Test bech32 decoder errors (#223)

Author: casey

src/bech32_decoder.rs

@@ -1,5 +1,6 @@
 use super::*;
 
+#[derive(Debug)]
 pub(crate) struct Bech32Decoder<'a> {
   data: &'a [u8],
   i: usize,
@@ -32,18 +33,8 @@ impl<'a> Bech32Decoder<'a> {
     if let Some((i, last)) = fes.clone().enumerate().last() {
       let padding_len = (i + 1) * 5 % 8;
 
-      if padding_len > 4 {
-        return Err(Bech32Error::Padding {
-          source: PaddingError::TooMuch,
-          ty: self.ty,
-        });
-      }
-
       if u64::from(last.to_u8().trailing_zeros()) < padding_len.into_u64() {
-        return Err(Bech32Error::Padding {
-          source: PaddingError::NonZero,
-          ty: self.ty,
-        });
+        return Err(Bech32Error::Padding { ty: self.ty });
       }
     }
 
@@ -99,6 +90,43 @@ impl<'a> Bech32Decoder<'a> {
 mod tests {
   use super::*;
 
+  fn checksum(s: &str) -> String {
+    let checked_hrpstring = CheckedHrpstring::new::<bech32::NoChecksum>(s).unwrap();
+
+    checked_hrpstring
+      .fe32_iter::<std::vec::IntoIter<u8>>()
+      .with_checksum::<bech32::Bech32m>(&checked_hrpstring.hrp())
+      .chars()
+      .collect()
+  }
+
+  #[test]
+  fn errors() {
+    #[track_caller]
+    fn case(s: &str, err: &str) {
+      assert_eq!(
+        Bech32Decoder::new(Bech32Type::PublicKey, &checksum(s))
+          .and_then(Bech32Decoder::byte_array::<1>)
+          .unwrap_err()
+          .to_string(),
+        err,
+      );
+    }
+
+    case(
+      "foo1",
+      "expected bech32 human-readable part `public1...` but found `foo1...`",
+    );
+
+    case("public1c", "bech32 public key version `c` not supported");
+
+    case("public1a", "bech32 public key truncated");
+
+    case("public1aqqq", "bech32 public key overlong by 1 character");
+
+    case("public1aql", "bech32 public key has nonzero padding");
+  }
+
   #[test]
   fn length() {
     #[track_caller]

src/bech32_error.rs

@@ -13,16 +13,13 @@ pub enum Bech32Error {
     ty.hrp(),
   ))]
   Hrp { ty: Bech32Type, actual: crate::Hrp },
-  #[snafu(display("bech32 {ty} overlong by {}", Count(*excess, "characters")))]
+  #[snafu(display("bech32 {ty} overlong by {}", Count(*excess, "character")))]
   Overlong { excess: usize, ty: Bech32Type },
-  #[snafu(display("bech32 {ty} has invalid padding"))]
-  Padding {
-    ty: Bech32Type,
-    source: PaddingError,
-  },
+  #[snafu(display("bech32 {ty} has nonzero padding"))]
+  Padding { ty: Bech32Type },
   #[snafu(display("bech32 {ty} truncated"))]
   Truncated { ty: Bech32Type },
-  #[snafu(display("bech32 {ty} version `{version}` is not supported"))]
+  #[snafu(display("bech32 {ty} version `{version}` not supported"))]
   UnsupportedVersion {
     ty: Bech32Type,
     version: bech32::Fe32,

src/lib.rs

@@ -66,7 +66,7 @@ use {
   },
   bech32::{
     ByteIterExt, Fe32, Fe32IterExt, Hrp,
-    primitives::decode::{CheckedHrpstring, CheckedHrpstringError, PaddingError},
+    primitives::decode::{CheckedHrpstring, CheckedHrpstringError},
   },
   blake3::Hasher,
   camino::{Utf8Component, Utf8Path, Utf8PathBuf},