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refactor(crypto): refactor crypto for download api
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,47 @@ | ||
package m115 | ||
|
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import ( | ||
"crypto/rand" | ||
"encoding/base64" | ||
"io" | ||
) | ||
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type Key [16]byte | ||
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func GenerateKey() Key { | ||
key := Key{} | ||
_, _ = io.ReadFull(rand.Reader, key[:]) | ||
return key | ||
} | ||
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func Encode(input []byte, key Key) (output string) { | ||
// Prepare buffer | ||
buf := make([]byte, 16+len(input)) | ||
// Copy key and data to buffer | ||
copy(buf, key[:]) | ||
copy(buf[16:], input) | ||
// XOR encode | ||
xorTransform(buf[16:], xorDeriveKey(key[:], 4)) | ||
reverseBytes(buf[16:]) | ||
xorTransform(buf[16:], xorClientKey) | ||
// Encrypt and encode | ||
output = base64.StdEncoding.EncodeToString(rsaEncrypt(buf)) | ||
return | ||
} | ||
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||
func Decode(input string, key Key) (output []byte, err error) { | ||
// Base64 decode | ||
data, err := base64.StdEncoding.DecodeString(input) | ||
if err != nil { | ||
return | ||
} | ||
// RSA decrypt | ||
data = rsaDecrypt(data) | ||
// XOR decode | ||
output = make([]byte, len(data)-16) | ||
copy(output, data[16:]) | ||
xorTransform(output, xorDeriveKey(data[:16], 12)) | ||
reverseBytes(output) | ||
xorTransform(output, xorDeriveKey(key[:], 4)) | ||
return | ||
} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,87 @@ | ||
package m115 | ||
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import ( | ||
"bytes" | ||
"crypto/rand" | ||
"io" | ||
"math/big" | ||
) | ||
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var ( | ||
_N, _ = big.NewInt(0).SetString( | ||
"8686980c0f5a24c4b9d43020cd2c22703ff3f450756529058b1cf88f09b86021"+ | ||
"36477198a6e2683149659bd122c33592fdb5ad47944ad1ea4d36c6b172aad633"+ | ||
"8c3bb6ac6227502d010993ac967d1aef00f0c8e038de2e4d3bc2ec368af2e9f1"+ | ||
"0a6f1eda4f7262f136420c07c331b871bf139f74f3010e3c4fe57df3afb71683", 16) | ||
_E, _ = big.NewInt(0).SetString("10001", 16) | ||
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_KeyLength = _N.BitLen() / 8 | ||
) | ||
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func rsaEncrypt(input []byte) []byte { | ||
buf := &bytes.Buffer{} | ||
for remainSize := len(input); remainSize > 0; { | ||
sliceSize := _KeyLength - 11 | ||
if sliceSize > remainSize { | ||
sliceSize = remainSize | ||
} | ||
rsaEncryptSlice(input[:sliceSize], buf) | ||
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input = input[sliceSize:] | ||
remainSize -= sliceSize | ||
} | ||
return buf.Bytes() | ||
} | ||
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func rsaEncryptSlice(input []byte, w io.Writer) { | ||
// Padding | ||
padSize := _KeyLength - len(input) - 3 | ||
padData := make([]byte, padSize) | ||
_, _ = rand.Read(padData) | ||
// Prepare message | ||
buf := make([]byte, _KeyLength) | ||
buf[0], buf[1] = 0, 2 | ||
for i, b := range padData { | ||
buf[2+i] = b%0xff + 0x01 | ||
} | ||
buf[padSize+2] = 0 | ||
copy(buf[padSize+3:], input) | ||
msg := big.NewInt(0).SetBytes(buf) | ||
// RSA Encrypt | ||
ret := big.NewInt(0).Exp(msg, _E, _N).Bytes() | ||
// Fill zeros at beginning | ||
if fillSize := _KeyLength - len(ret); fillSize > 0 { | ||
zeros := make([]byte, fillSize) | ||
_, _ = w.Write(zeros) | ||
} | ||
_, _ = w.Write(ret) | ||
} | ||
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func rsaDecrypt(input []byte) []byte { | ||
buf := &bytes.Buffer{} | ||
for remainSize := len(input); remainSize > 0; { | ||
sliceSize := _KeyLength | ||
if sliceSize > remainSize { | ||
sliceSize = remainSize | ||
} | ||
rsaDecryptSlice(input[:sliceSize], buf) | ||
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input = input[sliceSize:] | ||
remainSize -= sliceSize | ||
} | ||
return buf.Bytes() | ||
} | ||
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func rsaDecryptSlice(input []byte, w io.Writer) { | ||
// RSA Decrypt | ||
msg := big.NewInt(0).SetBytes(input) | ||
ret := big.NewInt(0).Exp(msg, _E, _N).Bytes() | ||
// Un-padding | ||
for i, b := range ret { | ||
// Find the beginning of plaintext | ||
if b == 0 && i != 0 { | ||
_, _ = w.Write(ret[i+1:]) | ||
break | ||
} | ||
} | ||
} |
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,8 @@ | ||
package m115 | ||
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// reverseBytes reverses data in place. | ||
func reverseBytes(data []byte) { | ||
for i, j := 0, len(data)-1; i < j; i, j = i+1, j-1 { | ||
data[i], data[j] = data[j], data[i] | ||
} | ||
} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,52 @@ | ||
package m115 | ||
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var ( | ||
// Pre-calculated key data | ||
xorKeySeed = []byte{ | ||
0xf0, 0xe5, 0x69, 0xae, 0xbf, 0xdc, 0xbf, 0x8a, | ||
0x1a, 0x45, 0xe8, 0xbe, 0x7d, 0xa6, 0x73, 0xb8, | ||
0xde, 0x8f, 0xe7, 0xc4, 0x45, 0xda, 0x86, 0xc4, | ||
0x9b, 0x64, 0x8b, 0x14, 0x6a, 0xb4, 0xf1, 0xaa, | ||
0x38, 0x01, 0x35, 0x9e, 0x26, 0x69, 0x2c, 0x86, | ||
0x00, 0x6b, 0x4f, 0xa5, 0x36, 0x34, 0x62, 0xa6, | ||
0x2a, 0x96, 0x68, 0x18, 0xf2, 0x4a, 0xfd, 0xbd, | ||
0x6b, 0x97, 0x8f, 0x4d, 0x8f, 0x89, 0x13, 0xb7, | ||
0x6c, 0x8e, 0x93, 0xed, 0x0e, 0x0d, 0x48, 0x3e, | ||
0xd7, 0x2f, 0x88, 0xd8, 0xfe, 0xfe, 0x7e, 0x86, | ||
0x50, 0x95, 0x4f, 0xd1, 0xeb, 0x83, 0x26, 0x34, | ||
0xdb, 0x66, 0x7b, 0x9c, 0x7e, 0x9d, 0x7a, 0x81, | ||
0x32, 0xea, 0xb6, 0x33, 0xde, 0x3a, 0xa9, 0x59, | ||
0x34, 0x66, 0x3b, 0xaa, 0xba, 0x81, 0x60, 0x48, | ||
0xb9, 0xd5, 0x81, 0x9c, 0xf8, 0x6c, 0x84, 0x77, | ||
0xff, 0x54, 0x78, 0x26, 0x5f, 0xbe, 0xe8, 0x1e, | ||
0x36, 0x9f, 0x34, 0x80, 0x5c, 0x45, 0x2c, 0x9b, | ||
0x76, 0xd5, 0x1b, 0x8f, 0xcc, 0xc3, 0xb8, 0xf5, | ||
} | ||
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xorClientKey = []byte{ | ||
0x78, 0x06, 0xad, 0x4c, 0x33, 0x86, 0x5d, 0x18, | ||
0x4c, 0x01, 0x3f, 0x46, | ||
} | ||
) | ||
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func xorDeriveKey(seed []byte, size int) []byte { | ||
key := make([]byte, size) | ||
for i := 0; i < size; i++ { | ||
key[i] = (seed[i] + xorKeySeed[size*i]) & 0xff | ||
key[i] ^= xorKeySeed[size*(size-i-1)] | ||
} | ||
return key | ||
} | ||
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func xorTransform(data []byte, key []byte) { | ||
dataSize, keySize := len(data), len(key) | ||
mod := dataSize % 4 | ||
if mod > 0 { | ||
for i := 0; i < mod; i++ { | ||
data[i] ^= key[i%keySize] | ||
} | ||
} | ||
for i := mod; i < dataSize; i++ { | ||
data[i] ^= key[(i-mod)%keySize] | ||
} | ||
} |
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