[LTP] [PATCH v2 24/33] keyctl31: Test KEYCTL_PKEY_ENCRYPT and KEYCTL_PKEY_DECRYPT

[Andrea Cervesato]

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

Test public key encryption and private key decryption with
KEYCTL_PKEY_ENCRYPT and KEYCTL_PKEY_DECRYPT: encrypt a 32-byte
plaintext using an RSA-2048 X.509 public key with enc=pkcs1,
decrypt with the matching PKCS#8 private key, and verify the
decrypted output matches the original plaintext.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 runtest/syscalls                            |   1 +
 testcases/kernel/syscalls/keyctl/.gitignore |   1 +
 testcases/kernel/syscalls/keyctl/keyctl31.c | 110 ++++++++++++++++++++++++++++
 3 files changed, 112 insertions(+)

diff --git a/runtest/syscalls b/runtest/syscalls
index 15f8c892c..e43dd02ab 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -748,6 +748,7 @@ keyctl27 keyctl27
 keyctl28 keyctl28
 keyctl29 keyctl29
 keyctl30 keyctl30
+keyctl31 keyctl31
 
 kcmp01 kcmp01
 kcmp02 kcmp02
diff --git a/testcases/kernel/syscalls/keyctl/.gitignore b/testcases/kernel/syscalls/keyctl/.gitignore
index d5b6955f3..025dc27fc 100644
--- a/testcases/kernel/syscalls/keyctl/.gitignore
+++ b/testcases/kernel/syscalls/keyctl/.gitignore
@@ -28,3 +28,4 @@
 /keyctl28
 /keyctl29
 /keyctl30
+/keyctl31
diff --git a/testcases/kernel/syscalls/keyctl/keyctl31.c b/testcases/kernel/syscalls/keyctl/keyctl31.c
new file mode 100644
index 000000000..c1e6723ac
--- /dev/null
+++ b/testcases/kernel/syscalls/keyctl/keyctl31.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Andrea Cervesato <andrea.cervesato@suse.com>
+ */
+
+/*\
+ * Test ``KEYCTL_PKEY_ENCRYPT`` and ``KEYCTL_PKEY_DECRYPT`` of :manpage:`keyctl(2)`.
+ *
+ * ``KEYCTL_PKEY_ENCRYPT`` encrypts a data blob using an asymmetric public key
+ * and ``KEYCTL_PKEY_DECRYPT`` decrypts the encrypted blob using the matching
+ * private key.
+ *
+ * Requires root (CAP_SYS_MODULE) to load the ``x509_key_parser`` and
+ * ``pkcs8_key_parser`` modules.
+ *
+ * [Algorithm]
+ *
+ * - encrypt a 32-byte plaintext using an RSA-2048 X.509 public key with ``enc=pkcs1``
+ * - decrypt the 256-byte ciphertext using the matching PKCS#8 private key
+ * - verify the decrypted output matches the original 32-byte plaintext
+ */
+
+#include "keyctl_common.h"
+#include "keyctl_pkey_data.h"
+#include "tst_module.h"
+
+#define CIPHERTEXT_SIZE	256
+
+static const char plaintext[] = "LTP_PKEY_ENCRYPT_DECRYPT_TEST_32";
+#define PLAINTEXT_SIZE	(sizeof(plaintext) - 1)
+static unsigned char ciphertext[CIPHERTEXT_SIZE];
+static unsigned char decrypted[CIPHERTEXT_SIZE];
+
+static key_serial_t cert_key, priv_key;
+static struct keyctl_pkey_params *enc_params;
+static struct keyctl_pkey_params *dec_params;
+
+static void setup(void)
+{
+	SAFE_KEYCTL(KEYCTL_JOIN_SESSION_KEYRING, 0, 0, 0, 0);
+
+	tst_modprobe("x509_key_parser", NULL);
+	tst_modprobe("pkcs8_key_parser", NULL);
+
+	cert_key = add_asymmetric_key_or_tconf("cert", rsa2048_cert,
+					       sizeof(rsa2048_cert),
+					       "CONFIG_X509_CERTIFICATE_PARSER");
+	priv_key = add_asymmetric_key_or_tconf("priv", rsa2048_pkcs8,
+					       sizeof(rsa2048_pkcs8),
+					       "CONFIG_PKCS8_PRIVATE_KEY_PARSER");
+}
+
+static void run(void)
+{
+	memset(ciphertext, 0, sizeof(ciphertext));
+	memset(decrypted, 0, sizeof(decrypted));
+
+	memset(enc_params, 0, sizeof(*enc_params));
+	enc_params->key_id = cert_key;
+	enc_params->in_len = PLAINTEXT_SIZE;
+	enc_params->out_len = CIPHERTEXT_SIZE;
+
+	TST_EXP_EQ_LI_SILENT(keyctl(KEYCTL_PKEY_ENCRYPT, (unsigned long)enc_params,
+				    (unsigned long)"enc=pkcs1",
+				    (unsigned long)plaintext,
+				    (unsigned long)ciphertext),
+			     CIPHERTEXT_SIZE);
+	if (!TST_PASS)
+		return;
+
+	memset(dec_params, 0, sizeof(*dec_params));
+	dec_params->key_id = priv_key;
+	dec_params->in_len = CIPHERTEXT_SIZE;
+	dec_params->out_len = CIPHERTEXT_SIZE;
+
+	TST_EXP_EQ_LI_SILENT(keyctl(KEYCTL_PKEY_DECRYPT, (unsigned long)dec_params,
+				    (unsigned long)"enc=pkcs1",
+				    (unsigned long)ciphertext,
+				    (unsigned long)decrypted),
+			     PLAINTEXT_SIZE);
+	if (!TST_PASS)
+		return;
+
+	if (memcmp(plaintext, decrypted, PLAINTEXT_SIZE)) {
+		tst_res(TFAIL, "decrypted text does not match original plaintext");
+		return;
+	}
+
+	tst_res(TPASS, "KEYCTL_PKEY_ENCRYPT and KEYCTL_PKEY_DECRYPT roundtrip succeeded");
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.test_all = run,
+	.min_kver = "4.20",
+	.needs_root = 1,
+	.needs_kconfigs = (const char *[]) {
+		"CONFIG_KEYS=y",
+		"CONFIG_ASYMMETRIC_KEY_TYPE=y",
+		"CONFIG_X509_CERTIFICATE_PARSER",
+		"CONFIG_PKCS8_PRIVATE_KEY_PARSER",
+		"CONFIG_CRYPTO_RSA",
+		NULL
+	},
+	.bufs = (struct tst_buffers []) {
+		{&enc_params, .size = sizeof(*enc_params)},
+		{&dec_params, .size = sizeof(*dec_params)},
+		{},
+	},
+};

-- 
2.51.0