fidorium 0.1.6

A FIDO2/CTAP2 authenticator daemon for Linux backed by TPM 2.0
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

use super::TpmError;
use sha2::Digest as ShaDigest;
use sha2::Sha256;
use std::convert::TryFrom;
use std::convert::TryInto;
use tss_esapi::Context;
use tss_esapi::attributes::ObjectAttributesBuilder;
use tss_esapi::constants::tss::TPM2_RH_NULL;
use tss_esapi::constants::tss::TPM2_ST_HASHCHECK;
use tss_esapi::handles::KeyHandle;
use tss_esapi::handles::ObjectHandle;
use tss_esapi::interface_types::algorithm::HashingAlgorithm;
use tss_esapi::interface_types::algorithm::PublicAlgorithm;
use tss_esapi::interface_types::ecc::EccCurve;
use tss_esapi::interface_types::reserved_handles::Hierarchy;
use tss_esapi::structures::Digest;
use tss_esapi::structures::EccPoint;
use tss_esapi::structures::EccScheme;
use tss_esapi::structures::HashScheme;
use tss_esapi::structures::HashcheckTicket;
use tss_esapi::structures::Private;
use tss_esapi::structures::Public;
use tss_esapi::structures::PublicBuilder;
use tss_esapi::structures::PublicEccParametersBuilder;
use tss_esapi::structures::Signature;
use tss_esapi::structures::SignatureScheme;
use tss_esapi::structures::SymmetricDefinitionObject;
use tss_esapi::traits::Marshall;
use tss_esapi::traits::UnMarshall;
use tss_esapi::tss2_esys::TPMT_TK_HASHCHECK;

pub fn create_primary(ctx: &mut Context) -> Result<KeyHandle, TpmError> {
    let ecc_params = PublicEccParametersBuilder::new_restricted_decryption_key(
        SymmetricDefinitionObject::AES_128_CFB,
        EccCurve::NistP256,
    )
    .build()
    .map_err(|e| TpmError::Key(e.to_string()))?;

    let attrs = ObjectAttributesBuilder::new()
        .with_fixed_tpm(true)
        .with_fixed_parent(true)
        .with_sensitive_data_origin(true)
        .with_user_with_auth(true)
        .with_restricted(true)
        .with_decrypt(true)
        .build()
        .map_err(|e| TpmError::Key(e.to_string()))?;

    let pub_template = PublicBuilder::new()
        .with_public_algorithm(PublicAlgorithm::Ecc)
        .with_name_hashing_algorithm(HashingAlgorithm::Sha256)
        .with_object_attributes(attrs)
        .with_ecc_parameters(ecc_params)
        .with_ecc_unique_identifier(EccPoint::default())
        .build()
        .map_err(|e| TpmError::Key(e.to_string()))?;

    let result = ctx
        .execute_with_nullauth_session(|ctx| {
            ctx.create_primary(Hierarchy::Owner, pub_template, None, None, None, None)
        })
        .map_err(|e: tss_esapi::Error| TpmError::Key(e.to_string()))?;

    Ok(result.key_handle)
}

pub fn create_child_key(
    ctx: &mut Context,
    primary: KeyHandle,
) -> Result<(Vec<u8>, Vec<u8>), TpmError> {
    let scheme = EccScheme::EcDsa(HashScheme::new(HashingAlgorithm::Sha256));
    let ecc_params =
        PublicEccParametersBuilder::new_unrestricted_signing_key(scheme, EccCurve::NistP256)
            .build()
            .map_err(|e| TpmError::Key(e.to_string()))?;

    let attrs = ObjectAttributesBuilder::new()
        .with_fixed_tpm(true)
        .with_fixed_parent(true)
        .with_sensitive_data_origin(true)
        .with_user_with_auth(true)
        .with_sign_encrypt(true)
        .with_no_da(true)
        .build()
        .map_err(|e| TpmError::Key(e.to_string()))?;

    let pub_template = PublicBuilder::new()
        .with_public_algorithm(PublicAlgorithm::Ecc)
        .with_name_hashing_algorithm(HashingAlgorithm::Sha256)
        .with_object_attributes(attrs)
        .with_ecc_parameters(ecc_params)
        .with_ecc_unique_identifier(EccPoint::default())
        .build()
        .map_err(|e| TpmError::Key(e.to_string()))?;

    let result = ctx
        .execute_with_nullauth_session(|ctx| {
            ctx.create(primary, pub_template, None, None, None, None)
        })
        .map_err(|e: tss_esapi::Error| TpmError::Key(e.to_string()))?;

    let private_bytes = result.out_private.as_bytes().to_vec();
    let public_bytes = result
        .out_public
        .marshall()
        .map_err(|e| TpmError::Key(e.to_string()))?;

    Ok((private_bytes, public_bytes))
}

pub fn load_key(
    ctx: &mut Context,
    primary: KeyHandle,
    private_bytes: &[u8],
    public_bytes: &[u8],
) -> Result<KeyHandle, TpmError> {
    let private =
        Private::try_from(private_bytes.to_vec()).map_err(|e| TpmError::Key(e.to_string()))?;
    let public = Public::unmarshall(public_bytes).map_err(|e| TpmError::Key(e.to_string()))?;

    ctx.execute_with_nullauth_session(|ctx| ctx.load(primary, private, public))
        .map_err(|e: tss_esapi::Error| TpmError::Key(e.to_string()))
}

/// Sign `data` with the loaded key.
/// Returns raw (r, s) concatenated — 64 bytes, each component zero-padded to 32 bytes.
/// The `_up` parameter is a user presence proof token, ensuring this function
/// is only callable after user presence has been confirmed.
pub fn sign(
    ctx: &mut Context,
    key: KeyHandle,
    data: &[u8],
    _up: &crate::up::UserPresenceProof,
) -> Result<[u8; 64], TpmError> {
    let hash_bytes = Sha256::digest(data);
    let digest = Digest::try_from(hash_bytes.as_slice().to_vec())
        .map_err(|e| TpmError::Key(e.to_string()))?;

    let raw_ticket = TPMT_TK_HASHCHECK {
        tag: TPM2_ST_HASHCHECK,
        hierarchy: TPM2_RH_NULL,
        digest: Default::default(),
    };
    let validation: HashcheckTicket = raw_ticket
        .try_into()
        .map_err(|e: tss_esapi::Error| TpmError::Key(e.to_string()))?;

    let scheme = SignatureScheme::Null;

    let signature = ctx
        .execute_with_nullauth_session(|ctx| ctx.sign(key, digest, scheme, validation))
        .map_err(|e: tss_esapi::Error| TpmError::Key(e.to_string()))?;

    match signature {
        Signature::EcDsa(ecc_sig) => {
            let r = ecc_sig.signature_r().as_bytes();
            let s = ecc_sig.signature_s().as_bytes();
            let mut result = [0u8; 64];
            let r_len = r.len().min(32);
            let s_len = s.len().min(32);
            result[32 - r_len..32].copy_from_slice(&r[r.len() - r_len..]);
            result[64 - s_len..].copy_from_slice(&s[s.len() - s_len..]);
            Ok(result)
        }
        _ => Err(TpmError::Key("Expected ECDSA signature".into())),
    }
}

pub fn flush(ctx: &mut Context, handle: KeyHandle) -> Result<(), TpmError> {
    ctx.flush_context(ObjectHandle::from(handle))
        .map_err(|e| TpmError::Key(e.to_string()))
}

/// Extract (x, y) coordinates from a marshalled TPM2B_PUBLIC blob.
pub fn ecc_public_coords(public_bytes: &[u8]) -> Result<([u8; 32], [u8; 32]), TpmError> {
    let public = Public::unmarshall(public_bytes).map_err(|e| TpmError::Key(e.to_string()))?;

    match public {
        Public::Ecc { unique, .. } => {
            let x_bytes = unique.x().as_bytes();
            let y_bytes = unique.y().as_bytes();
            let mut x = [0u8; 32];
            let mut y = [0u8; 32];
            let x_len = x_bytes.len().min(32);
            let y_len = y_bytes.len().min(32);
            x[32 - x_len..].copy_from_slice(&x_bytes[x_bytes.len() - x_len..]);
            y[32 - y_len..].copy_from_slice(&y_bytes[y_bytes.len() - y_len..]);
            Ok((x, y))
        }
        _ => Err(TpmError::Key("Not an ECC key".into())),
    }
}