hare

commit c5d94e5c3834651b8a0d2753dd775a4363b934e7
parent 59e47486b111886fc6de8f6be54f6b6715e53d2d
Author: Armin Preiml <apreiml@strohwolke.at>
Date:   Fri,  3 Nov 2023 15:38:10 +0100

crypto::bigint: decode only actual encoded words

Signed-off-by: Armin Preiml <apreiml@strohwolke.at>

Diffstat:
M
crypto/bigint/+test/encoding_test.ha
 | 
14
++++++++++++++
M
crypto/bigint/encoding.ha
 | 
3
++-

2 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/crypto/bigint/+test/encoding_test.ha b/crypto/bigint/+test/encoding_test.ha
@@ -3,6 +3,7 @@
 
 use bytes;
 
+
 @test fn encode() void = {
 	const decoded: [12]u8 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
 	let result: [12]u8 = [0...];
@@ -32,6 +33,19 @@ use bytes;
 	assert(bytes::equal(result, decoded));
 };
 
+@test fn decodebigger() void = {
+	const encoded: [_]word = [
+		0x32, // only 50 effective bits
+		0x7fffffff, 0x0007ffff, 0x7fffffff,
+	];
+
+	let result: [8]u8 = [0xaa...];
+
+	decode(result, encoded);
+	assert(bytes::equal(result,
+		[0x00, 0x03, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff]));
+};
+
 
 @test fn encmoddec() void = {
 	const input: [4]u8 = [0, 0, 0, 10];
diff --git a/crypto/bigint/encoding.ha b/crypto/bigint/encoding.ha
@@ -119,9 +119,10 @@ export fn decode(dest: []u8, src: const []word) void = {
 	let acc: u64 = 0;
 	let accbits: u64 = 0;
 	let sidx: size = 1;
+	let sz = ewordlen(src);
 	for (let i = len(dest) - 1; i < len(dest); i -= 1) {
 		if (accbits < 8) {
-			if (sidx < len(src)) {
+			if (sidx <= sz) {
 				acc |= ((src[sidx]: u64) << accbits: u64): u64;
 				sidx += 1;
 			};