[GitHub/mt8127/android_kernel_alcatel_ttab.git] / samples / seccomp / bpf-direct.c

/*
 * Seccomp filter example for x86 (32-bit and 64-bit) with BPF macros
 *
 * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
 * Author: Will Drewry <wad@chromium.org>
 *
 * The code may be used by anyone for any purpose,
 * and can serve as a starting point for developing
 * applications using prctl(PR_SET_SECCOMP, 2, ...).
 */
#if defined(__i386__) || defined(__x86_64__)
#define SUPPORTED_ARCH 1
#endif

#if defined(SUPPORTED_ARCH)
#define __USE_GNU 1
#define _GNU_SOURCE 1

#include <linux/types.h>
#include <linux/filter.h>
#include <linux/seccomp.h>
#include <linux/unistd.h>
#include <signal.h>
#include <stdio.h>
#include <stddef.h>
#include <string.h>
#include <sys/prctl.h>
#include <unistd.h>

#define syscall_arg(_n) (offsetof(struct seccomp_data, args[_n]))
#define syscall_nr (offsetof(struct seccomp_data, nr))

#if defined(__i386__)
#define REG_RESULT	REG_EAX
#define REG_SYSCALL	REG_EAX
#define REG_ARG0	REG_EBX
#define REG_ARG1	REG_ECX
#define REG_ARG2	REG_EDX
#define REG_ARG3	REG_ESI
#define REG_ARG4	REG_EDI
#define REG_ARG5	REG_EBP
#elif defined(__x86_64__)
#define REG_RESULT	REG_RAX
#define REG_SYSCALL	REG_RAX
#define REG_ARG0	REG_RDI
#define REG_ARG1	REG_RSI
#define REG_ARG2	REG_RDX
#define REG_ARG3	REG_R10
#define REG_ARG4	REG_R8
#define REG_ARG5	REG_R9
#endif

#ifndef PR_SET_NO_NEW_PRIVS
#define PR_SET_NO_NEW_PRIVS 38
#endif

#ifndef SYS_SECCOMP
#define SYS_SECCOMP 1
#endif

static void emulator(int nr, siginfo_t *info, void *void_context)
{
	ucontext_t *ctx = (ucontext_t *)(void_context);
	int syscall;
	char *buf;
	ssize_t bytes;
	size_t len;
	if (info->si_code != SYS_SECCOMP)
		return;
	if (!ctx)
		return;
	syscall = ctx->uc_mcontext.gregs[REG_SYSCALL];
	buf = (char *) ctx->uc_mcontext.gregs[REG_ARG1];
	len = (size_t) ctx->uc_mcontext.gregs[REG_ARG2];

	if (syscall != __NR_write)
		return;
	if (ctx->uc_mcontext.gregs[REG_ARG0] != STDERR_FILENO)
		return;
	/* Redirect stderr messages to stdout. Doesn't handle EINTR, etc */
	ctx->uc_mcontext.gregs[REG_RESULT] = -1;
	if (write(STDOUT_FILENO, "[ERR] ", 6) > 0) {
		bytes = write(STDOUT_FILENO, buf, len);
		ctx->uc_mcontext.gregs[REG_RESULT] = bytes;
	}
	return;
}

static int install_emulator(void)
{
	struct sigaction act;
	sigset_t mask;
	memset(&act, 0, sizeof(act));
	sigemptyset(&mask);
	sigaddset(&mask, SIGSYS);

	act.sa_sigaction = &emulator;
	act.sa_flags = SA_SIGINFO;
	if (sigaction(SIGSYS, &act, NULL) < 0) {
		perror("sigaction");
		return -1;
	}
	if (sigprocmask(SIG_UNBLOCK, &mask, NULL)) {
		perror("sigprocmask");
		return -1;
	}
	return 0;
}

static int install_filter(void)
{
	struct sock_filter filter[] = {
		/* Grab the system call number */
		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_nr),
		/* Jump table for the allowed syscalls */
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_rt_sigreturn, 0, 1),
		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
#ifdef __NR_sigreturn
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_sigreturn, 0, 1),
		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
#endif
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit_group, 0, 1),
		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit, 0, 1),
		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_read, 1, 0),
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_write, 3, 2),

		/* Check that read is only using stdin. */
		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDIN_FILENO, 4, 0),
		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),

		/* Check that write is only using stdout */
		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDOUT_FILENO, 1, 0),
		/* Trap attempts to write to stderr */
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDERR_FILENO, 1, 2),

		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_TRAP),
		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),
	};
	struct sock_fprog prog = {
		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
		.filter = filter,
	};

	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
		perror("prctl(NO_NEW_PRIVS)");
		return 1;
	}


	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
		perror("prctl");
		return 1;
	}
	return 0;
}

#define payload(_c) (_c), sizeof((_c))
int main(int argc, char **argv)
{
	char buf[4096];
	ssize_t bytes = 0;
	if (install_emulator())
		return 1;
	if (install_filter())
		return 1;
	syscall(__NR_write, STDOUT_FILENO,
		payload("OHAI! WHAT IS YOUR NAME? "));
	bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf));
	syscall(__NR_write, STDOUT_FILENO, payload("HELLO, "));
	syscall(__NR_write, STDOUT_FILENO, buf, bytes);
	syscall(__NR_write, STDERR_FILENO,
		payload("Error message going to STDERR\n"));
	return 0;
}
#else	/* SUPPORTED_ARCH */
/*
 * This sample is x86-only.  Since kernel samples are compiled with the
 * host toolchain, a non-x86 host will result in using only the main()
 * below.
 */
int main(void)
{
	return 1;
}
#endif	/* SUPPORTED_ARCH */
Commit	Line	Data
8ac270d1 WD	1	/*
	2	* Seccomp filter example for x86 (32-bit and 64-bit) with BPF macros
	3	*
	4	* Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
	5	* Author: Will Drewry <wad@chromium.org>
	6	*
	7	* The code may be used by anyone for any purpose,
	8	* and can serve as a starting point for developing
	9	* applications using prctl(PR_SET_SECCOMP, 2, ...).
	10	*/
561381a1 WD	11	#if defined(__i386__) \|\| defined(__x86_64__)
	12	#define SUPPORTED_ARCH 1
	13	#endif
	14
	15	#if defined(SUPPORTED_ARCH)
8ac270d1 WD	16	#define __USE_GNU 1
	17	#define _GNU_SOURCE 1
	18
	19	#include <linux/types.h>
	20	#include <linux/filter.h>
	21	#include <linux/seccomp.h>
	22	#include <linux/unistd.h>
	23	#include <signal.h>
	24	#include <stdio.h>
	25	#include <stddef.h>
	26	#include <string.h>
	27	#include <sys/prctl.h>
	28	#include <unistd.h>
	29
	30	#define syscall_arg(_n) (offsetof(struct seccomp_data, args[_n]))
	31	#define syscall_nr (offsetof(struct seccomp_data, nr))
	32
	33	#if defined(__i386__)
	34	#define REG_RESULT REG_EAX
	35	#define REG_SYSCALL REG_EAX
	36	#define REG_ARG0 REG_EBX
	37	#define REG_ARG1 REG_ECX
	38	#define REG_ARG2 REG_EDX
	39	#define REG_ARG3 REG_ESI
	40	#define REG_ARG4 REG_EDI
	41	#define REG_ARG5 REG_EBP
	42	#elif defined(__x86_64__)
	43	#define REG_RESULT REG_RAX
	44	#define REG_SYSCALL REG_RAX
	45	#define REG_ARG0 REG_RDI
	46	#define REG_ARG1 REG_RSI
	47	#define REG_ARG2 REG_RDX
	48	#define REG_ARG3 REG_R10
	49	#define REG_ARG4 REG_R8
	50	#define REG_ARG5 REG_R9
8ac270d1 WD	51	#endif
	52
	53	#ifndef PR_SET_NO_NEW_PRIVS
	54	#define PR_SET_NO_NEW_PRIVS 38
	55	#endif
	56
	57	#ifndef SYS_SECCOMP
	58	#define SYS_SECCOMP 1
	59	#endif
	60
	61	static void emulator(int nr, siginfo_t info, void void_context)
	62	{
	63	ucontext_t ctx = (ucontext_t )(void_context);
	64	int syscall;
	65	char *buf;
	66	ssize_t bytes;
	67	size_t len;
	68	if (info->si_code != SYS_SECCOMP)
	69	return;
	70	if (!ctx)
	71	return;
	72	syscall = ctx->uc_mcontext.gregs[REG_SYSCALL];
	73	buf = (char *) ctx->uc_mcontext.gregs[REG_ARG1];
	74	len = (size_t) ctx->uc_mcontext.gregs[REG_ARG2];
	75
	76	if (syscall != __NR_write)
	77	return;
	78	if (ctx->uc_mcontext.gregs[REG_ARG0] != STDERR_FILENO)
	79	return;
	80	/* Redirect stderr messages to stdout. Doesn't handle EINTR, etc */
	81	ctx->uc_mcontext.gregs[REG_RESULT] = -1;
	82	if (write(STDOUT_FILENO, "[ERR] ", 6) > 0) {
	83	bytes = write(STDOUT_FILENO, buf, len);
	84	ctx->uc_mcontext.gregs[REG_RESULT] = bytes;
	85	}
	86	return;
	87	}
	88
	89	static int install_emulator(void)
	90	{
	91	struct sigaction act;
	92	sigset_t mask;
	93	memset(&act, 0, sizeof(act));
	94	sigemptyset(&mask);
	95	sigaddset(&mask, SIGSYS);
	96
	97	act.sa_sigaction = &emulator;
	98	act.sa_flags = SA_SIGINFO;
	99	if (sigaction(SIGSYS, &act, NULL) < 0) {
	100	perror("sigaction");
	101	return -1;
	102	}
	103	if (sigprocmask(SIG_UNBLOCK, &mask, NULL)) {
	104	perror("sigprocmask");
	105	return -1;
	106	}
	107	return 0;
	108	}
	109
	110	static int install_filter(void)
	111	{
	112	struct sock_filter filter[] = {
	113	/* Grab the system call number */
	114	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_nr),
115	/* Jump table for the allowed syscalls */
116	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_rt_sigreturn, 0, 1),
117	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
118	#ifdef __NR_sigreturn
119	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_sigreturn, 0, 1),
120	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
121	#endif
122	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit_group, 0, 1),
123	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
124	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit, 0, 1),
125	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
126	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_read, 1, 0),
127	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_write, 3, 2),
128
129	/* Check that read is only using stdin. */
130	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
131	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDIN_FILENO, 4, 0),
132	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),
133
134	/* Check that write is only using stdout */
135	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
136	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDOUT_FILENO, 1, 0),
137	/* Trap attempts to write to stderr */
138	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDERR_FILENO, 1, 2),
139
140	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
141	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_TRAP),
142	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),
143	};
144	struct sock_fprog prog = {
145	.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
146	.filter = filter,
147	};
148
149	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
150	perror("prctl(NO_NEW_PRIVS)");
151	return 1;
152	}
153
154
155	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
156	perror("prctl");
157	return 1;
158	}
159	return 0;
160	}
161
162	#define payload(_c) (_c), sizeof((_c))
163	int main(int argc, char **argv)
164	{
165	char buf[4096];
166	ssize_t bytes = 0;
167	if (install_emulator())
168	return 1;
169	if (install_filter())
170	return 1;
171	syscall(__NR_write, STDOUT_FILENO,
172	payload("OHAI! WHAT IS YOUR NAME? "));
173	bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf));
174	syscall(__NR_write, STDOUT_FILENO, payload("HELLO, "));
175	syscall(__NR_write, STDOUT_FILENO, buf, bytes);
176	syscall(__NR_write, STDERR_FILENO,
177	payload("Error message going to STDERR\n"));
178	return 0;
179	}
561381a1 WD	180	#else /* SUPPORTED_ARCH */
	181	/*
	182	* This sample is x86-only. Since kernel samples are compiled with the
	183	* host toolchain, a non-x86 host will result in using only the main()
	184	* below.
	185	*/
	186	int main(void)
	187	{
	188	return 1;
	189	}
	190	#endif /* SUPPORTED_ARCH */