configure: use system libsodium if available and modern.

Also one less headache for reproducible builds.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

configure

@@ -156,7 +156,22 @@ if [ "$ASAN" = "1" ]; then
 fi
 
 rm -f $CONFIG_VAR_FILE.$$
-$CONFIGURATOR --autotools-style --var-file=$CONFIG_VAR_FILE.$$ --header-file=$CONFIG_HEADER --configurator-cc="$CONFIGURATOR_CC" "$CC" $CWARNFLAGS $CDEBUGFLAGS
+$CONFIGURATOR --extra-tests --autotools-style --var-file=$CONFIG_VAR_FILE.$$ --header-file=$CONFIG_HEADER --configurator-cc="$CONFIGURATOR_CC" "$CC" $CWARNFLAGS $CDEBUGFLAGS <<EOF
+var=HAVE_GOOD_LIBSODIUM
+desc=libsodium with IETF chacha20 variants
+style=DEFINES_EVERYTHING|EXECUTE|MAY_NOT_COMPILE
+link=-lsodium
+code=
+#include <sodium.h>
+#include <stdio.h>
+
+int main(void)
+{
+	printf("%p\n", crypto_aead_chacha20poly1305_ietf_encrypt);
+	exit(0);
+}
+/*END*/
+EOF
 mv $CONFIG_VAR_FILE.$$ $CONFIG_VAR_FILE
 
 add_var PREFIX "$PREFIX"

doc/INSTALL.md

@@ -36,7 +36,7 @@ Get dependencies:
     sudo apt-get update
     sudo apt-get install -y \
       autoconf automake build-essential git libtool libgmp-dev \
-      libsqlite3-dev python python3 net-tools zlib1g-dev
+      libsqlite3-dev python python3 net-tools zlib1g-dev libsodium
 
 If you don't have Bitcoin installed locally you'll need to install that
 as well:
@@ -93,7 +93,8 @@ $ sudo dnf update -y && \
                 net-tools \
                 valgrind \
                 wget \
-                zlib-devel && \
+                zlib-devel \
+				libsodium-devel && \
         sudo dnf clean all
 ```
 
@@ -132,7 +133,7 @@ OS version: FreeBSD 11.1-RELEASE or above
 Get dependencies:
 
     # pkg install -y \
-      autoconf automake git gmp asciidoc gmake libtool python python3 sqlite3
+      autoconf automake git gmp asciidoc gmake libtool python python3 sqlite3 libsodium
 
 If you don't have Bitcoin installed locally you'll need to install that
 as well:
@@ -167,7 +168,7 @@ Use nix-shell launch a shell with a full clightning dev environment:
 
 ```
 $ nix-shell -Q -p gdb sqlite autoconf git clang libtool gmp sqlite autoconf \
-autogen automake 'python3.withPackages (p: [p.bitcoinlib])' \
+autogen automake libsodium 'python3.withPackages (p: [p.bitcoinlib])' \
 valgrind asciidoc --run make
 ```
 
@@ -181,7 +182,7 @@ Assuming you have Xcode and Homebrew installed. Install dependencies:
 If you don't have bitcoind installed locally you'll need to install that
 as well:
 
-    $ brew install berkeley-db4 boost miniupnpc openssl pkg-config libevent
+    $ brew install berkeley-db4 boost miniupnpc openssl pkg-config libevent libsodium
     $ git clone https://github.com/bitcoin/bitcoin
     $ cd bitcoin
     $ ./autogen.sh

external/Makefile

@@ -15,10 +15,9 @@ JSMN_HEADERS := external/jsmn/jsmn.h
 LIBBASE58_HEADERS := external/libbase58/libbase58.h
 
 EXTERNAL_HEADERS := $(LIBSODIUM_HEADERS) $(LIBWALLY_HEADERS) $(LIBSECP_HEADERS) $(JSMN_HEADERS) $(LIBBASE58_HEADERS)
-EXTERNAL_LIBS := external/libwallycore.a external/libsecp256k1.a external/libsodium.a external/libjsmn.a external/libbase58.a external/libbacktrace.a
+EXTERNAL_LIBS := external/libwallycore.a external/libsecp256k1.a external/libjsmn.a external/libbase58.a external/libbacktrace.a
 
 EXTERNAL_INCLUDE_FLAGS :=					\
-	-I external/libsodium/src/libsodium/include		\
 	-I external/libwally-core/include/			\
 	-I external/libwally-core/src/secp256k1/include/	\
 	-I external/jsmn/					\
@@ -26,6 +25,13 @@ EXTERNAL_INCLUDE_FLAGS :=					\
 	-I external/libbacktrace/				\
 	-I external/libbacktrace-build
 
+ifneq ($(HAVE_GOOD_LIBSODIUM),1)
+EXTERNAL_INCLUDE_FLAGS += -I external/libsodium/src/libsodium/include
+EXTERNAL_LIBS += external/libsodium.a
+else
+LDLIBS += -lsodium
+endif
+
 EXTERNAL_LDLIBS := -Lexternal $(patsubst lib%.a,-l%,$(notdir $(EXTERNAL_LIBS)))
 
 submodcheck: FORCE