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Avoid BigInteger(int, byte[], int, int) for Android 12 and older - #379
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Android added this constructor only in API 33. On Android 12 and older the ECDSA and NIST ECDH point decoding throws NoSuchMethodError; since it is an Error, updateHostKeys does not catch it and the app dies right after login on servers with an ECDSA host key. Copy the coordinate bytes and use BigInteger(int, byte[]). The length is checked just before, so the ranges and values are the same.
kruton
approved these changes
Oct 26, 2026
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EcdsaSignatureAlgorithm.decodeEcPointandEcdhKeyExchange.decodeEcPointuseBigInteger(int signum, byte[] magnitude, int off, int len). Android added that constructor only in API 33, so on Android 12 and older these calls throwNoSuchMethodError. ConnectBot (minSdk 24) dies right after login on servers with an ECDSA host key: OpenSSH sends its host keys (hostkeys-00@openssh.com),updateHostKeysverifies the ECDSA proof, and theErroris not caught by thecatch (e: Exception)around it. Seen on Android 11:ecdh-sha2-nistp*key exchange takes the same path inEcdhKeyExchange.The fix copies the coordinate bytes and uses
BigInteger(int, byte[]). The length is checked just above, so the ranges are the same and the values are identical; behaviour on the JVM and on Android 13+ does not change. A JVM unit test cannot catch this, since the JVM has the constructor; checking against Android API signatures (e.g. animal-sniffer) could, if that is wanted as a follow-up.