Box: Let 32-/64-bit mode be configurable

[eval.git] / box / box.c

diff --git a/box/box.c b/box/box.c
index 65734db9b3c7a2ce6d1db0eae071c9c248dd6b7e..0788ac4b51ec54b3484b054d5b9ac67bef42e06d 100644 (file)
--- a/box/box.c
+++ b/box/box.c
@@ -7,6 +7,8 @@
 #define _LARGEFILE64_SOURCE
 #define _GNU_SOURCE
 
+#include "autoconf.h"
+
 #include <errno.h>
 #include <stdio.h>
 #include <fcntl.h>
@@ -23,10 +25,18 @@
 #include <sys/ptrace.h>
 #include <sys/signal.h>
 #include <sys/sysinfo.h>
-#include <sys/syscall.h>
 #include <sys/resource.h>
+#include <sys/utsname.h>
 #include <linux/ptrace.h>
 
+#if defined(CONFIG_BOX_KERNEL_AMD64) && !defined(CONFIG_BOX_USER_AMD64)
+#include <asm/unistd_32.h>
+#define NATIVE_NR_execve 59            /* 64-bit execve */
+#else
+#include <asm/unistd.h>
+#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]))
@@ -237,7 +247,7 @@ static unsigned char syscall_action[NUM_ACTIONS] = {
     S(stat) = A_FILENAME,
     S(lstat) = A_FILENAME,
     S(readlink) = A_FILENAME,
-#ifndef CONFIG_BOX_AMD64
+#ifndef CONFIG_BOX_USER_AMD64
     S(oldstat) = A_FILENAME,
     S(oldlstat) = A_FILENAME,
     S(truncate64) = A_FILENAME,
@@ -282,7 +292,7 @@ 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,
-#ifndef CONFIG_BOX_AMD64
+#ifndef CONFIG_BOX_USER_AMD64
     S(oldfstat) = A_YES,
     S(ftruncate64) = A_YES,
     S(_llseek) = A_YES,
@@ -318,7 +328,7 @@ 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_AMD64
+#ifndef CONFIG_BOX_USER_AMD64
     S(sigaction) = A_YES | A_LIBERAL,
     S(sgetmask) = A_YES | A_LIBERAL,
     S(ssetmask) = A_YES | A_LIBERAL,
@@ -597,7 +607,7 @@ setup_environment(void)
 
 /*** Low-level parsing of syscalls ***/
 
-#ifdef CONFIG_BOX_AMD64
+#ifdef CONFIG_BOX_KERNEL_AMD64
 typedef uint64_t arg_t;
 #else
 typedef uint32_t arg_t;
@@ -627,7 +637,7 @@ static int read_user_mem(arg_t addr, char *buf, int len)
   return read(mem_fd, buf, len);
 }
 
-#ifdef CONFIG_BOX_AMD64
+#ifdef CONFIG_BOX_KERNEL_AMD64
 
 static void
 get_syscall_args(struct syscall_args *a, int is_exit)
@@ -635,9 +645,6 @@ 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->arg1 = a->user.regs.rdi;
-  a->arg2 = a->user.regs.rsi;
-  a->arg3 = a->user.regs.rdx;
   a->result = a->user.regs.rax;
 
   /*
@@ -655,27 +662,53 @@ get_syscall_args(struct syscall_args *a, int is_exit)
   if (is_exit)
     return;
 
+  int sys_type;
+  uint16_t instr;
+
   switch (a->user.regs.cs)
     {
     case 0x23:
-      err("FO: Forbidden 32-bit mode syscall");
+      // 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);
     }
 
-  uint16_t instr;
-  if (read_user_mem(a->user.regs.rip-2, (char *) &instr, 2) != 2)
-    err("FO: Cannot read syscall instruction");
-  switch (instr)
+#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)
     {
-    case 0x050f:
-      break;
-    case 0x80cd:
-      err("FO: Forbidden 32-bit syscall in 64-bit mode");
-    default:
-      err("FO: Unknown syscall instruction %04x", instr);
+      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;
     }
 }
 
@@ -688,6 +721,11 @@ set_syscall_nr(struct syscall_args *a, arg_t sys)
     die("ptrace(PTRACE_SETREGS): %m");
 }
 
+static void
+sanity_check(void)
+{
+}
+
 #else
 
 static void
@@ -711,6 +749,19 @@ set_syscall_nr(struct syscall_args *a, arg_t sys)
     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 ***/
@@ -719,20 +770,12 @@ static void
 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
     {
@@ -744,15 +787,13 @@ valid_filename(arg_t 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++);
@@ -1064,7 +1105,7 @@ boxkeeper(void)
                  if (!exec_seen)
                    {
                      msg("[master] ");
-                     if (sys == __NR_execve)
+                     if (sys == NATIVE_NR_execve)
                        exec_seen = 1;
                    }
                  else if ((act = valid_syscall(&a)) >= 0)
@@ -1296,6 +1337,7 @@ main(int argc, char **argv)
   if (optind >= argc)
     usage();
 
+  sanity_check();
   uid = geteuid();
   if (setreuid(uid, uid) < 0)
     die("setreuid: %m");