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[Bug]: Wrong label used for resumption secret in DTLS 1.3 #6366

@Conradowatz

Description

@Conradowatz

Contact Details

conrad@owatz.de

Version

5.5.0

Description

While doing a psk session resumption in DTLS 1.3 wolfssl uses the wrong label in the HLDF-expand-function.
As of https://www.rfc-editor.org/rfc/rfc9147.html the label has to be dtls13. But what is used is the label from TLS 1.3 which is tls13 .
The label is used in the function DeriveResumptionPSK in tls13.c.

Reproduction steps

To use DTLS 1.3 you have to enable it in user_setting.h, as well as enable support for session ticket resumption:

#define WOLFSSL_DTLS
#define WOLFSSL_DTLS13
#define HAVE_SESSION_TICKET

To do a resumption start the wolfssl example server or client with -r. As both of them use the same wrong label, the work together. But if you use a different tls library, decryption errors occur. I testet with a yet unreleased version of TLS-Attacker.

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