[pve-devel] [PATCH v1 pve-firewall] fix #7068: show rule comments in iptables output

[Robert Obkircher <r.obkircher@proxmox.com>]

Use the iptables comment extension to include comments from the UI.
Prefix them with "PVECOMMENT:" to avoid interfering with the existing
"PVESIG:$sig" comments, which are used to store signatures for change
detection.

The total length of the (unescaped) comments is limited to 255 utf8
bytes. According to the man page it could be up to 256 characters, but
the actual implementation seems to zero terminate the buffer before
saving. For example, the following command produces a 255 char comment
ending in 'a':
iptables -A PVEFW-HOST-IN -m comment --comment $(python3 -c "print('ab'*256)")

Unlike the iptables command, this version truncates to valid utf8.

Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
---
 src/PVE/Firewall.pm | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/PVE/Firewall.pm b/src/PVE/Firewall.pm
index 93f8c34..688829a 100644
--- a/src/PVE/Firewall.pm
+++ b/src/PVE/Firewall.pm
@@ -2271,6 +2271,20 @@ sub ipt_gen_src_or_dst_match {
     return $match;
 }
 
+sub print_ipt_comment {
+    my ($comment) = @_;
+    return "" if !defined($comment) || $comment eq "";
+    $comment = encode("utf8", $comment, Encode::LEAVE_SRC);
+    $comment = "PVECOMMENT:$comment"; # avoid any confusion with PVESIG comments
+
+    # man iptables-extensions says 256 chars, but the code only saves 255
+    $comment = substr($comment, 0, 255);
+    $comment = encode('utf8', decode('utf8', $comment, Encode::FB_QUIET | Encode::LEAVE_SRC));
+
+    $comment =~ s/[\\"']/\\$1/g; # escape logic from xtables_save_string
+    return " -m comment --comment \"$comment\""; # never omit quotes because of the colon
+}
+
 # convert a %rule to an array of iptables commands
 sub ipt_rule_to_cmds {
     my ($rule, $chain, $ipversion, $cluster_conf, $fw_conf, $vmid) = @_;
@@ -2375,7 +2389,8 @@ sub ipt_rule_to_cmds {
         my $logaction = get_log_rule_base($chain, $vmid, $rule->{logmsg}, $loglevel);
         push @iptcmds, "-A $chain $matchstr $logaction";
     }
-    push @iptcmds, "-A $chain $matchstr $targetstr";
+    my $comment = print_ipt_comment($rule->{comment});
+    push @iptcmds, "-A $chain $matchstr $targetstr$comment";
     return @iptcmds;
 }
 
-- 
2.47.3



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