Adding upstream version 1:8.4p1.upstream/1%8.4p1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 429 insertions, 0 deletions

diff --git a/sandbox-seccomp-filter.c b/sandbox-seccomp-filter.c
new file mode 100644
index 0000000..e0768c0
--- /dev/null
+++ b/sandbox-seccomp-filter.c
@@ -0,0 +1,429 @@
+/*
+ * Copyright (c) 2012 Will Drewry <wad@dataspill.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * Uncomment the SANDBOX_SECCOMP_FILTER_DEBUG macro below to help diagnose
+ * filter breakage during development. *Do not* use this in production,
+ * as it relies on making library calls that are unsafe in signal context.
+ *
+ * Instead, live systems the auditctl(8) may be used to monitor failures.
+ * E.g.
+ *   auditctl -a task,always -F uid=<privsep uid>
+ */
+/* #define SANDBOX_SECCOMP_FILTER_DEBUG 1 */
+
+/* XXX it should be possible to do logging via the log socket safely */
+
+#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
+/* Use the kernel headers in case of an older toolchain. */
+# include <asm/siginfo.h>
+# define __have_siginfo_t 1
+# define __have_sigval_t 1
+# define __have_sigevent_t 1
+#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */
+
+#include "includes.h"
+
+#ifdef SANDBOX_SECCOMP_FILTER
+
+#include <sys/types.h>
+#include <sys/resource.h>
+#include <sys/prctl.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+
+#include <linux/net.h>
+#include <linux/audit.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <elf.h>
+
+#include <asm/unistd.h>
+#ifdef __s390__
+#include <asm/zcrypt.h>
+#endif
+
+#include <errno.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <stddef.h>  /* for offsetof */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "log.h"
+#include "ssh-sandbox.h"
+#include "xmalloc.h"
+
+/* Linux seccomp_filter sandbox */
+#define SECCOMP_FILTER_FAIL SECCOMP_RET_KILL
+
+/* Use a signal handler to emit violations when debugging */
+#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
+# undef SECCOMP_FILTER_FAIL
+# define SECCOMP_FILTER_FAIL SECCOMP_RET_TRAP
+#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+# define ARG_LO_OFFSET  0
+# define ARG_HI_OFFSET  sizeof(uint32_t)
+#elif __BYTE_ORDER == __BIG_ENDIAN
+# define ARG_LO_OFFSET  sizeof(uint32_t)
+# define ARG_HI_OFFSET  0
+#else
+#error "Unknown endianness"
+#endif
+
+/* Simple helpers to avoid manual errors (but larger BPF programs). */
+#define SC_DENY(_nr, _errno) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 1), \
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ERRNO|(_errno))
+#define SC_ALLOW(_nr) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 1), \
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
+#define SC_ALLOW_ARG(_nr, _arg_nr, _arg_val) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 6), \
+	/* load and test syscall argument, low word */ \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+	    offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_LO_OFFSET), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \
+	    ((_arg_val) & 0xFFFFFFFF), 0, 3), \
+	/* load and test syscall argument, high word */ \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+	    offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_HI_OFFSET), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \
+	    (((uint32_t)((uint64_t)(_arg_val) >> 32)) & 0xFFFFFFFF), 0, 1), \
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \
+	/* reload syscall number; all rules expect it in accumulator */ \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+		offsetof(struct seccomp_data, nr))
+/* Allow if syscall argument contains only values in mask */
+#define SC_ALLOW_ARG_MASK(_nr, _arg_nr, _arg_mask) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 8), \
+	/* load, mask and test syscall argument, low word */ \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+	    offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_LO_OFFSET), \
+	BPF_STMT(BPF_ALU+BPF_AND+BPF_K, ~((_arg_mask) & 0xFFFFFFFF)), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 4), \
+	/* load, mask and test syscall argument, high word */ \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+	    offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_HI_OFFSET), \
+	BPF_STMT(BPF_ALU+BPF_AND+BPF_K, \
+	    ~(((uint32_t)((uint64_t)(_arg_mask) >> 32)) & 0xFFFFFFFF)), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 1), \
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \
+	/* reload syscall number; all rules expect it in accumulator */ \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+		offsetof(struct seccomp_data, nr))
+
+/* Syscall filtering set for preauth. */
+static const struct sock_filter preauth_insns[] = {
+	/* Ensure the syscall arch convention is as expected. */
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
+		offsetof(struct seccomp_data, arch)),
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, SECCOMP_AUDIT_ARCH, 1, 0),
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),
+	/* Load the syscall number for checking. */
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
+		offsetof(struct seccomp_data, nr)),
+
+	/* Syscalls to non-fatally deny */
+#ifdef __NR_lstat
+	SC_DENY(__NR_lstat, EACCES),
+#endif
+#ifdef __NR_lstat64
+	SC_DENY(__NR_lstat64, EACCES),
+#endif
+#ifdef __NR_fstat
+	SC_DENY(__NR_fstat, EACCES),
+#endif
+#ifdef __NR_fstat64
+	SC_DENY(__NR_fstat64, EACCES),
+#endif
+#ifdef __NR_open
+	SC_DENY(__NR_open, EACCES),
+#endif
+#ifdef __NR_openat
+	SC_DENY(__NR_openat, EACCES),
+#endif
+#ifdef __NR_newfstatat
+	SC_DENY(__NR_newfstatat, EACCES),
+#endif
+#ifdef __NR_stat
+	SC_DENY(__NR_stat, EACCES),
+#endif
+#ifdef __NR_stat64
+	SC_DENY(__NR_stat64, EACCES),
+#endif
+#ifdef __NR_shmget
+	SC_DENY(__NR_shmget, EACCES),
+#endif
+#ifdef __NR_shmat
+	SC_DENY(__NR_shmat, EACCES),
+#endif
+#ifdef __NR_shmdt
+	SC_DENY(__NR_shmdt, EACCES),
+#endif
+#ifdef __NR_ipc
+	SC_DENY(__NR_ipc, EACCES),
+#endif
+
+	/* Syscalls to permit */
+#ifdef __NR_brk
+	SC_ALLOW(__NR_brk),
+#endif
+#ifdef __NR_clock_gettime
+	SC_ALLOW(__NR_clock_gettime),
+#endif
+#ifdef __NR_clock_gettime64
+	SC_ALLOW(__NR_clock_gettime64),
+#endif
+#ifdef __NR_close
+	SC_ALLOW(__NR_close),
+#endif
+#ifdef __NR_exit
+	SC_ALLOW(__NR_exit),
+#endif
+#ifdef __NR_exit_group
+	SC_ALLOW(__NR_exit_group),
+#endif
+#ifdef __NR_futex
+	SC_ALLOW(__NR_futex),
+#endif
+#ifdef __NR_geteuid
+	SC_ALLOW(__NR_geteuid),
+#endif
+#ifdef __NR_geteuid32
+	SC_ALLOW(__NR_geteuid32),
+#endif
+#ifdef __NR_getpgid
+	SC_ALLOW(__NR_getpgid),
+#endif
+#ifdef __NR_getpid
+	SC_ALLOW(__NR_getpid),
+#endif
+#ifdef __NR_getrandom
+	SC_ALLOW(__NR_getrandom),
+#endif
+#ifdef __NR_gettimeofday
+	SC_ALLOW(__NR_gettimeofday),
+#endif
+#ifdef __NR_getuid
+	SC_ALLOW(__NR_getuid),
+#endif
+#ifdef __NR_getuid32
+	SC_ALLOW(__NR_getuid32),
+#endif
+#ifdef __NR_madvise
+	SC_ALLOW(__NR_madvise),
+#endif
+#ifdef __NR_mmap
+	SC_ALLOW_ARG_MASK(__NR_mmap, 2, PROT_READ|PROT_WRITE|PROT_NONE),
+#endif
+#ifdef __NR_mmap2
+	SC_ALLOW_ARG_MASK(__NR_mmap2, 2, PROT_READ|PROT_WRITE|PROT_NONE),
+#endif
+#ifdef __NR_mprotect
+	SC_ALLOW_ARG_MASK(__NR_mprotect, 2, PROT_READ|PROT_WRITE|PROT_NONE),
+#endif
+#ifdef __NR_mremap
+	SC_ALLOW(__NR_mremap),
+#endif
+#ifdef __NR_munmap
+	SC_ALLOW(__NR_munmap),
+#endif
+#ifdef __NR_nanosleep
+	SC_ALLOW(__NR_nanosleep),
+#endif
+#ifdef __NR_clock_nanosleep
+	SC_ALLOW(__NR_clock_nanosleep),
+#endif
+#ifdef __NR_clock_nanosleep_time64
+	SC_ALLOW(__NR_clock_nanosleep_time64),
+#endif
+#ifdef __NR_clock_gettime64
+	SC_ALLOW(__NR_clock_gettime64),
+#endif
+#ifdef __NR__newselect
+	SC_ALLOW(__NR__newselect),
+#endif
+#ifdef __NR_poll
+	SC_ALLOW(__NR_poll),
+#endif
+#ifdef __NR_pselect6
+	SC_ALLOW(__NR_pselect6),
+#endif
+#ifdef __NR_read
+	SC_ALLOW(__NR_read),
+#endif
+#ifdef __NR_rt_sigprocmask
+	SC_ALLOW(__NR_rt_sigprocmask),
+#endif
+#ifdef __NR_select
+	SC_ALLOW(__NR_select),
+#endif
+#ifdef __NR_shutdown
+	SC_ALLOW(__NR_shutdown),
+#endif
+#ifdef __NR_sigprocmask
+	SC_ALLOW(__NR_sigprocmask),
+#endif
+#ifdef __NR_time
+	SC_ALLOW(__NR_time),
+#endif
+#ifdef __NR_write
+	SC_ALLOW(__NR_write),
+#endif
+#ifdef __NR_socketcall
+	SC_ALLOW_ARG(__NR_socketcall, 0, SYS_SHUTDOWN),
+	SC_DENY(__NR_socketcall, EACCES),
+#endif
+#if defined(__NR_ioctl) && defined(__s390__)
+	/* Allow ioctls for ICA crypto card on s390 */
+	SC_ALLOW_ARG(__NR_ioctl, 1, Z90STAT_STATUS_MASK),
+	SC_ALLOW_ARG(__NR_ioctl, 1, ICARSAMODEXPO),
+	SC_ALLOW_ARG(__NR_ioctl, 1, ICARSACRT),
+	SC_ALLOW_ARG(__NR_ioctl, 1, ZSECSENDCPRB),
+	/* Allow ioctls for EP11 crypto card on s390 */
+	SC_ALLOW_ARG(__NR_ioctl, 1, ZSENDEP11CPRB),
+#endif
+#if defined(__x86_64__) && defined(__ILP32__) && defined(__X32_SYSCALL_BIT)
+	/*
+	 * On Linux x32, the clock_gettime VDSO falls back to the
+	 * x86-64 syscall under some circumstances, e.g.
+	 * https://bugs.debian.org/849923
+	 */
+	SC_ALLOW(__NR_clock_gettime & ~__X32_SYSCALL_BIT),
+#endif
+
+	/* Default deny */
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),
+};
+
+static const struct sock_fprog preauth_program = {
+	.len = (unsigned short)(sizeof(preauth_insns)/sizeof(preauth_insns[0])),
+	.filter = (struct sock_filter *)preauth_insns,
+};
+
+struct ssh_sandbox {
+	pid_t child_pid;
+};
+
+struct ssh_sandbox *
+ssh_sandbox_init(struct monitor *monitor)
+{
+	struct ssh_sandbox *box;
+
+	/*
+	 * Strictly, we don't need to maintain any state here but we need
+	 * to return non-NULL to satisfy the API.
+	 */
+	debug3("%s: preparing seccomp filter sandbox", __func__);
+	box = xcalloc(1, sizeof(*box));
+	box->child_pid = 0;
+
+	return box;
+}
+
+#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
+extern struct monitor *pmonitor;
+void mm_log_handler(LogLevel level, const char *msg, void *ctx);
+
+static void
+ssh_sandbox_violation(int signum, siginfo_t *info, void *void_context)
+{
+	char msg[256];
+
+	snprintf(msg, sizeof(msg),
+	    "%s: unexpected system call (arch:0x%x,syscall:%d @ %p)",
+	    __func__, info->si_arch, info->si_syscall, info->si_call_addr);
+	mm_log_handler(SYSLOG_LEVEL_FATAL, msg, pmonitor);
+	_exit(1);
+}
+
+static void
+ssh_sandbox_child_debugging(void)
+{
+	struct sigaction act;
+	sigset_t mask;
+
+	debug3("%s: installing SIGSYS handler", __func__);
+	memset(&act, 0, sizeof(act));
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGSYS);
+
+	act.sa_sigaction = &ssh_sandbox_violation;
+	act.sa_flags = SA_SIGINFO;
+	if (sigaction(SIGSYS, &act, NULL) == -1)
+		fatal("%s: sigaction(SIGSYS): %s", __func__, strerror(errno));
+	if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
+		fatal("%s: sigprocmask(SIGSYS): %s",
+		      __func__, strerror(errno));
+}
+#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */
+
+void
+ssh_sandbox_child(struct ssh_sandbox *box)
+{
+	struct rlimit rl_zero;
+	int nnp_failed = 0;
+
+	/* Set rlimits for completeness if possible. */
+	rl_zero.rlim_cur = rl_zero.rlim_max = 0;
+	if (setrlimit(RLIMIT_FSIZE, &rl_zero) == -1)
+		fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s",
+			__func__, strerror(errno));
+	if (setrlimit(RLIMIT_NOFILE, &rl_zero) == -1)
+		fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s",
+			__func__, strerror(errno));
+	if (setrlimit(RLIMIT_NPROC, &rl_zero) == -1)
+		fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s",
+			__func__, strerror(errno));
+
+#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
+	ssh_sandbox_child_debugging();
+#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */
+
+	debug3("%s: setting PR_SET_NO_NEW_PRIVS", __func__);
+	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) {
+		debug("%s: prctl(PR_SET_NO_NEW_PRIVS): %s",
+		      __func__, strerror(errno));
+		nnp_failed = 1;
+	}
+	debug3("%s: attaching seccomp filter program", __func__);
+	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &preauth_program) == -1)
+		debug("%s: prctl(PR_SET_SECCOMP): %s",
+		      __func__, strerror(errno));
+	else if (nnp_failed)
+		fatal("%s: SECCOMP_MODE_FILTER activated but "
+		    "PR_SET_NO_NEW_PRIVS failed", __func__);
+}
+
+void
+ssh_sandbox_parent_finish(struct ssh_sandbox *box)
+{
+	free(box);
+	debug3("%s: finished", __func__);
+}
+
+void
+ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
+{
+	box->child_pid = child_pid;
+}
+
+#endif /* SANDBOX_SECCOMP_FILTER */