Merge pull request #513 from cjdelisle/feature-hardening

Hardening

src/makefile.unix

@@ -36,8 +36,36 @@ LIBS+= \
    -l pthread
 
 
+# Hardening
+# Make some classes of vulnerabilities unexploitable in case one is discovered.
+#
+    # Stack Canaries
+    # Put numbers at the beginning of each stack frame and check that they are the same.
+    # If a stack buffer if overflowed, it writes over the canary number and then on return
+    # when that number is checked, it won't be the same and the program will exit with
+    # a "Stack smashing detected" error instead of being exploited.
+    HARDENING=-fstack-protector-all -Wstack-protector
+
+    # Make some important things such as the global offset table read only as soon as
+    # the dynamic linker is finished building it. This will prevent overwriting of addresses
+    # which would later be jumped to.
+    HARDENING+=-Wl,-z,relro -Wl,-z,now
+
+    # Build position independent code to take advantage of Address Space Layout Randomization
+    # offered by some kernels.
+    # see doc/build-unix.txt for more information.
+    ifdef PIE
+        HARDENING+=-fPIE -pie
+    endif
+
+    # -D_FORTIFY_SOURCE=2 does some checking for potentially exploitable code patterns in
+    # the source such overflowing a statically defined buffer.
+    HARDENING+=-D_FORTIFY_SOURCE=2
+#
+
+
 DEBUGFLAGS=-g -D__WXDEBUG__
-CXXFLAGS=-O2 -Wno-invalid-offsetof -Wformat $(DEBUGFLAGS) $(DEFS)
+CXXFLAGS=-O2 -Wno-invalid-offsetof -Wformat $(DEBUGFLAGS) $(DEFS) $(HARDENING)
 HEADERS = \
     base58.h \
     bignum.h \