#24 Ambiguous PSK key length in "calculate_key_block"

[Achim Kraus]

Function "calculate_key_block" uses "DTLS_PSK_MAX_KEY_LEN" (32) when calling "get_psk_info" and "MAX_KEYBLOCK_LENGTH" (referring "DTLS_KEY_LENGTH" (16) as max key length) when calling "dtls_psk_pre_master_secret". This leads to "the psk was too long, for the pre master secret", if the key is longer the 16 bytes. So either the pre_master_secret may be enlarged or the psk key length may be reduced.

[Olaf Bergmann]

I agree that this is unconvenient. Although different cipher suites would allow for different key lengths, this case should be handled before dtls_psk_pre_master_secret() is called. As by now, only AES-128 is supported for PSK, commit 1719a06 solves this issue by limiting DTLS_PSK_MAX_KEY_LEN to DTLS_KEY_LENGTH.