Merge #14451: Add BIP70 deprecation warning and allow building GUI without BIP70 support

48439b3c10 Don't link SSL_LIBS with GUI unless BIP70 is enabled (James Hilliard)
fbb643d2a5 Add BIP70 deprecation warning (James Hilliard)
38b98507cd qt: cleanup: Move BIP70 functions together in paymentserver (Wladimir J. van der Laan)
9dcf6c0dfe build: Add --disable-bip70 configure option (Wladimir J. van der Laan)

Pull request description:

  This is based off of #11622 and adds a deprecation warning when a BIP70 URL is used.

  Rational:

  - BIP70 increases attack surface in multiple ways and is difficult for third party wallets to implement in a secure manner
  - Very few merchants use the standard BIP70 variant supported by Bitcoin Core
  - The one major payment processor that doesn't support BIP21 and currently uses a customized non-standard version of BIP70 has indicated that "Unfortunately the original BIP70 is not useful for us."

Tree-SHA512: 1e16ee8d2cdac9499f751ee7b50d058278150f9e38a87a47ddb5105dd0353cdedabe462903f54ead6209b249b249fe5e6a10d29631531be27400f2f69c25b9b9

src/Makefile.qt.include

@@ -176,9 +176,15 @@ QT_QRC = qt/bitcoin.qrc
 QT_QRC_LOCALE_CPP = qt/qrc_bitcoin_locale.cpp
 QT_QRC_LOCALE = qt/bitcoin_locale.qrc
 
+if ENABLE_BIP70
 PROTOBUF_CC = qt/paymentrequest.pb.cc
 PROTOBUF_H = qt/paymentrequest.pb.h
 PROTOBUF_PROTO = qt/paymentrequest.proto
+else
+PROTOBUF_CC =
+PROTOBUF_H =
+PROTOBUF_PROTO =
+endif
 
 BITCOIN_QT_H = \
   qt/addressbookpage.h \
@@ -327,7 +333,6 @@ BITCOIN_QT_WALLET_CPP = \
   qt/editaddressdialog.cpp \
   qt/openuridialog.cpp \
   qt/overviewpage.cpp \
-  qt/paymentrequestplus.cpp \
   qt/paymentserver.cpp \
   qt/receivecoinsdialog.cpp \
   qt/receiverequestdialog.cpp \
@@ -346,13 +351,19 @@ BITCOIN_QT_WALLET_CPP = \
   qt/walletmodeltransaction.cpp \
   qt/walletview.cpp
 
+BITCOIN_QT_WALLET_BIP70_CPP = \
+  qt/paymentrequestplus.cpp
+
 BITCOIN_QT_CPP = $(BITCOIN_QT_BASE_CPP)
 if TARGET_WINDOWS
 BITCOIN_QT_CPP += $(BITCOIN_QT_WINDOWS_CPP)
 endif
 if ENABLE_WALLET
 BITCOIN_QT_CPP += $(BITCOIN_QT_WALLET_CPP)
-endif
+if ENABLE_BIP70
+BITCOIN_QT_CPP += $(BITCOIN_QT_WALLET_BIP70_CPP)
+endif # ENABLE_BIP70
+endif # ENABLE_WALLET
 
 RES_IMAGES =
 
@@ -405,8 +416,11 @@ endif
 if ENABLE_ZMQ
 qt_bitcoin_qt_LDADD += $(LIBBITCOIN_ZMQ) $(ZMQ_LIBS)
 endif
+if ENABLE_BIP70
+qt_bitcoin_qt_LDADD += $(SSL_LIBS)
+endif
 qt_bitcoin_qt_LDADD += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) $(LIBLEVELDB) $(LIBLEVELDB_SSE42) $(LIBMEMENV) \
-  $(BOOST_LIBS) $(QT_LIBS) $(QT_DBUS_LIBS) $(QR_LIBS) $(PROTOBUF_LIBS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS) $(LIBSECP256K1) \
+  $(BOOST_LIBS) $(QT_LIBS) $(QT_DBUS_LIBS) $(QR_LIBS) $(PROTOBUF_LIBS) $(BDB_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS) $(LIBSECP256K1) \
   $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS)
 qt_bitcoin_qt_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(QT_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 qt_bitcoin_qt_LIBTOOLFLAGS = $(AM_LIBTOOLFLAGS) --tag CXX