taler-typescript-core

commit bf5979fb35fc50a0e94764cc0b73f1e440dea4b9
parent 7739f02be1cfe8bb15bcc4df8b39ac0776b00f00
Author: Florian Dold <dold@taler.net>
Date:   Tue, 21 Jul 2026 10:54:36 +0200

util: verify the bech32 checksum and the segwit version consistency

The checksum was only verified when the caller passed the expected
encoding, and the version guards used === where the reference uses !==, so
they rejected exactly the combinations they are meant to accept.

Diffstat:
M
packages/taler-util/src/bech32.ts
 | 
20
++++++++++++++++++--
M
packages/taler-util/src/segwit_addr.ts
 | 
6
++++--

2 files changed, 22 insertions(+), 4 deletions(-)
diff --git a/packages/taler-util/src/bech32.ts b/packages/taler-util/src/bech32.ts
@@ -129,6 +129,14 @@ export namespace BitcoinBech32 {
     WRONG_CHECKSUM,
   }
 
+  /**
+   * Decode a bech32 string and verify its checksum.
+   *
+   * When @param enc is given, the checksum must match that encoding.  When it
+   * is omitted, either encoding is accepted and the one that verified is
+   * reported back, so that callers such as the segwit address parser can check
+   * it against the witness version.
+   */
   export function decode(
     bechString: string,
     enc?: Encodings,
@@ -136,6 +144,7 @@ export namespace BitcoinBech32 {
     {
       hrp: string;
       data: number[];
+      enc: Encodings;
     },
     BitcoinParseError
   > {
@@ -176,9 +185,16 @@ export namespace BitcoinBech32 {
       }
       data.push(d);
     }
-    if (enc && !verifyChecksum(hrp, data, enc)) {
+    const candidates =
+      enc !== undefined ? [enc] : [Encodings.BECH32, Encodings.BECH32M];
+    const actualEnc = candidates.find((c) => verifyChecksum(hrp, data, c));
+    if (actualEnc === undefined) {
       return Result.error(BitcoinParseError.WRONG_CHECKSUM);
     }
-    return Result.of({ hrp, data: data.slice(0, data.length - 6) });
+    return Result.of({
+      hrp,
+      data: data.slice(0, data.length - 6),
+      enc: actualEnc,
+    });
   }
 }
diff --git a/packages/taler-util/src/segwit_addr.ts b/packages/taler-util/src/segwit_addr.ts
@@ -90,10 +90,12 @@ export namespace BitcoinSewgit {
     if (dec.data[0] === 0 && res.length !== 20 && res.length !== 32) {
       return Result.error(BitcoinSewgitParseError.DECODING_PROBLEM);
     }
-    if (dec.data[0] === 0 && enc === BitcoinBech32.Encodings.BECH32) {
+    // Version 0 programs are checksummed with bech32, later versions with
+    // bech32m (BIP-350).
+    if (dec.data[0] === 0 && dec.enc !== BitcoinBech32.Encodings.BECH32) {
       return Result.error(BitcoinSewgitParseError.DECODING_PROBLEM);
     }
-    if (dec.data[0] !== 0 && enc === BitcoinBech32.Encodings.BECH32M) {
+    if (dec.data[0] !== 0 && dec.enc !== BitcoinBech32.Encodings.BECH32M) {
       return Result.error(BitcoinSewgitParseError.DECODING_PROBLEM);
     }
     return Result.of({ version: dec.data[0], program: res });