add fortified readlink/readlinkat implementations

Change-Id: Ia4b1824d20cad3a072b9162047492dade8576779

5 files changed, 150 insertions, 0 deletions

diff --git a/libc/Android.mk b/libc/Android.mk
index 9d3b62a..814940c 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -74,6 +74,8 @@ libc_common_src_files += \
     bionic/__pread64_chk.cpp \
     bionic/__pread_chk.cpp \
     bionic/__read_chk.cpp \
+    bionic/__readlink_chk.cpp \
+    bionic/__readlinkat_chk.cpp \
     bionic/__recvfrom_chk.cpp \
     bionic/__stpcpy_chk.cpp \
     bionic/__stpncpy_chk.cpp \
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>
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index a601cb7..f0de29e 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -239,6 +239,16 @@ __errordecl(__read_dest_size_error, "read called with size bigger than destinati
 __errordecl(__read_count_toobig_error, "read called with count > SSIZE_MAX");
 extern ssize_t __read_real(int, void*, size_t) __RENAME(read);
 
+extern ssize_t __readlink_chk(const char*, char*, size_t, size_t);
+__errordecl(__readlink_dest_size_error, "readlink called with size bigger than destination");
+__errordecl(__readlink_size_toobig_error, "readlink called with size > SSIZE_MAX");
+extern ssize_t __readlink_real(const char*, char*, size_t) __RENAME(readlink);
+
+extern ssize_t __readlinkat_chk(int dirfd, const char*, char*, size_t, size_t);
+__errordecl(__readlinkat_dest_size_error, "readlinkat called with size bigger than destination");
+__errordecl(__readlinkat_size_toobig_error, "readlinkat called with size > SSIZE_MAX");
+extern ssize_t __readlinkat_real(int dirfd, const char*, char*, size_t) __RENAME(readlinkat);
+
 #if defined(__BIONIC_FORTIFY)
 
 #if defined(__USE_FILE_OFFSET64)
@@ -322,6 +332,56 @@ ssize_t read(int fd, void* buf, size_t count) {
     return __read_chk(fd, buf, count, bos);
 }
 
+__BIONIC_FORTIFY_INLINE
+ssize_t readlink(const char* path, char* buf, size_t size) {
+    size_t bos = __bos(buf);
+
+#if !defined(__clang__)
+    if (__builtin_constant_p(size) && (size > SSIZE_MAX)) {
+        __readlink_size_toobig_error();
+    }
+
+    if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
+        return __readlink_real(path, buf, size);
+    }
+
+    if (__builtin_constant_p(size) && (size > bos)) {
+        __readlink_dest_size_error();
+    }
+
+    if (__builtin_constant_p(size) && (size <= bos)) {
+        return __readlink_real(path, buf, size);
+    }
+#endif
+
+    return __readlink_chk(path, buf, size, bos);
+}
+
+__BIONIC_FORTIFY_INLINE
+ssize_t readlinkat(int dirfd, const char* path, char* buf, size_t size) {
+    size_t bos = __bos(buf);
+
+#if !defined(__clang__)
+    if (__builtin_constant_p(size) && (size > SSIZE_MAX)) {
+        __readlinkat_size_toobig_error();
+    }
+
+    if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
+        return __readlinkat_real(dirfd, path, buf, size);
+    }
+
+    if (__builtin_constant_p(size) && (size > bos)) {
+        __readlinkat_dest_size_error();
+    }
+
+    if (__builtin_constant_p(size) && (size <= bos)) {
+        return __readlinkat_real(dirfd, path, buf, size);
+    }
+#endif
+
+    return __readlinkat_chk(dirfd, path, buf, size, bos);
+}
+
 #endif /* defined(__BIONIC_FORTIFY) */
 
 __END_DECLS