92 lines
3.1 KiB
Rust
92 lines
3.1 KiB
Rust
// Copyright 2021 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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////////////////////////////////////////////////////////////////////////////////
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//! Example program demonstrating signature creation.
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use coset::{iana, CborSerializable};
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#[derive(Copy, Clone)]
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struct FakeSigner {}
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// Use a fake signer/verifier (to avoid pulling in lots of dependencies).
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impl FakeSigner {
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fn sign(&self, data: &[u8]) -> Vec<u8> {
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data.to_vec()
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}
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fn verify(&self, sig: &[u8], data: &[u8]) -> Result<(), String> {
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if sig != self.sign(data) {
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Err("failed to verify".to_owned())
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} else {
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Ok(())
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}
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}
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}
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fn main() {
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// Build a fake signer/verifier (to avoid pulling in lots of dependencies).
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let signer = FakeSigner {};
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let verifier = signer;
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// Inputs.
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let pt = b"This is the content";
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let aad = b"this is additional data";
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// Build a `CoseSign1` object.
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let protected = coset::HeaderBuilder::new()
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.algorithm(iana::Algorithm::ES256)
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.key_id(b"11".to_vec())
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.build();
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let sign1 = coset::CoseSign1Builder::new()
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.protected(protected)
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.payload(pt.to_vec())
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.create_signature(aad, |pt| signer.sign(pt))
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.build();
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// Serialize to bytes.
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let sign1_data = sign1.to_vec().unwrap();
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println!(
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"'{}' + '{}' => {}",
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String::from_utf8_lossy(pt),
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String::from_utf8_lossy(aad),
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hex::encode(&sign1_data)
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);
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// At the receiving end, deserialize the bytes back to a `CoseSign1` object.
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let mut sign1 = coset::CoseSign1::from_slice(&sign1_data).unwrap();
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// Check the signature, which needs to have the same `aad` provided.
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let result = sign1.verify_signature(aad, |sig, data| verifier.verify(sig, data));
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println!("Signature verified: {:?}.", result);
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assert!(result.is_ok());
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// Changing an unprotected header leaves the signature valid.
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sign1.unprotected.content_type = Some(coset::ContentType::Text("text/plain".to_owned()));
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assert!(sign1
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.verify_signature(aad, |sig, data| verifier.verify(sig, data))
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.is_ok());
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// Providing a different `aad` means the signature won't validate.
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assert!(sign1
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.verify_signature(b"not aad", |sig, data| verifier.verify(sig, data))
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.is_err());
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// Changing a protected header invalidates the signature.
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sign1.protected.header.content_type = Some(coset::ContentType::Text("text/plain".to_owned()));
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assert!(sign1
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.verify_signature(aad, |sig, data| verifier.verify(sig, data))
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.is_err());
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}
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