sandbox: Filter "chown32" syscall on i386

On i386 glibc uses the "chown32" system call instead of "chown".  Prevent
attempts to filter calls to chown() on this architecture from failing by
modifying the sandbox implementation to match.

src/lib/sandbox/sandbox.c

@@ -599,6 +599,32 @@ sb_chmod(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
   return 0;
 }
 
+#ifdef __i386__
+static int
+sb_chown32(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
+{
+  int rc;
+  sandbox_cfg_t *elem = NULL;
+
+  // for each dynamic parameter filters
+  for (elem = filter; elem != NULL; elem = elem->next) {
+    smp_param_t *param = elem->param;
+
+    if (param != NULL && param->prot == 1 && param->syscall
+        == SCMP_SYS(chown32)) {
+      rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(chown32),
+            SCMP_CMP_STR(0, SCMP_CMP_EQ, param->value));
+      if (rc != 0) {
+        log_err(LD_BUG,"(Sandbox) failed to add chown32 syscall, received "
+            "libseccomp error %d", rc);
+        return rc;
+      }
+    }
+  }
+
+  return 0;
+}
+#else
 static int
 sb_chown(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
 {
@@ -623,6 +649,7 @@ sb_chown(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
 
   return 0;
 }
+#endif /* defined(__i386__) */
 
 /**
  * Function responsible for setting up the rename syscall for
@@ -1270,7 +1297,11 @@ static sandbox_filter_func_t filter_func[] = {
 #ifdef __NR_mmap2
     sb_mmap2,
 #endif
+#ifdef __i386__
+    sb_chown32,
+#else
     sb_chown,
+#endif
     sb_chmod,
     sb_open,
     sb_openat,
@@ -1544,6 +1575,12 @@ new_element(int syscall, char *value)
   return new_element2(syscall, value, NULL);
 }
 
+#ifdef __i386__
+#define SCMP_chown SCMP_SYS(chown32)
+#else
+#define SCMP_chown SCMP_SYS(chown)
+#endif
+
 #ifdef __NR_stat64
 #define SCMP_stat SCMP_SYS(stat64)
 #else
@@ -1594,7 +1631,7 @@ sandbox_cfg_allow_chown_filename(sandbox_cfg_t **cfg, char *file)
 {
   sandbox_cfg_t *elem = NULL;
 
-  elem = new_element(SCMP_SYS(chown), file);
+  elem = new_element(SCMP_chown, file);
 
   elem->next = *cfg;
   *cfg = elem;