Converted matching of paths to a table-driven system.

[moe.git] / src / box.c

diff --git a/src/box.c b/src/box.c
index 11ab37e854c2d2a496804061f00edacffd24dc76..a2c5f683ce16af8dd2dd8d314917d7c3255054f2 100644 (file)
--- a/src/box.c
+++ b/src/box.c
@@ -27,6 +27,7 @@
 
 #define NONRET __attribute__((noreturn))
 #define UNUSED __attribute__((unused))
+#define ARRAY_SIZE(a) (int)(sizeof(a)/sizeof(a[0]))
 
 static int filter_syscalls;            /* 0=off, 1=liberal, 2=totalitarian */
 static int timeout;                    /* milliseconds */
@@ -96,7 +97,7 @@ static const char * const syscall_tab[] = {
 #define NUM_SYSCALLS (sizeof(syscall_tab)/sizeof(syscall_tab[0]))
 #define NUM_ACTIONS (NUM_SYSCALLS+64)
 
-enum syscall_action {
+enum action {
   SC_DEFAULT,          // Use the default action
   SC_NO,               // Always forbid
   SC_YES,              // Always permit
@@ -177,6 +178,7 @@ static unsigned char syscall_action[NUM_ACTIONS] = {
     S(sigpending) = SC_YES | SC_LIBERAL,
     S(getrlimit) = SC_YES | SC_LIBERAL,
     S(getrusage) = SC_YES | SC_LIBERAL,
+    S(ugetrlimit) = SC_YES | SC_LIBERAL,
     S(gettimeofday) = SC_YES | SC_LIBERAL,
     S(select) = SC_YES | SC_LIBERAL,
     S(readdir) = SC_YES | SC_LIBERAL,
@@ -221,9 +223,81 @@ static int
 syscall_by_name(char *name)
 {
   for (unsigned int i=0; i<sizeof(syscall_tab)/sizeof(syscall_tab[0]); i++)
-    if (!strcmp(syscall_tab[i], name))
+    if (syscall_tab[i] && !strcmp(syscall_tab[i], name))
       return i;
-  return -1;
+  if (name[0] == '#')
+    name++;
+  if (!*name)
+    return -1;
+  char *ep;
+  unsigned long l = strtoul(name, &ep, 0);
+  if (*ep)
+    return -1;
+  if (l >= NUM_ACTIONS)
+    return NUM_ACTIONS;
+  return l;
+}
+
+static int
+set_action(char *a)
+{
+  char *sep = strchr(a, '=');
+  enum action act = SC_YES;
+  if (sep)
+    {
+      *sep++ = 0;
+      if (!strcmp(sep, "yes"))
+       act = SC_YES;
+      else if (!strcmp(sep, "no"))
+       act = SC_NO;
+      else if (!strcmp(sep, "file"))
+       act = SC_FILENAME;
+      else
+       return 0;
+    }
+
+  int sys = syscall_by_name(a);
+  if (sys < 0)
+    die("Unknown syscall `%s'", a);
+  if (sys >= (int)NUM_ACTIONS)
+    die("Syscall `%s' out of range", a);
+  syscall_action[sys] = act;
+  return 1;
+}
+
+struct path_rule {
+  char *path;
+  enum action action;
+  struct path_rule *next;
+};
+
+static struct path_rule default_path_rules[] = {
+  { "/etc/", SC_YES },
+  { "/lib/", SC_YES },
+  { "/usr/lib/", SC_YES },
+  { "/opt/lib/", SC_YES },
+  { "/usr/share/zoneinfo/", SC_YES },
+  { "/dev/null", SC_YES },
+  { "/dev/zero", SC_YES },
+  { "/proc/meminfo", SC_YES },
+  { "/proc/self/stat", SC_YES },
+  { "/proc/self/exe", SC_YES },                        // Needed by FPC 2.0.x runtime
+};
+
+static enum action
+match_path_rule(struct path_rule *r, char *path)
+{
+  char *rr = r->path;
+  while (*rr)
+    if (*rr++ != *path++)
+      {
+       if (rr[-1] == '/' && !path[-1])
+         break;
+       return SC_DEFAULT;
+      }
+  if (rr > r->path && rr[-1] != '/' && *path)
+    return SC_DEFAULT;
+  return r->action;
 }
 
 static void
@@ -271,32 +345,30 @@ valid_filename(unsigned long addr)
   msg("[%s] ", namebuf);
   if (file_access >= 3)
     return;
+
+  // Everything in current directory is permitted
   if (!strchr(namebuf, '/') && strcmp(namebuf, ".."))
     return;
+
+  // ".." anywhere in the path is forbidden
+  enum action act = SC_DEFAULT;
+  if (strstr(namebuf, ".."))
+    act = SC_NO;
+
+  // Scan built-in rules
   if (file_access >= 2)
-    {
-      if ((!strncmp(namebuf, "/etc/", 5) ||
-          !strncmp(namebuf, "/lib/", 5) ||
-          !strncmp(namebuf, "/usr/lib/", 9) ||
-          !strncmp(namebuf, "/opt/lib/", 9))
-         && !strstr(namebuf, ".."))
-       return;
-      if (!strcmp(namebuf, "/dev/null") ||
-         !strcmp(namebuf, "/dev/zero") ||
-         !strcmp(namebuf, "/proc/meminfo") ||
-         !strcmp(namebuf, "/proc/self/stat") ||
-         !strcmp(namebuf, "/proc/self/exe") ||                 /* Needed by FPC 2.0.x runtime */
-         !strncmp(namebuf, "/usr/share/zoneinfo/", 20))
-       return;
-    }
-  die("Forbidden access to file `%s'", namebuf);
+    for (int i=0; i<ARRAY_SIZE(default_path_rules) && !act; i++)
+      act = match_path_rule(&default_path_rules[i], namebuf);
+
+  if (act != SC_YES)
+    die("Forbidden access to file `%s'", namebuf);
 }
 
 static int
 valid_syscall(struct user *u)
 {
   unsigned int sys = u->regs.orig_eax;
-  enum syscall_action act = (sys < NUM_ACTIONS) ? syscall_action[sys] : SC_DEFAULT;
+  enum action act = (sys < NUM_ACTIONS) ? syscall_action[sys] : SC_DEFAULT;
 
   if (act & SC_LIBERAL)
     {
@@ -583,6 +655,8 @@ Options:\n\
 -i <file>\tRedirect stdin from <file>\n\
 -m <size>\tLimit address space to <size> KB\n\
 -o <file>\tRedirect stdout to <file>\n\
+-s <sys>\tPermit the specified syscall (be careful)\n\
+-s <sys>=<act>\tDefine action for the specified syscall (<act>=yes/no/file)\n\
 -t <time>\tSet run time limit (seconds, fractions allowed)\n\
 -T\t\tAllow syscalls for measuring run time\n\
 -v\t\tBe verbose\n\
@@ -597,7 +671,7 @@ main(int argc, char **argv)
   int c;
   uid_t uid;
 
-  while ((c = getopt(argc, argv, "a:c:efi:m:o:t:Tvw:")) >= 0)
+  while ((c = getopt(argc, argv, "a:c:efi:m:o:s:t:Tvw:")) >= 0)
     switch (c)
       {
       case 'a':
@@ -621,6 +695,10 @@ main(int argc, char **argv)
       case 'o':
        redir_stdout = optarg;
        break;
+      case 's':
+       if (!set_action(optarg))
+         usage();
+       break;
       case 't':
        timeout = 1000*atof(optarg);
        break;