[LTP] [PATCH v2 19/33] keyctl27: Test KEYCTL_DH_COMPUTE KDF key derivation

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

Test KEYCTL_DH_COMPUTE SP800-56A KDF key derivation: verify that
deriving a key using SHA-256 and otherinfo matches the precomputed
mathematical test vector.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 runtest/syscalls                                  |  1 +
 testcases/kernel/syscalls/keyctl/.gitignore       |  1 +
 testcases/kernel/syscalls/keyctl/keyctl27.c       | 78 +++++++++++++++++++++++
 testcases/kernel/syscalls/keyctl/keyctl_dh_data.h |  5 ++
 4 files changed, 85 insertions(+)

diff --git a/runtest/syscalls b/runtest/syscalls
index 108efa4a8..d23461c4b 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -744,6 +744,7 @@ keyctl23 keyctl23
 keyctl24 keyctl24
 keyctl25 keyctl25
 keyctl26 keyctl26
+keyctl27 keyctl27
 
 kcmp01 kcmp01
 kcmp02 kcmp02
diff --git a/testcases/kernel/syscalls/keyctl/.gitignore b/testcases/kernel/syscalls/keyctl/.gitignore
index dd282b7ce..720ba1de6 100644
--- a/testcases/kernel/syscalls/keyctl/.gitignore
+++ b/testcases/kernel/syscalls/keyctl/.gitignore
@@ -24,3 +24,4 @@
 /keyctl24
 /keyctl25
 /keyctl26
+/keyctl27
diff --git a/testcases/kernel/syscalls/keyctl/keyctl27.c b/testcases/kernel/syscalls/keyctl/keyctl27.c
new file mode 100644
index 000000000..288bd0f37
--- /dev/null
+++ b/testcases/kernel/syscalls/keyctl/keyctl27.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Andrea Cervesato <andrea.cervesato@suse.com>
+ */
+
+/*\
+ * Test ``KEYCTL_DH_COMPUTE`` KDF key derivation of :manpage:`keyctl(2)`.
+ *
+ * The KDF extension to ``KEYCTL_DH_COMPUTE`` (SP800-56A) landed in Linux 4.12.
+ *
+ * [Algorithm]
+ *
+ * - derive key with SP800-56A KDF (SHA-256 + otherinfo), verify derived
+ *   key matches expected 32-byte value
+ */
+
+#include "keyctl_common.h"
+#include "keyctl_dh_data.h"
+
+#define KDF_OTHERINFO	"LTP-KDF-TEST-INFO"
+
+static struct keyctl_dh_params *dh_params;
+static struct keyctl_kdf_params *kdf_params;
+static unsigned char out_buf[32];
+
+static void setup(void)
+{
+	SAFE_KEYCTL(KEYCTL_JOIN_SESSION_KEYRING, 0, 0, 0, 0);
+
+	dh_params->priv = new_user_key("dh_priv", dh_priv, sizeof(dh_priv),
+				       KEY_SPEC_PROCESS_KEYRING);
+	dh_params->prime = new_user_key("dh_prime", dh_prime, sizeof(dh_prime),
+					KEY_SPEC_PROCESS_KEYRING);
+	dh_params->base = new_user_key("dh_base", dh_base, sizeof(dh_base),
+				       KEY_SPEC_PROCESS_KEYRING);
+}
+
+static void run(void)
+{
+	memset(kdf_params, 0, sizeof(*kdf_params));
+	kdf_params->hashname = "sha256";
+	kdf_params->otherinfo = (char *)KDF_OTHERINFO;
+	kdf_params->otherinfolen = strlen(KDF_OTHERINFO);
+
+	memset(out_buf, 0, sizeof(out_buf));
+	TST_EXP_EQ_LI_SILENT(keyctl(KEYCTL_DH_COMPUTE, (unsigned long)dh_params,
+				    (unsigned long)out_buf,
+				    sizeof(dh_kdf_expected),
+				    (unsigned long)kdf_params),
+			     (long)sizeof(dh_kdf_expected));
+	if (!TST_PASS)
+		return;
+
+	if (memcmp(out_buf, dh_kdf_expected, sizeof(dh_kdf_expected))) {
+		tst_res(TFAIL, "derived KDF key does not match expected value");
+		return;
+	}
+
+	tst_res(TPASS, "KEYCTL_DH_COMPUTE with KDF derived expected key");
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.test_all = run,
+	.min_kver = "4.12",
+	.needs_kconfigs = (const char *[]) {
+		"CONFIG_KEYS=y",
+		"CONFIG_KEY_DH_OPERATIONS=y",
+		"CONFIG_CRYPTO_DH",
+		"CONFIG_CRYPTO_SHA256",
+		NULL
+	},
+	.bufs = (struct tst_buffers []) {
+		{&dh_params, .size = sizeof(*dh_params)},
+		{&kdf_params, .size = sizeof(*kdf_params)},
+		{},
+	},
+};
diff --git a/testcases/kernel/syscalls/keyctl/keyctl_dh_data.h b/testcases/kernel/syscalls/keyctl/keyctl_dh_data.h
index bc1432dc3..7ac7876a0 100644
--- a/testcases/kernel/syscalls/keyctl/keyctl_dh_data.h
+++ b/testcases/kernel/syscalls/keyctl/keyctl_dh_data.h
@@ -71,4 +71,9 @@ static const unsigned char dh_expected_secret[] = {
 	0xfb, 0xeb, 0xdd, 0x18, 0x54, 0x0d, 0x4c, 0xa7, 0x65, 0xc1, 0x0c, 0x11, 0xad, 0xea, 0x83, 0x9f,
 };
 
+static const unsigned char dh_kdf_expected[] = {
+	0x66, 0x39, 0xec, 0x41, 0x31, 0x33, 0xe6, 0xc0, 0x61, 0x67, 0x28, 0x51, 0x61, 0xf7, 0x8c, 0xd7,
+	0xc0, 0x55, 0xc9, 0xcc, 0x83, 0x46, 0xf3, 0xaa, 0x62, 0xed, 0xca, 0x90, 0x99, 0x2d, 0xc4, 0x07,
+};
+
 #endif /* KEYCTL_DH_DATA_H__ */

-- 
2.51.0