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vfs/cbe_trust_anchor: encrypt symmetric keys

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By now, the symmetric keys were only XOR'ed with the private key as placeholder
for a real encryption. Now they are encrypted using AES256 with the TA's
private key as key

Ref #4032.
This commit is contained in:
Martin Stein 2021-04-10 22:38:40 +02:00 committed by Norman Feske
parent f41dec67e1
commit 641a738e3d
1 changed files with 48 additions and 19 deletions
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67
repos/gems/src/lib/vfs/cbe_trust_anchor/vfs.cc
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@ -105,15 +105,6 @@ void Aes_cbc::decrypt_without_iv(unsigned char *plaintext_base,
enum { PRIVATE_KEY_SIZE = 32 };
static void xor_bytes(unsigned char const *p, int p_len,
unsigned char *k, int k_len)
{
for (int i = 0; i < k_len; i++) {
k[i] ^= p[i % p_len];
}
}
namespace Vfs_cbe_trust_anchor {
using namespace Vfs;
@ -215,20 +206,58 @@ class Trust_anchor
Key _encrypt_key { };
Key _generated_key { };
void _xcrypt_key(Private_key const &priv_key, Key &key)
{
xor_bytes(priv_key.value, (int)PRIVATE_KEY_SIZE,
key.value, (int)Key::KEY_LEN);
}
bool _execute_xcrypt(Key &key)
bool _execute_encrypt()
{
switch (_job_state) {
case Job_state::PENDING:
_xcrypt_key(_private_key, key);
{
Key key_plaintext { };
Genode::memcpy(
key_plaintext.value, _encrypt_key.value, Key::KEY_LEN);
Aes_cbc::encrypt_without_iv(
_encrypt_key.value,
Key::KEY_LEN,
key_plaintext.value,
_private_key.value,
PRIVATE_KEY_SIZE);
_job_state = Job_state::COMPLETE;
_job_success = true;
[[fallthrough]];
}
case Job_state::COMPLETE:
return true;
case Job_state::IN_PROGRESS: [[fallthrough]];
case Job_state::NONE: [[fallthrough]];
default: return false;
}
/* never reached */
return false;
}
bool _execute_decrypt()
{
switch (_job_state) {
case Job_state::PENDING:
{
Key key_ciphertext { };
Genode::memcpy(
key_ciphertext.value, _decrypt_key.value, Key::KEY_LEN);
Aes_cbc::decrypt_without_iv(
_decrypt_key.value,
Key::KEY_LEN,
key_ciphertext.value,
_private_key.value,
PRIVATE_KEY_SIZE);
_job_state = Job_state::COMPLETE;
_job_success = true;
[[fallthrough]];
}
case Job_state::COMPLETE:
return true;
@ -526,8 +555,8 @@ class Trust_anchor
bool _execute()
{
switch (_job) {
case Job::DECRYPT: return _execute_xcrypt(_decrypt_key);
case Job::ENCRYPT: return _execute_xcrypt(_encrypt_key);
case Job::DECRYPT: return _execute_decrypt();
case Job::ENCRYPT: return _execute_encrypt();
case Job::GENERATE: return _execute_generate(_generated_key);
case Job::INIT: return _execute_init();
case Job::READ_HASH: return _execute_read_hash();