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298aa0fcbf
Since otp_encrypt_api_key only encrypts API keys, it doesn't require access to the full UserProfile object to work properly. Now the parameter it accepts is just the API key. This is preparatory refactoring for removing the api_key field on UserProfile.
48 lines
1.9 KiB
Python
48 lines
1.9 KiB
Python
# Simple one-time-pad library, to be used for encrypting Zulip API
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# keys when sending them to the mobile apps via new standard mobile
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# authentication flow. This encryption is used to protect against
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# credential-stealing attacks where a malicious app registers the
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# zulip:// URL on a device, which might otherwise allow it to hijack a
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# user's API key.
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#
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# The decryption logic here isn't actually used by the flow; we just
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# have it here as part of testing the overall library.
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import binascii
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from zerver.models import UserProfile
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def xor_hex_strings(bytes_a: str, bytes_b: str) -> str:
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"""Given two hex strings of equal length, return a hex string with
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the bitwise xor of the two hex strings."""
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assert len(bytes_a) == len(bytes_b)
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return ''.join(["%x" % (int(x, 16) ^ int(y, 16))
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for x, y in zip(bytes_a, bytes_b)])
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def ascii_to_hex(input_string: str) -> str:
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"""Given an ascii string, encode it as a hex string"""
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return "".join([hex(ord(c))[2:].zfill(2) for c in input_string])
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def hex_to_ascii(input_string: str) -> str:
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"""Given a hex array, decode it back to a string"""
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return binascii.unhexlify(input_string).decode('utf8')
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def otp_encrypt_api_key(api_key: str, otp: str) -> str:
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assert len(otp) == UserProfile.API_KEY_LENGTH * 2
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hex_encoded_api_key = ascii_to_hex(api_key)
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assert len(hex_encoded_api_key) == UserProfile.API_KEY_LENGTH * 2
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return xor_hex_strings(hex_encoded_api_key, otp)
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def otp_decrypt_api_key(otp_encrypted_api_key: str, otp: str) -> str:
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assert len(otp) == UserProfile.API_KEY_LENGTH * 2
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assert len(otp_encrypted_api_key) == UserProfile.API_KEY_LENGTH * 2
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hex_encoded_api_key = xor_hex_strings(otp_encrypted_api_key, otp)
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return hex_to_ascii(hex_encoded_api_key)
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def is_valid_otp(otp: str) -> bool:
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try:
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assert len(otp) == UserProfile.API_KEY_LENGTH * 2
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[int(c, 16) for c in otp]
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return True
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except Exception:
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return False
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