upstream: github.com/mirleft/ocaml-tls
tls: Add fuzz tests for TLS protocol parsing
Add crash-safety fuzz tests for TLS record and handshake parsing:
- Record parsing (CVE-2014-0160 Heartbleed pattern)
- Handshake message parsing
- Alert and change cipher spec parsing
- Version negotiation
- Certificate parsing (TLS 1.0/1.2/1.3)
- DH/EC parameter parsing
- Digitally signed parsing
- Record overflow detection
+224
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fuzz/dune
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fuzz/dune
···
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(executable
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(name fuzz_tls)
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(modules fuzz_tls)
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(libraries tls crowbar))
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; Quick check with Crowbar (no AFL instrumentation)
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(rule
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(alias fuzz)
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(deps fuzz_tls.exe)
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(action
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(run %{exe:fuzz_tls.exe})))
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; AFL-instrumented build target (use with --profile=afl)
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(rule
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(alias fuzz-afl)
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(deps
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(source_tree input)
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fuzz_tls.exe)
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(action
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(echo "AFL fuzzer built: %{exe:fuzz_tls.exe}\n")))
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fuzz/fuzz_tls.ml
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fuzz/fuzz_tls.ml
···
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(*---------------------------------------------------------------------------
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Copyright (c) 2025 Thomas Gazagnaire. All rights reserved.
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SPDX-License-Identifier: ISC
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---------------------------------------------------------------------------*)
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(** Fuzz tests for TLS protocol parsing.
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Key properties tested: 1. TLS record parsing crash safety 2. Handshake
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message parsing 3. Alert message parsing 4. Version negotiation 5. Extension
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parsing
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CVE references:
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- CVE-2014-0160 (OpenSSL): Heartbleed - buffer overread
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- CVE-2016-2107 (OpenSSL): Padding oracle attack
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- CVE-2021-3449 (OpenSSL): Renegotiation crash
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- CVE-2015-0204 (FREAK): Weak export ciphers
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See:
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https://www.cvedetails.com/vulnerability-list/vendor_id-217/Openssl.html *)
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open Crowbar
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(** Truncate input to reasonable size. *)
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let truncate ?(max_len = 16384) buf =
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if String.length buf > max_len then String.sub buf 0 max_len else buf
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(** TLS record parsing - must not crash on arbitrary input. CVE-2014-0160:
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Heartbleed was a buffer overread in record parsing. *)
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let test_record_parse buf =
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let buf = truncate buf in
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(try ignore (Tls.Reader.parse_record buf) with _ -> ());
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()
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(** Handshake message parsing - must handle malformed handshakes. Many TLS
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vulnerabilities involve malformed handshake messages. *)
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let test_handshake_parse buf =
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let buf = truncate buf in
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(try ignore (Tls.Reader.parse_handshake buf) with _ -> ());
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()
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(** Handshake frame parsing - must not crash. *)
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let test_handshake_frame buf =
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let buf = truncate buf in
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(try ignore (Tls.Reader.parse_handshake_frame buf) with _ -> ());
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()
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(** Alert parsing - must handle invalid alert codes. *)
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let test_alert_parse buf =
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let buf = truncate ~max_len:256 buf in
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(try ignore (Tls.Reader.parse_alert buf) with _ -> ());
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()
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(** Change cipher spec parsing. *)
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let test_change_cipher_spec buf =
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let buf = truncate ~max_len:16 buf in
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(try ignore (Tls.Reader.parse_change_cipher_spec buf) with _ -> ());
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()
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(** Version parsing - must handle invalid versions. *)
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let test_version_parse buf =
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let buf = truncate ~max_len:8 buf in
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(try
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ignore (Tls.Reader.parse_version buf);
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ignore (Tls.Reader.parse_any_version buf)
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with _ -> ());
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()
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(** Certificate parsing - must handle malformed certificates. CVE-2015-0204
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(FREAK) involved certificate handling. *)
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let test_certificate_parse buf =
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let buf = truncate ~max_len:8192 buf in
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(try ignore (Tls.Reader.parse_certificates buf) with _ -> ());
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()
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(** Certificate request parsing (TLS 1.0/1.1). *)
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let test_certificate_request_parse buf =
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let buf = truncate ~max_len:4096 buf in
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(try ignore (Tls.Reader.parse_certificate_request buf) with _ -> ());
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()
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(** Certificate request parsing (TLS 1.2). *)
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let test_certificate_request_1_2_parse buf =
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let buf = truncate ~max_len:4096 buf in
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(try ignore (Tls.Reader.parse_certificate_request_1_2 buf) with _ -> ());
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()
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(** Certificate request parsing (TLS 1.3). *)
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let test_certificate_request_1_3_parse buf =
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let buf = truncate ~max_len:4096 buf in
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(try ignore (Tls.Reader.parse_certificate_request_1_3 buf) with _ -> ());
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()
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(** DH parameters parsing. *)
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let test_dh_parameters_parse buf =
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let buf = truncate ~max_len:2048 buf in
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(try ignore (Tls.Reader.parse_dh_parameters buf) with _ -> ());
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()
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(** EC parameters parsing. *)
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let test_ec_parameters_parse buf =
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let buf = truncate ~max_len:1024 buf in
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(try ignore (Tls.Reader.parse_ec_parameters buf) with _ -> ());
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()
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(** Client DH key exchange parsing. *)
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let test_client_dh_key_exchange buf =
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let buf = truncate ~max_len:1024 buf in
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(try ignore (Tls.Reader.parse_client_dh_key_exchange buf) with _ -> ());
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()
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(** Client EC key exchange parsing. *)
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let test_client_ec_key_exchange buf =
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let buf = truncate ~max_len:256 buf in
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(try ignore (Tls.Reader.parse_client_ec_key_exchange buf) with _ -> ());
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()
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(** Digitally signed parsing (TLS < 1.2). *)
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let test_digitally_signed buf =
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let buf = truncate ~max_len:1024 buf in
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(try ignore (Tls.Reader.parse_digitally_signed buf) with _ -> ());
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()
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(** Digitally signed parsing (TLS 1.2). *)
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let test_digitally_signed_1_2 buf =
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let buf = truncate ~max_len:1024 buf in
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(try ignore (Tls.Reader.parse_digitally_signed_1_2 buf) with _ -> ());
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()
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(** Certificates TLS 1.3 parsing. *)
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let test_certificates_1_3 buf =
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let buf = truncate ~max_len:8192 buf in
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(try ignore (Tls.Reader.parse_certificates_1_3 buf) with _ -> ());
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()
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(** Test record with specific content types. CVE references often involve
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specific content type handling. *)
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let test_record_content_types n buf =
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let buf = truncate ~max_len:16384 buf in
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(* Build a TLS record with various content types *)
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let content_type = Char.chr (abs n mod 256) in
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(* TLS 1.2 version *)
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let version = "\x03\x03" in
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let len_hi = Char.chr (String.length buf / 256 mod 256) in
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let len_lo = Char.chr (String.length buf mod 256) in
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let record =
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String.make 1 content_type ^ version ^ String.make 1 len_hi
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^ String.make 1 len_lo ^ buf
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in
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(try ignore (Tls.Reader.parse_record record) with _ -> ());
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()
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(** Test record overflow detection. CVE-2014-0160 (Heartbleed) exploited missing
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length validation. *)
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let test_record_overflow claimed_len buf =
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let buf = truncate ~max_len:1024 buf in
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let actual_len = String.length buf in
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let claimed = abs claimed_len mod 20000 in
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(* TLS record: content_type + version (2) + length (2) + data *)
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let content_type = "\x17" in
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(* Application data *)
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let version = "\x03\x03" in
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(* TLS 1.2 *)
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let len_hi = Char.chr (claimed / 256 mod 256) in
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let len_lo = Char.chr (claimed mod 256) in
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let record =
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content_type ^ version ^ String.make 1 len_hi ^ String.make 1 len_lo ^ buf
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in
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(* If claimed > actual, this should not crash or read OOB *)
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if claimed > actual_len then begin
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match Tls.Reader.parse_record record with
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| Ok (`Fragment _) -> ()
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| Ok (`Record _) -> ()
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| Error _ -> ()
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end;
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()
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let () =
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add_test ~name:"tls: record parse" [ bytes ] test_record_parse;
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add_test ~name:"tls: handshake parse" [ bytes ] test_handshake_parse;
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add_test ~name:"tls: handshake frame" [ bytes ] test_handshake_frame;
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add_test ~name:"tls: alert parse" [ bytes ] test_alert_parse;
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add_test ~name:"tls: change cipher spec" [ bytes ] test_change_cipher_spec;
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add_test ~name:"tls: version parse" [ bytes ] test_version_parse;
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add_test ~name:"tls: certificate parse" [ bytes ] test_certificate_parse;
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add_test ~name:"tls: certificate request" [ bytes ]
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test_certificate_request_parse;
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add_test ~name:"tls: certificate request 1.2" [ bytes ]
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test_certificate_request_1_2_parse;
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add_test ~name:"tls: certificate request 1.3" [ bytes ]
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test_certificate_request_1_3_parse;
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add_test ~name:"tls: DH parameters" [ bytes ] test_dh_parameters_parse;
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add_test ~name:"tls: EC parameters" [ bytes ] test_ec_parameters_parse;
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add_test ~name:"tls: client DH key exchange" [ bytes ]
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test_client_dh_key_exchange;
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add_test ~name:"tls: client EC key exchange" [ bytes ]
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test_client_ec_key_exchange;
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add_test ~name:"tls: digitally signed" [ bytes ] test_digitally_signed;
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add_test ~name:"tls: digitally signed 1.2" [ bytes ] test_digitally_signed_1_2;
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add_test ~name:"tls: certificates 1.3" [ bytes ] test_certificates_1_3;
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add_test ~name:"tls: record content types" [ int; bytes ]
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test_record_content_types;
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add_test ~name:"tls: record overflow" [ int; bytes ] test_record_overflow