cast.go

     1  // Copyright 2024 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package ed25519
     6  
     7  import (
     8  	"bytes"
     9  	"crypto/internal/fips140"
    10  	_ "crypto/internal/fips140/check"
    11  	"errors"
    12  	"sync"
    13  )
    14  
    15  func fipsPCT(k *PrivateKey) error {
    16  	return fips140.PCT("Ed25519 sign and verify PCT", func() error {
    17  		return pairwiseTest(k)
    18  	})
    19  }
    20  
    21  // pairwiseTest needs to be a top-level function declaration to let the calls
    22  // inline and their allocations not escape.
    23  func pairwiseTest(k *PrivateKey) error {
    24  	msg := []byte("PCT")
    25  	sig := Sign(k, msg)
    26  	// Note that this runs pub.a.SetBytes. If we wanted to make key generation
    27  	// in FIPS mode faster, we could reuse A from GenerateKey. But another thing
    28  	// that could make it faster is just _not doing a useless self-test_.
    29  	pub, err := NewPublicKey(k.PublicKey())
    30  	if err != nil {
    31  		return err
    32  	}
    33  	return Verify(pub, msg, sig)
    34  }
    35  
    36  func signWithoutSelfTest(priv *PrivateKey, message []byte) []byte {
    37  	signature := make([]byte, signatureSize)
    38  	return signWithDom(signature, priv, message, domPrefixPure, "")
    39  }
    40  
    41  func verifyWithoutSelfTest(pub *PublicKey, message, sig []byte) error {
    42  	return verifyWithDom(pub, message, sig, domPrefixPure, "")
    43  }
    44  
    45  var fipsSelfTest = sync.OnceFunc(func() {
    46  	fips140.CAST("Ed25519 sign and verify", func() error {
    47  		seed := [32]byte{
    48  			0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
    49  			0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10,
    50  			0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
    51  			0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
    52  		}
    53  		msg := []byte("CAST")
    54  		want := []byte{
    55  			0xbd, 0xe7, 0xa5, 0xf3, 0x40, 0x73, 0xb9, 0x5a,
    56  			0x2e, 0x6d, 0x63, 0x20, 0x0a, 0xd5, 0x92, 0x9b,
    57  			0xa2, 0x3d, 0x00, 0x44, 0xb4, 0xc5, 0xfd, 0x62,
    58  			0x1d, 0x5e, 0x33, 0x2f, 0xe4, 0x61, 0x42, 0x31,
    59  			0x5b, 0x10, 0x53, 0x13, 0x4d, 0xcb, 0xd1, 0x1b,
    60  			0x2a, 0xf6, 0xcd, 0x0e, 0xdb, 0x9a, 0xd3, 0x1e,
    61  			0x35, 0xdb, 0x0b, 0xcf, 0x58, 0x90, 0x4f, 0xd7,
    62  			0x69, 0x38, 0xed, 0x30, 0x51, 0x0f, 0xaa, 0x03,
    63  		}
    64  		k := &PrivateKey{seed: seed}
    65  		precomputePrivateKey(k)
    66  		pub, err := NewPublicKey(k.PublicKey())
    67  		if err != nil {
    68  			return err
    69  		}
    70  		sig := signWithoutSelfTest(k, msg)
    71  		if !bytes.Equal(sig, want) {
    72  			return errors.New("unexpected result")
    73  		}
    74  		return verifyWithoutSelfTest(pub, msg, sig)
    75  	})
    76  })
    77
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