/usr/share/gocode/src/golang.org/x/crypto/openpgp/s2k/s2k.go is in golang-golang-x-crypto-dev 1:0.0~git20170629.0.5ef0053-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 | // Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package s2k implements the various OpenPGP string-to-key transforms as
// specified in RFC 4800 section 3.7.1.
package s2k // import "golang.org/x/crypto/openpgp/s2k"
import (
"crypto"
"hash"
"io"
"strconv"
"golang.org/x/crypto/openpgp/errors"
)
// Config collects configuration parameters for s2k key-stretching
// transformatioms. A nil *Config is valid and results in all default
// values. Currently, Config is used only by the Serialize function in
// this package.
type Config struct {
// Hash is the default hash function to be used. If
// nil, SHA1 is used.
Hash crypto.Hash
// S2KCount is only used for symmetric encryption. It
// determines the strength of the passphrase stretching when
// the said passphrase is hashed to produce a key. S2KCount
// should be between 1024 and 65011712, inclusive. If Config
// is nil or S2KCount is 0, the value 65536 used. Not all
// values in the above range can be represented. S2KCount will
// be rounded up to the next representable value if it cannot
// be encoded exactly. When set, it is strongly encrouraged to
// use a value that is at least 65536. See RFC 4880 Section
// 3.7.1.3.
S2KCount int
}
func (c *Config) hash() crypto.Hash {
if c == nil || uint(c.Hash) == 0 {
// SHA1 is the historical default in this package.
return crypto.SHA1
}
return c.Hash
}
func (c *Config) encodedCount() uint8 {
if c == nil || c.S2KCount == 0 {
return 96 // The common case. Correspoding to 65536
}
i := c.S2KCount
switch {
// Behave like GPG. Should we make 65536 the lowest value used?
case i < 1024:
i = 1024
case i > 65011712:
i = 65011712
}
return encodeCount(i)
}
// encodeCount converts an iterative "count" in the range 1024 to
// 65011712, inclusive, to an encoded count. The return value is the
// octet that is actually stored in the GPG file. encodeCount panics
// if i is not in the above range (encodedCount above takes care to
// pass i in the correct range). See RFC 4880 Section 3.7.7.1.
func encodeCount(i int) uint8 {
if i < 1024 || i > 65011712 {
panic("count arg i outside the required range")
}
for encoded := 0; encoded < 256; encoded++ {
count := decodeCount(uint8(encoded))
if count >= i {
return uint8(encoded)
}
}
return 255
}
// decodeCount returns the s2k mode 3 iterative "count" corresponding to
// the encoded octet c.
func decodeCount(c uint8) int {
return (16 + int(c&15)) << (uint32(c>>4) + 6)
}
// Simple writes to out the result of computing the Simple S2K function (RFC
// 4880, section 3.7.1.1) using the given hash and input passphrase.
func Simple(out []byte, h hash.Hash, in []byte) {
Salted(out, h, in, nil)
}
var zero [1]byte
// Salted writes to out the result of computing the Salted S2K function (RFC
// 4880, section 3.7.1.2) using the given hash, input passphrase and salt.
func Salted(out []byte, h hash.Hash, in []byte, salt []byte) {
done := 0
var digest []byte
for i := 0; done < len(out); i++ {
h.Reset()
for j := 0; j < i; j++ {
h.Write(zero[:])
}
h.Write(salt)
h.Write(in)
digest = h.Sum(digest[:0])
n := copy(out[done:], digest)
done += n
}
}
// Iterated writes to out the result of computing the Iterated and Salted S2K
// function (RFC 4880, section 3.7.1.3) using the given hash, input passphrase,
// salt and iteration count.
func Iterated(out []byte, h hash.Hash, in []byte, salt []byte, count int) {
combined := make([]byte, len(in)+len(salt))
copy(combined, salt)
copy(combined[len(salt):], in)
if count < len(combined) {
count = len(combined)
}
done := 0
var digest []byte
for i := 0; done < len(out); i++ {
h.Reset()
for j := 0; j < i; j++ {
h.Write(zero[:])
}
written := 0
for written < count {
if written+len(combined) > count {
todo := count - written
h.Write(combined[:todo])
written = count
} else {
h.Write(combined)
written += len(combined)
}
}
digest = h.Sum(digest[:0])
n := copy(out[done:], digest)
done += n
}
}
// Parse reads a binary specification for a string-to-key transformation from r
// and returns a function which performs that transform.
func Parse(r io.Reader) (f func(out, in []byte), err error) {
var buf [9]byte
_, err = io.ReadFull(r, buf[:2])
if err != nil {
return
}
hash, ok := HashIdToHash(buf[1])
if !ok {
return nil, errors.UnsupportedError("hash for S2K function: " + strconv.Itoa(int(buf[1])))
}
if !hash.Available() {
return nil, errors.UnsupportedError("hash not available: " + strconv.Itoa(int(hash)))
}
h := hash.New()
switch buf[0] {
case 0:
f := func(out, in []byte) {
Simple(out, h, in)
}
return f, nil
case 1:
_, err = io.ReadFull(r, buf[:8])
if err != nil {
return
}
f := func(out, in []byte) {
Salted(out, h, in, buf[:8])
}
return f, nil
case 3:
_, err = io.ReadFull(r, buf[:9])
if err != nil {
return
}
count := decodeCount(buf[8])
f := func(out, in []byte) {
Iterated(out, h, in, buf[:8], count)
}
return f, nil
}
return nil, errors.UnsupportedError("S2K function")
}
// Serialize salts and stretches the given passphrase and writes the
// resulting key into key. It also serializes an S2K descriptor to
// w. The key stretching can be configured with c, which may be
// nil. In that case, sensible defaults will be used.
func Serialize(w io.Writer, key []byte, rand io.Reader, passphrase []byte, c *Config) error {
var buf [11]byte
buf[0] = 3 /* iterated and salted */
buf[1], _ = HashToHashId(c.hash())
salt := buf[2:10]
if _, err := io.ReadFull(rand, salt); err != nil {
return err
}
encodedCount := c.encodedCount()
count := decodeCount(encodedCount)
buf[10] = encodedCount
if _, err := w.Write(buf[:]); err != nil {
return err
}
Iterated(key, c.hash().New(), passphrase, salt, count)
return nil
}
// hashToHashIdMapping contains pairs relating OpenPGP's hash identifier with
// Go's crypto.Hash type. See RFC 4880, section 9.4.
var hashToHashIdMapping = []struct {
id byte
hash crypto.Hash
name string
}{
{1, crypto.MD5, "MD5"},
{2, crypto.SHA1, "SHA1"},
{3, crypto.RIPEMD160, "RIPEMD160"},
{8, crypto.SHA256, "SHA256"},
{9, crypto.SHA384, "SHA384"},
{10, crypto.SHA512, "SHA512"},
{11, crypto.SHA224, "SHA224"},
}
// HashIdToHash returns a crypto.Hash which corresponds to the given OpenPGP
// hash id.
func HashIdToHash(id byte) (h crypto.Hash, ok bool) {
for _, m := range hashToHashIdMapping {
if m.id == id {
return m.hash, true
}
}
return 0, false
}
// HashIdToString returns the name of the hash function corresponding to the
// given OpenPGP hash id.
func HashIdToString(id byte) (name string, ok bool) {
for _, m := range hashToHashIdMapping {
if m.id == id {
return m.name, true
}
}
return "", false
}
// HashIdToHash returns an OpenPGP hash id which corresponds the given Hash.
func HashToHashId(h crypto.Hash) (id byte, ok bool) {
for _, m := range hashToHashIdMapping {
if m.hash == h {
return m.id, true
}
}
return 0, false
}
|