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der: read_nested: check header length matches contents of IMPLICIT #1739

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Merged
tarcieri merged 2 commits into from
Apr 21, 2025
Merged

der: read_nested: check header length matches contents of IMPLICIT #1739

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442e3e3
der: read_nested: check header length matches contents of IMPLICIT
dishmaker Mar 25, 2025
4ae9dc5
x509-cert: fix idp negative test due to der implicit reader fix
dishmaker Apr 21, 2025
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14 changes: 12 additions & 2 deletions der/src/asn1/context_specific.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -63,8 +63,14 @@ impl<T> ContextSpecific<T> {
T: DecodeValue<'a> + Tagged,
{
Self::decode_with::<_, _, T::Error>(reader, tag_number, |reader| {
// Decode IMPLICIT header
let header = Header::decode(reader)?;
let value = T::decode_value(reader, header)?;

// read_nested checks if header matches decoded length
let value = reader.read_nested(header.length, |reader| {
// Decode inner IMPLICIT value
T::decode_value(reader, header)
})?;

if header.tag.is_constructed() != value.tag().is_constructed() {
return Err(header.tag.non_canonical_error().into());
Expand Down Expand Up @@ -119,6 +125,7 @@ where
type Error = T::Error;

fn decode<R: Reader<'a>>(reader: &mut R) -> Result<Self, Self::Error> {
// Decode EXPLICIT header
let header = Header::decode(reader)?;

match header.tag {
Expand All @@ -128,7 +135,10 @@ where
} => Ok(Self {
tag_number: number,
tag_mode: TagMode::default(),
value: reader.read_nested(header.length, |reader| T::decode(reader))?,
value: reader.read_nested(header.length, |reader| {
// Decode inner tag-length-value of EXPLICIT
T::decode(reader)
})?,
}),
tag => Err(tag.unexpected_error(None).into()),
}
Expand Down
16 changes: 12 additions & 4 deletions x509-cert/tests/pkix_extensions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -843,8 +843,6 @@ fn decode_cert() {

#[test]
fn decode_idp() {
use der::TagNumber;

// IDP from 04A8739769B3C090A11DCDFABA3CF33F4BEF21F3.crl in PKITS 2048 in ficam-scvp-testing repo
let idp = IssuingDistributionPoint::from_der(&hex!("30038201FF")).unwrap();
assert_eq!(idp.only_contains_ca_certs, true);
Expand Down Expand Up @@ -1112,7 +1110,11 @@ fn decode_idp() {
panic!("Expected FullName")
}
}
}

#[test]
fn decode_idp_negative() {
use der::TagNumber;
//---------------------------------
// Negative tests
//---------------------------------
Expand Down Expand Up @@ -1143,7 +1145,7 @@ fn decode_idp() {
"3067A060A05EA45C305A310B3009060355040613025553311F301D060355040A131654657374204365727469666963617465732032303137311C301A060355040B13136F6E6C79536F6D65526561736F6E7320434133310C300A0603550403130343524C8304079F80"
));
let err = idp.err().unwrap();
assert_eq!(err.position().unwrap(), 103u8.into());
assert_eq!(err.position().unwrap(), 105u8.into());
assert_eq!(
ErrorKind::Incomplete {
expected_len: 106u8.into(),
Expand Down Expand Up @@ -1197,7 +1199,13 @@ fn decode_idp() {
"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"
));
let err = idp.err().unwrap();
assert_eq!(ErrorKind::Length { tag: Tag::Boolean }, err.kind());
assert_eq!(
ErrorKind::Incomplete {
expected_len: Length::new(365),
actual_len: Length::new(364)
},
err.kind()
);

// Boolean value is neither 0x00 nor 0xFF
let idp = IssuingDistributionPoint::from_der(&hex!(
Expand Down