add fortified readlink/readlinkat implementations

Change-Id: Ia4b1824d20cad3a072b9162047492dade8576779

3 files changed, 88 insertions, 0 deletions

diff --git a/libc/bionic/__readlink_chk.cpp b/libc/bionic/__readlink_chk.cpp
new file mode 100644
index 0000000..f19f917
--- /dev/null
+++ b/libc/bionic/__readlink_chk.cpp
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#undef _FORTIFY_SOURCE
+#include <unistd.h>
+#include "private/libc_logging.h"
+
+extern "C" ssize_t __readlink_chk(const char* path, char* buf, size_t size, size_t buf_size) {
+  if (__predict_false(size > buf_size)) {
+    __fortify_chk_fail("readlink: prevented write past end of buffer", 0);
+  }
+
+  if (__predict_false(size > SSIZE_MAX)) {
+    __fortify_chk_fail("readlink: size > SSIZE_MAX", 0);
+  }
+
+  return readlink(path, buf, size);
+}
diff --git a/libc/bionic/__readlinkat_chk.cpp b/libc/bionic/__readlinkat_chk.cpp
new file mode 100644
index 0000000..a11db8e
--- /dev/null
+++ b/libc/bionic/__readlinkat_chk.cpp
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#undef _FORTIFY_SOURCE
+#include <unistd.h>
+#include "private/libc_logging.h"
+
+extern "C" ssize_t __readlinkat_chk(int dirfd, const char* path, char* buf, size_t size, size_t buf_size) {
+  if (__predict_false(size > buf_size)) {
+    __fortify_chk_fail("readlinkat: prevented write past end of buffer", 0);
+  }
+
+  if (__predict_false(size > SSIZE_MAX)) {
+    __fortify_chk_fail("readlinkat: size > SSIZE_MAX", 0);
+  }
+
+  return readlinkat(dirfd, path, buf, size);
+}
diff --git a/libc/bionic/readlink.cpp b/libc/bionic/readlink.cpp
index 3bb7bc1..a53f933 100644
--- a/libc/bionic/readlink.cpp
+++ b/libc/bionic/readlink.cpp
@@ -26,6 +26,8 @@
  * SUCH DAMAGE.
  */
 
+#undef _FORTIFY_SOURCE
+
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/types.h>