tink_mac/
aes_cmac_key_manager.rs

1// Copyright 2020 The Tink-Rust Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//      http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14//
15////////////////////////////////////////////////////////////////////////////////
16
17//! Key manager for AES-CMAC keys for MAC.
18
19use tink_core::{utils::wrap_err, TinkError};
20use tink_proto::prost::Message;
21
22/// Maximal version of AES-CMAC keys.
23pub const CMAC_KEY_VERSION: u32 = 0;
24/// Type URL of AES-CMAC keys that Tink supports.
25pub const CMAC_TYPE_URL: &str = "type.googleapis.com/google.crypto.tink.AesCmacKey";
26
27/// Generates new AES-CMAC keys and produces new instances of AES-CMAC.
28#[derive(Default)]
29pub(crate) struct AesCmacKeyManager;
30
31impl tink_core::registry::KeyManager for AesCmacKeyManager {
32    /// Create an [`AesCmac`](crate::subtle::AesCmac) instance for the given serialized
33    /// [`AesCmacKey`](tink_proto::AesCmacKey) proto.
34    fn primitive(&self, serialized_key: &[u8]) -> Result<tink_core::Primitive, TinkError> {
35        if serialized_key.is_empty() {
36            return Err("AesCmacKeyManager: invalid key".into());
37        }
38
39        let key = tink_proto::AesCmacKey::decode(serialized_key)
40            .map_err(|e| wrap_err("AesCmacKeyManager: decode failed", e))?;
41        let tag_size = validate_key(&key)?;
42        match crate::subtle::AesCmac::new(&key.key_value, tag_size) {
43            Ok(p) => Ok(tink_core::Primitive::Mac(Box::new(p))),
44            Err(e) => Err(wrap_err(
45                "AesCmacKeyManager: cannot create new primitive",
46                e,
47            )),
48        }
49    }
50
51    /// Generate a new serialized [`AesCmacKey`](tink_proto::AesCmacKey) according to
52    /// specification in the given [`AesCmacKeyFormat`](tink_proto::AesCmacKeyFormat).
53    fn new_key(&self, serialized_key_format: &[u8]) -> Result<Vec<u8>, TinkError> {
54        if serialized_key_format.is_empty() {
55            return Err("AesCmacKeyManager: invalid key format".into());
56        }
57        let key_format = tink_proto::AesCmacKeyFormat::decode(serialized_key_format)
58            .map_err(|_| "AesCmacKeyManager: invalid key format")?;
59        validate_key_format(&key_format)
60            .map_err(|e| wrap_err("AesCmacKeyManager: invalid key format", e))?;
61        let key_value = tink_core::subtle::random::get_random_bytes(key_format.key_size as usize);
62        let mut sk = Vec::new();
63        tink_proto::AesCmacKey {
64            version: CMAC_KEY_VERSION,
65            params: key_format.params,
66            key_value,
67        }
68        .encode(&mut sk)
69        .map_err(|e| wrap_err("AesCmacKeyManager: failed to encode new key", e))?;
70        Ok(sk)
71    }
72
73    fn type_url(&self) -> &'static str {
74        CMAC_TYPE_URL
75    }
76
77    fn key_material_type(&self) -> tink_proto::key_data::KeyMaterialType {
78        tink_proto::key_data::KeyMaterialType::Symmetric
79    }
80}
81
82/// Validate the given [`AesCmacKey`](tink_proto::AesCmacKey). It only validates the version of the
83/// key because other parameters will be validated in primitive construction.
84fn validate_key(key: &tink_proto::AesCmacKey) -> Result<usize, TinkError> {
85    tink_core::keyset::validate_key_version(key.version, CMAC_KEY_VERSION)
86        .map_err(|e| wrap_err("AesCmacKeyManager: invalid version", e))?;
87    let key_size = key.key_value.len();
88    match &key.params {
89        None => Err("AesCmacKeyManager: missing AES-CMAC params".into()),
90        Some(params) => {
91            crate::subtle::validate_cmac_params(key_size, params.tag_size as usize)?;
92            Ok(params.tag_size as usize)
93        }
94    }
95}
96
97/// Validate the given [`AesCmacKeyFormat`](tink_proto::AesCmacKeyFormat).
98fn validate_key_format(format: &tink_proto::AesCmacKeyFormat) -> Result<(), TinkError> {
99    match &format.params {
100        None => Err("missing AES-CMAC params".into()),
101        Some(params) => {
102            crate::subtle::validate_cmac_params(format.key_size as usize, params.tag_size as usize)
103        }
104    }
105}
tink_mac/aes_cmac_key_manager.rs

tink_mac/
aes_cmac_key_manager.rs
