2adda9c12c
When the NTS client and server negotiated use of AES-128-GCM-SIV keys, the keys exported from the TLS session and used for authentication and encryption of NTP messages do not comply to RFC8915. The exporter context value specified in the section 5.1 of RFC8915 function is incorrect. It is a hardcoded string which contains 15 (AES-SIV-CMAC-256) instead of 30 (AES-128-GCM-SIV). This causes chrony to not interoperate with NTS implementations that follow RFC8915 correctly. (At this time, there doesn't seem to be another implementation with AES-128-GCM-SIV support yet.) Replace the string with a proper construction of the exporter context from a specified AEAD ID and next protocol. Keep using the incorrect AEAD ID for AES-128-GCM-SIV to not break compatibility with existing chrony servers and clients. A new NTS-KE record will be added to negotiate the compliant exporter context. Reported-by: Martin Mayer <martin.mayer@m2-it-solutions.de> |
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