linux-kernel - [RFC 02/11] oid_registry: allow arbitrary size OIDs

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Message-ID: <20251211021257.1208712-3-bboscaccy@linux.microsoft.com>
Date: Wed, 10 Dec 2025 18:11:57 -0800
From: Blaise Boscaccy <bboscaccy@...ux.microsoft.com>
To: Blaise Boscaccy <bboscaccy@...ux.microsoft.com>,
	Jonathan Corbet <corbet@....net>,
	Paul Moore <paul@...l-moore.com>,
	James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Mickaël Salaün <mic@...ikod.net>,
	Günther Noack <gnoack@...gle.com>,
	"Dr. David Alan Gilbert" <linux@...blig.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	James.Bottomley@...senPartnership.com,
	dhowells@...hat.com,
	linux-security-module@...r.kernel.org,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org
Subject: [RFC 02/11] oid_registry: allow arbitrary size OIDs

From: James Bottomley <James.Bottomley@...senPartnership.com>

The current OID registry parser uses 64 bit arithmetic which limits us
to supporting 64 bit or smaller OIDs.  This isn't usually a problem
except that it prevents us from representing the 2.25. prefix OIDs
which are the OID representation of UUIDs and have a 128 bit number
following the prefix.  Rather than import not often used perl
arithmetic modules, replace the current perl 64 bit arithmetic with a
callout to bc, which is arbitrary precision, for decimal to base 2
conversion, then do pure string operations on the base 2 number.

Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
---
 lib/build_OID_registry | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/lib/build_OID_registry b/lib/build_OID_registry
index 8267e8d71338b..30493ac190c0c 100755
--- a/lib/build_OID_registry
+++ b/lib/build_OID_registry
@@ -60,10 +60,12 @@ for (my $i = 0; $i <= $#names; $i++) {
     # Determine the encoded length of this OID
     my $size = $#components;
     for (my $loop = 2; $loop <= $#components; $loop++) {
-	my $c = $components[$loop];
+	$ENV{'BC_LINE_LENGTH'} = "0";
+	my $c = `echo "ibase=10; obase=2; $components[$loop]" | bc`;
+	chomp($c);
 
 	# We will base128 encode the number
-	my $tmp = ($c == 0) ? 0 : int(log($c)/log(2));
+	my $tmp = length($c) - 1;
 	$tmp = int($tmp / 7);
 	$size += $tmp;
     }
@@ -100,16 +102,24 @@ for (my $i = 0; $i <= $#names; $i++) {
     push @octets, $components[0] * 40 + $components[1];
 
     for (my $loop = 2; $loop <= $#components; $loop++) {
-	my $c = $components[$loop];
+	# get the base 2 representation of the component
+	$ENV{'BC_LINE_LENGTH'} = "0";
+	my $c = `echo "ibase=10; obase=2; $components[$loop]" | bc`;
+	chomp($c);
 
-	# Base128 encode the number
-	my $tmp = ($c == 0) ? 0 : int(log($c)/log(2));
+	my $tmp = length($c) - 1;
 	$tmp = int($tmp / 7);
 
-	for (; $tmp > 0; $tmp--) {
-	    push @octets, (($c >> $tmp * 7) & 0x7f) | 0x80;
+	# zero pad upto length multiple of 7
+	$c = substr("0000000", 0, ($tmp + 1) * 7 - length($c)).$c;
+
+	# Base128 encode the number
+	for (my $j = 0; $j < $tmp; $j++) {
+	    my $b = oct("0b".substr($c, $j * 7, 7));
+
+	    push @octets, $b | 0x80;
 	}
-	push @octets, $c & 0x7f;
+	push @octets, oct("0b".substr($c, $tmp * 7, 7));
     }
 
     push @encoded_oids, \@octets;
-- 
2.52.0