1// Copyright 2020 Google LLC 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14// 15//////////////////////////////////////////////////////////////////////////////// 16 17// Package subtle provides common methods needed in subtle implementations. 18package subtle 19 20import ( 21 "crypto/elliptic" 22 "crypto/sha1" 23 "crypto/sha256" 24 "crypto/sha512" 25 "encoding/hex" 26 "errors" 27 "hash" 28 "math/big" 29) 30 31var errNilHashFunc = errors.New("nil hash function") 32 33// hashDigestSize maps hash algorithms to their digest size in bytes. 34var hashDigestSize = map[string]uint32{ 35 "SHA1": uint32(20), 36 "SHA224": uint32(28), 37 "SHA256": uint32(32), 38 "SHA384": uint32(48), 39 "SHA512": uint32(64), 40} 41 42// GetHashDigestSize returns the digest size of the specified hash algorithm. 43func GetHashDigestSize(hash string) (uint32, error) { 44 digestSize, ok := hashDigestSize[hash] 45 if !ok { 46 return 0, errors.New("invalid hash algorithm") 47 } 48 return digestSize, nil 49} 50 51// TODO(ckl): Perhaps return an explicit error instead of ""/nil for the 52// following functions. 53 54// ConvertHashName converts different forms of a hash name to the 55// hash name that tink recognizes. 56func ConvertHashName(name string) string { 57 switch name { 58 case "SHA-224": 59 return "SHA224" 60 case "SHA-256": 61 return "SHA256" 62 case "SHA-384": 63 return "SHA384" 64 case "SHA-512": 65 return "SHA512" 66 case "SHA-1": 67 return "SHA1" 68 default: 69 return "" 70 } 71} 72 73// ConvertCurveName converts different forms of a curve name to the 74// name that tink recognizes. 75func ConvertCurveName(name string) string { 76 switch name { 77 case "secp256r1", "P-256": 78 return "NIST_P256" 79 case "secp384r1", "P-384": 80 return "NIST_P384" 81 case "secp521r1", "P-521": 82 return "NIST_P521" 83 default: 84 return "" 85 } 86} 87 88// GetHashFunc returns the corresponding hash function of the given hash name. 89func GetHashFunc(hash string) func() hash.Hash { 90 switch hash { 91 case "SHA1": 92 return sha1.New 93 case "SHA224": 94 return sha256.New224 95 case "SHA256": 96 return sha256.New 97 case "SHA384": 98 return sha512.New384 99 case "SHA512": 100 return sha512.New 101 default: 102 return nil 103 } 104} 105 106// GetCurve returns the curve object that corresponds to the given curve type. 107// It returns null if the curve type is not supported. 108func GetCurve(curve string) elliptic.Curve { 109 switch curve { 110 case "NIST_P256": 111 return elliptic.P256() 112 case "NIST_P384": 113 return elliptic.P384() 114 case "NIST_P521": 115 return elliptic.P521() 116 default: 117 return nil 118 } 119} 120 121// ComputeHash calculates a hash of the given data using the given hash function. 122func ComputeHash(hashFunc func() hash.Hash, data []byte) ([]byte, error) { 123 if hashFunc == nil { 124 return nil, errNilHashFunc 125 } 126 h := hashFunc() 127 128 _, err := h.Write(data) 129 if err != nil { 130 return nil, err 131 } 132 133 return h.Sum(nil), nil 134} 135 136// NewBigIntFromHex returns a big integer from a hex string. 137func NewBigIntFromHex(s string) (*big.Int, error) { 138 if len(s)%2 == 1 { 139 s = "0" + s 140 } 141 b, err := hex.DecodeString(s) 142 if err != nil { 143 return nil, err 144 } 145 ret := new(big.Int).SetBytes(b) 146 return ret, nil 147} 148