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Kernel: Make Random work on CPUs without rdrand

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- If rdseed is not available, fallback to rdrand.
- If rdrand is not available, block for entropy, or use insecure prng
  depending on if user wants fast or good random.
This commit is contained in:
Peter Elliott 2020-06-27 11:10:01 -06:00 • committed by Andreas Kling
parent 1eb338ab71
commit e1aef94a40
4 changed files with 71 additions and 12 deletions
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21
Kernel/Random.h
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@ -61,7 +61,7 @@ public:
this->reseed();
}
ASSERT(m_reseed_number > 0);
ASSERT(is_seeded());
// FIXME: More than 2^20 bytes cannot be generated without refreshing the key.
ASSERT(n < (1 << 20));
@ -86,6 +86,16 @@ public:
m_pools[pool].update(reinterpret_cast<const u8*>(&event_data), sizeof(T));
}
bool is_seeded() const
{
return m_reseed_number > 0;
}
bool is_ready() const
{
return is_seeded() || m_p0_len >= reseed_threshold;
}
private:
void reseed()
{
@ -118,8 +128,14 @@ class KernelRng : public Lockable<FortunaPRNG<Crypto::Cipher::AESCipher, Crypto:
public:
static KernelRng& the();
void wait_for_entropy();
void wake_if_ready();
private:
KernelRng();
WaitQueue m_seed_queue;
};
class EntropySource {
@ -143,6 +159,7 @@ public:
Event<T> event = { read_tsc(), m_source, event_data };
KernelRng::the().resource().add_random_event(event, m_pool);
m_pool++;
KernelRng::the().wake_if_ready();
}
private:
@ -153,7 +170,7 @@ private:
};
// NOTE: These API's are primarily about expressing intent/needs in the calling code.
// We don't make any guarantees about actual fastness or goodness yet.
// The only difference is that get_fast_random is guaranteed not to block.
void get_fast_random_bytes(u8*, size_t);
void get_good_random_bytes(u8*, size_t);