X-Git-Url: http://mj.ucw.cz/gitweb/?a=blobdiff_plain;ds=sidebyside;f=box%2Fbox.c;h=7fe08a7398d652ecde081561d78d82b1de06dddc;hb=1636b318830d64ec5c393d1a2d043f595f0342c4;hp=b4f47ef05300c96b0c7aba4ca2555ceb93475cb0;hpb=7e45f095c27e00114e57d97ea1b70a5900dd65af;p=eval.git diff --git a/box/box.c b/box/box.c index b4f47ef..7fe08a7 100644 --- a/box/box.c +++ b/box/box.c @@ -1,18 +1,21 @@ /* - * A Simple Sandbox for MO-Eval + * A Simple Sandbox for Moe * - * (c) 2001--2008 Martin Mares + * (c) 2001--2010 Martin Mares */ #define _LARGEFILE64_SOURCE #define _GNU_SOURCE +#include "autoconf.h" + #include #include #include #include #include #include +#include #include #include #include @@ -22,10 +25,18 @@ #include #include #include -#include #include +#include #include +#if defined(CONFIG_BOX_KERNEL_AMD64) && !defined(CONFIG_BOX_USER_AMD64) +#include +#define NATIVE_NR_execve 59 /* 64-bit execve */ +#else +#include +#define NATIVE_NR_execve __NR_execve +#endif + #define NONRET __attribute__((noreturn)) #define UNUSED __attribute__((unused)) #define ARRAY_SIZE(a) (int)(sizeof(a)/sizeof(a[0])) @@ -231,16 +242,18 @@ static unsigned char syscall_action[NUM_ACTIONS] = { S(open) = A_FILENAME, S(creat) = A_FILENAME, S(unlink) = A_FILENAME, - S(oldstat) = A_FILENAME, S(access) = A_FILENAME, - S(oldlstat) = A_FILENAME, S(truncate) = A_FILENAME, S(stat) = A_FILENAME, S(lstat) = A_FILENAME, + S(readlink) = A_FILENAME, +#ifndef CONFIG_BOX_USER_AMD64 + S(oldstat) = A_FILENAME, + S(oldlstat) = A_FILENAME, S(truncate64) = A_FILENAME, S(stat64) = A_FILENAME, S(lstat64) = A_FILENAME, - S(readlink) = A_FILENAME, +#endif // Syscalls permitted always S(exit) = A_YES | A_SAMPLE_MEM, @@ -250,7 +263,6 @@ static unsigned char syscall_action[NUM_ACTIONS] = { S(lseek) = A_YES, S(getpid) = A_YES, S(getuid) = A_YES, - S(oldfstat) = A_YES, S(dup) = A_YES, S(brk) = A_YES, S(getgid) = A_YES, @@ -260,7 +272,6 @@ static unsigned char syscall_action[NUM_ACTIONS] = { S(ftruncate) = A_YES, S(fstat) = A_YES, S(personality) = A_YES, - S(_llseek) = A_YES, S(readv) = A_YES, S(writev) = A_YES, S(getresuid) = A_YES, @@ -271,12 +282,8 @@ static unsigned char syscall_action[NUM_ACTIONS] = { S(pread) = A_YES, S(pwrite) = A_YES, #endif - S(ftruncate64) = A_YES, - S(fstat64) = A_YES, S(fcntl) = A_YES, - S(fcntl64) = A_YES, S(mmap) = A_YES, - S(mmap2) = A_YES, S(munmap) = A_YES, S(ioctl) = A_YES, S(uname) = A_YES, @@ -285,32 +292,31 @@ static unsigned char syscall_action[NUM_ACTIONS] = { S(get_thread_area) = A_YES, S(set_tid_address) = A_YES, S(exit_group) = A_YES | A_SAMPLE_MEM, +#ifdef CONFIG_BOX_USER_AMD64 + S(arch_prctl) = A_YES, +#else + S(oldfstat) = A_YES, + S(ftruncate64) = A_YES, + S(_llseek) = A_YES, + S(fstat64) = A_YES, + S(fcntl64) = A_YES, + S(mmap2) = A_YES, +#endif // Syscalls permitted only in liberal mode S(time) = A_YES | A_LIBERAL, S(alarm) = A_YES | A_LIBERAL, S(pause) = A_YES | A_LIBERAL, - S(signal) = A_YES | A_LIBERAL, S(fchmod) = A_YES | A_LIBERAL, - S(sigaction) = A_YES | A_LIBERAL, - S(sgetmask) = A_YES | A_LIBERAL, - S(ssetmask) = A_YES | A_LIBERAL, - S(sigsuspend) = A_YES | A_LIBERAL, - S(sigpending) = A_YES | A_LIBERAL, S(getrlimit) = A_YES | A_LIBERAL, S(getrusage) = A_YES | A_LIBERAL, - S(ugetrlimit) = A_YES | A_LIBERAL, S(gettimeofday) = A_YES | A_LIBERAL, S(select) = A_YES | A_LIBERAL, - S(readdir) = A_YES | A_LIBERAL, S(setitimer) = A_YES | A_LIBERAL, S(getitimer) = A_YES | A_LIBERAL, - S(sigreturn) = A_YES | A_LIBERAL | A_NO_RETVAL, S(mprotect) = A_YES | A_LIBERAL, - S(sigprocmask) = A_YES | A_LIBERAL, S(getdents) = A_YES | A_LIBERAL, S(getdents64) = A_YES | A_LIBERAL, - S(_newselect) = A_YES | A_LIBERAL, S(fdatasync) = A_YES | A_LIBERAL, S(mremap) = A_YES | A_LIBERAL, S(poll) = A_YES | A_LIBERAL, @@ -324,6 +330,20 @@ static unsigned char syscall_action[NUM_ACTIONS] = { S(rt_sigqueueinfo) = A_YES | A_LIBERAL, S(rt_sigsuspend) = A_YES | A_LIBERAL, S(_sysctl) = A_YES | A_LIBERAL, +#ifndef CONFIG_BOX_USER_AMD64 + S(sigaction) = A_YES | A_LIBERAL, + S(sgetmask) = A_YES | A_LIBERAL, + S(ssetmask) = A_YES | A_LIBERAL, + S(sigsuspend) = A_YES | A_LIBERAL, + S(sigpending) = A_YES | A_LIBERAL, + S(sigreturn) = A_YES | A_LIBERAL | A_NO_RETVAL, + S(sigprocmask) = A_YES | A_LIBERAL, + S(ugetrlimit) = A_YES | A_LIBERAL, + S(readdir) = A_YES | A_LIBERAL, + S(signal) = A_YES | A_LIBERAL, + S(_newselect) = A_YES | A_LIBERAL, +#endif + #undef S }; @@ -405,6 +425,7 @@ static struct path_rule default_path_rules[] = { { "/proc/meminfo", A_YES }, { "/proc/self/stat", A_YES }, { "/proc/self/exe", A_YES }, // Needed by FPC 2.0.x runtime + { "/proc/self/maps", A_YES }, // Needed by glibc when it reports arena corruption }; static struct path_rule *user_path_rules; @@ -587,26 +608,186 @@ setup_environment(void) return env; } +/*** Low-level parsing of syscalls ***/ + +#ifdef CONFIG_BOX_KERNEL_AMD64 +typedef uint64_t arg_t; +#else +typedef uint32_t arg_t; +#endif + +struct syscall_args { + arg_t sys; + arg_t arg1, arg2, arg3; + arg_t result; + struct user user; +}; + +static int user_mem_fd; + +static int read_user_mem(arg_t addr, char *buf, int len) +{ + if (!user_mem_fd) + { + char memname[64]; + sprintf(memname, "/proc/%d/mem", (int) box_pid); + user_mem_fd = open(memname, O_RDONLY); + if (user_mem_fd < 0) + die("open(%s): %m", memname); + } + if (lseek64(user_mem_fd, addr, SEEK_SET) < 0) + die("lseek64(mem): %m"); + return read(user_mem_fd, buf, len); +} + +static void close_user_mem(void) +{ + if (user_mem_fd) + { + close(user_mem_fd); + user_mem_fd = 0; + } +} + +#ifdef CONFIG_BOX_KERNEL_AMD64 + +static void +get_syscall_args(struct syscall_args *a, int is_exit) +{ + if (ptrace(PTRACE_GETREGS, box_pid, NULL, &a->user) < 0) + die("ptrace(PTRACE_GETREGS): %m"); + a->sys = a->user.regs.orig_rax; + a->result = a->user.regs.rax; + + /* + * CAVEAT: We have to check carefully that this is a real 64-bit syscall. + * We test whether the process runs in 64-bit mode, but surprisingly this + * is not enough: a 64-bit process can still issue the INT 0x80 instruction + * which performs a 32-bit syscall. Currently, the only known way how to + * detect this situation is to inspect the instruction code (the kernel + * keeps a syscall type flag internally, but it is not accessible from + * user space). Hopefully, there is no instruction whose suffix is the + * code of the SYSCALL instruction. Sometimes, one would wish the + * instruction codes to be unique even when read backwards :) + */ + + if (is_exit) + return; + + int sys_type; + uint16_t instr; + + switch (a->user.regs.cs) + { + case 0x23: + // 32-bit CPU mode => only 32-bit syscalls can be issued + sys_type = 32; + break; + case 0x33: + // 64-bit CPU mode + if (read_user_mem(a->user.regs.rip-2, (char *) &instr, 2) != 2) + err("FO: Cannot read syscall instruction"); + switch (instr) + { + case 0x050f: + break; + case 0x80cd: + err("FO: Forbidden 32-bit syscall in 64-bit mode"); + default: + err("XX: Unknown syscall instruction %04x", instr); + } + sys_type = 64; + break; + default: + err("XX: Unknown code segment %04jx", (intmax_t) a->user.regs.cs); + } + +#ifdef CONFIG_BOX_USER_AMD64 + if (sys_type != 64) + err("FO: Forbidden %d-bit mode syscall", sys_type); +#else + if (sys_type != (exec_seen ? 32 : 64)) + err("FO: Forbidden %d-bit mode syscall", sys_type); +#endif + + if (sys_type == 32) + { + a->arg1 = a->user.regs.rbx; + a->arg2 = a->user.regs.rcx; + a->arg3 = a->user.regs.rdx; + } + else + { + a->arg1 = a->user.regs.rdi; + a->arg2 = a->user.regs.rsi; + a->arg3 = a->user.regs.rdx; + } +} + +static void +set_syscall_nr(struct syscall_args *a, arg_t sys) +{ + a->sys = sys; + a->user.regs.orig_rax = sys; + if (ptrace(PTRACE_SETREGS, box_pid, NULL, &a->user) < 0) + die("ptrace(PTRACE_SETREGS): %m"); +} + +static void +sanity_check(void) +{ +} + +#else + +static void +get_syscall_args(struct syscall_args *a, int is_exit UNUSED) +{ + if (ptrace(PTRACE_GETREGS, box_pid, NULL, &a->user) < 0) + die("ptrace(PTRACE_GETREGS): %m"); + a->sys = a->user.regs.orig_eax; + a->arg1 = a->user.regs.ebx; + a->arg2 = a->user.regs.ecx; + a->arg3 = a->user.regs.edx; + a->result = a->user.regs.eax; +} + +static void +set_syscall_nr(struct syscall_args *a, arg_t sys) +{ + a->sys = sys; + a->user.regs.orig_eax = sys; + if (ptrace(PTRACE_SETREGS, box_pid, NULL, &a->user) < 0) + die("ptrace(PTRACE_SETREGS): %m"); +} + +static void +sanity_check(void) +{ +#if !defined(CONFIG_BOX_ALLOW_INSECURE) + struct utsname uts; + if (uname(&uts) < 0) + die("uname() failed: %m"); + + if (!strcmp(uts.machine, "x86_64")) + die("Running 32-bit sandbox on 64-bit kernels is inherently unsafe. Please get a 64-bit version."); +#endif +} + +#endif + /*** Syscall checks ***/ static void -valid_filename(unsigned long addr) +valid_filename(arg_t addr) { char namebuf[4096], *p, *end; - static int mem_fd; if (!file_access) err("FA: File access forbidden"); if (file_access >= 9) return; - if (!mem_fd) - { - sprintf(namebuf, "/proc/%d/mem", (int) box_pid); - mem_fd = open(namebuf, O_RDONLY); - if (mem_fd < 0) - die("open(%s): %m", namebuf); - } p = end = namebuf; do { @@ -618,15 +799,13 @@ valid_filename(unsigned long addr) l = remains; if (!l) err("FA: Access to file with name too long"); - if (lseek64(mem_fd, addr, SEEK_SET) < 0) - die("lseek64(mem): %m"); - remains = read(mem_fd, end, l); + remains = read_user_mem(addr, end, l); if (remains < 0) die("read(mem): %m"); if (!remains) err("FA: Access to file with name out of memory"); - end += l; - addr += l; + end += remains; + addr += remains; } } while (*p++); @@ -659,9 +838,9 @@ valid_filename(unsigned long addr) // Check syscall. If invalid, return -1, otherwise return the action mask. static int -valid_syscall(struct user *u) +valid_syscall(struct syscall_args *a) { - unsigned int sys = u->regs.orig_eax; + unsigned int sys = a->sys; unsigned int act = (sys < NUM_ACTIONS) ? syscall_action[sys] : A_DEFAULT; if (act & A_LIBERAL) @@ -677,7 +856,7 @@ valid_syscall(struct user *u) case A_NO: return -1; case A_FILENAME: - valid_filename(u->regs.ebx); + valid_filename(a->arg1); return act; default: ; } @@ -685,17 +864,17 @@ valid_syscall(struct user *u) switch (sys) { case __NR_kill: - if (u->regs.ebx == box_pid) + if (a->arg1 == (arg_t) box_pid) { - meta_printf("exitsig:%d\n", (int)u->regs.ecx); - err("SG: Committed suicide by signal %d", (int)u->regs.ecx); + meta_printf("exitsig:%d\n", (int) a->arg2); + err("SG: Committed suicide by signal %d", (int) a->arg2); } return -1; case __NR_tgkill: - if (u->regs.ebx == box_pid && u->regs.ecx == box_pid) + if (a->arg1 == (arg_t) box_pid && a->arg2 == (arg_t) box_pid) { - meta_printf("exitsig:%d\n", (int)u->regs.edx); - err("SG: Committed suicide by signal %d", (int)u->regs.edx); + meta_printf("exitsig:%d\n", (int) a->arg3); + err("SG: Committed suicide by signal %d", (int) a->arg3); } return -1; default: @@ -830,23 +1009,27 @@ sample_mem_peak(void) static void boxkeeper(void) { - int syscall_count = 0; + int syscall_count = (filter_syscalls ? 0 : 1); struct sigaction sa; is_ptraced = 1; + bzero(&sa, sizeof(sa)); sa.sa_handler = signal_int; sigaction(SIGINT, &sa, NULL); + gettimeofday(&start_time, NULL); ticks_per_sec = sysconf(_SC_CLK_TCK); if (ticks_per_sec <= 0) die("Invalid ticks_per_sec!"); + if (timeout || wall_timeout) { sa.sa_handler = signal_alarm; sigaction(SIGALRM, &sa, NULL); alarm(1); } + for(;;) { struct rusage rus; @@ -920,23 +1103,27 @@ boxkeeper(void) { if (verbose > 2) msg("[ptrace status %08x] ", stat); - struct user u; - static unsigned int sys_tick, last_sys, last_act; - if (ptrace(PTRACE_GETREGS, box_pid, NULL, &u) < 0) - die("ptrace(PTRACE_GETREGS): %m"); - unsigned int sys = u.regs.orig_eax; + struct syscall_args a; + static unsigned int sys_tick, last_act; + static arg_t last_sys; if (++sys_tick & 1) /* Syscall entry */ { char namebuf[32]; int act; - msg(">> Syscall %-12s (%08lx,%08lx,%08lx) ", syscall_name(sys, namebuf), u.regs.ebx, u.regs.ecx, u.regs.edx); + + get_syscall_args(&a, 0); + arg_t sys = a.sys; + msg(">> Syscall %-12s (%08jx,%08jx,%08jx) ", syscall_name(sys, namebuf), (intmax_t) a.arg1, (intmax_t) a.arg2, (intmax_t) a.arg3); if (!exec_seen) { msg("[master] "); - if (sys == __NR_execve) - exec_seen = 1; + if (sys == NATIVE_NR_execve) + { + exec_seen = 1; + close_user_mem(); + } } - else if ((act = valid_syscall(&u)) >= 0) + else if ((act = valid_syscall(&a)) >= 0) { last_act = act; syscall_count++; @@ -950,16 +1137,15 @@ boxkeeper(void) * so we have to change it to something harmless (e.g., an undefined * syscall) and make the program continue. */ - u.regs.orig_eax = 0xffffffff; - if (ptrace(PTRACE_SETREGS, box_pid, NULL, &u) < 0) - die("ptrace(PTRACE_SETREGS): %m"); + set_syscall_nr(&a, ~(arg_t)0); err("FO: Forbidden syscall %s", syscall_name(sys, namebuf)); } last_sys = sys; } else /* Syscall return */ { - if (sys == 0xffffffff) + get_syscall_args(&a, 1); + if (a.sys == ~(arg_t)0) { /* Some syscalls (sigreturn et al.) do not return a value */ if (!(last_act & A_NO_RETVAL)) @@ -967,13 +1153,13 @@ boxkeeper(void) } else { - if (sys != last_sys) + if (a.sys != last_sys) err("XX: Mismatched syscall entry/exit"); } if (last_act & A_NO_RETVAL) msg("= ?\n"); else - msg("= %ld\n", u.regs.eax); + msg("= %jd\n", (intmax_t) a.result); } ptrace(PTRACE_SYSCALL, box_pid, 0, 0); } @@ -1166,6 +1352,7 @@ main(int argc, char **argv) if (optind >= argc) usage(); + sanity_check(); uid = geteuid(); if (setreuid(uid, uid) < 0) die("setreuid: %m");