Add runtime FORTIFY support

Gingerbread libc.a missing symbols

native/jni/Application.mk

@@ -11,12 +11,6 @@ ifndef B_SHARED
 # Fix static variables' ctor/dtor when using LTO
 # See: https://github.com/android/ndk/issues/1461
 APP_LDFLAGS      += -T jni/lto_fix.lds
-ifneq ($(TARGET_ARCH),arm64)
-ifneq ($(TARGET_ARCH),x86_64)
-# Disable fortify on static 32-bit targets
-APP_CFLAGS       += -D_FORTIFY_SOURCE=0 -Wno-macro-redefined
-endif
-endif
 endif
 
 # Busybox should use stock libc.a

native/jni/utils/fortify.hpp

@@ -0,0 +1,110 @@
+// Original source: https://android.googlesource.com/platform/bionic/+/master/libc/bionic/fortify.cpp
+// License: AOSP, full copyright notice please check original source
+
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "logging.hpp"
+
+#undef _FORTIFY_SOURCE
+
+static inline __noreturn __printflike(1, 2) void __fortify_fatal(const char* fmt, ...) {
+    va_list args;
+    va_start(args, fmt);
+    log_cb.e(fmt, args);
+    va_end(args);
+    abort();
+}
+static inline void __check_count(const char* fn, const char* identifier, size_t value) {
+    if (__predict_false(value > SSIZE_MAX)) {
+        __fortify_fatal("%s: %s %zu > SSIZE_MAX", fn, identifier, value);
+    }
+}
+static inline void __check_buffer_access(const char* fn, const char* action,
+                                         size_t claim, size_t actual) {
+    if (__predict_false(claim > actual)) {
+        __fortify_fatal("%s: prevented %zu-byte %s %zu-byte buffer", fn, claim, action, actual);
+    }
+}
+char* __strcpy_chk(char* dst, const char* src, size_t dst_len) {
+    // TODO: optimize so we don't scan src twice.
+    size_t src_len = __builtin_strlen(src) + 1;
+    __check_buffer_access("strcpy", "write into", src_len, dst_len);
+    return __builtin_strcpy(dst, src);
+}
+size_t __strlcpy_chk(char* dst, const char* src,
+                     size_t supplied_size, size_t dst_len_from_compiler) {
+    __check_buffer_access("strlcpy", "write into", supplied_size, dst_len_from_compiler);
+    return __call_bypassing_fortify(strlcpy)(dst, src, supplied_size);
+}
+char* __strchr_chk(const char* p, int ch, size_t s_len) {
+    for (;; ++p, s_len--) {
+        if (__predict_false(s_len == 0)) {
+            __fortify_fatal("strchr: prevented read past end of buffer");
+        }
+        if (*p == static_cast<char>(ch)) {
+            return const_cast<char*>(p);
+        }
+        if (*p == '\0') {
+            return nullptr;
+        }
+    }
+}
+char* __strcat_chk(char* dst, const char* src, size_t dst_buf_size) {
+    char* save = dst;
+    size_t dst_len = __strlen_chk(dst, dst_buf_size);
+    dst += dst_len;
+    dst_buf_size -= dst_len;
+    while ((*dst++ = *src++) != '\0') {
+        dst_buf_size--;
+        if (__predict_false(dst_buf_size == 0)) {
+            __fortify_fatal("strcat: prevented write past end of %zu-byte buffer", dst_buf_size);
+        }
+    }
+    return save;
+}
+size_t __strlen_chk(const char* s, size_t s_len) {
+    // TODO: "prevented" here would be a lie because this strlen can run off the end.
+    // strlen is too important to be expensive, so we wanted to be able to call the optimized
+    // implementation, but I think we need to implement optimized assembler __strlen_chk routines.
+    size_t ret = __builtin_strlen(s);
+    if (__predict_false(ret >= s_len)) {
+        __fortify_fatal("strlen: detected read past end of buffer");
+    }
+    return ret;
+}
+int __vsprintf_chk(char* dst, int /*flags*/,
+                   size_t dst_len_from_compiler, const char* format, va_list va) {
+    // The compiler uses SIZE_MAX to mean "no idea", but our vsnprintf rejects sizes that large.
+    int result = __call_bypassing_fortify(vsnprintf)(dst,
+                           dst_len_from_compiler == SIZE_MAX ? SSIZE_MAX : dst_len_from_compiler,
+                           format, va);
+    // Try to catch failures after the fact...
+    __check_buffer_access("vsprintf", "write into", result + 1, dst_len_from_compiler);
+    return result;
+}
+mode_t __umask_chk(mode_t mode) {
+    if (__predict_false((mode & 0777) != mode)) {
+        __fortify_fatal("umask: called with invalid mask %o", mode);
+    }
+    return __umask_real(mode);
+}
+ssize_t __read_chk(int fd, void* buf, size_t count, size_t buf_size) {
+    __check_count("read", "count", count);
+    __check_buffer_access("read", "write into", count, buf_size);
+    return __call_bypassing_fortify(read)(fd, buf, count);
+}
+static inline bool needs_mode(int flags) {
+    return ((flags & O_CREAT) == O_CREAT) || ((flags & O_TMPFILE) == O_TMPFILE);
+}
+static inline int force_O_LARGEFILE(int flags) {
+    return flags | O_LARGEFILE;
+}
+int __open_2(const char* pathname, int flags) {
+    if (needs_mode(flags)) __fortify_fatal("open: called with O_CREAT/O_TMPFILE but no mode");
+    return __openat_real(AT_FDCWD, pathname, force_O_LARGEFILE(flags), 0);
+}
+int __openat_2(int fd, const char* pathname, int flags) {
+    if (needs_mode(flags)) __fortify_fatal("open: called with O_CREAT/O_TMPFILE but no mode");
+    return __openat_real(fd, pathname, force_O_LARGEFILE(flags), 0);
+}

native/jni/utils/missing.cpp

@@ -165,6 +165,9 @@ int sigemptyset(sigset_t *set) {
     memset(set, 0, sizeof(sigset_t));
     return 0;
 }
+
+#include "fortify.hpp"
+
 #endif
 
 } // extern "C"