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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,244 @@ | ||
| //! [BerTlvParser] is an [Iterator]-based BER-TLV parser. | ||
| /// An [Iterator]-based Compact-TLV parser. | ||
| pub(crate) struct BerTlvParser<'a> { | ||
| b: &'a [u8], | ||
| } | ||
|
|
||
| impl BerTlvParser<'_> { | ||
| /// Parses a BER-TLV structure in the given slice. | ||
| pub fn new(tlv: &[u8]) -> BerTlvParser { | ||
| // Skip null bytes at the start | ||
| let mut i = 0; | ||
| loop { | ||
| if i >= tlv.len() || tlv[i] != 0 { | ||
| break; | ||
| } | ||
| i += 1; | ||
| } | ||
|
|
||
| BerTlvParser { b: &tlv[i..] } | ||
| } | ||
|
|
||
| #[inline] | ||
| fn brick(&mut self) { | ||
| self.b = &self.b[0..0]; | ||
| } | ||
|
|
||
| fn stop_if_empty(&self) -> Option<()> { | ||
| if self.b.is_empty() { | ||
| None | ||
| } else { | ||
| Some(()) | ||
| } | ||
| } | ||
|
|
||
| fn stop_and_brick_if_less_than(&mut self, bytes: usize) -> Option<()> { | ||
| if self.b.len() < bytes { | ||
| error!("bricked: less than {bytes} bytes: {}", self.b.len()); | ||
| self.brick(); | ||
| None | ||
| } else { | ||
| Some(()) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<'a> Iterator for BerTlvParser<'a> { | ||
| /// A BER-TLV item, a tuple of `class, tag, value`. | ||
| type Item = (u8, u16, &'a [u8]); | ||
|
|
||
| fn next(&mut self) -> Option<Self::Item> { | ||
| self.stop_if_empty()?; | ||
|
|
||
| // 5.2.2.1: BER-TLV tag fields | ||
| let class = self.b[0] >> 5; | ||
| let mut tag = u16::from(self.b[0] & 0x1f); | ||
| // trace!(?class, ?tag); | ||
| self.b = &self.b[1..]; | ||
| if tag == 0x1f { | ||
| self.stop_if_empty()?; | ||
| // 0b???1_1111 = 2 or 3 byte tag value | ||
| tag = u16::from(self.b[0]); | ||
| self.b = &self.b[1..]; | ||
|
|
||
| // 2 byte tag value as 0b0???_???? (31..=127) | ||
| // 3 byte tag value as 0b1???_???? 0b0???_???? (128..=16383) | ||
| if tag & 0x80 == 0x80 { | ||
| self.stop_if_empty()?; | ||
|
|
||
| tag = (tag & 0x7f) << 7; | ||
| tag |= u16::from(self.b[0]) & 0x7f; | ||
| self.b = &self.b[1..]; | ||
| } | ||
| } | ||
|
|
||
| // 5.2.2.2 BER-TLV length fields | ||
| self.stop_if_empty()?; | ||
| let len = self.b[0]; | ||
| self.b = &self.b[1..]; | ||
|
|
||
| let len = match len { | ||
| 0..=0x7f => u32::from(len), | ||
|
|
||
| 0x80 => { | ||
| error!("indefinite length not supported"); | ||
| self.brick(); | ||
| return None; | ||
| } | ||
|
|
||
| 0x81 => { | ||
| self.stop_if_empty()?; | ||
| let len = u32::from(self.b[0]); | ||
| self.b = &self.b[1..]; | ||
| len | ||
| } | ||
|
|
||
| 0x82 => { | ||
| self.stop_and_brick_if_less_than(2); | ||
| let len = u32::from(u16::from_be_bytes(self.b[..2].try_into().ok()?)); | ||
| self.b = &self.b[2..]; | ||
| len | ||
| } | ||
|
|
||
| 0x83 => { | ||
| self.stop_and_brick_if_less_than(3)?; | ||
| let mut buf = [0; 4]; | ||
| buf[1..].copy_from_slice(&self.b[..3]); | ||
| let len = u32::from_be_bytes(buf); | ||
| self.b = &self.b[3..]; | ||
| len | ||
| } | ||
|
|
||
| 0x84 => { | ||
| self.stop_and_brick_if_less_than(4)?; | ||
| let len = u32::from_be_bytes(self.b[..4].try_into().ok()?); | ||
| self.b = &self.b[4..]; | ||
| len | ||
| } | ||
|
|
||
| 0x85..=0xff => { | ||
| error!("invalid BER-TLV length field length: {len:#x}"); | ||
| self.brick(); | ||
| return None; | ||
| } | ||
| }; | ||
| // info!(?len); | ||
|
|
||
| let len = len as usize; | ||
| self.stop_and_brick_if_less_than(len)?; | ||
| let v = &self.b[..len]; | ||
| self.b = &self.b[len..]; | ||
| Some((class, tag, v)) | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
|
|
||
| fn assert_tlv_parser(expected: &[(u8, u16, &[u8])], p: BerTlvParser<'_>) { | ||
| let mut i = 0; | ||
| for (actual_cls, actual_tag, actual_val) in p { | ||
| let (expected_cls, expected_tag, expected_val) = expected[i]; | ||
| assert_eq!(expected_cls, actual_cls, "cls mismatch at {i}"); | ||
| assert_eq!(expected_tag, actual_tag, "tag mismatch at {i}"); | ||
| assert_eq!( | ||
| expected_val, actual_val, | ||
| "val mismatch at {i} (tag={expected_tag})" | ||
| ); | ||
| i += 1; | ||
| } | ||
| assert_eq!(expected.len(), i); | ||
| } | ||
|
|
||
| #[test] | ||
| fn yubico_security_key_c_nfc() { | ||
| let _ = tracing_subscriber::fmt().try_init(); | ||
|
|
||
| let v = hex::decode(concat!( | ||
| "28", // length byte, not TLV | ||
| "0102", // cls=0, tag=1, len=2 | ||
| "0202", // | ||
| "0302", // cls=0, tag=3, len=2 | ||
| "0200", // | ||
| "0401", // cls=0, tag=4, len=1 | ||
| "43", // | ||
| "0503", // cls=0, tag=5, len=3 | ||
| "050403", // | ||
| "0602", // cls=0, tag=6, len=2 | ||
| "0000", // | ||
| "0701", // cls=0, tag=7, len=1 | ||
| "0f", // | ||
| "0801", // cls=0, tag=8, len=1 | ||
| "00", // | ||
| "0d02", // cls=0, tag=13, len=2 | ||
| "0206", // | ||
| "0e02", // cls=0, tag=14, len=2 | ||
| "0200", // | ||
| "0a01", // cls=0, tag=10, len=1 | ||
| "00", // | ||
| "0f01", // cls=0, tag=15, len=1 | ||
| "00", // | ||
| )) | ||
| .unwrap(); | ||
| let expected: [(u8, u16, &[u8]); 11] = [ | ||
| (0, 1, b"\x02\x02"), | ||
| (0, 3, b"\x02\0"), | ||
| (0, 4, b"\x43"), | ||
| (0, 5, b"\x05\x04\x03"), | ||
| (0, 6, b"\0\0"), | ||
| (0, 7, b"\x0f"), | ||
| (0, 8, b"\0"), | ||
| (0, 13, b"\x02\x06"), | ||
| (0, 14, b"\x02\0"), | ||
| (0, 10, b"\0"), | ||
| (0, 15, b"\0"), | ||
| ]; | ||
|
|
||
| let p = BerTlvParser::new(&v[1..]); | ||
| assert_tlv_parser(expected.as_slice(), p); | ||
| } | ||
|
|
||
| #[test] | ||
| fn yubikey_5c() { | ||
| let _ = tracing_subscriber::fmt().try_init(); | ||
|
|
||
| let v = hex::decode(concat!( | ||
| "23", // length byte, not TLV | ||
| "0102", // cls=0, tag=1, len=2 | ||
| "023f", // | ||
| "0302", // cls=0, tag=3, len=2 | ||
| "0218", // | ||
| "0204", // cls=0, tag=2, len=4 | ||
| "cafe1234", // | ||
| "0401", // cls=0, tag=4, len=1 | ||
| "03", // | ||
| "0503", // cls=0, tag=5, len=3 | ||
| "050102", // | ||
| "0602", // cls=0, tag=6, len=2 | ||
| "0000", // | ||
| "0701", // cls=0, tag=7, len=1 | ||
| "0f", // | ||
| "0801", // cls=0, tag=8, len=1 | ||
| "00", // | ||
| "0a01", // cls=0, tag=10, len=1 | ||
| "00", // | ||
| )) | ||
| .unwrap(); | ||
| let expected: [(u8, u16, &[u8]); 9] = [ | ||
| (0, 1, b"\x02\x3f"), | ||
| (0, 3, b"\x02\x18"), | ||
| (0, 2, b"\xca\xfe\x12\x34"), | ||
| (0, 4, b"\x03"), | ||
| (0, 5, b"\x05\x01\x02"), | ||
| (0, 6, b"\0\0"), | ||
| (0, 7, b"\x0f"), | ||
| (0, 8, b"\0"), | ||
| (0, 10, b"\0"), | ||
| ]; | ||
|
|
||
| let p = BerTlvParser::new(&v[1..]); | ||
| assert_tlv_parser(expected.as_slice(), p); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1 @@ | ||
| pub mod ber; |
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