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LibTLS: Allow using other hash algorithms for HMAC

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The standard allows for ciphers to define which hash to use.
Fixes #7348
This commit is contained in:
DexesTTP 2021-05-29 08:26:10 +02:00 • committed by Ali Mohammad Pur
parent cb4a0dec8a
commit 4bbf954ad0
4 changed files with 56 additions and 14 deletions
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39
Userland/Libraries/LibTLS/TLSv12.cpp
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@ -232,19 +232,14 @@ bool Context::verify_chain() const
return true;
}
void TLSv12::pseudorandom_function(Bytes output, ReadonlyBytes secret, const u8* label, size_t label_length, ReadonlyBytes seed, ReadonlyBytes seed_b)
template<typename HMACType>
static void hmac_pseudorandom_function(Bytes output, ReadonlyBytes secret, const u8* label, size_t label_length, ReadonlyBytes seed, ReadonlyBytes seed_b)
{
if (!secret.size()) {
dbgln("null secret");
return;
}
// RFC 5246: "In this section, we define one PRF, based on HMAC. This PRF with the
// SHA-256 hash function is used for all cipher suites defined in this
// document and in TLS documents published prior to this document when
// TLS 1.2 is negotiated."
// Apparently this PRF _always_ uses SHA256
auto append_label_seed = [&](auto& hmac) {
hmac.update(label, label_length);
hmac.update(seed);
@ -252,7 +247,7 @@ void TLSv12::pseudorandom_function(Bytes output, ReadonlyBytes secret, const u8*
hmac.update(seed_b);
};
Crypto::Authentication::HMAC<Crypto::Hash::SHA256> hmac(secret);
HMACType hmac(secret);
append_label_seed(hmac);
constexpr auto digest_size = hmac.digest_size();
@ -276,6 +271,34 @@ void TLSv12::pseudorandom_function(Bytes output, ReadonlyBytes secret, const u8*
}
}
void TLSv12::pseudorandom_function(Bytes output, ReadonlyBytes secret, const u8* label, size_t label_length, ReadonlyBytes seed, ReadonlyBytes seed_b)
{
// Simplification: We only support the HMAC PRF with the hash function SHA-256 or stronger.
// RFC 5246: "In this section, we define one PRF, based on HMAC. This PRF with the
// SHA-256 hash function is used for all cipher suites defined in this
// document and in TLS documents published prior to this document when
// TLS 1.2 is negotiated. New cipher suites MUST explicitly specify a
// PRF and, in general, SHOULD use the TLS PRF with SHA-256 or a
// stronger standard hash function."
switch (hmac_hash()) {
case Crypto::Hash::HashKind::SHA512:
hmac_pseudorandom_function<Crypto::Authentication::HMAC<Crypto::Hash::SHA512>>(output, secret, label, label_length, seed, seed_b);
break;
case Crypto::Hash::HashKind::SHA384:
hmac_pseudorandom_function<Crypto::Authentication::HMAC<Crypto::Hash::SHA384>>(output, secret, label, label_length, seed, seed_b);
break;
case Crypto::Hash::HashKind::SHA256:
hmac_pseudorandom_function<Crypto::Authentication::HMAC<Crypto::Hash::SHA256>>(output, secret, label, label_length, seed, seed_b);
break;
default:
dbgln("Failed to find a suitable HMAC hash");
VERIFY_NOT_REACHED();
break;
}
}
TLSv12::TLSv12(Core::Object* parent, Options options)
: Core::Socket(Core::Socket::Type::TCP, parent)
{