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CVPN-1681 Fix failed Kyber/ML-KEM handshake with non-AVX2 CPU #211

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Dec 27, 2024
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CVPN-1681 Fix failed Kyber/ML-KEM handshake with non-AVX2 CPU #211

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1 change: 1 addition & 0 deletions wolfssl-sys/build.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@ const PATCHES: &[&str] = &[
"fix-kyber-mlkem-benchmark.patch",
"fix-mlkem-get-curve-name.patch",
"fix-kyber-get-curve-name.patch",
"fix-kyber-prf-non-avx2.patch",
];

/**
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51 changes: 51 additions & 0 deletions wolfssl-sys/patches/fix-kyber-prf-non-avx2.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,51 @@
From e507c466d5b97f1b1b063783f4ae020c38ebae4b Mon Sep 17 00:00:00 2001
From: Sean Parkinson <[email protected]>
Date: Fri, 20 Dec 2024 11:03:58 +1000
Subject: [PATCH] ML-KEM/Kyber: fix kyber_prf() for when no AVX2

When no AVX2 available, kyber_prf() is called to produce more than one
SHAKE-256 blocks worth of ouput. Otherwise only one block is needed.
Changed function to support an outlen of greater than one block.
---
wolfcrypt/src/wc_kyber_poly.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/wolfcrypt/src/wc_kyber_poly.c b/wolfcrypt/src/wc_kyber_poly.c
index d947d37e95..76b5cd5d77 100644
--- a/wolfcrypt/src/wc_kyber_poly.c
+++ b/wolfcrypt/src/wc_kyber_poly.c
@@ -2074,17 +2074,24 @@ static int kyber_prf(wc_Shake* shake256, byte* out, unsigned int outLen,
(25 - KYBER_SYM_SZ / 8 - 1) * sizeof(word64));
state[WC_SHA3_256_COUNT - 1] = W64LIT(0x8000000000000000);

- if (IS_INTEL_BMI2(cpuid_flags)) {
- sha3_block_bmi2(state);
- }
- else if (IS_INTEL_AVX2(cpuid_flags) && (SAVE_VECTOR_REGISTERS2() == 0)) {
- sha3_block_avx2(state);
- RESTORE_VECTOR_REGISTERS();
- }
- else {
- BlockSha3(state);
+ while (outLen > 0) {
+ unsigned int len = min(outLen, WC_SHA3_256_BLOCK_SIZE);
+
+ if (IS_INTEL_BMI2(cpuid_flags)) {
+ sha3_block_bmi2(state);
+ }
+ else if (IS_INTEL_AVX2(cpuid_flags) &&
+ (SAVE_VECTOR_REGISTERS2() == 0)) {
+ sha3_block_avx2(state);
+ RESTORE_VECTOR_REGISTERS();
+ }
+ else {
+ BlockSha3(state);
+ }
+ XMEMCPY(out, state, len);
+ out += len;
+ outLen -= len;
}
- XMEMCPY(out, state, outLen);

return 0;
#else
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