68 lines
2.5 KiB
Markdown
68 lines
2.5 KiB
Markdown
TLS 1.3 Experimental Developments
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=================================
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Overview
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--------
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Mbed TLS doesn't support the TLS 1.3 protocol yet, but a prototype is in development.
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Stable parts of this prototype that can be independently tested are being successively
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upstreamed under the guard of the following macro:
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```
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MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL
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```
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This macro will likely be renamed to `MBEDTLS_SSL_PROTO_TLS1_3` once a minimal viable
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implementation of the TLS 1.3 protocol is available.
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See the [documentation of `MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL`](../../include/mbedtls/config.h)
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for more information.
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Status
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------
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The following lists which parts of the TLS 1.3 prototype have already been upstreamed
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together with their level of testing:
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* TLS 1.3 record protection mechanisms
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The record protection routines `mbedtls_ssl_{encrypt|decrypt}_buf()` have been extended
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to support the modified TLS 1.3 record protection mechanism, including modified computation
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of AAD, IV, and the introduction of a flexible padding.
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Those record protection routines have unit tests in `test_suite_ssl` alongside the
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tests for the other record protection routines.
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TODO: Add some test vectors from RFC 8448.
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- The HKDF key derivation function on which the TLS 1.3 key schedule is based,
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is already present as an independent module controlled by `MBEDTLS_HKDF_C`
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independently of the development of the TLS 1.3 prototype.
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- The TLS 1.3-specific HKDF-based key derivation functions (see RFC 8446):
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* HKDF-Expand-Label
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* Derive-Secret
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- Secret evolution
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* The traffic {Key,IV} generation from secret
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Those functions are implemented in `library/ssl_tls13_keys.c` and
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tested in `test_suite_ssl` using test vectors from RFC 8448 and
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https://tls13.ulfheim.net/.
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- New TLS Message Processing Stack (MPS)
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The TLS 1.3 prototype is developed alongside a rewrite of the TLS messaging layer,
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encompassing low-level details such as record parsing, handshake reassembly, and
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DTLS retransmission state machine.
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MPS has the following components:
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- Layer 1 (Datagram handling)
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- Layer 2 (Record handling)
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- Layer 3 (Message handling)
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- Layer 4 (Retransmission State Machine)
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- Reader (Abstracted pointer arithmetic and reassembly logic for incoming data)
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- Writer (Abstracted pointer arithmetic and fragmentation logic for outgoing data)
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Of those components, the following have been upstreamed
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as part of `MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL`:
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- Reader ([`library/mps_reader.h`](../../library/mps_reader.h))
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