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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376
|
package mega
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"encoding/base64"
"encoding/binary"
"encoding/json"
"errors"
"math/big"
"net"
"net/http"
"regexp"
"strings"
"time"
)
func newHttpClient(timeout time.Duration) *http.Client {
// TODO: Need to test this out
// Doesn't seem to work as expected
c := &http.Client{
Transport: &http.Transport{
Dial: func(netw, addr string) (net.Conn, error) {
c, err := net.DialTimeout(netw, addr, timeout)
if err != nil {
return nil, err
}
return c, nil
},
Proxy: http.ProxyFromEnvironment,
},
}
return c
}
// bytes_to_a32 converts the byte slice b to uint32 slice considering
// the bytes to be in big endian order.
func bytes_to_a32(b []byte) ([]uint32, error) {
length := len(b) + 3
a := make([]uint32, length/4)
buf := bytes.NewBuffer(b)
for i, _ := range a {
err := binary.Read(buf, binary.BigEndian, &a[i])
if err != nil {
return nil, err
}
}
return a, nil
}
// a32_to_bytes converts the uint32 slice a to byte slice where each
// uint32 is decoded in big endian order.
func a32_to_bytes(a []uint32) ([]byte, error) {
buf := new(bytes.Buffer)
buf.Grow(len(a) * 4) // To prevent reallocations in Write
for _, v := range a {
err := binary.Write(buf, binary.BigEndian, v)
if err != nil {
return nil, err
}
}
return buf.Bytes(), nil
}
// base64urlencode encodes byte slice b using base64 url encoding
// without `=` padding.
func base64urlencode(b []byte) string {
return base64.RawURLEncoding.EncodeToString(b)
}
// base64urldecode decodes the byte slice b using unpadded base64 url
// decoding. It also allows the characters from standard base64 to be
// compatible with the mega decoder.
func base64urldecode(s string) ([]byte, error) {
enc := base64.RawURLEncoding
// mega base64 decoder accepts the characters from both URLEncoding and StdEncoding
// though nearly all strings are URL encoded
s = strings.Replace(s, "+", "-", -1)
s = strings.Replace(s, "/", "_", -1)
return enc.DecodeString(s)
}
// base64_to_a32 converts base64 encoded byte slice b to uint32 slice.
func base64_to_a32(s string) ([]uint32, error) {
d, err := base64urldecode(s)
if err != nil {
return nil, err
}
return bytes_to_a32(d)
}
// a32_to_base64 converts uint32 slice to base64 encoded byte slice.
func a32_to_base64(a []uint32) (string, error) {
d, err := a32_to_bytes(a)
if err != nil {
return "", err
}
return base64urlencode(d), nil
}
// paddnull pads byte slice b such that the size of resulting byte
// slice is a multiple of q.
func paddnull(b []byte, q int) []byte {
if rem := len(b) % q; rem != 0 {
l := q - rem
for i := 0; i < l; i++ {
b = append(b, 0)
}
}
return b
}
// password_key calculates password hash from the user password.
func password_key(p string) ([]byte, error) {
a, err := bytes_to_a32(paddnull([]byte(p), 4))
if err != nil {
return nil, err
}
pkey, err := a32_to_bytes([]uint32{0x93C467E3, 0x7DB0C7A4, 0xD1BE3F81, 0x0152CB56})
if err != nil {
return nil, err
}
n := (len(a) + 3) / 4
ciphers := make([]cipher.Block, n)
for j := 0; j < len(a); j += 4 {
key := []uint32{0, 0, 0, 0}
for k := 0; k < 4; k++ {
if j+k < len(a) {
key[k] = a[k+j]
}
}
bkey, err := a32_to_bytes(key)
if err != nil {
return nil, err
}
ciphers[j/4], err = aes.NewCipher(bkey) // Uses AES in ECB mode
if err != nil {
return nil, err
}
}
for i := 65536; i > 0; i-- {
for j := 0; j < n; j++ {
ciphers[j].Encrypt(pkey, pkey)
}
}
return pkey, nil
}
// stringhash computes generic string hash. Uses k as the key for AES
// cipher.
func stringhash(s string, k []byte) (string, error) {
a, err := bytes_to_a32(paddnull([]byte(s), 4))
if err != nil {
return "", err
}
h := []uint32{0, 0, 0, 0}
for i, v := range a {
h[i&3] ^= v
}
hb, err := a32_to_bytes(h)
if err != nil {
return "", err
}
cipher, err := aes.NewCipher(k)
if err != nil {
return "", err
}
for i := 16384; i > 0; i-- {
cipher.Encrypt(hb, hb)
}
ha, err := bytes_to_a32(paddnull(hb, 4))
if err != nil {
return "", err
}
return a32_to_base64([]uint32{ha[0], ha[2]})
}
// getMPI returns the length encoded Int and the next slice.
func getMPI(b []byte) (*big.Int, []byte) {
p := new(big.Int)
plen := (uint64(b[0])*256 + uint64(b[1]) + 7) >> 3
p.SetBytes(b[2 : plen+2])
b = b[plen+2:]
return p, b
}
// getRSAKey decodes the RSA Key from the byte slice b.
func getRSAKey(b []byte) (*big.Int, *big.Int, *big.Int) {
p, b := getMPI(b)
q, b := getMPI(b)
d, _ := getMPI(b)
return p, q, d
}
// decryptRSA decrypts message m using RSA private key (p,q,d)
func decryptRSA(m, p, q, d *big.Int) []byte {
n := new(big.Int)
r := new(big.Int)
n.Mul(p, q)
r.Exp(m, d, n)
return r.Bytes()
}
// blockDecrypt decrypts using the block cipher blk in ECB mode.
func blockDecrypt(blk cipher.Block, dst, src []byte) error {
if len(src) > len(dst) || len(src)%blk.BlockSize() != 0 {
return errors.New("Block decryption failed")
}
l := len(src) - blk.BlockSize()
for i := 0; i <= l; i += blk.BlockSize() {
blk.Decrypt(dst[i:], src[i:])
}
return nil
}
// blockEncrypt encrypts using the block cipher blk in ECB mode.
func blockEncrypt(blk cipher.Block, dst, src []byte) error {
if len(src) > len(dst) || len(src)%blk.BlockSize() != 0 {
return errors.New("Block encryption failed")
}
l := len(src) - blk.BlockSize()
for i := 0; i <= l; i += blk.BlockSize() {
blk.Encrypt(dst[i:], src[i:])
}
return nil
}
// decryptSeessionId decrypts the session id using the given private
// key.
func decryptSessionId(privk string, csid string, mk []byte) (string, error) {
block, err := aes.NewCipher(mk)
if err != nil {
return "", err
}
pk, err := base64urldecode(privk)
if err != nil {
return "", err
}
err = blockDecrypt(block, pk, pk)
if err != nil {
return "", err
}
c, err := base64urldecode(csid)
if err != nil {
return "", err
}
m, _ := getMPI(c)
p, q, d := getRSAKey(pk)
r := decryptRSA(m, p, q, d)
return base64urlencode(r[:43]), nil
}
// chunkSize describes a size and position of chunk
type chunkSize struct {
position int64
size int
}
func getChunkSizes(size int64) (chunks []chunkSize) {
p := int64(0)
for i := 1; size > 0; i++ {
var chunk int
if i <= 8 {
chunk = i * 131072
} else {
chunk = 1048576
}
if size < int64(chunk) {
chunk = int(size)
}
chunks = append(chunks, chunkSize{position: p, size: chunk})
p += int64(chunk)
size -= int64(chunk)
}
return chunks
}
var attrMatch = regexp.MustCompile(`{".*"}`)
func decryptAttr(key []byte, data string) (attr FileAttr, err error) {
err = EBADATTR
block, err := aes.NewCipher(key)
if err != nil {
return attr, err
}
iv, err := a32_to_bytes([]uint32{0, 0, 0, 0})
if err != nil {
return attr, err
}
mode := cipher.NewCBCDecrypter(block, iv)
buf := make([]byte, len(data))
ddata, err := base64urldecode(data)
if err != nil {
return attr, err
}
mode.CryptBlocks(buf, ddata)
if string(buf[:4]) == "MEGA" {
str := strings.TrimRight(string(buf[4:]), "\x00")
trimmed := attrMatch.FindString(str)
if trimmed != "" {
str = trimmed
}
err = json.Unmarshal([]byte(str), &attr)
}
return attr, err
}
func encryptAttr(key []byte, attr FileAttr) (b string, err error) {
err = EBADATTR
block, err := aes.NewCipher(key)
if err != nil {
return "", err
}
data, err := json.Marshal(attr)
if err != nil {
return "", err
}
attrib := []byte("MEGA")
attrib = append(attrib, data...)
attrib = paddnull(attrib, 16)
iv, err := a32_to_bytes([]uint32{0, 0, 0, 0})
if err != nil {
return "", err
}
mode := cipher.NewCBCEncrypter(block, iv)
mode.CryptBlocks(attrib, attrib)
b = base64urlencode(attrib)
return b, nil
}
func randString(l int) (string, error) {
encoding := "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789AB"
b := make([]byte, l)
_, err := rand.Read(b)
if err != nil {
return "", err
}
enc := base64.NewEncoding(encoding)
d := make([]byte, enc.EncodedLen(len(b)))
enc.Encode(d, b)
d = d[:l]
return string(d), nil
}
|