465 lines
18 KiB
C
465 lines
18 KiB
C
/*
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* Copyright (c) 2019 OSU OPEnS Lab
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "bearssl.h"
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#include "bearssl_ssl.h"
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#include "time_macros.h"
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/*
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* A "profile" is an initialisation function for a SSL context, that
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* configures a list of cipher suites and algorithm implementations.
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* While BearSSL comes with a few predefined profiles, you might one
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* to define you own, using the example below as guidance.
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*
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* Each individual initialisation call sets a parameter or an algorithm
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* support. Setting a specific algorithm pulls in the implementation of
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* that algorithm in the compiled binary, as per static linking
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* behaviour. Removing some of this calls will then reduce total code
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* footprint, but also mechanically prevents some features to be
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* supported (protocol versions and cipher suites).
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*
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* The two below define profiles for the client and the server contexts,
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* respectively. Of course, in a typical size-constrained application,
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* you would use one or the other, not both, to avoid pulling in code
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* for both.
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*
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* This profile has been modified to the following criteria
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* * support only TLS 1.2 for security
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* * Use a minimal size footprint
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* * remove RSA_WITH_AES ciphers for above
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*/
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void
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br_client_init_TLS12_only(br_ssl_client_context *cc,
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br_x509_minimal_context *xc,
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const br_x509_trust_anchor *trust_anchors, size_t trust_anchors_num)
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{
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/*
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* The TLS1.2 profile supports widely used implemented cipher suites.
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*
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* Rationale for suite order, from most important to least
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* important rule:
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*
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* -- Only support TLS 1.2
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* -- Don't support RSA and 3DES as primary encryption as they are weaker protocols
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* -- Try to have Forward Secrecy (ECDHE suite) if possible.
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* -- When not using Forward Secrecy, ECDH key exchange is
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* better than RSA key exchange (slightly more expensive on the
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* client, but much cheaper on the server, and it implies smaller
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* messages).
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* -- AES-128 is preferred over AES-256 (AES-128 is already
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* strong enough, and AES-256 is 40% more expensive).
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*/
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static const uint16_t suites[] = {
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BR_TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
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BR_TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
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BR_TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
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BR_TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
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BR_TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256,
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BR_TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256,
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};
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/*
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* Client context must be cleared at some point. This sets
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* every value and pointer to 0 or NULL.
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*/
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br_ssl_client_zero(cc);
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/*
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* Define minimum and maximum protocol versions. Supported
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* versions are:
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* BR_TLS10 TLS 1.0
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* BR_TLS11 TLS 1.1
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* BR_TLS12 TLS 1.2
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*/
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br_ssl_engine_set_versions(&cc->eng, BR_TLS12, BR_TLS12);
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/*
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* Set the PRF implementation(s).
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* For TLS 1.0 and 1.1, the "prf10" is needed.
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* For TLS 1.2, this depends on the cipher suite:
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* -- cipher suites with a name ending in "SHA384" need "prf_sha384";
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* -- all others need "prf_sha256".
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*
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* Note that a cipher suite like TLS_RSA_WITH_AES_128_CBC_SHA will
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* use SHA-1 for the per-record MAC (that's what the final "SHA"
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* means), but still SHA-256 for the PRF when selected along with
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* the TLS-1.2 protocol version.
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*/
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// br_ssl_engine_set_prf10(&cc->eng, &br_tls10_prf);
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br_ssl_engine_set_prf_sha256(&cc->eng, &br_tls12_sha256_prf);
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// br_ssl_engine_set_prf_sha384(&cc->eng, &br_tls12_sha384_prf);
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/*
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* Set hash functions for the engine. Required hash functions
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* depend on the protocol and cipher suite:
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*
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* -- TLS 1.0 and 1.1 require both MD5 and SHA-1.
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* -- With TLS 1.2, cipher suites with a name ending in "SHA384"
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* require SHA-384.
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* -- With TLS 1.2, cipher suites with a name ending in "SHA256"
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* require SHA-256.
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* -- With TLS 1.2, cipher suites with a name ending in "SHA"
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* require both SHA-256 and SHA-1.
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*
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* Moreover, these hash functions are also used to compute
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* hashes supporting signatures on the server side (for ECDHE_*
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* cipher suites), and on the client side (for client
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* certificates, except in the case of full static ECDH). In TLS
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* 1.0 and 1.1, SHA-1 (and also MD5) will be used, but with TLS
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* 1.2 these hash functions are negotiated between client and
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* server; SHA-256 and/or SHA-384 should be sufficient in
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* practice.
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*
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* Note that with current implementations, SHA-224 and SHA-256
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* share the same file, so if you use one, you may have the other
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* one with no additional overhead. Similarly, SHA-384 and SHA-512
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* share the same implementation code.
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*/
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// br_ssl_engine_set_hash(&cc->eng, br_md5_ID, &br_md5_vtable);
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// br_ssl_engine_set_hash(&cc->eng, br_sha1_ID, &br_sha1_vtable);
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br_ssl_engine_set_hash(&cc->eng, br_sha224_ID, &br_sha224_vtable);
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br_ssl_engine_set_hash(&cc->eng, br_sha256_ID, &br_sha256_vtable);
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br_ssl_engine_set_hash(&cc->eng, br_sha384_ID, &br_sha384_vtable);
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br_ssl_engine_set_hash(&cc->eng, br_sha512_ID, &br_sha512_vtable);
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/*
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* Set the cipher suites. All specified cipher suite MUST be
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* supported, and the relevant algorithms MUST have been
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* configured (failure to provide needed implementations may
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* trigger unwanted behaviours like segfaults or overflows).
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*/
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br_ssl_engine_set_suites(&cc->eng, suites,
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(sizeof suites) / (sizeof suites[0]));
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/*
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* Public-key algorithm implementations.
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*
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* -- RSA public core ("rsapub") is needed for "RSA" key exchange
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* (cipher suites whose name starts with TLS_RSA).
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*
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* -- RSA signature verification ("rsavrfy") is needed for
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* "ECDHE_RSA" cipher suites (not ECDH_RSA).
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*
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* -- Elliptic curve implementation ("ec") is needed for cipher
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* suites that use elliptic curves (both "ECDH" and "ECDHE"
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* cipher suites).
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*
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* -- ECDSA signature verification is needed for "ECDHE_ECDSA"
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* cipher suites (but not for ECDHE_RSA, ECDH_ECDSA or ECDH_RSA).
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*
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* Normally, you use the "default" implementations, obtained
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* through relevant function calls. These functions return
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* implementations that are deemed "best" for the current
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* platform, where "best" means "fastest within constant-time
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* implementations". Selecting the default implementation is a
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* mixture of compile-time and runtime checks.
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*
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* Nevertheless, specific implementations may be selected
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* explicitly, e.g. to use code which is slower but with a
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* smaller footprint.
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*
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* The RSA code comes in three variants, called "i15", "i31" and
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* "i32". The "i31" code is somewhat faster than the "i32" code.
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* Usually, "i31" is faster than "i15", except on some specific
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* architectures (ARM Cortex M0, M0+, M1 and M3) where the "i15"
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* should be preferred (the "i15" code is constant-time, while
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* the "i31" is not, and the "i15" code is faster anyway).
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*
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* ECDSA code also comes in "i15" and "i31" variants. As in the
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* case of RSA, the "i31" code is faster, except on the small
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* ARM Cortex M, where the "i15" code is faster and safer.
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*
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* There are no less than 10 elliptic curve implementations:
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*
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* - ec_c25519_i15, ec_c25519_i31, ec_c25519_m15 and ec_c25519_m31
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* implement Curve25519.
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*
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* - ec_p256_m15 and ec_p256_m31 implement NIST curve P-256.
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*
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* - ec_prime_i15 and ec_prime_i31 implement NIST curves P-256,
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* P-384 and P-521.
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*
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* - ec_all_m15 is an aggregate implementation that uses
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* ec_c25519_m15, ec_p256_m15 and ec_prime_i15.
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*
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* - ec_all_m31 is an aggregate implementation that uses
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* ec_c25519_m31, ec_p256_m31 and ec_prime_i31.
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*
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* For a given curve, "m15" is faster than "i15" (but possibly
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* with a larger code footprint) and "m31" is faster than "i31"
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* (there again with a larger code footprint). For best
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* performance, use ec_all_m31, except on the small ARM Cortex M
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* where ec_all_m15 should be used. Referencing the other
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* implementations directly will result in smaller code, but
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* support for fewer curves and possibly lower performance.
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*/
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// br_ssl_client_set_default_rsapub(cc);
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// br_ssl_engine_set_default_rsavrfy(&cc->eng);
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// br_ssl_engine_set_default_ecdsa(&cc->eng);
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//* Alternate: set implementations explicitly.
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// br_ssl_client_set_rsapub(cc, &br_rsa_i31_public);
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br_ssl_engine_set_rsavrfy(&cc->eng, &br_rsa_i15_pkcs1_vrfy);
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br_ssl_engine_set_ec(&cc->eng, &br_ec_p256_m15);
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br_ssl_engine_set_ecdsa(&cc->eng, &br_ecdsa_i15_vrfy_asn1);
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//*/
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/*
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* Record handler:
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* -- Cipher suites in AES_128_CBC, AES_256_CBC and 3DES_EDE_CBC
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* need the CBC record handler ("set_cbc").
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* -- Cipher suites in AES_128_GCM and AES_256_GCM need the GCM
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* record handler ("set_gcm").
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* -- Cipher suites in CHACHA20_POLY1305 need the ChaCha20+Poly1305
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* record handler ("set_chapol").
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*/
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// br_ssl_engine_set_cbc(&cc->eng,
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// &br_sslrec_in_cbc_vtable,
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// &br_sslrec_out_cbc_vtable);
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br_ssl_engine_set_gcm(&cc->eng,
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&br_sslrec_in_gcm_vtable,
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&br_sslrec_out_gcm_vtable);
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// br_ssl_engine_set_chapol(&cc->eng,
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// &br_sslrec_in_chapol_vtable,
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// &br_sslrec_out_chapol_vtable);
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/*
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* Set the ChaCha20 and Poly1305 implementations
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* Not included in this file orignally for some reason
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*/
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br_ssl_engine_set_default_chapol(&cc->eng);
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/*
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* Symmetric encryption:
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* -- AES_128_CBC and AES_256_CBC require an "aes_cbc" implementation
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* (actually two implementations, for encryption and decryption).
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* -- 3DES_EDE_CBC requires a "des_cbc" implementation
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* (actually two implementations, for encryption and decryption).
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* -- AES_128_GCM and AES_256_GCM require an "aes_ctr" imeplementation
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* and also a GHASH implementation.
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*
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* Two 3DES implementations are provided:
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*
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* des_tab Classical table-based implementation; it is
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* not constant-time.
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*
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* dest_ct Constant-time DES/3DES implementation. It is
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* slower than des_tab.
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*
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* Four AES implementations are provided:
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*
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* aes_ct Constant-time AES implementation, for 32-bit
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* systems.
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*
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* aes_ct64 Constant-time AES implementation, for 64-bit
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* systems. It actually also runs on 32-bit systems,
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* but, on such systems, it yields larger code and
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* slightly worse performance. On 64-bit systems,
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* aes_ct64 is about twice faster than aes_ct for
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* CTR processing (GCM encryption and decryption),
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* and for CBC (decryption only).
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*
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* aes_small Smallest implementation provided, but also the
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* slowest, and it is not constant-time. Use it
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* only if desperate for code size.
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*
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* aes_big Classical table-based AES implementation. This
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* is decently fast and still resonably compact,
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* but it is not constant-time.
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*
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* aes_x86ni Very fast implementation that uses the AES-NI
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* opcodes on recent x86 CPU. But it may not be
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* compiled in the library if the compiler or
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* architecture is not supported; and the CPU
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* may also not support the opcodes. Selection
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* functions are provided to test for availability
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* of the code and the opcodes.
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*
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* Whether having constant-time implementations is absolutely
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* required for security depends on the context (in particular
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* whether the target architecture actually has cache memory),
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* and while side-channel analysis for non-constant-time AES
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* code has been demonstrated in lab conditions, it certainly
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* does not apply to all actual usages, and it has never been
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* spotted in the wild. It is still considered cautious to use
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* constant-time code by default, and to consider the other
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* implementations only if duly measured performance issues make
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* it mandatory.
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*/
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/*
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br_ssl_engine_set_aes_cbc(&cc->eng,
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&br_aes_ct_cbcenc_vtable,
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&br_aes_ct_cbcdec_vtable);
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br_ssl_engine_set_aes_ctr(&cc->eng,
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&br_aes_ct_ctr_vtable); */
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/* Alternate: aes_ct64
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br_ssl_engine_set_aes_cbc(&cc->eng,
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&br_aes_ct64_cbcenc_vtable,
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&br_aes_ct64_cbcdec_vtable);
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br_ssl_engine_set_aes_ctr(&cc->eng,
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&br_aes_ct64_ctr_vtable);
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*/
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// Alternate: aes_small
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// br_ssl_engine_set_aes_cbc(&cc->eng,
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// &br_aes_small_cbcenc_vtable,
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// &br_aes_small_cbcdec_vtable);*/
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br_ssl_engine_set_aes_ctr(&cc->eng,
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&br_aes_small_ctr_vtable);
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/* Alternate: aes_big
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br_ssl_engine_set_aes_cbc(&cc->eng,
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&br_aes_big_cbcenc_vtable,
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&br_aes_big_cbcdec_vtable);
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br_ssl_engine_set_aes_ctr(&cc->eng,
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&br_aes_big_ctr_vtable);
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*/
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/* 3DES Disabled
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br_ssl_engine_set_des_cbc(&cc->eng,
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&br_des_ct_cbcenc_vtable,
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&br_des_ct_cbcdec_vtable);
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*/
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/* Alternate: des_tab
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br_ssl_engine_set_des_cbc(&cc->eng,
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&br_des_tab_cbcenc_vtable,
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&br_des_tab_cbcdec_vtable);
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*/
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/*
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* GHASH is needed for AES_128_GCM and AES_256_GCM. Three
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* implementations are provided:
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*
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* ctmul Uses 32-bit multiplications with a 64-bit result.
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*
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* ctmul32 Uses 32-bit multiplications with a 32-bit result.
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*
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* ctmul64 Uses 64-bit multiplications with a 64-bit result.
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*
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* On 64-bit platforms, ctmul64 is the smallest and fastest of
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* the three. On 32-bit systems, ctmul should be preferred. The
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* ctmul32 implementation is meant to be used for the specific
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* 32-bit systems that do not have a 32x32->64 multiplier (i.e.
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* the ARM Cortex-M0 and Cortex-M0+).
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*
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* These implementations are all constant-time as long as the
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* underlying multiplication opcode is constant-time (which is
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* true for all modern systems, but not for older architectures
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* such that ARM9 or 80486).
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*/
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/*
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br_ssl_engine_set_ghash(&cc->eng,
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&br_ghash_ctmul); */
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//* Alternate: ghash_ctmul32
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br_ssl_engine_set_ghash(&cc->eng,
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&br_ghash_ctmul32);
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//*/
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/* Alternate: ghash_ctmul64
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br_ssl_engine_set_ghash(&cc->eng,
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&br_ghash_ctmul64);
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*/
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/*
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* For a client, the normal case is to validate the server
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* certificate with regards to a set of trust anchors. This
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* entails using a br_x509_minimal_context structure, configured
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* with the relevant algorithms, as shown below.
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*
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* Alternatively, the client could "know" the intended server
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* public key through an out-of-band mechanism, in which case
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* a br_x509_knownkey_context is appropriate, for a much reduced
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* code footprint.
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*
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* We assume here that the following extra parameters have been
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* provided:
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*
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* xc engine context (br_x509_minimal_context *)
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* trust_anchors trust anchors (br_x509_trust_anchor *)
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* trust_anchors_num number of trust anchors (size_t)
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*/
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/*
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* The X.509 engine needs a hash function for processing the
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* subject and issuer DN of certificates and trust anchors. Any
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* supported hash function is appropriate; here we use SHA-256.
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* The trust an
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*/
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memset(xc, 0, sizeof *xc);
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br_x509_minimal_init(xc, &br_sha256_vtable,
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trust_anchors, trust_anchors_num);
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/*
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* Set a fixed epoch time to validate certificates against.
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* Since we are working with an embedded device, there isn't
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* really a reliable source of time. To remedy this, we simply
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* store the time this program was compiled, and assume that
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* any certificate valid under that time is also valid at the
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* current time. This is vulnerable to the use of expired
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* certificates, however an attacker would have to use a
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* certificate valid after the compile date, which is fairly
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* difficult given the lifespan of projects here at the lab.
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* For now, this solution is good enough.
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*/
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br_x509_minimal_set_time(xc,
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// days since 1970 + days from 1970 to year 0
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(UNIX_TIMESTAMP_UTC / SEC_PER_DAY) + 719528UL,
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// seconds over start of day
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UNIX_TIMESTAMP_UTC % SEC_PER_DAY);
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/*
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* Set suites and asymmetric crypto implementations. We use the
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* "i31" code for RSA (it is somewhat faster than the "i32"
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* implementation). These implementations are used for
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* signature verification on certificates, but not for the
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* SSL-specific usage of the server's public key. For instance,
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* if the server has an EC public key but the rest of the chain
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* (intermediate CA, root...) use RSA, then you would need only
|
|
* the RSA verification function below.
|
|
*/
|
|
// br_x509_minimal_set_rsa(xc, &br_rsa_i31_pkcs1_vrfy);
|
|
br_x509_minimal_set_rsa(xc, br_ssl_engine_get_rsavrfy(&cc->eng));
|
|
// br_x509_minimal_set_ecdsa(xc,
|
|
// &br_ec_prime_i31, &br_ecdsa_i31_vrfy_asn1);
|
|
br_x509_minimal_set_ecdsa(xc,
|
|
&br_ec_prime_fast_256,
|
|
br_ssl_engine_get_ecdsa(&cc->eng));
|
|
|
|
/*
|
|
* Set supported hash functions. These are for signatures on
|
|
* certificates. There again, you only need the hash functions
|
|
* that are actually used in certificates, but if a given
|
|
* function was included for the SSL engine, you may as well
|
|
* add it here.
|
|
*
|
|
* Note: the engine explicitly rejects signatures that use MD5.
|
|
* Thus, there is no need for MD5 here.
|
|
*/
|
|
// br_x509_minimal_set_hash(xc, br_sha1_ID, &br_sha1_vtable);
|
|
br_x509_minimal_set_hash(xc, br_sha224_ID, &br_sha224_vtable);
|
|
br_x509_minimal_set_hash(xc, br_sha256_ID, &br_sha256_vtable);
|
|
br_x509_minimal_set_hash(xc, br_sha384_ID, &br_sha384_vtable);
|
|
br_x509_minimal_set_hash(xc, br_sha512_ID, &br_sha512_vtable);
|
|
|
|
/*
|
|
* Link the X.509 engine in the SSL engine.
|
|
*/
|
|
br_ssl_engine_set_x509(&cc->eng, &xc->vtable);
|
|
}
|