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Fix the TLS 1.3 obfuscated_ticket_age caclulation #377

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Fix the TLS 1.3 obfuscated_ticket_age caclulation #377

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2 changes: 1 addition & 1 deletion library/ssl_tls13_client.c
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Original file line number Diff line number Diff line change
Expand Up @@ -939,7 +939,7 @@ int mbedtls_ssl_write_pre_shared_key_ext( mbedtls_ssl_context *ssl,
}

obfuscated_ticket_age =
(uint32_t)( now - ssl->session_negotiate->ticket_received ) +
(uint32_t)( ( now - ssl->session_negotiate->ticket_received ) * 1000 ) +
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It seems a fix is needed at line 934 as well as now - ssl->session_negotiate->ticket_received (age in seconds) seems to be compared to the number of milliseconds in one week.

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Agreed. The intention is to keep the fix simple.

Regarding the L934, the fix is not straightforward. If we just return MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED, the request will fail. But a better approach is to fall back to full handshake (as if there is no session ticket). What do you think on this approach?

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Falling back to the full handshake is certainly better than having the exchange fail

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I agree with Ron that this change needs to be aligned with the calculation in line 934

ssl->session_negotiate->ticket_age_add;

MBEDTLS_SSL_DEBUG_MSG( 4, ( "obfuscated_ticket_age: %u",
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