Joel Galenson | ca0efb1 | 2020-10-01 14:32:30 -0700 | [diff] [blame] | 1 | // Copyright 2020, The Android Open Source Project |
| 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 | |
Janis Danisevskis | 9d90b81 | 2020-11-25 21:02:11 -0800 | [diff] [blame^] | 15 | //! This module implements safe wrappers for some crypto operations required by |
| 16 | //! Keystore 2.0. |
| 17 | |
| 18 | mod error; |
| 19 | mod zvec; |
| 20 | pub use error::Error; |
| 21 | use keystore2_crypto_bindgen::{ |
| 22 | generateKeyFromPassword, randomBytes, size_t, AES_gcm_decrypt, AES_gcm_encrypt, |
| 23 | }; |
| 24 | pub use zvec::ZVec; |
| 25 | |
| 26 | /// Length of the expected initialization vector. |
| 27 | pub const IV_LENGTH: usize = 16; |
| 28 | /// Length of the expected AEAD TAG. |
| 29 | pub const TAG_LENGTH: usize = 16; |
| 30 | /// Length of an AES 256 key in bytes. |
| 31 | pub const AES_256_KEY_LENGTH: usize = 32; |
| 32 | /// Length of an AES 128 key in bytes. |
| 33 | pub const AES_128_KEY_LENGTH: usize = 16; |
| 34 | /// Length of the expected salt for key from password generation. |
| 35 | pub const SALT_LENGTH: usize = 16; |
| 36 | |
| 37 | // This is the number of bytes of the GCM IV that is expected to be initialized |
| 38 | // with random bytes. |
| 39 | const GCM_IV_LENGTH: usize = 12; |
| 40 | |
| 41 | /// Generate an AES256 key, essentially 32 random bytes from the underlying |
| 42 | /// boringssl library discretely stuffed into a ZVec. |
| 43 | pub fn generate_aes256_key() -> Result<ZVec, Error> { |
| 44 | // Safety: key has the same length as the requested number of random bytes. |
| 45 | let mut key = ZVec::new(AES_256_KEY_LENGTH)?; |
| 46 | if unsafe { randomBytes(key.as_mut_ptr(), AES_256_KEY_LENGTH as size_t) } { |
| 47 | Ok(key) |
| 48 | } else { |
| 49 | Err(Error::RandomNumberGenerationFailed) |
| 50 | } |
| 51 | } |
| 52 | |
| 53 | /// Generate a salt. |
| 54 | pub fn generate_salt() -> Result<Vec<u8>, Error> { |
| 55 | // Safety: salt has the same length as the requested number of random bytes. |
| 56 | let mut salt = vec![0; SALT_LENGTH]; |
| 57 | if unsafe { randomBytes(salt.as_mut_ptr(), SALT_LENGTH as size_t) } { |
| 58 | Ok(salt) |
| 59 | } else { |
| 60 | Err(Error::RandomNumberGenerationFailed) |
| 61 | } |
| 62 | } |
| 63 | |
| 64 | /// Uses AES GCM to decipher a message given an initialization vector, aead tag, and key. |
| 65 | /// This function accepts 128 and 256-bit keys and uses AES128 and AES256 respectively based |
| 66 | /// on the key length. |
| 67 | /// This function returns the plaintext message in a ZVec because it is assumed that |
| 68 | /// it contains sensitive information that should be zeroed from memory before its buffer is |
| 69 | /// freed. Input key is taken as a slice for flexibility, but it is recommended that it is held |
| 70 | /// in a ZVec as well. |
| 71 | pub fn aes_gcm_decrypt(data: &[u8], iv: &[u8], tag: &[u8], key: &[u8]) -> Result<ZVec, Error> { |
| 72 | if iv.len() != IV_LENGTH { |
| 73 | return Err(Error::InvalidIvLength); |
| 74 | } |
| 75 | |
| 76 | if tag.len() != TAG_LENGTH { |
| 77 | return Err(Error::InvalidAeadTagLength); |
| 78 | } |
| 79 | |
| 80 | match key.len() { |
| 81 | AES_128_KEY_LENGTH | AES_256_KEY_LENGTH => {} |
| 82 | _ => return Err(Error::InvalidKeyLength), |
| 83 | } |
| 84 | |
| 85 | let mut result = ZVec::new(data.len())?; |
| 86 | |
| 87 | // Safety: The first two arguments must point to buffers with a size given by the third |
| 88 | // argument. The key must have a size of 16 or 32 bytes which we check above. |
| 89 | // The iv and tag arguments must be 16 bytes, which we also check above. |
| 90 | match unsafe { |
| 91 | AES_gcm_decrypt( |
| 92 | data.as_ptr(), |
| 93 | result.as_mut_ptr(), |
| 94 | data.len() as size_t, |
| 95 | key.as_ptr(), |
| 96 | key.len() as size_t, |
| 97 | iv.as_ptr(), |
| 98 | tag.as_ptr(), |
| 99 | ) |
| 100 | } { |
| 101 | true => Ok(result), |
| 102 | false => Err(Error::DecryptionFailed), |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | /// Uses AES GCM to encrypt a message given a key. |
| 107 | /// This function accepts 128 and 256-bit keys and uses AES128 and AES256 respectively based on |
| 108 | /// the key length. The function generates an initialization vector. The return value is a tuple |
| 109 | /// of `(ciphertext, iv, tag)`. |
| 110 | pub fn aes_gcm_encrypt(data: &[u8], key: &[u8]) -> Result<(Vec<u8>, Vec<u8>, Vec<u8>), Error> { |
| 111 | let mut iv = vec![0; IV_LENGTH]; |
| 112 | // Safety: iv is longer than GCM_IV_LENGTH, which is 12 while IV_LENGTH is 16. |
| 113 | // The iv needs to be 16 bytes long, but the last 4 bytes remain zeroed. |
| 114 | if !unsafe { randomBytes(iv.as_mut_ptr(), GCM_IV_LENGTH as size_t) } { |
| 115 | return Err(Error::RandomNumberGenerationFailed); |
| 116 | } |
| 117 | |
| 118 | match key.len() { |
| 119 | AES_128_KEY_LENGTH | AES_256_KEY_LENGTH => {} |
| 120 | _ => return Err(Error::InvalidKeyLength), |
| 121 | } |
| 122 | |
| 123 | let mut result: Vec<u8> = vec![0; data.len()]; |
| 124 | let mut tag: Vec<u8> = vec![0; TAG_LENGTH]; |
| 125 | match unsafe { |
| 126 | AES_gcm_encrypt( |
| 127 | data.as_ptr(), |
| 128 | result.as_mut_ptr(), |
| 129 | data.len() as size_t, |
| 130 | key.as_ptr(), |
| 131 | key.len() as size_t, |
| 132 | iv.as_ptr(), |
| 133 | tag.as_mut_ptr(), |
| 134 | ) |
| 135 | } { |
| 136 | true => Ok((result, iv, tag)), |
| 137 | false => Err(Error::EncryptionFailed), |
| 138 | } |
| 139 | } |
| 140 | |
| 141 | /// Generates a key from the given password and salt. |
| 142 | /// The salt must be exactly 16 bytes long. |
| 143 | /// Two key sizes are accepted: 16 and 32 bytes. |
| 144 | pub fn derive_key_from_password( |
| 145 | pw: &[u8], |
| 146 | salt: Option<&[u8]>, |
| 147 | key_length: usize, |
| 148 | ) -> Result<ZVec, Error> { |
| 149 | let salt: *const u8 = match salt { |
| 150 | Some(s) => { |
| 151 | if s.len() != SALT_LENGTH { |
| 152 | return Err(Error::InvalidSaltLength); |
| 153 | } |
| 154 | s.as_ptr() |
| 155 | } |
| 156 | None => std::ptr::null(), |
| 157 | }; |
| 158 | |
| 159 | match key_length { |
| 160 | AES_128_KEY_LENGTH | AES_256_KEY_LENGTH => {} |
| 161 | _ => return Err(Error::InvalidKeyLength), |
| 162 | } |
| 163 | |
| 164 | let mut result = ZVec::new(key_length)?; |
| 165 | |
| 166 | unsafe { |
| 167 | generateKeyFromPassword( |
| 168 | result.as_mut_ptr(), |
| 169 | result.len() as size_t, |
| 170 | pw.as_ptr() as *const std::os::raw::c_char, |
| 171 | pw.len() as size_t, |
| 172 | salt, |
| 173 | ) |
| 174 | }; |
| 175 | |
| 176 | Ok(result) |
| 177 | } |
Joel Galenson | 46d6fd0 | 2020-11-19 17:58:33 -0800 | [diff] [blame] | 178 | |
Joel Galenson | ca0efb1 | 2020-10-01 14:32:30 -0700 | [diff] [blame] | 179 | #[cfg(test)] |
| 180 | mod tests { |
| 181 | |
Janis Danisevskis | 9d90b81 | 2020-11-25 21:02:11 -0800 | [diff] [blame^] | 182 | use super::*; |
Joel Galenson | ca0efb1 | 2020-10-01 14:32:30 -0700 | [diff] [blame] | 183 | use keystore2_crypto_bindgen::{ |
| 184 | generateKeyFromPassword, AES_gcm_decrypt, AES_gcm_encrypt, CreateKeyId, |
| 185 | }; |
| 186 | |
| 187 | #[test] |
Janis Danisevskis | 9d90b81 | 2020-11-25 21:02:11 -0800 | [diff] [blame^] | 188 | fn test_wrapper_roundtrip() { |
| 189 | let key = generate_aes256_key().unwrap(); |
| 190 | let message = b"totally awesome message"; |
| 191 | let (cipher_text, iv, tag) = aes_gcm_encrypt(message, &key).unwrap(); |
| 192 | let message2 = aes_gcm_decrypt(&cipher_text, &iv, &tag, &key).unwrap(); |
| 193 | assert_eq!(message[..], message2[..]) |
| 194 | } |
| 195 | |
| 196 | #[test] |
Joel Galenson | ca0efb1 | 2020-10-01 14:32:30 -0700 | [diff] [blame] | 197 | fn test_encrypt_decrypt() { |
| 198 | let input = vec![0; 16]; |
| 199 | let mut out = vec![0; 16]; |
| 200 | let mut out2 = vec![0; 16]; |
| 201 | let key = vec![0; 16]; |
| 202 | let iv = vec![0; 12]; |
| 203 | let mut tag = vec![0; 16]; |
| 204 | unsafe { |
| 205 | let res = AES_gcm_encrypt( |
| 206 | input.as_ptr(), |
| 207 | out.as_mut_ptr(), |
| 208 | 16, |
| 209 | key.as_ptr(), |
| 210 | 16, |
| 211 | iv.as_ptr(), |
| 212 | tag.as_mut_ptr(), |
| 213 | ); |
| 214 | assert!(res); |
| 215 | assert_ne!(out, input); |
| 216 | assert_ne!(tag, input); |
| 217 | let res = AES_gcm_decrypt( |
| 218 | out.as_ptr(), |
| 219 | out2.as_mut_ptr(), |
| 220 | 16, |
| 221 | key.as_ptr(), |
| 222 | 16, |
| 223 | iv.as_ptr(), |
| 224 | tag.as_ptr(), |
| 225 | ); |
| 226 | assert!(res); |
| 227 | assert_eq!(out2, input); |
| 228 | } |
| 229 | } |
| 230 | |
| 231 | #[test] |
| 232 | fn test_create_key_id() { |
| 233 | let blob = vec![0; 16]; |
| 234 | let mut out: u64 = 0; |
| 235 | unsafe { |
| 236 | let res = CreateKeyId(blob.as_ptr(), 16, &mut out); |
| 237 | assert!(res); |
| 238 | assert_ne!(out, 0); |
| 239 | } |
| 240 | } |
| 241 | |
| 242 | #[test] |
| 243 | fn test_generate_key_from_password() { |
| 244 | let mut key = vec![0; 16]; |
| 245 | let pw = vec![0; 16]; |
| 246 | let mut salt = vec![0; 16]; |
| 247 | unsafe { |
| 248 | generateKeyFromPassword(key.as_mut_ptr(), 16, pw.as_ptr(), 16, salt.as_mut_ptr()); |
| 249 | } |
| 250 | assert_ne!(key, vec![0; 16]); |
| 251 | } |
| 252 | } |