[LTP] [PATCH v2] syscalls/keyctl05: new test for key_update() crash

Eric Biggers
2017-08-01T00:47:17Z

From: Eric Biggers <ebiggers@google.com>

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>
---
runtest/syscalls | 1 +
testcases/kernel/syscalls/.gitignore | 1 +
testcases/kernel/syscalls/keyctl/keyctl05.c | 230 ++++++++++++++++++++++++++++
3 files changed, 232 insertions(+)
create mode 100644 testcases/kernel/syscalls/keyctl/keyctl05.c

diff --git a/runtest/syscalls b/runtest/syscalls
index 5c7fd8e94..cfc1cbfa1 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -495,6 +495,7 @@ keyctl01 keyctl01
keyctl02 keyctl02
keyctl03 keyctl03
keyctl04 keyctl04
+keyctl05 keyctl05

kcmp01 kcmp01
kcmp02 kcmp02
diff --git a/testcases/kernel/syscalls/.gitignore b/testcases/kernel/syscalls/.gitignore
index e311ba3f8..82dfb8293 100644
--- a/testcases/kernel/syscalls/.gitignore
+++ b/testcases/kernel/syscalls/.gitignore
@@ -458,6 +458,7 @@
/keyctl/keyctl02
/keyctl/keyctl03
/keyctl/keyctl04
+/keyctl/keyctl05
/kcmp/kcmp01
/kcmp/kcmp02
/kcmp/kcmp03
diff --git a/testcases/kernel/syscalls/keyctl/keyctl05.c b/testcases/kernel/syscalls/keyctl/keyctl05.c
new file mode 100644
index 000000000..a11b788c6
--- /dev/null
+++ b/testcases/kernel/syscalls/keyctl/keyctl05.c
@@ -0,0 +1,230 @@
+/*
+ * 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"
+
+typedef int32_t key_serial_t;
+
+#define KEYCTL_JOIN_SESSION_KEYRING 1
+#define KEYCTL_UPDATE 2
+#define KEYCTL_SETPERM 5
+
+#define KEY_SPEC_SESSION_KEYRING -3
+
+#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,
+};
--
2.14.0.rc0.400.g1c36432dff-goog