lib: Add post-quantum cryptography support

This adds initial support for runtime-configurable encryption and
post-quantum Key Encapsulation Mechanisms (KEMs) and authentication
(ML-DSA).

Supported key exchange algorithms:

  ECDH: prime256v1, secp384r1, secp521r1, X25519, X448
  Finite Field DH: ffdhe2048, ffdhe3072, ffdhe4096
  ML-KEM (FIPS 203): ML-KEM-512, ML-KEM-768, ML-KEM-1024
  Hybrid KEMs: X25519MLKEM768, X448MLKEM1024

Supported ciphers:
  AEAD: aes-128-gcm, aes-192-gcm, aes-256-gcm, chacha20-poly1305
  CTR: aes-128-ctr, aes-192-ctr, aes-256-ctr

Supported HKDFs:
  sha256, sha384, sha512, sha3-256, sha3-384, sha3-512,
  blake2b512, blake2s256

Supported Digests for DSA:
  sha256, sha384, sha512, sha3-256, sha3-384, sha3-512,
  blake2b512, blake2s256

PQC support requires OpenSSL 3.4.0+ and is detected automatically via
CMake. A DISABLE_PQC option allows building without PQC even when
available.

KEMs differ from traditional DH in that they require asymmetric roles:
one party encapsulates to the other's public key. This creates a
coordination problem during simultaneous reconnection attempts. The
kem_mode configuration parameter resolves this by pre-assigning roles:

  kem_mode=server  # Server encapsulates (1-RTT, full forward secrecy)
  kem_mode=client  # Client encapsulates (0-RTT, cached server key)

The enc.conf file format supports:

  kex=<algorithm>      # Key exchange algorithm
  cipher=<algorithm>   # Symmetric cipher
  kdf=<KDF>            # Key derivation function
  digest=<digest>      # Digest for DSA
  kem_mode=<mode>      # Server (default) or client
  none                 # Disable encryption

The OAP protocol is extended to negotiate algorithms and exchange KEX
data. All KEX messages are signed using existing authentication
infrastructure for integrity and replay protection.

Tests are split into base and _pqc variants to handle conditional PQC
compilation (kex_test.c/kex_test_pqc.c, oap_test.c/oap_test_pqc.c).

Bumped minimum required OpenSSL version for encryption to 3.0
(required for HKDF API). 1.1.1 is long time EOL.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

1 files changed, 100 insertions, 0 deletions

diff --git a/src/irmd/oap/tests/common.h b/src/irmd/oap/tests/common.h
new file mode 100644
index 00000000..d4b6733a
--- /dev/null
+++ b/src/irmd/oap/tests/common.h
@@ -0,0 +1,100 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2026
+ *
+ * Common test helper functions for OAP tests
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#ifndef IRMD_TESTS_COMMON_H
+#define IRMD_TESTS_COMMON_H
+
+#include <ouroboros/utils.h>
+#include <ouroboros/flow.h>
+#include <ouroboros/name.h>
+#include <test/test.h>
+
+#include <stdbool.h>
+
+/* Per-side security configuration for tests */
+struct test_sec_cfg {
+        int  kex;       /* KEX algorithm NID */
+        int  cipher;    /* Cipher NID for encryption */
+        int  kdf;       /* KDF NID for key derivation */
+        int  md;        /* Digest NID for signatures */
+        int  kem_mode;  /* KEM encapsulation mode (0 for ECDH) */
+        bool auth;      /* Use authentication (certificates) */
+};
+
+/* Test configuration - set by each test before running roundtrip */
+extern struct test_cfg {
+        struct test_sec_cfg srv;
+        struct test_sec_cfg cli;
+} test_cfg;
+
+/* Each test file defines this with its own certificates */
+extern int mock_load_credentials(void ** pkp,
+                                 void ** crt);
+
+/* Per-side test context */
+struct oap_test_side {
+        struct name_info info;
+        struct flow_info flow;
+        uint8_t          key[SYMMKEYSZ];
+        int              nid;
+        void *           state;
+};
+
+/* Test context - holds all common state for OAP tests */
+struct oap_test_ctx {
+        struct oap_test_side srv;
+        struct oap_test_side cli;
+
+        buffer_t             req_hdr;
+        buffer_t             resp_hdr;
+        buffer_t             data;
+        void *               root_ca;
+        void *               im_ca;
+};
+
+int  oap_test_setup(struct oap_test_ctx * ctx,
+                    const char *          root_ca_str,
+                    const char *          im_ca_str);
+
+void oap_test_teardown(struct oap_test_ctx * ctx);
+
+int  oap_cli_prepare_ctx(struct oap_test_ctx * ctx);
+
+int  oap_srv_process_ctx(struct oap_test_ctx * ctx);
+
+int  oap_cli_complete_ctx(struct oap_test_ctx * ctx);
+
+int  roundtrip_auth_only(const char * root_ca,
+                         const char * im_ca_str);
+
+int  roundtrip_kex_only(void);
+
+int  corrupted_request(const char * root_ca,
+                       const char * im_ca_str);
+
+int  corrupted_response(const char * root_ca,
+                        const char * im_ca_str);
+
+int  truncated_request(const char * root_ca,
+                       const char * im_ca_str);
+
+#endif /* IRMD_TESTS_COMMON_H */