[RFC PATCH 1/1] selinux-testsuite: Add binder tests

[Richard Haines <richard_c_haines@btinternet.com>]

Add binder tests. See tests/binder/test_binder.c for details on
message flows to test security_binder*() functions.

Signed-off-by: Richard Haines <richard_c_haines@btinternet.com>
---
 README.md                   |   8 +
 defconfig                   |   8 +
 policy/Makefile             |   2 +-
 policy/test_binder.te       |  83 +++++++
 tests/Makefile              |   2 +-
 tests/binder/Makefile       |   7 +
 tests/binder/check_binder.c |  80 +++++++
 tests/binder/test           | 131 +++++++++++
 tests/binder/test_binder.c  | 543 ++++++++++++++++++++++++++++++++++++++++++++
 9 files changed, 862 insertions(+), 2 deletions(-)
 create mode 100644 policy/test_binder.te
 create mode 100644 tests/binder/Makefile
 create mode 100644 tests/binder/check_binder.c
 create mode 100644 tests/binder/test
 create mode 100644 tests/binder/test_binder.c

diff --git a/README.md b/README.md
index c9f3b2b..60a249e 100644
--- a/README.md
+++ b/README.md
@@ -141,6 +141,14 @@ directory or you can follow these broken-out steps:
 The broken-out steps allow you to run the tests multiple times without
 loading policy each time.
 
+Note that if leaving the test policy in-place for further testing, the
+policy build process changes a boolean:
+   On policy load:   setsebool allow_domain_fd_use=0
+   On policy unload: setsebool allow_domain_fd_use=1
+The consequence of this is that after a system reboot, the boolean
+defaults to true. Therefore if running the fdreceive or binder tests,
+reset the boolean to false, otherwise some tests will fail.
+
 4) Review the test results.
 
 As each test script is run, the name of the script will be displayed followed
diff --git a/defconfig b/defconfig
index 7dce8bc..dc6ef30 100644
--- a/defconfig
+++ b/defconfig
@@ -51,3 +51,11 @@ CONFIG_CRYPTO_USER=m
 # This is enabled to test overlayfs SELinux integration.
 # It is not required for SELinux operation itself.
 CONFIG_OVERLAY_FS=m
+
+# Android binder implementations.
+# These are enabled to test the binder controls in
+# tests/binder; they are not required for SELinux operation itself.
+CONFIG_ANDROID=y
+CONFIG_ANDROID_BINDER_IPC=y
+CONFIG_ANDROID_BINDER_DEVICES="binder"
+# CONFIG_ANDROID_BINDER_IPC_SELFTEST is not set
diff --git a/policy/Makefile b/policy/Makefile
index 8ed5e46..5a9d411 100644
--- a/policy/Makefile
+++ b/policy/Makefile
@@ -25,7 +25,7 @@ TARGETS = \
 	test_task_getsid.te test_task_setpgid.te test_task_setsched.te \
 	test_transition.te test_inet_socket.te test_unix_socket.te \
 	test_mmap.te test_overlayfs.te test_mqueue.te test_mac_admin.te \
-	test_ibpkey.te test_atsecure.te
+	test_ibpkey.te test_atsecure.te test_binder.te
 
 ifeq ($(shell [ $(POL_VERS) -ge 24 ] && echo true),true)
 TARGETS += test_bounds.te
diff --git a/policy/test_binder.te b/policy/test_binder.te
new file mode 100644
index 0000000..c4ad2ae
--- /dev/null
+++ b/policy/test_binder.te
@@ -0,0 +1,83 @@
+
+attribute binderdomain;
+
+#
+################################## Manager ###################################
+#
+type test_binder_mgr_t;
+domain_type(test_binder_mgr_t)
+unconfined_runs_test(test_binder_mgr_t)
+typeattribute test_binder_mgr_t testdomain;
+typeattribute test_binder_mgr_t binderdomain;
+allow test_binder_mgr_t self:binder { set_context_mgr call };
+allow test_binder_mgr_t device_t:chr_file { ioctl open read write map };
+allow test_binder_mgr_t self:capability { sys_nice };
+allow test_binder_client_t test_binder_mgr_t:fd use;
+
+#
+################################# Client ####################################
+#
+type test_binder_client_t;
+domain_type(test_binder_client_t)
+unconfined_runs_test(test_binder_client_t)
+typeattribute test_binder_client_t testdomain;
+typeattribute test_binder_client_t binderdomain;
+allow test_binder_client_t self:binder { call };
+allow test_binder_client_t test_binder_mgr_t:binder { call transfer impersonate };
+allow test_binder_client_t device_t:chr_file { ioctl open read write map };
+# For fstat:
+allow test_binder_client_t device_t:chr_file getattr;
+
+#
+############################## Client no call ################################
+#
+type test_binder_client_no_call_t;
+domain_type(test_binder_client_no_call_t)
+unconfined_runs_test(test_binder_client_no_call_t)
+typeattribute test_binder_client_no_call_t testdomain;
+typeattribute test_binder_client_no_call_t binderdomain;
+allow test_binder_client_no_call_t device_t:chr_file { ioctl open read write map };
+
+#
+############################ Client no transfer #############################
+#
+type test_binder_client_no_transfer_t;
+domain_type(test_binder_client_no_transfer_t)
+unconfined_runs_test(test_binder_client_no_transfer_t)
+typeattribute test_binder_client_no_transfer_t testdomain;
+typeattribute test_binder_client_no_transfer_t binderdomain;
+allow test_binder_client_no_transfer_t test_binder_mgr_t:binder { call };
+allow test_binder_client_no_transfer_t device_t:chr_file { ioctl open read write map };
+
+#
+########################## Manager no fd {use} ###############################
+#
+type test_binder_mgr_no_fd_t;
+domain_type(test_binder_mgr_no_fd_t)
+unconfined_runs_test(test_binder_mgr_no_fd_t)
+typeattribute test_binder_mgr_no_fd_t testdomain;
+typeattribute test_binder_mgr_no_fd_t binderdomain;
+allow test_binder_mgr_no_fd_t self:binder { set_context_mgr call };
+allow test_binder_mgr_no_fd_t device_t:chr_file { ioctl open read write map };
+allow test_binder_mgr_no_fd_t self:capability { sys_nice };
+allow test_binder_client_t test_binder_mgr_no_fd_t:binder { call transfer };
+
+#
+########################### Client no impersonate ############################
+#
+type test_binder_client_no_im_t;
+domain_type(test_binder_client_no_im_t)
+unconfined_runs_test(test_binder_client_no_im_t)
+typeattribute test_binder_client_no_im_t testdomain;
+typeattribute test_binder_client_no_im_t binderdomain;
+allow test_binder_client_no_im_t self:binder { call };
+allow test_binder_client_no_im_t test_binder_mgr_t:binder { call transfer };
+allow test_binder_client_no_im_t device_t:chr_file { ioctl open read write map };
+allow test_binder_client_no_im_t test_binder_mgr_t:fd use;
+allow test_binder_client_no_im_t device_t:chr_file getattr;
+
+#
+############ Allow these domains to be entered from sysadm domain ############
+#
+miscfiles_domain_entry_test_files(binderdomain)
+userdom_sysadm_entry_spec_domtrans_to(binderdomain)
diff --git a/tests/Makefile b/tests/Makefile
index 27ed6eb..7607c22 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -10,7 +10,7 @@ SUBDIRS:= domain_trans entrypoint execshare exectrace execute_no_trans \
 	task_setnice task_setscheduler task_getscheduler task_getsid \
 	task_getpgid task_setpgid file ioctl capable_file capable_net \
 	capable_sys dyntrans dyntrace bounds nnp_nosuid mmap unix_socket \
-        inet_socket overlay checkreqprot mqueue mac_admin atsecure
+        inet_socket overlay checkreqprot mqueue mac_admin atsecure binder
 
 ifeq ($(shell grep -q cap_userns $(POLDEV)/include/support/all_perms.spt && echo true),true)
 ifneq ($(shell ./kvercmp $$(uname -r) 4.7),-1)
diff --git a/tests/binder/Makefile b/tests/binder/Makefile
new file mode 100644
index 0000000..a60eeb3
--- /dev/null
+++ b/tests/binder/Makefile
@@ -0,0 +1,7 @@
+TARGETS = check_binder test_binder
+
+LDLIBS += -lselinux
+
+all: $(TARGETS)
+clean:
+	rm -f $(TARGETS)
diff --git a/tests/binder/check_binder.c b/tests/binder/check_binder.c
new file mode 100644
index 0000000..3d553a0
--- /dev/null
+++ b/tests/binder/check_binder.c
@@ -0,0 +1,80 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+#include <linux/android/binder.h>
+
+static void usage(char *progname)
+{
+	fprintf(stderr,
+		"usage:  %s [-v]\n"
+		"Where:\n\t"
+		"-v Print binder version.\n", progname);
+	exit(-1);
+}
+
+int main(int argc, char **argv)
+{
+	int opt, result, fd;
+	char *driver = "/dev/binder";
+	bool verbose;
+	void *mapped;
+	size_t mapsize = 1024;
+	struct binder_version vers;
+
+	while ((opt = getopt(argc, argv, "v")) != -1) {
+		switch (opt) {
+		case 'v':
+			verbose = true;
+			break;
+		default:
+			usage(argv[0]);
+		}
+	}
+
+	fd = open(driver, O_RDWR | O_CLOEXEC);
+	if (fd < 0) {
+		fprintf(stderr, "Cannot open: %s error: %s\n",
+			driver, strerror(errno));
+		exit(-1);
+	}
+
+	/* Need this or no VMA error from kernel */
+	mapped = mmap(NULL, mapsize, PROT_READ, MAP_PRIVATE, fd, 0);
+	if (mapped == MAP_FAILED) {
+		fprintf(stderr, "mmap error: %s\n", strerror(errno));
+		close(fd);
+		exit(-1);
+	}
+
+	result = ioctl(fd, BINDER_VERSION, &vers);
+	if (result < 0) {
+		fprintf(stderr, "ioctl BINDER_VERSION: %s\n",
+			strerror(errno));
+		goto brexit;
+	}
+
+	if (vers.protocol_version != BINDER_CURRENT_PROTOCOL_VERSION) {
+		fprintf(stderr,
+			"Binder kernel version: %d differs from user space version: %d\n",
+			vers.protocol_version,
+			BINDER_CURRENT_PROTOCOL_VERSION);
+		result = -1;
+		goto brexit;
+	}
+
+	if (verbose)
+		fprintf(stderr, "Binder kernel version: %d\n",
+			vers.protocol_version);
+
+brexit:
+	munmap(mapped, mapsize);
+	close(fd);
+
+	return result;
+}
diff --git a/tests/binder/test b/tests/binder/test
new file mode 100644
index 0000000..434ae32
--- /dev/null
+++ b/tests/binder/test
@@ -0,0 +1,131 @@
+#!/usr/bin/perl
+use Test::More;
+
+BEGIN {
+    $basedir = $0;
+    $basedir =~ s|(.*)/[^/]*|$1|;
+
+    # allow binder info to be shown
+    $v = $ARGV[0];
+    if ($v) {
+        if ( $v ne "-v" ) {
+            plan skip_all => "Invalid option (use -v)";
+        }
+    }
+
+    # check if binder driver available and the kernel/userspace versions.
+    if ( system("$basedir/check_binder 2> /dev/null") != 0 ) {
+        plan skip_all =>
+          "Binder not supported or kernel/userspace versions differ";
+    }
+    else {
+        plan tests => 6;
+    }
+}
+
+if ($v) {
+    if ( ( $pid = fork() ) == 0 ) {
+        exec "runcon -t test_binder_mgr_t $basedir/test_binder -v manager";
+    }
+
+    select( undef, undef, undef, 0.25 );    # Give it a moment to initialize.
+
+    # Verify that authorized client can transact with the manager.
+    $result =
+      system "runcon -t test_binder_client_t $basedir/test_binder -v client";
+    ok( $result eq 0 );
+
+    # Verify that client cannot call manager (no call perm).
+    $result = system
+"runcon -t test_binder_client_no_call_t $basedir/test_binder -v client 2>&1";
+    ok( $result >> 8 eq 9 );
+
+    # Verify that client cannot communicate with manager (no impersonate perm).
+    $result = system
+"runcon -t test_binder_client_no_im_t $basedir/test_binder -v client 2>&1";
+    ok( $result >> 8 eq 102 );
+
+    # Verify that client cannot communicate with manager (no transfer perm).
+    $result = system
+"runcon -t test_binder_client_no_transfer_t $basedir/test_binder -v client 2>&1";
+    ok( $result >> 8 eq 9 );
+
+    # Kill the manager.
+    kill TERM, $pid;
+
+    # Verify that client cannot become a manager (no set_context_mgr perm).
+    $result =
+      system
+      "runcon -t test_binder_client_t $basedir/test_binder -v manager 2>&1";
+    ok( $result >> 8 eq 4 );
+
+# Start manager to test that selinux_binder_transfer_file() fails when fd { use } is denied by policy.
+    if ( ( $pid = fork() ) == 0 ) {
+        exec
+          "runcon -t test_binder_mgr_no_fd_t $basedir/test_binder -v manager";
+    }
+
+    select( undef, undef, undef, 0.25 );    # Give it a moment to initialize.
+
+# Verify that authorized client can communicate with the server, however the fd passed will not be valid for manager
+# domain and binder will return BR_FAILED_REPLY.
+    $result =
+      system
+      "runcon -t test_binder_client_t $basedir/test_binder -v client 2>&1";
+    ok( $result >> 8 eq 9 );
+
+    # Kill the manager
+    kill TERM, $pid;
+}
+else {
+    if ( ( $pid = fork() ) == 0 ) {
+        exec "runcon -t test_binder_mgr_t $basedir/test_binder manager";
+    }
+
+    select( undef, undef, undef, 0.25 );    # Give it a moment to initialize.
+
+    # Verify that authorized client can transact with the manager.
+    $result =
+      system "runcon -t test_binder_client_t $basedir/test_binder client";
+    ok( $result eq 0 );
+
+    # Verify that client cannot call manager (no call perm).
+    $result = system
+      "runcon -t test_binder_client_no_call_t $basedir/test_binder client 2>&1";
+    ok( $result >> 8 eq 9 );
+
+    # Verify that client cannot communicate with manager (no impersonate perm).
+    $result = system
+      "runcon -t test_binder_client_no_im_t $basedir/test_binder client 2>&1";
+    ok( $result >> 8 eq 102 );
+
+    # Verify that client cannot communicate with manager (no transfer perm).
+    $result = system
+"runcon -t test_binder_client_no_transfer_t $basedir/test_binder client 2>&1";
+    ok( $result >> 8 eq 9 );
+
+    # Kill the manager.
+    kill TERM, $pid;
+
+    # Verify that client cannot become a manager (no set_context_mgr perm).
+    $result =
+      system "runcon -t test_binder_client_t $basedir/test_binder manager 2>&1";
+    ok( $result >> 8 eq 4 );
+
+# Start manager to test that selinux_binder_transfer_file() fails when fd { use } is denied by policy.
+    if ( ( $pid = fork() ) == 0 ) {
+        exec "runcon -t test_binder_mgr_no_fd_t $basedir/test_binder manager";
+    }
+
+    select( undef, undef, undef, 0.25 );    # Give it a moment to initialize.
+
+# Verify that authorized client can communicate with the server, however the fd passed will not be valid for manager
+# domain and binder will return BR_FAILED_REPLY.
+    $result =
+      system "runcon -t test_binder_client_t $basedir/test_binder client 2>&1";
+    ok( $result >> 8 eq 9 );
+
+    # Kill the manager
+    kill TERM, $pid;
+}
+exit;
diff --git a/tests/binder/test_binder.c b/tests/binder/test_binder.c
new file mode 100644
index 0000000..8881cce
--- /dev/null
+++ b/tests/binder/test_binder.c
@@ -0,0 +1,543 @@
+/*
+ * This is a simple binder client/server(manager) that only uses the
+ * raw ioctl commands. It does not rely on a 'service manager' as in
+ * the Android world as it only uses one 'target' = 0.
+ *
+ * The transaction/reply flow is basically:
+ *      Client                                  Manager
+ *     ========                                =========
+ *
+ *                                        Becomes context manager
+ *   Send transaction
+ *   requesting file
+ *   descriptor from
+ *    the Manager
+ *         --------------------------------------->
+ *                                       Manager replies with its
+ *                                        binder file descriptor
+ *         <--------------------------------------
+ *     Check fd valid, if so send
+ *  TF_ONE_WAY transaction to Manager
+ *  using the received fd
+ *          --------------------------------------->
+ *                                        End of tests so Manager
+ *                                          waits to be killed
+ *   Client exits
+ *
+ * Using binder test policy the following will be validated:
+ *    security_binder_set_context_mgr() binder { set_context_mgr }
+ *    security_binder_transaction()     binder { call impersonate }
+ *    security_binder_transfer_binder() binder { transfer }
+ *    security_binder_transfer_file()   fd { use }
+ *
+ * TODO security_binder_transfer_file() uses BPF if configured in kernel.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <stdbool.h>
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+#include <selinux/selinux.h>
+#include <linux/android/binder.h>
+
+static uint32_t target; /* This will be set to '0' as only need one target */
+static bool verbose;
+
+static int binder_parse(int fd, uintptr_t ptr, size_t size, char *text);
+
+static void usage(char *progname)
+{
+	fprintf(stderr,
+		"usage:  %s [-v] manager | client\n"
+		"Where:\n\t"
+		"-v       Print context and command information.\n\t"
+		"manager  Act as binder context manager.\n\t"
+		"client   Act as binder client.\n"
+		"\nNote: Ensure this boolean command is run when "
+		"testing after a reboot:\n\t"
+		"setsebool allow_domain_fd_use=0\n", progname);
+	exit(1);
+}
+
+static const char *cmd_name(uint32_t cmd)
+{
+	switch (cmd) {
+	case BR_NOOP:
+		return "BR_NOOP";
+	case BR_TRANSACTION_COMPLETE:
+		return "BR_TRANSACTION_COMPLETE";
+	case BR_INCREFS:
+		return "BR_INCREFS";
+	case BR_ACQUIRE:
+		return "BR_ACQUIRE";
+	case BR_RELEASE:
+		return "BR_RELEASE";
+	case BR_DECREFS:
+		return "BR_DECREFS";
+	case BR_TRANSACTION:
+		return "BR_TRANSACTION";
+	case BR_REPLY:
+		return "BR_REPLY";
+	case BR_FAILED_REPLY:
+		return "BR_FAILED_REPLY";
+	case BR_DEAD_REPLY:
+		return "BR_DEAD_REPLY";
+	case BR_DEAD_BINDER:
+		return "BR_DEAD_BINDER";
+	case BR_ERROR:
+		return "BR_ERROR";
+	/* fallthrough */
+	default:
+		return "Unknown command";
+	}
+}
+
+void print_trans_data(struct binder_transaction_data *txn)
+{
+	printf("\thandle: %ld\n", (unsigned long)txn->target.handle);
+	printf("\tcookie: %lld\n", txn->cookie);
+	printf("\tcode: %u\n", txn->code);
+	switch (txn->flags) {
+	case TF_ONE_WAY:
+		printf("\tflag: TF_ONE_WAY\n");
+		break;
+	case TF_ROOT_OBJECT:
+		printf("\tflag: TF_ROOT_OBJECT\n");
+		break;
+	case TF_STATUS_CODE:
+		printf("\tflag: TF_STATUS_CODE\n");
+		break;
+	case TF_ACCEPT_FDS:
+		printf("\tflag: TF_ACCEPT_FDS\n");
+		break;
+	default:
+		printf("Unknown flag: %u\n", txn->flags);
+	}
+	printf("\tsender pid: %u\n", txn->sender_pid);
+	printf("\tsender euid: %u\n", txn->sender_euid);
+	printf("\tdata_size: %llu\n", txn->data_size);
+	printf("\toffsets_size: %llu\n", txn->offsets_size);
+}
+
+
+static int send_reply(int fd, struct binder_transaction_data *txn_in)
+{
+	int result;
+	unsigned int writebuf[1024];
+	struct flat_binder_object obj;
+	struct binder_write_read bwr;
+	struct binder_transaction_data *txn;
+
+	if (txn_in->flags == TF_ONE_WAY) {
+		if (verbose)
+			printf("No reply to BC_TRANSACTION as flags = TF_ONE_WAY\n");
+		return 0;
+	}
+
+	if (verbose)
+		printf("Sending BC_REPLY\n");
+
+	writebuf[0] = BC_REPLY;
+	txn = (struct binder_transaction_data *)(&writebuf[1]);
+
+	memset(txn, 0, sizeof(*txn));
+	txn->target.handle = txn_in->target.handle;
+	txn->cookie = txn_in->cookie;
+	txn->code = txn_in->code;
+	txn->flags = TF_ACCEPT_FDS;
+
+	memset(&obj, 0, sizeof(struct flat_binder_object));
+	obj.hdr.type = BINDER_TYPE_FD;
+	obj.flags = 0x7f | FLAT_BINDER_FLAG_ACCEPTS_FDS;
+	obj.binder = txn->target.handle;
+	obj.cookie = txn->cookie;
+	/* The binder fd is used for testing as it allows policy to set
+	 * whether the Client/Manager can be allowed access (fd use) or
+	 * not. For example test_binder_mgr_t has:
+	 *        allow test_binder_client_t test_binder_mgr_t:fd use;
+	 * whereas test_binder_mgr_no_fd_t does not allow this fd use.
+	 *
+	 * This also allows a check for the impersonate permission later as
+	 * the Client will use this (the Managers fd) to send a transaction.
+	 */
+	obj.handle = fd;
+
+	txn->data_size = sizeof(struct flat_binder_object);
+	txn->data.ptr.buffer = (uintptr_t)&obj;
+	txn->data.ptr.offsets = (uintptr_t)&obj +
+				sizeof(struct flat_binder_object);
+	txn->offsets_size = sizeof(binder_size_t);
+
+	memset(&bwr, 0, sizeof(bwr));
+	bwr.write_buffer = (unsigned long)writebuf;
+	bwr.write_size = sizeof(writebuf[0]) + sizeof(*txn);
+
+	result = ioctl(fd, BINDER_WRITE_READ, &bwr);
+	if (result < 0) {
+		fprintf(stderr, "%s ioctl BINDER_WRITE_READ: %s\n",
+			__func__, strerror(errno));
+		return -1;
+	}
+
+	return result;
+}
+
+/* This retrieves the requested Managers file descriptor, then using this
+ * sends a simple transaction to trigger the impersonate permission.
+ */
+static void extract_fd_and_respond(struct binder_transaction_data *txn_in)
+{
+	int result;
+	uint32_t cmd;
+	struct stat sb;
+	struct binder_write_read bwr;
+	struct flat_binder_object *obj;
+	struct binder_transaction_data *txn;
+	unsigned int readbuf[32];
+	unsigned int writebuf[1024];
+	binder_size_t *offs = (binder_size_t *)(uintptr_t)txn_in->data.ptr.offsets;
+
+	/* Get the fbo that contains the Managers binder file descriptor. */
+	obj = (struct flat_binder_object *)
+	      (((char *)(uintptr_t)txn_in->data.ptr.buffer) + *offs);
+
+	/* fstat this just to see if a valid fd */
+	result = fstat(obj->handle, &sb);
+	if (result < 0) {
+		fprintf(stderr, "Not a valid fd: %s\n", strerror(errno));
+		exit(100);
+	}
+
+	if (verbose)
+		printf("Retrieved Managers fd: %d st_dev: %ld\n",
+		       obj->handle, sb.st_dev);
+
+	/* Send response using Managers fd to trigger impersonate check. */
+	writebuf[0] = BC_TRANSACTION;
+	txn = (struct binder_transaction_data *)(&writebuf[1]);
+	memset(txn, 0, sizeof(*txn));
+	txn->target.handle = target;
+	txn->cookie = 0;
+	txn->code = 0;
+	txn->flags = TF_ONE_WAY;
+
+	txn->data_size = 0;
+	txn->data.ptr.buffer = (uintptr_t)NULL;
+	txn->data.ptr.offsets = (uintptr_t)NULL;
+	txn->offsets_size = 0;
+
+	memset(&bwr, 0, sizeof(bwr));
+	bwr.write_buffer = (unsigned long)writebuf;
+	bwr.write_size = sizeof(writebuf[0]) + sizeof(*txn);
+
+	bwr.read_size = sizeof(readbuf);
+	bwr.read_consumed = 0;
+	bwr.read_buffer = (uintptr_t)readbuf;
+
+	result = ioctl(obj->handle, BINDER_WRITE_READ, &bwr);
+	if (result < 0) {
+		fprintf(stderr,
+			"CLIENT ioctl BINDER_WRITE_READ: %s\n",
+			strerror(errno));
+		exit(101);
+	}
+
+	if (verbose)
+		printf("Client read_consumed: %lld\n", bwr.read_consumed);
+
+	cmd = binder_parse(obj->handle, (uintptr_t)readbuf,
+			   bwr.read_consumed,
+			   "Client using Managers FD");
+
+	if (cmd == BR_FAILED_REPLY ||
+	    cmd == BR_DEAD_REPLY ||
+	    cmd == BR_DEAD_BINDER) {
+		fprintf(stderr,
+			"Client using Managers received FD failed response\n");
+		exit(102);
+	}
+}
+
+/* Parse response, reply as required and then return last CMD */
+static int binder_parse(int fd, uintptr_t ptr, size_t size, char *text)
+{
+	uintptr_t end = ptr + (uintptr_t)size;
+	uint32_t cmd;
+
+	while (ptr < end) {
+		cmd = *(uint32_t *)ptr;
+		ptr += sizeof(uint32_t);
+
+		if (verbose)
+			printf("%s command: %s\n", text, cmd_name(cmd));
+
+		switch (cmd) {
+		case BR_NOOP:
+			break;
+		case BR_TRANSACTION_COMPLETE:
+			break;
+		case BR_INCREFS:
+		case BR_ACQUIRE:
+		case BR_RELEASE:
+		case BR_DECREFS:
+			ptr += sizeof(struct binder_ptr_cookie);
+			break;
+		case BR_TRANSACTION: {
+			struct binder_transaction_data *txn =
+				(struct binder_transaction_data *)ptr;
+
+			if (verbose) {
+				printf("BR_TRANSACTION data:\n");
+				print_trans_data(txn);
+			}
+
+			/* The manager sends reply that will contain its fd */
+			if (send_reply(fd, txn) < 0) {
+				fprintf(stderr, "send_reply() failed.\n");
+				return -1;
+			}
+			ptr += sizeof(*txn);
+			break;
+		}
+		case BR_REPLY: {
+			struct binder_transaction_data *txn =
+				(struct binder_transaction_data *)ptr;
+
+			if (verbose) {
+				printf("BR_REPLY data:\n");
+				print_trans_data(txn);
+			}
+
+			/* Client extracts the Manager fd, and responds */
+			extract_fd_and_respond(txn);
+			ptr += sizeof(*txn);
+			break;
+		}
+		case BR_DEAD_BINDER:
+			break;
+		case BR_FAILED_REPLY:
+			break;
+		case BR_DEAD_REPLY:
+			break;
+		case BR_ERROR:
+			ptr += sizeof(uint32_t);
+			break;
+		default:
+			if (verbose)
+				printf("%s Parsed unknown command: %d\n",
+				       text, cmd);
+			return -1;
+		}
+	}
+
+	return cmd;
+}
+
+int main(int argc, char **argv)
+{
+	int opt, option, result, fd, count;
+	uint32_t cmd;
+	pid_t pid;
+	char *driver = "/dev/binder";
+	char *context;
+	void *mapped;
+	size_t mapsize = 2048;
+	struct binder_write_read bwr;
+	struct flat_binder_object obj;
+	struct binder_transaction_data *txn;
+	unsigned int readbuf[32];
+	unsigned int writebuf[1024];
+
+	target = 0; /* Only need one target - the Manager */
+	verbose = false;
+
+	while ((opt = getopt(argc, argv, "v")) != -1) {
+		switch (opt) {
+		case 'v':
+			verbose = true;
+			break;
+		default:
+			usage(argv[0]);
+		}
+	}
+
+	if ((argc - optind) != 1)
+		usage(argv[0]);
+
+	if (!strcmp(argv[optind], "manager"))
+		option = 1;
+	else if (!strcmp(argv[optind], "client"))
+		option = 2;
+	else
+		usage(argv[0]);
+
+	fd = open(driver, O_RDWR | O_CLOEXEC);
+	if (fd < 0) {
+		fprintf(stderr, "Cannot open %s error: %s\n", driver,
+			strerror(errno));
+		exit(1);
+	}
+
+	/* Need this or "no VMA" error from kernel */
+	mapped = mmap(NULL, mapsize, PROT_READ, MAP_PRIVATE, fd, 0);
+	if (mapped == MAP_FAILED) {
+		fprintf(stderr, "mmap error: %s\n", strerror(errno));
+		close(fd);
+		exit(2);
+	}
+
+	/* Get our context and pid */
+	result = getcon(&context);
+	if (result < 0) {
+		fprintf(stderr, "Failed to obtain SELinux context\n");
+		result = 3;
+		goto brexit;
+	}
+	pid = getpid();
+
+	switch (option) {
+	case 1: /* manager */
+		if (verbose) {
+			printf("Manager PID: %d Process context:\n\t%s\n",
+			       pid, context);
+		}
+
+		result = ioctl(fd, BINDER_SET_CONTEXT_MGR, 0);
+		if (result < 0) {
+			fprintf(stderr,
+				"Failed to become context manager: %s\n",
+				strerror(errno));
+			result = 4;
+			goto brexit;
+		}
+
+		readbuf[0] = BC_ENTER_LOOPER;
+		bwr.write_size = sizeof(readbuf[0]);
+		bwr.write_consumed = 0;
+		bwr.write_buffer = (uintptr_t)readbuf;
+
+		bwr.read_size = 0;
+		bwr.read_consumed = 0;
+		bwr.read_buffer = 0;
+
+		result = ioctl(fd, BINDER_WRITE_READ, &bwr);
+		if (result < 0) {
+			fprintf(stderr,
+				"Manager ioctl BINDER_WRITE_READ: %s\n",
+				strerror(errno));
+			result = 5;
+			goto brexit;
+		}
+
+		while (true) {
+			bwr.read_size = sizeof(readbuf);
+			bwr.read_consumed = 0;
+			bwr.read_buffer = (uintptr_t)readbuf;
+
+			result = ioctl(fd, BINDER_WRITE_READ, &bwr);
+			if (result < 0) {
+				fprintf(stderr,
+					"Manager ioctl BINDER_WRITE_READ: %s\n",
+					strerror(errno));
+				result = 6;
+				goto brexit;
+			}
+
+			if (bwr.read_consumed == 0)
+				continue;
+
+			if (verbose)
+				printf("Manager read_consumed: %lld\n",
+				       bwr.read_consumed);
+
+			cmd = binder_parse(fd, (uintptr_t)readbuf,
+					   bwr.read_consumed, "Manager");
+		}
+		break;
+
+	case 2: /* client */
+		if (verbose) {
+			printf("Client PID: %d Process context:\n\t%s\n",
+			       pid, context);
+		}
+
+		writebuf[0] = BC_TRANSACTION;
+		txn = (struct binder_transaction_data *)(&writebuf[1]);
+		memset(txn, 0, sizeof(*txn));
+		txn->target.handle = target;
+		txn->cookie = 0;
+		txn->code = 0;
+		txn->flags = TF_ACCEPT_FDS;
+
+		memset(&obj, 0, sizeof(struct flat_binder_object));
+		obj.hdr.type = BINDER_TYPE_WEAK_BINDER;
+		obj.flags = 0x7f | FLAT_BINDER_FLAG_ACCEPTS_FDS;
+		obj.binder = target;
+		obj.handle = 0;
+		obj.cookie = 0;
+
+		txn->data_size = sizeof(struct flat_binder_object);
+		txn->data.ptr.buffer = (uintptr_t)&obj;
+		txn->data.ptr.offsets = (uintptr_t)&obj +
+					sizeof(struct flat_binder_object);
+		txn->offsets_size = sizeof(binder_size_t);
+
+		memset(&bwr, 0, sizeof(bwr));
+		bwr.write_buffer = (unsigned long)writebuf;
+		bwr.write_size = sizeof(writebuf[0]) + sizeof(*txn);
+
+		/* Expect client to get max two responses:
+		 *	1) From the above BC_TRANSACTION
+		 *	2) The responding BC_REPLY from send_reply()
+		 * unless an error.
+		 */
+		count = 0;
+		while (count != 2) {
+			bwr.read_size = sizeof(readbuf);
+			bwr.read_consumed = 0;
+			bwr.read_buffer = (uintptr_t)readbuf;
+
+			result = ioctl(fd, BINDER_WRITE_READ, &bwr);
+			if (result < 0) {
+				fprintf(stderr,
+					"Client ioctl BINDER_WRITE_READ: %s\n",
+					strerror(errno));
+				result = 8;
+				goto brexit;
+			}
+
+			if (verbose)
+				printf("Client read_consumed: %lld\n",
+				       bwr.read_consumed);
+
+			cmd = binder_parse(fd, (uintptr_t)readbuf,
+					   bwr.read_consumed, "Client");
+
+			if (cmd == BR_FAILED_REPLY ||
+			    cmd == BR_DEAD_REPLY ||
+			    cmd == BR_DEAD_BINDER) {
+				result = 9;
+				goto brexit;
+			}
+			count++;
+		}
+		break;
+
+	default:
+		result = -1;
+	}
+
+brexit:
+	free(context);
+	munmap(mapped, mapsize);
+	close(fd);
+
+	return result;
+}
-- 
2.14.3