aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--doc/build-unix.txt42
-rw-r--r--src/makefile.unix30
2 files changed, 71 insertions, 1 deletions
diff --git a/doc/build-unix.txt b/doc/build-unix.txt
index 8f0c568eda..62abb7b99a 100644
--- a/doc/build-unix.txt
+++ b/doc/build-unix.txt
@@ -107,3 +107,45 @@ If you need to build Boost yourself:
sudo su
./bootstrap.sh
./bjam install
+
+
+Security
+--------
+To help make your bitcoin installation more secure by making certain attacks impossible to
+exploit even if a vulnerability is found, you can take the following measures:
+
+* Position Independent Executable
+ Build position independent code to take advantage of Address Space Layout Randomization
+ offered by some kernels. An attacker who is able to cause execution of code at an arbitrary
+ memory location is thwarted if he doesn't know where anything useful is located.
+ The stack and heap are randomly located by default but this allows the code section to be
+ randomly located as well.
+
+ On an Amd64 processor where a library was not compiled with -fPIC, this will cause an error
+ such as: "relocation R_X86_64_32 against `......' can not be used when making a shared object;"
+
+ To build with PIE, use:
+ make -f makefile.unix ... -e PIE=1
+
+ To test that you have built PIE executable, install scanelf, part of paxutils, and use:
+ scanelf -e ./bitcoin
+
+ The output should contain:
+ TYPE
+ ET_DYN
+
+* Non-executable Stack
+ If the stack is executable then trivial stack based buffer overflow exploits are possible if
+ vulnerable buffers are found. By default, bitcoin should be built with a non-executable stack
+ but if one of the libraries it uses asks for an executable stack or someone makes a mistake
+ and uses a compiler extension which requires an executable stack, it will silently build an
+ executable without the non-executable stack protection.
+
+ To verify that the stack is non-executable after compiling use:
+ scanelf -e ./bitcoin
+
+ the output should contain:
+ STK/REL/PTL
+ RW- R-- RW-
+
+ The STK RW- means that the stack is readable and writeable but not executable.
diff --git a/src/makefile.unix b/src/makefile.unix
index 298d856ecb..43c3ea7f50 100644
--- a/src/makefile.unix
+++ b/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 \