Do not require padding when decoding base64 bytes (#1448)

Author: bschoenmaeckers

src/validators/config.rs

@@ -1,8 +1,9 @@
 use std::borrow::Cow;
 use std::str::FromStr;
 
-use base64::engine::general_purpose::{STANDARD, URL_SAFE};
-use base64::{DecodeError, Engine};
+use base64::engine::general_purpose::GeneralPurpose;
+use base64::engine::{DecodePaddingMode, GeneralPurposeConfig};
+use base64::{alphabet, DecodeError, Engine};
 use pyo3::types::{PyDict, PyString};
 use pyo3::{intern, prelude::*};
 
@@ -11,6 +12,15 @@ use crate::input::EitherBytes;
 use crate::serializers::BytesMode;
 use crate::tools::SchemaDict;
 
+const URL_SAFE_OPTIONAL_PADDING: GeneralPurpose = GeneralPurpose::new(
+    &alphabet::URL_SAFE,
+    GeneralPurposeConfig::new().with_decode_padding_mode(DecodePaddingMode::Indifferent),
+);
+const STANDARD_OPTIONAL_PADDING: GeneralPurpose = GeneralPurpose::new(
+    &alphabet::STANDARD,
+    GeneralPurposeConfig::new().with_decode_padding_mode(DecodePaddingMode::Indifferent),
+);
+
 #[derive(Default, Debug, Clone, Copy, PartialEq, Eq)]
 pub struct ValBytesMode {
     pub ser: BytesMode,
@@ -29,10 +39,10 @@ impl ValBytesMode {
     pub fn deserialize_string<'py>(self, s: &str) -> Result<EitherBytes<'_, 'py>, ErrorType> {
         match self.ser {
             BytesMode::Utf8 => Ok(EitherBytes::Cow(Cow::Borrowed(s.as_bytes()))),
-            BytesMode::Base64 => URL_SAFE
+            BytesMode::Base64 => URL_SAFE_OPTIONAL_PADDING
                 .decode(s)
                 .or_else(|err| match err {
-                    DecodeError::InvalidByte(_, b'/' | b'+') => STANDARD.decode(s),
+                    DecodeError::InvalidByte(_, b'/' | b'+') => STANDARD_OPTIONAL_PADDING.decode(s),
                     _ => Err(err),
                 })
                 .map(EitherBytes::from)

tests/test_json.py

@@ -401,6 +401,12 @@ def test_json_bytes_base64_round_trip():
     assert v.validate_json(b'{"key":' + encoded_url + b'}') == {'key': data}
 
 
+def test_json_bytes_base64_no_padding():
+    v = SchemaValidator({'type': 'bytes'}, {'val_json_bytes': 'base64'})
+    base_64_without_padding = 'bm8tcGFkZGluZw'
+    assert v.validate_json(json.dumps(base_64_without_padding)) == b'no-padding'
+
+
 def test_json_bytes_base64_invalid():
     v = SchemaValidator({'type': 'bytes'}, {'val_json_bytes': 'base64'})
     wrong_input = 'wrong!'