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1 /*
2  * Copyright (C) 2024 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 //! Module providing access to platform specific functions used by the library.
18 use hwcryptohal_common::{err::HwCryptoError, hwcrypto_err};
19 use kmr_common::crypto;
20 use log::error;
21 
22 use crate::ffi_bindings;
23 
24 const NANOSECONDS_IN_1_MS: u64 = 1000000;
25 
26 // Placeholder for function to compare VM identities. Identities will probably be based on DICE,
27 // a simple comparison could be done if the DICE chains are unencrypted and the order of fields is
28 // always the same.
29 #[allow(dead_code)]
compare_vm_identities(vm1_identity: &[u8], vm2_identity: &[u8]) -> bool30 pub(crate) fn compare_vm_identities(vm1_identity: &[u8], vm2_identity: &[u8]) -> bool {
31     (vm1_identity.len() == vm2_identity.len()) && openssl::memcmp::eq(vm1_identity, vm2_identity)
32 }
33 
34 #[derive(Default)]
35 pub(crate) struct PlatformRng;
36 
37 impl crypto::Rng for PlatformRng {
add_entropy(&mut self, data: &[u8])38     fn add_entropy(&mut self, data: &[u8]) {
39         trusty_rng_add_entropy(data);
40     }
fill_bytes(&mut self, dest: &mut [u8])41     fn fill_bytes(&mut self, dest: &mut [u8]) {
42         openssl::rand::rand_bytes(dest)
43             .expect("shouldn't happen, function never fails on BoringSSL");
44     }
45 }
46 
47 /// Add entropy to Trusty's RNG.
trusty_rng_add_entropy(data: &[u8])48 pub fn trusty_rng_add_entropy(data: &[u8]) {
49     // Safety: `data` is a valid slice
50     let rc = unsafe { ffi_bindings::sys::trusty_rng_add_entropy(data.as_ptr(), data.len()) };
51     if rc != 0 {
52         panic!("trusty_rng_add_entropy() failed, {}", rc)
53     }
54 }
55 
current_epoch_time_ms() -> Result<u64, HwCryptoError>56 pub fn current_epoch_time_ms() -> Result<u64, HwCryptoError> {
57     let mut secure_time_ns = 0;
58     // Safety: external syscall gets valid raw pointer to a `u64`.
59     let rc = unsafe { trusty_sys::gettime(0, 0, &mut secure_time_ns) };
60     if rc < 0 {
61         // Couldn't get time
62         error!("Error calling trusty_gettime: {:#x}", rc);
63         Err(hwcrypto_err!(GENERIC_ERROR, "error calling trusty_gettime: {:#x}", rc))
64     } else {
65         // secure_time_ns is positive, so casting is correct
66         Ok((secure_time_ns as u64) / NANOSECONDS_IN_1_MS)
67     }
68 }
69