shadowsocks evpBytesToKey

Python:

def EVP_BytesToKey(password, key_len, iv_len):
# equivalent to OpenSSL’s EVP_BytesToKey() with count 1
# so that we make the same key and iv as nodejs version
cached_key = ‘%s-%d-%d’ % (password, key_len, iv_len)
r = cached_keys.get(cached_key, None)
if r:
return r
m = []
i = 0
while len(b”.join(m)) < (key_len + iv_len):
md5 = hashlib.md5()
data = password
if i > 0:
data = m[i – 1] + password
md5.update(data)
m.append(md5.digest())
i += 1
ms = b”.join(m)
key = ms[:key_len]
iv = ms[key_len:key_len + iv_len]
cached_keys[cached_key] = (key, iv)
return key, iv

 

Golang:

func evpBytesToKey(password string, keyLen int) (key []byte) {
const md5Len = 16

cnt := (keyLen-1)/md5Len + 1
m := make([]byte, cnt*md5Len)
copy(m, md5sum([]byte(password)))

// Repeatedly call md5 until bytes generated is enough.
// Each call to md5 uses data: prev md5 sum + password.
d := make([]byte, md5Len+len(password))
start := 0
for i := 1; i < cnt; i++ {
start += md5Len
copy(d, m[start-md5Len:start])
copy(d[md5Len:], password)
copy(m[start:], md5sum(d))
}
return m[:keyLen]
}

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