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Diffstat (limited to 'sandbox-systrace.c')
| -rw-r--r-- | sandbox-systrace.c | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/sandbox-systrace.c b/sandbox-systrace.c new file mode 100644 index 0000000..e61d581 --- /dev/null +++ b/sandbox-systrace.c @@ -0,0 +1,218 @@ +/* $OpenBSD: sandbox-systrace.c,v 1.18 2015/10/02 01:39:26 deraadt Exp $ */ +/* + * Copyright (c) 2011 Damien Miller <djm@mindrot.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. + */ + +#include "includes.h" + +#ifdef SANDBOX_SYSTRACE + +#include <sys/types.h> +#include <sys/ioctl.h> +#include <sys/syscall.h> +#include <sys/socket.h> +#include <sys/wait.h> + +#include <dev/systrace.h> + +#include <errno.h> +#include <fcntl.h> +#include <limits.h> +#include <signal.h> +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#include "atomicio.h" +#include "log.h" +#include "ssh-sandbox.h" +#include "xmalloc.h" + +struct sandbox_policy { + int syscall; + int action; +}; + +/* Permitted syscalls in preauth. Unlisted syscalls get SYSTR_POLICY_KILL */ +static const struct sandbox_policy preauth_policy[] = { + { SYS_exit, SYSTR_POLICY_PERMIT }, +#ifdef SYS_kbind + { SYS_kbind, SYSTR_POLICY_PERMIT }, +#endif + + { SYS_getpid, SYSTR_POLICY_PERMIT }, + { SYS_getpgid, SYSTR_POLICY_PERMIT }, + { SYS_clock_gettime, SYSTR_POLICY_PERMIT }, + { SYS_gettimeofday, SYSTR_POLICY_PERMIT }, + { SYS_nanosleep, SYSTR_POLICY_PERMIT }, + { SYS_sigprocmask, SYSTR_POLICY_PERMIT }, + +#ifdef SYS_getentropy + /* OpenBSD 5.6 and newer use getentropy(2) to seed arc4random(3). */ + { SYS_getentropy, SYSTR_POLICY_PERMIT }, +#else + /* Previous releases used sysctl(3)'s kern.arnd variable. */ + { SYS___sysctl, SYSTR_POLICY_PERMIT }, +#endif +#ifdef SYS_sendsyslog + { SYS_sendsyslog, SYSTR_POLICY_PERMIT }, +#endif + + { SYS_madvise, SYSTR_POLICY_PERMIT }, + { SYS_mmap, SYSTR_POLICY_PERMIT }, + { SYS_mprotect, SYSTR_POLICY_PERMIT }, + { SYS_mquery, SYSTR_POLICY_PERMIT }, + { SYS_munmap, SYSTR_POLICY_PERMIT }, + + { SYS_poll, SYSTR_POLICY_PERMIT }, + { SYS_select, SYSTR_POLICY_PERMIT }, + { SYS_read, SYSTR_POLICY_PERMIT }, + { SYS_write, SYSTR_POLICY_PERMIT }, + { SYS_shutdown, SYSTR_POLICY_PERMIT }, + { SYS_close, SYSTR_POLICY_PERMIT }, + + { SYS_open, SYSTR_POLICY_NEVER }, + + { -1, -1 } +}; + +struct ssh_sandbox { + int systrace_fd; + pid_t child_pid; + void (*osigchld)(int); +}; + +struct ssh_sandbox * +ssh_sandbox_init(struct monitor *monitor) +{ + struct ssh_sandbox *box; + + debug3("%s: preparing systrace sandbox", __func__); + box = xcalloc(1, sizeof(*box)); + box->systrace_fd = -1; + box->child_pid = 0; + box->osigchld = ssh_signal(SIGCHLD, SIG_IGN); + + return box; +} + +void +ssh_sandbox_child(struct ssh_sandbox *box) +{ + debug3("%s: ready", __func__); + ssh_signal(SIGCHLD, box->osigchld); + if (kill(getpid(), SIGSTOP) != 0) + fatal("%s: kill(%d, SIGSTOP)", __func__, getpid()); + debug3("%s: started", __func__); +} + +static void +ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid, + const struct sandbox_policy *allowed_syscalls) +{ + int dev_systrace, i, j, found, status; + pid_t pid; + struct systrace_policy policy; + + /* Wait for the child to send itself a SIGSTOP */ + debug3("%s: wait for child %ld", __func__, (long)child_pid); + do { + pid = waitpid(child_pid, &status, WUNTRACED); + } while (pid == -1 && errno == EINTR); + ssh_signal(SIGCHLD, box->osigchld); + if (!WIFSTOPPED(status)) { + if (WIFSIGNALED(status)) + fatal("%s: child terminated with signal %d", + __func__, WTERMSIG(status)); + if (WIFEXITED(status)) + fatal("%s: child exited with status %d", + __func__, WEXITSTATUS(status)); + fatal("%s: child not stopped", __func__); + } + debug3("%s: child %ld stopped", __func__, (long)child_pid); + box->child_pid = child_pid; + + /* Set up systracing of child */ + if ((dev_systrace = open("/dev/systrace", O_RDONLY)) == -1) + fatal("%s: open(\"/dev/systrace\"): %s", __func__, + strerror(errno)); + if (ioctl(dev_systrace, STRIOCCLONE, &box->systrace_fd) == -1) + fatal("%s: ioctl(STRIOCCLONE, %d): %s", __func__, + dev_systrace, strerror(errno)); + close(dev_systrace); + debug3("%s: systrace attach, fd=%d", __func__, box->systrace_fd); + if (ioctl(box->systrace_fd, STRIOCATTACH, &child_pid) == -1) + fatal("%s: ioctl(%d, STRIOCATTACH, %d): %s", __func__, + box->systrace_fd, child_pid, strerror(errno)); + + /* Allocate and assign policy */ + memset(&policy, 0, sizeof(policy)); + policy.strp_op = SYSTR_POLICY_NEW; + policy.strp_maxents = SYS_MAXSYSCALL; + if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1) + fatal("%s: ioctl(%d, STRIOCPOLICY (new)): %s", __func__, + box->systrace_fd, strerror(errno)); + + policy.strp_op = SYSTR_POLICY_ASSIGN; + policy.strp_pid = box->child_pid; + if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1) + fatal("%s: ioctl(%d, STRIOCPOLICY (assign)): %s", + __func__, box->systrace_fd, strerror(errno)); + + /* Set per-syscall policy */ + for (i = 0; i < SYS_MAXSYSCALL; i++) { + found = 0; + for (j = 0; allowed_syscalls[j].syscall != -1; j++) { + if (allowed_syscalls[j].syscall == i) { + found = 1; + break; + } + } + policy.strp_op = SYSTR_POLICY_MODIFY; + policy.strp_code = i; + policy.strp_policy = found ? + allowed_syscalls[j].action : SYSTR_POLICY_KILL; + if (found) + debug3("%s: policy: enable syscall %d", __func__, i); + if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1) + fatal("%s: ioctl(%d, STRIOCPOLICY (modify)): %s", + __func__, box->systrace_fd, strerror(errno)); + } + + /* Signal the child to start running */ + debug3("%s: start child %ld", __func__, (long)child_pid); + if (kill(box->child_pid, SIGCONT) != 0) + fatal("%s: kill(%d, SIGCONT)", __func__, box->child_pid); +} + +void +ssh_sandbox_parent_finish(struct ssh_sandbox *box) +{ + /* Closing this before the child exits will terminate it */ + close(box->systrace_fd); + + free(box); + debug3("%s: finished", __func__); +} + +void +ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid) +{ + ssh_sandbox_parent(box, child_pid, preauth_policy); +} + +#endif /* SANDBOX_SYSTRACE */ |