xml-sec 0.1.23

Pure Rust XML Security: XMLDSig, XMLEnc, C14N. Drop-in replacement for libxmlsec1.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207

#![cfg(feature = "xmlenc")]

use base64::{Engine as _, engine::general_purpose::STANDARD};
use std::collections::HashMap;
use xml_sec::policy::DecryptionPolicy;
use xml_sec::xmldsig::UriTypeSet;
use xml_sec::xmlenc::{
    DataEncryptionAlgorithm, DecryptContext, DecryptedContent, EncryptedDataBuilder, KekDecryptor,
    KeyWrapAlgorithm, SymmetricKeyDecryptor, XmlEncError,
};

const ENC: &str = "http://www.w3.org/2001/04/xmlenc#";
const DS: &str = "http://www.w3.org/2000/09/xmldsig#";

fn external_policy() -> DecryptionPolicy {
    let mut policy = DecryptionPolicy::default();
    policy.uris.references = UriTypeSet::ALL;
    policy
}

#[test]
fn cipher_reference_enveloped_transform_uses_its_actual_signature_ancestor() {
    // XMLDSig 1.1 section 6.6.4 removes the Signature containing the transform,
    // even when its Reference-like origin is an encrypted Object descendant.
    let key = [0x55; 16];
    let encrypted = EncryptedDataBuilder::new(DataEncryptionAlgorithm::Aes128Gcm)
        .direct_key(key)
        .encrypt_xml("<payload>restored</payload>")
        .unwrap();
    let parsed = xml_sec::xmlenc::parse_encrypted_data(&encrypted.encrypted_data_xml).unwrap();
    let encoded = parsed.cipher_data.inline_value().unwrap();
    let fragment = encrypted.encrypted_data_xml.replace(
        &format!("<xenc:CipherValue>{encoded}</xenc:CipherValue>"),
        &format!("<xenc:CipherReference URI=''><xenc:Transforms><ds:Transform xmlns:ds='{DS}' Algorithm='{DS}enveloped-signature'/><ds:Transform xmlns:ds='{DS}' Algorithm='{DS}base64'/></xenc:Transforms></xenc:CipherReference>"));
    let wire = format!(
        "<root><cipher>{encoded}</cipher><ds:Signature xmlns:ds='{DS}'><ds:SignatureValue>QUFBQQ==</ds:SignatureValue><ds:Object>{fragment}</ds:Object></ds:Signature></root>"
    );
    let mut document = xml_sec::XmlDocument::parse(wire).unwrap();
    DecryptContext::new(&SymmetricKeyDecryptor::new(key))
        .decrypt_owned_document(&mut document, None)
        .unwrap();
    assert!(
        document
            .as_xml()
            .contains("<ds:Object><payload>restored</payload></ds:Object>")
    );
}

#[test]
fn external_cipher_reference_decrypts_authenticated_content() {
    // The public decrypt path consumes caller bytes directly, without creating
    // an artificial inline CipherValue or weakening GCM authentication.
    let key = [0x31; 16];
    let encrypted = EncryptedDataBuilder::new(DataEncryptionAlgorithm::Aes128Gcm)
        .direct_key(key)
        .encrypt_binary(b"external ciphertext")
        .unwrap();
    let parsed = xml_sec::xmlenc::parse_encrypted_data(&encrypted.encrypted_data_xml).unwrap();
    let encoded = parsed.cipher_data.inline_value().unwrap();
    let ciphertext = STANDARD.decode(encoded).unwrap();
    let xml = encrypted.encrypted_data_xml.replace(
        &format!("<xenc:CipherValue>{encoded}</xenc:CipherValue>"),
        "<xenc:CipherReference URI=\"urn:cipher\"/>",
    );
    let resources = HashMap::from([("urn:cipher".into(), ciphertext.clone())]);
    let resolver = SymmetricKeyDecryptor::new(key);
    let context = DecryptContext::new(&resolver)
        .policy(external_policy())
        .external_resources(&resources);
    assert_eq!(
        context.decrypt(&xml).unwrap(),
        DecryptedContent::Bytes(b"external ciphertext".to_vec())
    );
    assert!(matches!(
        DecryptContext::new(&resolver)
            .external_resources(&resources)
            .decrypt(&xml),
        Err(XmlEncError::Policy(_))
    ));
    let mut corrupted = ciphertext;
    *corrupted.last_mut().unwrap() ^= 1;
    let resources = HashMap::from([("urn:cipher".into(), corrupted)]);
    assert!(
        DecryptContext::new(&resolver)
            .policy(external_policy())
            .external_resources(&resources)
            .decrypt(&xml)
            .is_err()
    );
}

#[test]
fn referenced_wrapped_key_and_content_share_external_budget() {
    // Both levels belong to one decrypt operation. Independently permitted
    // resources must not each receive a fresh aggregate allowance.
    let kek = [0x24; 16];
    let encrypted = EncryptedDataBuilder::new(DataEncryptionAlgorithm::Aes128Gcm)
        .recipient_aes_kw(kek, KeyWrapAlgorithm::AesKw128)
        .encrypt_binary(b"wrapped reference")
        .unwrap();
    let parsed = xml_sec::xmlenc::parse_encrypted_data(&encrypted.encrypted_data_xml).unwrap();
    let key_value = parsed.encrypted_keys[0].cipher_data.inline_value().unwrap();
    let content_value = parsed.cipher_data.inline_value().unwrap();
    let key_bytes = STANDARD.decode(key_value).unwrap();
    let content_bytes = STANDARD.decode(content_value).unwrap();
    let xml = encrypted
        .encrypted_data_xml
        .replace(
            &format!("<xenc:CipherValue>{key_value}</xenc:CipherValue>"),
            "<xenc:CipherReference URI=\"urn:key\"/>",
        )
        .replace(
            &format!("<xenc:CipherValue>{content_value}</xenc:CipherValue>"),
            "<xenc:CipherReference URI=\"urn:data\"/>",
        );
    let total = key_bytes.len() + content_bytes.len();
    let resources = HashMap::from([
        ("urn:key".into(), key_bytes),
        ("urn:data".into(), content_bytes),
    ]);
    let resolver = KekDecryptor::new(kek);
    let mut policy = external_policy();
    policy.resources.max_external_resource_total_bytes = total;
    assert_eq!(
        DecryptContext::new(&resolver)
            .policy(policy.clone())
            .external_resources(&resources)
            .decrypt(&xml)
            .unwrap(),
        DecryptedContent::Bytes(b"wrapped reference".to_vec())
    );
    policy.resources.max_external_resource_total_bytes = total - 1;
    assert!(
        DecryptContext::new(&resolver)
            .policy(policy)
            .external_resources(&resources)
            .decrypt(&xml)
            .is_err()
    );
}

#[test]
fn owned_document_same_document_reference_keeps_source_and_generation() {
    // Reference resolution must see siblings outside the selected encrypted
    // subtree, and a failed authenticated decrypt must not mutate the owner.
    let key = [0x55; 16];
    let encrypted = EncryptedDataBuilder::new(DataEncryptionAlgorithm::Aes128Gcm)
        .direct_key(key)
        .encrypt_xml("<payload>restored</payload>")
        .unwrap();
    let parsed = xml_sec::xmlenc::parse_encrypted_data(&encrypted.encrypted_data_xml).unwrap();
    let encoded = parsed.cipher_data.inline_value().unwrap();
    let fragment = encrypted.encrypted_data_xml.replace(
        &format!("<xenc:CipherValue>{encoded}</xenc:CipherValue>"),
        &format!("<xenc:CipherReference URI=\"#cipher\"><xenc:Transforms><ds:Transform xmlns:ds=\"{DS}\" Algorithm=\"{DS}base64\"/></xenc:Transforms></xenc:CipherReference>"),
    );
    let xml = format!("<root><cipher xml:id=\"cipher\">{encoded}</cipher>{fragment}</root>");
    let mut document = xml_sec::XmlDocument::parse(xml.clone()).unwrap();
    let identity = document.identity();
    let generation = document.generation();
    let wrong = SymmetricKeyDecryptor::new([0x56; 16]);
    assert!(
        DecryptContext::new(&wrong)
            .decrypt_owned_document(&mut document, None)
            .is_err()
    );
    assert_eq!(document.as_xml(), xml);
    assert_eq!(document.generation(), generation);
    let resolver = SymmetricKeyDecryptor::new(key);
    DecryptContext::new(&resolver)
        .decrypt_owned_document(&mut document, None)
        .unwrap();
    assert_eq!(document.identity(), identity);
    assert_eq!(document.generation(), generation + 1);
    assert_eq!(
        document.as_xml(),
        format!(
            "<root><cipher xml:id=\"cipher\">{encoded}</cipher><payload>restored</payload></root>"
        )
    );
}

#[test]
fn cipher_reference_syntax_and_transform_permission_are_not_implicit() {
    // An allowed external resource does not grant permission for an unknown or
    // disallowed transform, and missing URI is distinct from URI="".
    let resolver = SymmetricKeyDecryptor::new([0; 16]);
    let resources = HashMap::from([("urn:data".into(), b"not ciphertext".to_vec())]);
    for reference in [
        "<xenc:CipherReference/>",
        "<xenc:CipherReference URI='urn:data'><ds:Transforms/></xenc:CipherReference>",
        "<xenc:CipherReference URI='urn:data'><xenc:Transforms/></xenc:CipherReference>",
        "<xenc:CipherReference URI='urn:data'><xenc:Transforms><ds:Transform Algorithm='urn:unknown'/></xenc:Transforms></xenc:CipherReference>",
    ] {
        let xml = format!(
            "<xenc:EncryptedData xmlns:xenc='{ENC}' xmlns:ds='{DS}'><xenc:EncryptionMethod Algorithm='http://www.w3.org/2009/xmlenc11#aes128-gcm'/><xenc:CipherData>{reference}</xenc:CipherData></xenc:EncryptedData>"
        );
        assert!(
            DecryptContext::new(&resolver)
                .policy(external_policy())
                .external_resources(&resources)
                .decrypt(&xml)
                .is_err(),
            "{reference}"
        );
    }
}