076cd77469
Signed-off-by: Stephan Renatus <srenatus@chef.io>
105 lines
3.3 KiB
Go
105 lines
3.3 KiB
Go
// cryptopasta - basic cryptography examples
|
|
//
|
|
// Written in 2015 by George Tankersley <george.tankersley@gmail.com>
|
|
//
|
|
// To the extent possible under law, the author(s) have dedicated all copyright
|
|
// and related and neighboring rights to this software to the public domain
|
|
// worldwide. This software is distributed without any warranty.
|
|
//
|
|
// You should have received a copy of the CC0 Public Domain Dedication along
|
|
// with this software. If not, see // <http://creativecommons.org/publicdomain/zero/1.0/>.
|
|
|
|
// Provides message authentication and asymmetric signatures.
|
|
//
|
|
// Message authentication: HMAC SHA512/256
|
|
// This is a slight twist on the highly dependable HMAC-SHA256 that gains
|
|
// performance on 64-bit systems and consistency with our hashing
|
|
// recommendation.
|
|
//
|
|
// Asymmetric Signature: ECDSA using P256 and SHA256
|
|
// ECDSA is the best compromise between cryptographic concerns and support for
|
|
// our internal use cases (e.g. RFC7518). The Go standard library
|
|
// implementation has some protection against entropy problems, but is not
|
|
// deterministic. See
|
|
// https://github.com/golang/go/commit/8d7bf2291b095d3a2ecaa2609e1101be46d80deb
|
|
package cryptopasta
|
|
|
|
import (
|
|
"crypto/ecdsa"
|
|
"crypto/elliptic"
|
|
"crypto/hmac"
|
|
"crypto/rand"
|
|
"crypto/sha256"
|
|
"crypto/sha512"
|
|
"io"
|
|
"math/big"
|
|
)
|
|
|
|
// NewHMACKey generates a random 256-bit secret key for HMAC use.
|
|
// Because key generation is critical, it panics if the source of randomness fails.
|
|
func NewHMACKey() *[32]byte {
|
|
key := &[32]byte{}
|
|
_, err := io.ReadFull(rand.Reader, key[:])
|
|
if err != nil {
|
|
panic(err)
|
|
}
|
|
return key
|
|
}
|
|
|
|
// GenerateHMAC produces a symmetric signature using a shared secret key.
|
|
func GenerateHMAC(data []byte, key *[32]byte) []byte {
|
|
h := hmac.New(sha512.New512_256, key[:])
|
|
h.Write(data)
|
|
return h.Sum(nil)
|
|
|
|
}
|
|
|
|
// CheckHMAC securely checks the supplied MAC against a message using the shared secret key.
|
|
func CheckHMAC(data, suppliedMAC []byte, key *[32]byte) bool {
|
|
expectedMAC := GenerateHMAC(data, key)
|
|
return hmac.Equal(expectedMAC, suppliedMAC)
|
|
}
|
|
|
|
// NewSigningKey generates a random P-256 ECDSA private key.
|
|
func NewSigningKey() (*ecdsa.PrivateKey, error) {
|
|
key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
|
|
return key, err
|
|
}
|
|
|
|
// Sign signs arbitrary data using ECDSA.
|
|
func Sign(data []byte, privkey *ecdsa.PrivateKey) ([]byte, error) {
|
|
// hash message
|
|
digest := sha256.Sum256(data)
|
|
|
|
// sign the hash
|
|
r, s, err := ecdsa.Sign(rand.Reader, privkey, digest[:])
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// encode the signature {R, S}
|
|
// big.Int.Bytes() will need padding in the case of leading zero bytes
|
|
params := privkey.Curve.Params()
|
|
curveOrderByteSize := params.P.BitLen() / 8
|
|
rBytes, sBytes := r.Bytes(), s.Bytes()
|
|
signature := make([]byte, curveOrderByteSize*2)
|
|
copy(signature[curveOrderByteSize-len(rBytes):], rBytes)
|
|
copy(signature[curveOrderByteSize*2-len(sBytes):], sBytes)
|
|
|
|
return signature, nil
|
|
}
|
|
|
|
// Verify checks a raw ECDSA signature.
|
|
// Returns true if it's valid and false if not.
|
|
func Verify(data, signature []byte, pubkey *ecdsa.PublicKey) bool {
|
|
// hash message
|
|
digest := sha256.Sum256(data)
|
|
|
|
curveOrderByteSize := pubkey.Curve.Params().P.BitLen() / 8
|
|
|
|
r, s := new(big.Int), new(big.Int)
|
|
r.SetBytes(signature[:curveOrderByteSize])
|
|
s.SetBytes(signature[curveOrderByteSize:])
|
|
|
|
return ecdsa.Verify(pubkey, digest[:], r, s)
|
|
}
|