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37 lines
1.2 KiB
37 lines
1.2 KiB
3 years ago
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package crypto
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import (
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"crypto/sha1" // #nosec
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"math/big"
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)
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// sha1BigInt returns SHA1(a + b).
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func sha1BigInt(a, b *big.Int) []byte {
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var buf []byte
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buf = append(buf, a.Bytes()...)
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buf = append(buf, b.Bytes()...)
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h := sha1.Sum(buf) // #nosec
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return h[:]
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}
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// TempAESKeys returns tmp_aes_key and tmp_aes_iv based on new_nonce and
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// server_nonce as defined in "Creating an Authorization Key".
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func TempAESKeys(newNonce, serverNonce *big.Int) (key, iv []byte) {
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// See https://core.telegram.org/mtproto/auth_key#presenting-proof-of-work-server-authentication
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// 5. Server responds in one of two ways: [...]
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// tmp_aes_key := SHA1(new_nonce + server_nonce) + substr (SHA1(server_nonce + new_nonce), 0, 12);
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// SHA1(new_nonce + server_nonce)
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key = append(key, sha1BigInt(newNonce, serverNonce)...)
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// substr (SHA1(server_nonce + new_nonce), 0, 12);
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key = append(key, sha1BigInt(serverNonce, newNonce)[:12]...)
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// tmp_aes_iv := substr (SHA1(server_nonce + new_nonce), 12, 8) + SHA1(new_nonce + new_nonce) + substr (new_nonce, 0, 4);
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iv = append(iv, sha1BigInt(serverNonce, newNonce)[12:12+8]...)
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iv = append(iv, sha1BigInt(newNonce, newNonce)...)
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iv = append(iv, newNonce.Bytes()[:4]...)
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return key, iv
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}
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