syscalls/keyctl05: new test for key_update() crash

Add a test for a kernel bug that caused a key type's ->free_preparse()
method to be called on an uninitialized key_preparsed_payload,
potentially causing a NULL pointer dereference or other kernel crash.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>

1 files changed, 225 insertions, 0 deletions

diff --git a/testcases/kernel/syscalls/keyctl/keyctl05.c b/testcases/kernel/syscalls/keyctl/keyctl05.c
new file mode 100644
index 000000000..922d2b46a
--- /dev/null
+++ b/testcases/kernel/syscalls/keyctl/keyctl05.c
@@ -0,0 +1,225 @@
+/*
+ * Copyright (c) 2017 Google, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * Regression test for commit 63a0b0509e70 ("KEYS: fix freeing uninitialized
+ * memory in key_update()").  Try to reproduce the crash in two different ways:
+ *
+ * 1. Try to update a key of a type that has a ->preparse() method but not an
+ *    ->update() method.  Examples are the "asymmetric" and "dns_resolver" key
+ *    types.  It crashes reliably for the "asymmetric" key type, since the
+ *    "asymmetric" key type's ->free_preparse() method will dereference a
+ *    pointer in the uninitialized memory, whereas other key types often just
+ *    free a pointer which tends be NULL in practice, depending on how the stack
+ *    is laid out.  However, to actually be able to add an "asymmetric" key, we
+ *    need a specially-formatted payload and several kernel config options.  We
+ *    do try it, but for completeness we also try the "dns_resolver" key type
+ *    (though that's not guaranteed to be available either).
+ *
+ * 2. Race keyctl_update() with another task removing write permission from the
+ *    key using keyctl_setperm().  This can cause a crash with almost any key
+ *    type.  "user" is a good one to try, since it's always available if
+ *    keyrings are supported at all.  However, depending on how the stack is
+ *    laid out the crash may not actually occur.
+ */
+
+#include <stdlib.h>
+#include "tst_test.h"
+#include "lapi/syscalls.h"
+#include "lapi/keyctl.h"
+
+typedef int32_t key_serial_t;
+
+#define KEY_POS_WRITE	0x04000000
+#define KEY_POS_ALL	0x3f000000
+
+/*
+ * A valid payload for the "asymmetric" key type.  This is an x509 certificate
+ * in DER format, generated using:
+ *
+ *	openssl req -x509 -newkey rsa:512 -batch -nodes -outform der \
+ *		| ~/linux/scripts/bin2c
+ */
+static const char x509_cert[] =
+	"\x30\x82\x01\xd3\x30\x82\x01\x7d\xa0\x03\x02\x01\x02\x02\x09\x00"
+	"\x92\x2a\x76\xff\x0c\x00\xfb\x9a\x30\x0d\x06\x09\x2a\x86\x48\x86"
+	"\xf7\x0d\x01\x01\x0b\x05\x00\x30\x45\x31\x0b\x30\x09\x06\x03\x55"
+	"\x04\x06\x13\x02\x41\x55\x31\x13\x30\x11\x06\x03\x55\x04\x08\x0c"
+	"\x0a\x53\x6f\x6d\x65\x2d\x53\x74\x61\x74\x65\x31\x21\x30\x1f\x06"
+	"\x03\x55\x04\x0a\x0c\x18\x49\x6e\x74\x65\x72\x6e\x65\x74\x20\x57"
+	"\x69\x64\x67\x69\x74\x73\x20\x50\x74\x79\x20\x4c\x74\x64\x30\x1e"
+	"\x17\x0d\x31\x37\x30\x37\x32\x38\x32\x31\x34\x31\x33\x34\x5a\x17"
+	"\x0d\x31\x37\x30\x38\x32\x37\x32\x31\x34\x31\x33\x34\x5a\x30\x45"
+	"\x31\x0b\x30\x09\x06\x03\x55\x04\x06\x13\x02\x41\x55\x31\x13\x30"
+	"\x11\x06\x03\x55\x04\x08\x0c\x0a\x53\x6f\x6d\x65\x2d\x53\x74\x61"
+	"\x74\x65\x31\x21\x30\x1f\x06\x03\x55\x04\x0a\x0c\x18\x49\x6e\x74"
+	"\x65\x72\x6e\x65\x74\x20\x57\x69\x64\x67\x69\x74\x73\x20\x50\x74"
+	"\x79\x20\x4c\x74\x64\x30\x5c\x30\x0d\x06\x09\x2a\x86\x48\x86\xf7"
+	"\x0d\x01\x01\x01\x05\x00\x03\x4b\x00\x30\x48\x02\x41\x00\xde\x0b"
+	"\x1c\x24\xe2\x0d\xf8\x17\xf2\xc3\x6f\xc9\x72\x3e\x9d\xb0\x2d\x47"
+	"\xe4\xc4\x85\x87\xed\xde\x06\xe3\xf3\xe9\x4c\x35\x6c\xe4\xcb\x0e"
+	"\x44\x28\x23\x66\x76\xec\x4e\xdf\x10\x93\x92\x1e\x52\xfb\xdf\x5c"
+	"\x08\xe7\x24\x04\x66\xe3\x06\x05\x27\x56\xfb\x3e\x91\x31\x02\x03"
+	"\x01\x00\x01\xa3\x50\x30\x4e\x30\x1d\x06\x03\x55\x1d\x0e\x04\x16"
+	"\x04\x14\x6f\x39\x3a\x46\xdf\x29\x63\xde\x54\x7b\x6c\x31\x06\xd0"
+	"\x9f\x36\x16\xfb\x9c\xbf\x30\x1f\x06\x03\x55\x1d\x23\x04\x18\x30"
+	"\x16\x80\x14\x6f\x39\x3a\x46\xdf\x29\x63\xde\x54\x7b\x6c\x31\x06"
+	"\xd0\x9f\x36\x16\xfb\x9c\xbf\x30\x0c\x06\x03\x55\x1d\x13\x04\x05"
+	"\x30\x03\x01\x01\xff\x30\x0d\x06\x09\x2a\x86\x48\x86\xf7\x0d\x01"
+	"\x01\x0b\x05\x00\x03\x41\x00\x73\xf0\x4b\x62\x56\xed\xf0\x8b\x7e"
+	"\xc4\x75\x78\x98\xa2\x7a\x6e\x75\x1f\xde\x9b\xa0\xbe\x1a\x1f\x86"
+	"\x44\x13\xcd\x45\x06\x7f\x86\xde\xf6\x36\x4e\xb6\x15\xfa\xf5\xb0"
+	"\x34\xd2\x5e\x0b\xb3\x2c\x03\x5a\x5a\x28\x97\x5e\x7b\xdf\x63\x75"
+	"\x83\x8d\x69\xda\xd6\x59\xbd"
+	;
+
+static void new_session_keyring(void)
+{
+	TEST(tst_syscall(__NR_keyctl, KEYCTL_JOIN_SESSION_KEYRING, NULL));
+	if (TEST_RETURN < 0)
+		tst_brk(TBROK | TTERRNO, "failed to join new session keyring");
+}
+
+static void test_update_nonupdatable(const char *type,
+				     const void *payload, size_t plen)
+{
+	key_serial_t keyid;
+
+	new_session_keyring();
+
+	TEST(tst_syscall(__NR_add_key, type, "desc", payload, plen,
+			 KEY_SPEC_SESSION_KEYRING));
+	if (TEST_RETURN < 0) {
+		if (TEST_ERRNO == ENODEV) {
+			tst_res(TCONF, "kernel doesn't support key type '%s'",
+				type);
+			return;
+		}
+		if (TEST_ERRNO == EBADMSG && !strcmp(type, "asymmetric")) {
+			tst_res(TCONF, "kernel is missing x509 cert parser "
+				"(CONFIG_X509_CERTIFICATE_PARSER)");
+			return;
+		}
+		if (TEST_ERRNO == ENOENT && !strcmp(type, "asymmetric")) {
+			tst_res(TCONF, "kernel is missing crypto algorithms "
+				"needed to parse x509 cert (CONFIG_CRYPTO_RSA "
+				"and/or CONFIG_CRYPTO_SHA256)");
+			return;
+		}
+		tst_res(TBROK | TTERRNO, "unexpected error adding '%s' key",
+			type);
+		return;
+	}
+	keyid = TEST_RETURN;
+
+	/*
+	 * Non-updatable keys don't start with write permission, so we must
+	 * explicitly grant it.
+	 */
+	TEST(tst_syscall(__NR_keyctl, KEYCTL_SETPERM, keyid, KEY_POS_ALL));
+	if (TEST_RETURN != 0) {
+		tst_res(TBROK | TTERRNO,
+			"failed to grant write permission to '%s' key", type);
+		return;
+	}
+
+	tst_res(TINFO, "Try to update the '%s' key...", type);
+	TEST(tst_syscall(__NR_keyctl, KEYCTL_UPDATE, keyid, payload, plen));
+	if (TEST_RETURN == 0) {
+		tst_res(TBROK,
+			"updating '%s' key unexpectedly succeeded", type);
+		return;
+	}
+	if (TEST_ERRNO != EOPNOTSUPP) {
+		tst_res(TBROK | TTERRNO,
+			"updating '%s' key unexpectedly failed", type);
+		return;
+	}
+	tst_res(TPASS, "updating '%s' key expectedly failed with EOPNOTSUPP",
+		type);
+}
+
+/*
+ * Try to update a key, racing with removing write permission.
+ * This may crash buggy kernels.
+ */
+static void test_update_setperm_race(void)
+{
+	static const char payload[] = "payload";
+	key_serial_t keyid;
+	int i;
+
+	new_session_keyring();
+
+	TEST(tst_syscall(__NR_add_key, "user", "desc", payload, sizeof(payload),
+			 KEY_SPEC_SESSION_KEYRING));
+	if (TEST_RETURN < 0) {
+		tst_res(TBROK | TTERRNO, "failed to add 'user' key");
+		return;
+	}
+	keyid = TEST_RETURN;
+
+	if (SAFE_FORK() == 0) {
+		uint32_t perm = KEY_POS_ALL;
+
+		for (i = 0; i < 10000; i++) {
+			perm ^= KEY_POS_WRITE;
+			TEST(syscall(__NR_keyctl, KEYCTL_SETPERM, keyid, perm));
+			if (TEST_RETURN != 0)
+				tst_brk(TBROK | TTERRNO, "setperm failed");
+		}
+		exit(0);
+	}
+
+	tst_res(TINFO, "Try to update the 'user' key...");
+	for (i = 0; i < 10000; i++) {
+		TEST(tst_syscall(__NR_keyctl, KEYCTL_UPDATE, keyid,
+				 payload, sizeof(payload)));
+		if (TEST_RETURN != 0 && TEST_ERRNO != EACCES) {
+			tst_res(TBROK | TTERRNO, "failed to update 'user' key");
+			return;
+		}
+	}
+	tst_reap_children();
+	tst_res(TPASS, "didn't crash while racing to update 'user' key");
+}
+
+static void do_test(unsigned int i)
+{
+	/* two 0 bytes is accepted as a dns_resolver key payload */
+	static char zeroes[2];
+
+	switch (i) {
+	case 0:
+		test_update_nonupdatable("asymmetric",
+					 x509_cert, sizeof(x509_cert));
+		break;
+	case 1:
+		test_update_nonupdatable("dns_resolver",
+					 zeroes, sizeof(zeroes));
+		break;
+	case 2:
+		test_update_setperm_race();
+		break;
+	}
+}
+
+static struct tst_test test = {
+	.tcnt = 3,
+	.test = do_test,
+	.forks_child = 1,
+};