der/asn1/
context_specific.rs

1//! Context-specific field.
2
3use crate::{
4    Choice, Class, Decode, DecodeValue, DerOrd, Encode, EncodeValue, EncodeValueRef, Error, Header,
5    Length, Reader, Tag, TagMode, TagNumber, Tagged, ValueOrd, Writer, asn1::AnyRef,
6    tag::IsConstructed,
7};
8use core::cmp::Ordering;
9
10#[cfg(doc)]
11use crate::ErrorKind;
12
13impl_custom_class!(
14    ContextSpecific,
15    ContextSpecific,
16    "CONTEXT-SPECIFIC",
17    "0b10000000"
18);
19impl_custom_class_ref!(
20    ContextSpecificRef,
21    ContextSpecific,
22    "CONTEXT-SPECIFIC",
23    "0b10000000"
24);
25
26#[cfg(test)]
27#[allow(clippy::unwrap_used)]
28mod tests {
29    use super::ContextSpecific;
30    use crate::{Decode, Encode, SliceReader, TagMode, TagNumber, asn1::BitStringRef};
31    use hex_literal::hex;
32
33    #[cfg(feature = "heapless")]
34    use crate::asn1::{ContextSpecificRef, SetOf, Utf8StringRef};
35
36    // Public key data from `pkcs8` crate's `ed25519-pkcs8-v2.der`
37    const EXAMPLE_BYTES: &[u8] =
38        &hex!("A123032100A3A7EAE3A8373830BC47E1167BC50E1DB551999651E0E2DC587623438EAC3F31");
39
40    #[test]
41    fn round_trip() {
42        let field = ContextSpecific::<BitStringRef<'_>>::from_der(EXAMPLE_BYTES).unwrap();
43        assert_eq!(field.tag_number.value(), 1);
44        assert_eq!(
45            field.value,
46            BitStringRef::from_bytes(&EXAMPLE_BYTES[5..]).unwrap()
47        );
48
49        let mut buf = [0u8; 128];
50        let encoded = field.encode_to_slice(&mut buf).unwrap();
51        assert_eq!(encoded, EXAMPLE_BYTES);
52    }
53
54    #[test]
55    fn context_specific_with_explicit_field() {
56        let tag_number = TagNumber(0);
57
58        // Empty message
59        let mut reader = SliceReader::new(&[]).unwrap();
60        assert_eq!(
61            ContextSpecific::<u8>::decode_explicit(&mut reader, tag_number).unwrap(),
62            None
63        );
64
65        // Message containing a non-context-specific type
66        let mut reader = SliceReader::new(&hex!("020100")).unwrap();
67        assert_eq!(
68            ContextSpecific::<u8>::decode_explicit(&mut reader, tag_number).unwrap(),
69            None
70        );
71
72        // Message containing an EXPLICIT context-specific field
73        let mut reader = SliceReader::new(&hex!("A003020100")).unwrap();
74        let field = ContextSpecific::<u8>::decode_explicit(&mut reader, tag_number)
75            .unwrap()
76            .unwrap();
77
78        assert_eq!(field.tag_number, tag_number);
79        assert_eq!(field.tag_mode, TagMode::Explicit);
80        assert_eq!(field.value, 0);
81    }
82
83    #[test]
84    fn context_specific_with_implicit_field() {
85        // From RFC8410 Section 10.3:
86        // <https://datatracker.ietf.org/doc/html/rfc8410#section-10.3>
87        //
88        //    81  33:   [1] 00 19 BF 44 09 69 84 CD FE 85 41 BA C1 67 DC 3B
89        //                  96 C8 50 86 AA 30 B6 B6 CB 0C 5C 38 AD 70 31 66
90        //                  E1
91        let context_specific_implicit_bytes =
92            hex!("81210019BF44096984CDFE8541BAC167DC3B96C85086AA30B6B6CB0C5C38AD703166E1");
93
94        let tag_number = TagNumber(1);
95
96        let mut reader = SliceReader::new(&context_specific_implicit_bytes).unwrap();
97        let field = ContextSpecific::<BitStringRef<'_>>::decode_implicit(&mut reader, tag_number)
98            .unwrap()
99            .unwrap();
100
101        assert_eq!(field.tag_number, tag_number);
102        assert_eq!(field.tag_mode, TagMode::Implicit);
103        assert_eq!(
104            field.value.as_bytes().unwrap(),
105            &context_specific_implicit_bytes[3..]
106        );
107    }
108
109    #[test]
110    fn context_specific_not_skipping_unknown_field() {
111        let tag = TagNumber(1);
112        let mut reader = SliceReader::new(&hex!("A003020100A103020101")).unwrap();
113        let field = ContextSpecific::<u8>::decode_explicit(&mut reader, tag).unwrap();
114        assert_eq!(field, None);
115    }
116
117    #[test]
118    fn context_specific_returns_none_on_greater_tag_number() {
119        let tag = TagNumber(0);
120        let mut reader = SliceReader::new(&hex!("A103020101")).unwrap();
121        assert_eq!(
122            ContextSpecific::<u8>::decode_explicit(&mut reader, tag).unwrap(),
123            None
124        );
125    }
126
127    #[test]
128    #[cfg(feature = "heapless")]
129    fn context_specific_explicit_ref() {
130        let mut set = SetOf::new();
131        set.insert(8u16).unwrap();
132        set.insert(7u16).unwrap();
133
134        let field = ContextSpecificRef::<SetOf<u16, 2>> {
135            value: &set,
136            tag_number: TagNumber(2),
137            tag_mode: TagMode::Explicit,
138        };
139
140        let mut buf = [0u8; 16];
141        let encoded = field.encode_to_slice(&mut buf).unwrap();
142        assert_eq!(
143            encoded,
144            &[
145                /* CONTEXT-SPECIFIC [2] */ 0xA2, 0x08, /* SET 0x11 | 0x20 */ 0x31, 0x06,
146                /* INTEGER */ 0x02, 0x01, 0x07, /* INTEGER */ 0x02, 0x01, 0x08
147            ]
148        );
149
150        let mut reader = SliceReader::new(encoded).unwrap();
151        let field = ContextSpecific::<SetOf<u16, 2>>::decode_explicit(&mut reader, TagNumber(2))
152            .unwrap()
153            .unwrap();
154
155        assert_eq!(field.value.len(), 2);
156        assert_eq!(field.value.get(0).cloned(), Some(7));
157        assert_eq!(field.value.get(1).cloned(), Some(8));
158    }
159
160    #[test]
161    #[cfg(feature = "heapless")]
162    fn context_specific_implicit_ref() {
163        let hello = Utf8StringRef::new("Hello").unwrap();
164        let world = Utf8StringRef::new("world").unwrap();
165
166        let mut set = SetOf::new();
167        set.insert(hello).unwrap();
168        set.insert(world).unwrap();
169
170        let field = ContextSpecificRef::<SetOf<Utf8StringRef<'_>, 2>> {
171            value: &set,
172            tag_number: TagNumber(2),
173            tag_mode: TagMode::Implicit,
174        };
175
176        let mut buf = [0u8; 16];
177        let encoded = field.encode_to_slice(&mut buf).unwrap();
178        assert_eq!(
179            encoded,
180            &[
181                0xA2, 0x0E, // CONTEXT-SPECIFIC [2]
182                0x0C, 0x05, b'H', b'e', b'l', b'l', b'o', // UTF8String "Hello"
183                0x0C, 0x05, b'w', b'o', b'r', b'l', b'd', // UTF8String "world"
184            ]
185        );
186
187        let mut reader = SliceReader::new(encoded).unwrap();
188        let field = ContextSpecific::<SetOf<Utf8StringRef<'_>, 2>>::decode_implicit(
189            &mut reader,
190            TagNumber(2),
191        )
192        .unwrap()
193        .unwrap();
194
195        assert_eq!(field.value.len(), 2);
196        assert_eq!(field.value.get(0).cloned(), Some(hello));
197        assert_eq!(field.value.get(1).cloned(), Some(world));
198    }
199}
der/asn1/context_specific.rs

der/asn1/
context_specific.rs
