On Wed, Oct 14, 2020 at 07:02:09PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
>
> The mapping rule system implemented in the last few patches is
> extremely flexible, but not easy to use. Add a simple
> 'map' type as a sprinkling of sugar to make it easy.
>
> e.g.
>
> -o xattrmap=":map::user.virtiofs.:"
>
> would be sufficient to prefix all xattr's
> or
>
> -o xattrmap=":map:trusted.:user.virtiofs.:"
>
> would just prefix 'trusted.' xattr's and leave
> everything else alone.
Will it block "user.virtiofs.trusted." from client? As we discussed
that either we need to block it or we need to prefix it with another
user.virtiofs. I mean this rule alone is problematic and needs
to be coupled with more rules.
I am assuming one can specify multiple xattrmap on single line. So
one can also say.
-o xattrmap=":map:trusted.:user.virtiofs.:" -o
xattrmap=":map:user.virtiofs.:user.virtiofs."
Thanks
Vivek
>
> Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> docs/tools/virtiofsd.rst | 18 ++++++
> tools/virtiofsd/passthrough_ll.c | 108 ++++++++++++++++++++++++++++++-
> 2 files changed, 125 insertions(+), 1 deletion(-)
>
> diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> index 5cb64612ed..e388ef253e 100644
> --- a/docs/tools/virtiofsd.rst
> +++ b/docs/tools/virtiofsd.rst
> @@ -127,6 +127,7 @@ Each rule consists of a number of fields separated with a
> separator that is the
> first non-white space character in the rule. This separator must then be
> used
> for the whole rule.
> White space may be added before and after each rule.
> +
> Using ':' as the separator a rule is of the form:
>
> ``:type:scope:key:prepend:``
> @@ -162,6 +163,13 @@ on the server, and used as a new prefix. It may be empty
> in which case a 'server' rule will always match on all names from
> the server.
>
> +A simpler 'map' type provides a shorter syntax for the common case:
> +
> +``:map:key:prepend:``
> +
> +The 'map' type adds a number of separate rules to add **prepend** as a prefix
> +to the matched **key** (or all attributes if **key** is empty).
> +There may be at most one 'map' rule and it must be the last rule in the set.
>
> xattr-mapping Examples
> ----------------------
> @@ -178,6 +186,11 @@ the first rule prefixes and strips 'user.virtiofs.',
> the second rule hides any non-prefixed attributes that
> the host set.
>
> +This is equivalent to the 'map' rule:
> +
> +::
> +-o xattrmap=":map::user.virtiofs.:"
> +
> 2) Prefix 'trusted.' attributes, allow others through
>
> ::
> @@ -200,6 +213,11 @@ the 'user.viritofs.' path directly.
> Finally, the fourth rule lets all remaining attributes
> through.
>
> +This is equivalent to the 'map' rule:
> +
> +::
> +-o xattrmap="/map/trusted./user.virtiofs./"
> +
> 3) Hide 'security.' attributes, and allow everything else
>
> ::
> diff --git a/tools/virtiofsd/passthrough_ll.c
> b/tools/virtiofsd/passthrough_ll.c
> index 8406a2ae86..a1b3364ba3 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -2074,6 +2074,106 @@ static void free_xattrmap(XattrMapEntry *map)
> g_free(map);
> }
>
> +/*
> + * Handle the 'map' type, which is sugar for a set of commands
> + * for the common case of prefixing a subset or everything,
> + * and allowing anything not prefixed through.
> + * It must be the last entry in the stream, although there
> + * can be other entries before it.
> + * The form is:
> + * :map:key:prefix:
> + *
> + * key maybe empty in which case all entries are prefixed.
> + */
> +static XattrMapEntry *parse_xattrmap_map(const char *rule,
> + XattrMapEntry *map,
> + size_t *nentries)
> +{
> + char sep = *rule++;
> + const char *tmp;
> + char *key;
> + char *prefix;
> + XattrMapEntry tmp_entry;
> +
> + /* At start of 'key' field */
> + tmp = strchr(rule, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of key field in map rule\n",
> + __func__, sep);
> + exit(1);
> + }
> +
> + key = g_strndup(rule, tmp - rule);
> + rule = tmp + 1;
> +
> + /* At start of prefix field */
> + tmp = strchr(rule, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of prefix field in map rule\n",
> + __func__, sep);
> + exit(1);
> + }
> +
> + prefix = g_strndup(rule, tmp - rule);
> + rule = tmp + 1;
> +
> + /*
> + * This should be the end of the string, we don't allow
> + * any more commands after 'map'.
> + */
> + if (*rule) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Expecting end of command after map, found '%c'\n",
> + __func__, *rule);
> + exit(1);
> + }
> +
> + /* 1st: Prefix matches/everything */
> + tmp_entry.flags = XATTR_MAP_FLAG_PREFIX | XATTR_MAP_FLAG_ALL;
> + tmp_entry.key = g_strdup(key);
> + tmp_entry.prepend = g_strdup(prefix);
> + map = add_xattrmap_entry(map, nentries, &tmp_entry);
> +
> + if (!*key) {
> + /* Prefix all case */
> +
> + /* 2nd: Hide any non-prefixed entries on the host */
> + tmp_entry.flags = XATTR_MAP_FLAG_END_BAD | XATTR_MAP_FLAG_ALL |
> + XATTR_MAP_FLAG_LAST;
> + tmp_entry.key = g_strdup("");
> + tmp_entry.prepend = g_strdup("");
> + map = add_xattrmap_entry(map, nentries, &tmp_entry);
> + } else {
> + /* Prefix matching case */
> +
> + /* 2nd: Hide non-prefixed but matching entries on the host */
> + tmp_entry.flags = XATTR_MAP_FLAG_END_BAD | XATTR_MAP_FLAG_SERVER;
> + tmp_entry.key = g_strdup(""); /* Not used */
> + tmp_entry.prepend = g_strdup(key);
> + map = add_xattrmap_entry(map, nentries, &tmp_entry);
> +
> + /* 3rd: Stop the client accessing prefixed attributes directly */
> + tmp_entry.flags = XATTR_MAP_FLAG_END_BAD | XATTR_MAP_FLAG_CLIENT;
> + tmp_entry.key = g_strdup(prefix);
> + tmp_entry.prepend = g_strdup(""); /* Not used */
> + map = add_xattrmap_entry(map, nentries, &tmp_entry);
> +
> + /* 4th: Everything else is OK */
> + tmp_entry.flags = XATTR_MAP_FLAG_END_OK | XATTR_MAP_FLAG_ALL |
> + XATTR_MAP_FLAG_LAST;
> + tmp_entry.key = g_strdup("");
> + tmp_entry.prepend = g_strdup("");
> + map = add_xattrmap_entry(map, nentries, &tmp_entry);
> + }
> +
> + g_free(key);
> + g_free(prefix);
> +
> + return map;
> +}
> +
> static XattrMapEntry *parse_xattrmap(struct lo_data *lo)
> {
> XattrMapEntry *res = NULL;
> @@ -2102,10 +2202,16 @@ static XattrMapEntry *parse_xattrmap(struct lo_data
> *lo)
> tmp_entry.flags |= XATTR_MAP_FLAG_END_OK;
> } else if (strstart(map, "bad", &map)) {
> tmp_entry.flags |= XATTR_MAP_FLAG_END_BAD;
> + } else if (strstart(map, "map", &map)) {
> + /*
> + * map is sugar that adds a number of rules, and must be
> + * the last entry.
> + */
> + return parse_xattrmap_map(map, res, &nentries);
> } else {
> fuse_log(FUSE_LOG_ERR,
> "%s: Unexpected type;"
> - "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
> + "Expecting 'prefix', 'ok', 'bad' or 'map' in rule
> %zu\n",
> __func__, nentries);
> exit(1);
> }
> --
> 2.28.0
>
