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Use Span-based CreateHMAC where possible #43541

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Merged
merged 2 commits into from
Oct 19, 2020
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Use Span-based CreateHMAC where possible #43541

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c6eefb5
Use Span-based CreateHMAC where possible.
vcsjones Oct 16, 2020
d5523ef
Use arrays for downlevel targets.
vcsjones Oct 17, 2020
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5 changes: 3 additions & 2 deletions src/libraries/Common/src/System/Security/Cryptography/Asn1/Pkcs12/PfxAsn.manual.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,8 +52,9 @@ internal bool VerifyMac(
throw new CryptographicException(SR.Cryptography_Der_Invalid_Encoding);
}

// Cannot use the ArrayPool or stackalloc here because CreateHMAC needs a properly bounded array.
byte[] derived = new byte[expectedOutputSize];
Debug.Assert(expectedOutputSize <= 64); // SHA512 is the largest digest size we know about
Span<byte> derived = stackalloc byte[expectedOutputSize];


int iterationCount =
PasswordBasedEncryption.NormalizeIterationCount(MacData.Value.IterationCount);
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82 changes: 33 additions & 49 deletions src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanDerivation.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -191,68 +191,52 @@ private static unsafe void PHash(
//
// This is called via PRF, which turns (label || seed) into seed.

byte[] secretTmp = new byte[secret.Length];
Span<byte> retSpan = ret;

// Keep secretTmp pinned the whole time it has a secret in it, so it
// doesn't get copied around during heap compaction.
fixed (byte* pinnedSecretTmp = secretTmp)
using (IncrementalHash hasher = IncrementalHash.CreateHMAC(algorithmName, secret))
{
secret.CopyTo(secretTmp);
Span<byte> a = stackalloc byte[hashOutputSize];
Span<byte> p = stackalloc byte[hashOutputSize];

try
{
Span<byte> retSpan = ret;

using (IncrementalHash hasher = IncrementalHash.CreateHMAC(algorithmName, secretTmp))
{
Span<byte> a = stackalloc byte[hashOutputSize];
Span<byte> p = stackalloc byte[hashOutputSize];

// A(1)
hasher.AppendData(prfLabel);
hasher.AppendData(prfSeed);
// A(1)
hasher.AppendData(prfLabel);
hasher.AppendData(prfSeed);

if (!hasher.TryGetHashAndReset(a, out int bytesWritten) || bytesWritten != hashOutputSize)
{
throw new CryptographicException();
}
if (!hasher.TryGetHashAndReset(a, out int bytesWritten) || bytesWritten != hashOutputSize)
{
throw new CryptographicException();
}

while (true)
{
// HMAC_hash(secret, A(i) || seed) => p
hasher.AppendData(a);
hasher.AppendData(prfLabel);
hasher.AppendData(prfSeed);
while (true)
{
// HMAC_hash(secret, A(i) || seed) => p
hasher.AppendData(a);
hasher.AppendData(prfLabel);
hasher.AppendData(prfSeed);

if (!hasher.TryGetHashAndReset(p, out bytesWritten) || bytesWritten != hashOutputSize)
{
throw new CryptographicException();
}
if (!hasher.TryGetHashAndReset(p, out bytesWritten) || bytesWritten != hashOutputSize)
{
throw new CryptographicException();
}

int len = Math.Min(p.Length, retSpan.Length);
int len = Math.Min(p.Length, retSpan.Length);

p.Slice(0, len).CopyTo(retSpan);
retSpan = retSpan.Slice(len);
p.Slice(0, len).CopyTo(retSpan);
retSpan = retSpan.Slice(len);

if (retSpan.Length == 0)
{
return;
}
if (retSpan.Length == 0)
{
return;
}

// Build the next A(i)
hasher.AppendData(a);
// Build the next A(i)
hasher.AppendData(a);

if (!hasher.TryGetHashAndReset(a, out bytesWritten) || bytesWritten != hashOutputSize)
{
throw new CryptographicException();
}
}
if (!hasher.TryGetHashAndReset(a, out bytesWritten) || bytesWritten != hashOutputSize)
{
throw new CryptographicException();
}
}
finally
{
Array.Clear(secretTmp, 0, secretTmp.Length);
}
}
}
}
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