[pve-devel] [PATCH installer 4/5] sys: net: do not allow overlong FQDNs as per RFCs and Debian spec

[Christoph Heiss <c.heiss@proxmox.com>]

Debian limits labels to 63 characters each and the total length to 253
characters [0].

[0] https://manpages.debian.org/stable/manpages/hostname.7.en.html

Signed-off-by: Christoph Heiss <c.heiss@proxmox.com>
---
 Proxmox/Sys/Net.pm | 5 ++++-
 test/parse-fqdn.pl | 4 ++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Proxmox/Sys/Net.pm b/Proxmox/Sys/Net.pm
index 3e01d37..2d29116 100644
--- a/Proxmox/Sys/Net.pm
+++ b/Proxmox/Sys/Net.pm
@@ -6,7 +6,7 @@ use warnings;
 use base qw(Exporter);
 our @EXPORT_OK = qw(parse_ip_address parse_ip_mask parse_fqdn);
 
-our $HOSTNAME_RE = "(?:[a-zA-Z0-9](?:[a-zA-Z0-9\-]*[a-zA-Z0-9])?)";
+our $HOSTNAME_RE = "(?:[a-zA-Z0-9](?:[a-zA-Z0-9\-]{,61}?[a-zA-Z0-9])?)";
 our $FQDN_RE = "(?:${HOSTNAME_RE}\.)*${HOSTNAME_RE}";
 
 my $IPV4OCTET = "(?:25[0-5]|(?:2[0-4]|1[0-9]|[1-9])?[0-9])";
@@ -221,6 +221,9 @@ sub parse_fqdn : prototype($) {
     die "FQDN cannot be empty\n"
 	if !$text || length($text) == 0;
 
+    die "FQDN too long\n"
+	if length($text) > 253;
+
     die "Purely numeric hostnames are not allowed\n"
 	if $text =~ /^[0-9]+(?:\.|$)/;
 
diff --git a/test/parse-fqdn.pl b/test/parse-fqdn.pl
index 1ffb300..3009984 100755
--- a/test/parse-fqdn.pl
+++ b/test/parse-fqdn.pl
@@ -47,4 +47,8 @@ is_invalid('123.com', ERR_NUMERIC);
 is_parsed('foo123.com', ['foo123', 'com']);
 is_parsed('123foo.com', ['123foo', 'com']);
 
+is_parsed('a' x 63 . '.com', ['a' x 63, 'com']);
+is_invalid('a' x 250 . '.com', ERR_TOOLONG);
+is_invalid('a' x 64 . '.com', ERR_ALPHANUM);
+
 done_testing();
-- 
2.43.0