + * semantics for each namespace, but the 'user' namespace is + * available for arbitrary use, which comes closest to + * Windows EA semantics. Hence, we map POSIX EAs from the + * 'user' namespace to Windows EAs, and just ignore all the + * other namespaces. Also, a few specific names in the 'user' + * namespace are used by Samba internally. Filter them out as + * well, and only present the EAs that are available for + * arbitrary use. + */ + if (!strnequal(names[i], "user.", 5) || samba_private_attr_name(names[i])) continue; @@ -780,7 +792,14 @@ NTSTATUS set_ea(connection_struct *conn, files_struct *fsp, int ret; fstring unix_ea_name; - fstrcpy(unix_ea_name, "user."); /* All EA's must start with user. */ + /* + * Complementing the forward mapping from POSIX EAs to + * Windows EAs in get_ea_list_from_fsp(), here we map in the + * opposite direction from Windows EAs to the 'user' namespace + * of POSIX EAs. Hence, all POSIX EA names the we set here must + * start with a 'user.' prefix. + */ + fstrcpy(unix_ea_name, "user."); fstrcat(unix_ea_name, ea_list->ea.name); canonicalize_ea_name(fsp, unix_ea_name); -- 2.34.1 From e3c919132d743ce96bcbd0f4415259f638561ade Mon Sep 17 00:00:00 2001 From: Daniel Kobras Date: Fri, 21 Oct 2022 16:40:14 +0200 Subject: [PATCH 2/2] docs-xml: ea support option restricted to user ns Update documentation to match current behavior. Signed-off-by: Daniel Kobras Reviewed-by: Jeremy Allison Reviewed-by: Volker Lendecke BUG: https://bugzilla.samba.org/show_bug.cgi?id=15186 Autobuild-User(master): Volker Lendecke Autobuild-Date(master): Fri Oct 28 07:24:18 UTC 2022 on sn-devel-184 (cherry picked from commit 69273c3a836ede97c7fde74e2f1fdc84e92ec86f) --- docs-xml/smbdotconf/protocol/easupport.xml | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/docs-xml/smbdotconf/protocol/easupport.xml b/docs-xml/smbdotconf/protocol/easupport.xml index 403e48f5a89..0ff9d32f964 100644 --- a/docs-xml/smbdotconf/protocol/easupport.xml +++ b/docs-xml/smbdotconf/protocol/easupport.xml @@ -14,8 +14,17 @@ attributes (e.g. the getfattr1 / setfattr1 utilities must work). + Access to extended user attributes must be allowed by the underlying + filesystem (e.g. when mounted with a system-dependent option like user_xattr on Linux). + + This option exposes the "user" attribute namespace from the underlying filesystem to + clients. In order to match Windows conventions, the namespace prefix ("user.") is + stripped from the attribute name on the client side. The handling of further attribute + namespaces (like "security", "system", or "trusted") is not affected by this option. + + Note that the SMB protocol allows setting attributes whose value is 64K bytes long, and that on NTFS, the maximum storage space for extended attributes per file is 64K. On most UNIX systems (Solaris and ZFS file system being the exception), the limits -- 2.34.1