Aditya Belsare | ff911b4 | 2022-02-04 23:57:51 +0000 | [diff] [blame] | 1 | // Copyright 2021 Google LLC |
| 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 | //! Example program demonstrating signature creation. |
| 18 | use coset::{iana, CborSerializable}; |
| 19 | |
| 20 | #[derive(Copy, Clone)] |
| 21 | struct FakeSigner {} |
| 22 | |
| 23 | // Use a fake signer/verifier (to avoid pulling in lots of dependencies). |
| 24 | impl FakeSigner { |
| 25 | fn sign(&self, data: &[u8]) -> Vec<u8> { |
| 26 | data.to_vec() |
| 27 | } |
| 28 | |
| 29 | fn verify(&self, sig: &[u8], data: &[u8]) -> Result<(), String> { |
| 30 | if sig != self.sign(data) { |
| 31 | Err("failed to verify".to_owned()) |
| 32 | } else { |
| 33 | Ok(()) |
| 34 | } |
| 35 | } |
| 36 | } |
| 37 | |
| 38 | fn main() { |
| 39 | // Build a fake signer/verifier (to avoid pulling in lots of dependencies). |
| 40 | let signer = FakeSigner {}; |
| 41 | let verifier = signer; |
| 42 | |
| 43 | // Inputs. |
| 44 | let pt = b"This is the content"; |
| 45 | let aad = b"this is additional data"; |
| 46 | |
| 47 | // Build a `CoseSign1` object. |
| 48 | let protected = coset::HeaderBuilder::new() |
| 49 | .algorithm(iana::Algorithm::ES256) |
| 50 | .key_id(b"11".to_vec()) |
| 51 | .build(); |
| 52 | let sign1 = coset::CoseSign1Builder::new() |
| 53 | .protected(protected) |
| 54 | .payload(pt.to_vec()) |
| 55 | .create_signature(aad, |pt| signer.sign(pt)) |
| 56 | .build(); |
| 57 | |
| 58 | // Serialize to bytes. |
| 59 | let sign1_data = sign1.to_vec().unwrap(); |
| 60 | println!( |
| 61 | "'{}' + '{}' => {}", |
| 62 | String::from_utf8_lossy(pt), |
| 63 | String::from_utf8_lossy(aad), |
| 64 | hex::encode(&sign1_data) |
| 65 | ); |
| 66 | |
| 67 | // At the receiving end, deserialize the bytes back to a `CoseSign1` object. |
| 68 | let mut sign1 = coset::CoseSign1::from_slice(&sign1_data).unwrap(); |
| 69 | |
| 70 | // Check the signature, which needs to have the same `aad` provided. |
| 71 | let result = sign1.verify_signature(aad, |sig, data| verifier.verify(sig, data)); |
| 72 | println!("Signature verified: {:?}.", result); |
| 73 | assert!(result.is_ok()); |
| 74 | |
| 75 | // Changing an unprotected header leaves the signature valid. |
| 76 | sign1.unprotected.content_type = Some(coset::ContentType::Text("text/plain".to_owned())); |
| 77 | assert!(sign1 |
| 78 | .verify_signature(aad, |sig, data| verifier.verify(sig, data)) |
| 79 | .is_ok()); |
| 80 | |
| 81 | // Providing a different `aad` means the signature won't validate. |
| 82 | assert!(sign1 |
| 83 | .verify_signature(b"not aad", |sig, data| verifier.verify(sig, data)) |
| 84 | .is_err()); |
| 85 | |
| 86 | // Changing a protected header invalidates the signature. |
| 87 | sign1.protected.header.content_type = Some(coset::ContentType::Text("text/plain".to_owned())); |
| 88 | assert!(sign1 |
| 89 | .verify_signature(aad, |sig, data| verifier.verify(sig, data)) |
| 90 | .is_err()); |
| 91 | } |