From 60f6d2f6230c5085ad25a9e3ebdaaae2aefdfe36 Mon Sep 17 00:00:00 2001
From: Filippo Valsorda <filippo@golang.org>
Date: Wed, 8 Oct 2025 13:02:36 +0200
Subject: [PATCH] crypto/internal/fips140/entropy: support SHA-384 sizes for
 ACVP tests
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Change-Id: I6a6a6964decc662d753ee3eec357570bd3c95e2d
Reviewed-on: https://go-review.googlesource.com/c/go/+/710056
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Nooras Saba‎ <noorassaba@google.com>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
---
 src/crypto/internal/fips140/entropy/sha384.go | 57 +++++++++++++++----
 .../internal/fips140test/entropy_test.go      | 13 ++++-
 2 files changed, 58 insertions(+), 12 deletions(-)

diff --git a/src/crypto/internal/fips140/entropy/sha384.go b/src/crypto/internal/fips140/entropy/sha384.go
index ec23cfc9ad..c20f76b579 100644
--- a/src/crypto/internal/fips140/entropy/sha384.go
+++ b/src/crypto/internal/fips140/entropy/sha384.go
@@ -8,19 +8,22 @@ import "math/bits"
 
 // This file includes a SHA-384 implementation to insulate the entropy source
 // from any changes in the FIPS 140-3 module's crypto/internal/fips140/sha512
-// package. We only support 1024-byte inputs.
+// package. We support 1024-byte inputs for the entropy source, and arbitrary
+// length inputs for ACVP testing.
+
+var initState = [8]uint64{
+	0xcbbb9d5dc1059ed8,
+	0x629a292a367cd507,
+	0x9159015a3070dd17,
+	0x152fecd8f70e5939,
+	0x67332667ffc00b31,
+	0x8eb44a8768581511,
+	0xdb0c2e0d64f98fa7,
+	0x47b5481dbefa4fa4,
+}
 
 func SHA384(p *[1024]byte) [48]byte {
-	h := [8]uint64{
-		0xcbbb9d5dc1059ed8,
-		0x629a292a367cd507,
-		0x9159015a3070dd17,
-		0x152fecd8f70e5939,
-		0x67332667ffc00b31,
-		0x8eb44a8768581511,
-		0xdb0c2e0d64f98fa7,
-		0x47b5481dbefa4fa4,
-	}
+	h := initState
 
 	sha384Block(&h, (*[128]byte)(p[0:128]))
 	sha384Block(&h, (*[128]byte)(p[128:256]))
@@ -36,6 +39,38 @@ func SHA384(p *[1024]byte) [48]byte {
 	bePutUint64(padlen[112+8:], 1024*8)
 	sha384Block(&h, &padlen)
 
+	return digestBytes(&h)
+}
+
+func TestingOnlySHA384(p []byte) [48]byte {
+	if len(p) == 1024 {
+		return SHA384((*[1024]byte)(p))
+	}
+
+	h := initState
+	bitLen := uint64(len(p)) * 8
+
+	// Process full 128-byte blocks.
+	for len(p) >= 128 {
+		sha384Block(&h, (*[128]byte)(p[:128]))
+		p = p[128:]
+	}
+
+	// Process final block and padding.
+	var finalBlock [128]byte
+	copy(finalBlock[:], p)
+	finalBlock[len(p)] = 0x80
+	if len(p) >= 112 {
+		sha384Block(&h, &finalBlock)
+		finalBlock = [128]byte{}
+	}
+	bePutUint64(finalBlock[112+8:], bitLen)
+	sha384Block(&h, &finalBlock)
+
+	return digestBytes(&h)
+}
+
+func digestBytes(h *[8]uint64) [48]byte {
 	var digest [48]byte
 	bePutUint64(digest[0:], h[0])
 	bePutUint64(digest[8:], h[1])
diff --git a/src/crypto/internal/fips140test/entropy_test.go b/src/crypto/internal/fips140test/entropy_test.go
index a84b50c62b..ef6909efba 100644
--- a/src/crypto/internal/fips140test/entropy_test.go
+++ b/src/crypto/internal/fips140test/entropy_test.go
@@ -11,6 +11,7 @@ import (
 	"crypto/internal/cryptotest"
 	"crypto/internal/fips140/drbg"
 	"crypto/internal/fips140/entropy"
+	"crypto/rand"
 	"crypto/sha256"
 	"crypto/sha512"
 	"encoding/hex"
@@ -159,6 +160,16 @@ func TestEntropySHA384(t *testing.T) {
 	if got != want {
 		t.Errorf("SHA384() = %x, want %x", got, want)
 	}
+
+	for l := range 1024*3 + 1 {
+		input := make([]byte, l)
+		rand.Read(input)
+		want := sha512.Sum384(input)
+		got := entropy.TestingOnlySHA384(input)
+		if got != want {
+			t.Errorf("TestingOnlySHA384(%d bytes) = %x, want %x", l, got, want)
+		}
+	}
 }
 
 func TestEntropyRepetitionCountTest(t *testing.T) {
@@ -230,7 +241,7 @@ func TestEntropyUnchanged(t *testing.T) {
 	// entropy source through the Entropy Source Validation program,
 	// independently of the FIPS 140-3 module. It must not change even across
 	// FIPS 140-3 module versions, in order to reuse the ESV certificate.
-	exp := "35976eb8a11678c79777da07aaab5511d4325701f837777df205f6e7b20c6821"
+	exp := "1b68d4c091ef66c6006602e4ed3ac10f8a82ad193708ec99d63b145e3baa3e6c"
 	if got := hex.EncodeToString(h.Sum(nil)); got != exp {
 		t.Errorf("hash of crypto/internal/fips140/entropy = %s, want %s", got, exp)
 	}
-- 
2.52.0