From eed73082f54f9235b91af8311f0da9d05aad880a Mon Sep 17 00:00:00 2001
From: Matt Morehouse <mattmorehouse@gmail.com>
Date: Tue, 16 May 2023 10:48:18 -0500
Subject: [PATCH] make: build dependencies with fuzzing flags

By using fuzzer instrumentation for dependencies, we get more coverage
signal during fuzzing. This is useful when the fuzzer must figure out
how to take certain branches in a dependency.

In our case, the fuzz-bip32 target was failing to create a data buffer
that successfully passed fromwire_ext_key() parsing because the fuzzer
couldn't see what was happening inside libwally-core.
---
 configure         | 5 ++++-
 external/Makefile | 6 +++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/configure b/configure
index 9295c461a..144f3f90d 100755
--- a/configure
+++ b/configure
@@ -148,6 +148,7 @@ set_defaults()
     ASAN=${ASAN:-0}
     UBSAN=${UBSAN:-0}
     FUZZING=${FUZZING:-0}
+    FUZZFLAGS=""
     CSANFLAGS=""
     if [ "$ASAN" != 0 ]; then
 	CSANFLAGS="$CSANFLAGS -fsanitize=address"
@@ -162,7 +163,8 @@ set_defaults()
 	fi
     fi
     if [ "$FUZZING" != 0 ]; then
-	CSANFLAGS="$CSANFLAGS -fsanitize=fuzzer-no-link"
+	FUZZFLAGS="-fsanitize=fuzzer-no-link"
+	CSANFLAGS="$CSANFLAGS $FUZZFLAGS"
     fi
     echo CSANFLAGS = $CSANFLAGS
     PYTEST=${PYTEST-$(default_pytest)}
@@ -473,6 +475,7 @@ add_var CWARNFLAGS "$CWARNFLAGS"
 add_var CDEBUGFLAGS "$CDEBUGFLAGS"
 add_var COPTFLAGS "$COPTFLAGS"
 add_var CSANFLAGS "$CSANFLAGS"
+add_var FUZZFLAGS "$FUZZFLAGS"
 add_var SQLITE3_CFLAGS "$SQLITE3_CFLAGS"
 add_var SQLITE3_LDLIBS "$SQLITE3_LDLIBS"
 add_var POSTGRES_INCLUDE "$POSTGRES_INCLUDE"
diff --git a/external/Makefile b/external/Makefile
index a41aa1c03..725019576 100644
--- a/external/Makefile
+++ b/external/Makefile
@@ -71,7 +71,7 @@ $(TARGET_DIR)/libsodium.a: $(TARGET_DIR)/libsodium-build/src/libsodium/libsodium
 $(TARGET_DIR)/libsodium-build/src/libsodium/libsodium.la: external/libsodium/src/libsodium/include/sodium.h
 	cd external/libsodium && ./autogen.sh
 	mkdir -p ${TARGET_DIR}/libsodium-build
-	cd $(TARGET_DIR)/libsodium-build && $(TOP)/libsodium/configure CC="$(CC)" --enable-static=yes $(CROSSCOMPILE_OPTS) --enable-shared=no --prefix=/ --libdir=/ && $(MAKE)
+	cd $(TARGET_DIR)/libsodium-build && $(TOP)/libsodium/configure CC="$(CC)" CFLAGS="$(FUZZFLAGS)" LDFLAGS="$(FUZZFLAGS)" --enable-static=yes $(CROSSCOMPILE_OPTS) --enable-shared=no --prefix=/ --libdir=/ && $(MAKE)
 
 # libsecp included in libwally.
 # Wildcards here are magic.  See http://stackoverflow.com/questions/2973445/gnu-makefile-rule-generating-a-few-targets-from-a-single-source-file
@@ -83,7 +83,7 @@ $(TARGET_DIR)/libwally-core-build/src/libwallycore.% $(TARGET_DIR)/libwally-core
 	cd external/libwally-core && ./tools/autogen.sh
 	mkdir -p ${TARGET_DIR}/libwally-core-build
 	cd ${TARGET_DIR}/libwally-core-build \
-	&& PYTHON_VERSION=3 CFLAGS=-std=c99 ${TOP}/libwally-core/configure CC="$(CC)" \
+	&& PYTHON_VERSION=3 CFLAGS="-std=c99 $(FUZZFLAGS)" LDFLAGS="$(FUZZFLAGS)" ${TOP}/libwally-core/configure CC="$(CC)" \
 		--enable-static=yes \
 		$(CROSSCOMPILE_OPTS) \
 		--enable-module-recovery \
@@ -115,7 +115,7 @@ $(TARGET_DIR)/libbacktrace.a: external/libbacktrace/backtrace.h
 	$(MAKE) -C $(TARGET_DIR)/libbacktrace-build DESTDIR=$$(pwd)/$(TARGET_DIR) install-exec
 
 $(TARGET_DIR)/lowdown-build/bin/lowdown: external/lowdown/lowdown.h
-	cd external/lowdown && CC="$(CC)" ./configure PREFIX=`pwd`/$(TOP)/$(TARGET_DIR)/lowdown-build/
+	cd external/lowdown && CC="$(CC)" CFLAGS="$(FUZZFLAGS)" ./configure LDFLAGS="$(FUZZFLAGS)" PREFIX=`pwd`/$(TOP)/$(TARGET_DIR)/lowdown-build/
 	$(MAKE) -C external/lowdown install
 
 distclean: external-distclean