https://gitlab.synchro.net/main/sbbs/-/commit/04a86211e6041ce899b9c74a
Added Files:
src/ssh/crypto/botan.cpp openssl.c src/ssh/deucessh-crypto.h deucesshConfig.cmake.in src/ssh/enc/aes256-ctr-botan.c aes256-ctr-botan.cpp aes256-ctr-openssl.c src/ssh/kex/curve25519-sha256-botan.c curve25519-sha256-botan.cpp curve25519-sha256-openssl.c curve25519-sha256-ops.h dh-gex-groups.c dh-gex-groups.h dh-gex-sha256-botan.c dh-gex-sha256-botan.cpp dh-gex-sha256-openssl.c dh-gex-sha256-ops.h hybrid-pq-kex-ops.h hybrid-pq-kex.c mlkem768x25519-sha256-botan.c mlkem768x25519-sha256-botan.cpp mlkem768x25519-sha256-openssl.c sntrup761x25519-sha512-botan.c sntrup761x25519-sha512-botan.cpp sntrup761x25519-sha512-openssl.c src/ssh/key_algo/rsa-sha2-256-botan.c rsa-sha2-256-botan.cpp rsa-sha2-256-openssl.c rsa-sha2-512-botan.c rsa-sha2-512-botan.cpp rsa-sha2-512-openssl.c ssh-ed25519-botan.c ssh-ed25519-botan.cpp ssh-ed25519-openssl.c src/ssh/mac/hmac-sha2-256-botan.c hmac-sha2-256-botan.cpp hmac-sha2-256-openssl.c hmac-sha2-512-botan.c hmac-sha2-512-botan.cpp hmac-sha2-512-openssl.c src/ssh/test/kex_test.c test_botan_algo_key.cpp test_botan_transport.cpp test_crypto.c
Modified Files:
src/ssh/CLAUDE.md CMakeLists.txt TODO.md deucessh-comp.h deucessh-enc.h deucessh-kex.h deucessh-key-algo.h deucessh-lang.h deucessh-mac.h deucessh-portable.h deucessh.pc.in src/ssh/docs/audit-4251.md audit-4253.md src/ssh/kex/curve25519-sha256.c dh-gex-sha256.c libcrux_mlkem768_sha3.h mlkem768.c sntrup761.c sntrup761.h src/ssh/ssh-auth.c ssh-internal.h ssh-trans.c ssh.c src/ssh/test/CMakeLists.txt dssh_test_internal.h dssh_test_ossl.c test_algo_enc.c test_algo_key.c test_algo_mac.c test_alloc.c test_transport.c
Removed Files:
src/ssh/kex/mlkem768x25519-sha256.c sntrup761x25519-sha512.c
Log Message:
Add Botan3 crypto backend with native C++ API, deduplicate KEX modules

Add a second crypto backend using Botan3's native C++ API alongside the existing OpenSSL backend. Selected at build time via -DDEUCESSH_CRYPTO_BACKEND=Botan (default remains OpenSSL). CXX is
enabled conditionally only when Botan is selected Ä OpenSSL-only builds
no longer require a C++ compiler.

Backend-agnostic crypto layer:
- New deucessh-crypto.h public API: dssh_hash_*, dssh_random,
dssh_cleanse, dssh_crypto_memcmp, dssh_base64_encode
- crypto/openssl.c and crypto/botan.cpp implement the same interface
- All algorithm modules use only the public crypto API and module
headers; no backend headers leak into production builds

Algorithm module deduplication:
- KEX: protocol logic (curve25519-sha256.c, dh-gex-sha256.c,
hybrid-pq-kex.c) split from crypto operations via ops vtables
(curve25519-sha256-ops.h, dh-gex-sha256-ops.h, hybrid-pq-kex-ops.h);
dhgex_handler_impl() and hybrid_pq_handler_impl() further split into
separate static client/server helpers with single goto-cleanup labels
- Each backend provides only the crypto ops (*-openssl.c, *-botan.cpp)
- DH-GEX groups extracted to kex/dh-gex-groups.c (shared between
backends)
- Botan modules use native C++ API (not FFI): Botan::system_rng(),
Botan::X25519_PrivateKey, Botan::RSA_PrivateKey, Botan::BigInt,
Botan::Cipher_Mode, Botan::MessageAuthenticationCode, etc.
- Each Botan module split into .cpp (crypto impl with extern "C"
wrappers and try/catch) + .c (struct allocation and registration)

Renamed files for consistency:
- enc/aes256-ctr.c -> enc/aes256-ctr-openssl.c
- mac/hmac-sha2-{256,512}.c -> mac/hmac-sha2-{256,512}-openssl.c
- key_algo/{ssh-ed25519,rsa-sha2-256,rsa-sha2-512}.c -> *-openssl.c

Other changes:
- derive_key(): replace hardcoded uint8_t tmp[64] with malloc(md_len)
for forward-compatibility with any hash digest size
- mlkem768.c: replace #undef htole64/le64toh/le32toh system macro
overrides with libcrux-local lcx_htole64/lcx_le64toh/lcx_le32toh

Pre-existing bug fixes (in OpenSSL code that predates this commit):
- Password callback buffer overflow (missing upper bound check, 6 sites)
- mpint parse uint32_t overflow (4 + len > bufsz wraps on large len)
- DH-GEX server reply buffer overflow (unchecked sum of 5 fields)
- RSA verify missing error codes at n-parse failure
- dssh_hash_final NULL output check

Testing:
- New test/test_crypto.c for backend-agnostic crypto API
- New test/test_botan_algo_key.cpp (18 Botan-specific tests)
- New test/test_botan_transport.cpp (12 Botan-specific tests)
- Backend-specific tests properly guarded with DSSH_CRYPTO_OPENSSL /
DSSH_CRYPTO_BOTAN
- OpenSSL: 3490/3490 tests pass
- Botan: 3491/3491 tests pass

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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