Signature support: decouple mupdf from the pkcs7 implementation

The mupdf build included an implimentation of the pkcs7 functions that
are needed for signing documents and verifying signatures, the
implementation being either an openssl-based one, or a stub that returned
errors. This commit removes the pkcs7 functions from the main mupdf
library.

For the sake of verification, there wasn't really a need for the pkcs7
functions to be part of mupdf. It was only the checking function that used
them. The checking function is now provided as a helper, outside of the
main build. The openssl-based pkcs7 functions area also supplied as a
helper. Users wishing to verify signatures can either use the checking
function directly, or use the source on which to base their own.

Document signing requires more integration between mupdf and pkcs7
because part of the process is performed at time of signing and part when
saving the document. Mupdf already had a pdf_pkcs7_signer object that
kept information between the two phases. That object has now been extended
to include the pkcs7 functions involved in signing, and the signing
function now requires such an object, rather than a file path to a
certificate. The openssl-based pkcs7 helper provides a function that, given
the path to a certificate, will return a pdf_pkcs7_signer object.

The intention is that different implementations can be produced for
different platforms, based on cryptographic routines built into the
operationg system. In each case, for the sake of document signing, the
routines would be wrapped up as a pdf_pkcs7_signer object.

1 files changed, 20 insertions, 6 deletions

diff --git a/Makefile b/Makefile
index 3959ccf4..acf559fe 100644
--- a/Makefile
+++ b/Makefile
@@ -53,6 +53,7 @@ ALL_DIR += $(OUT)/source/gprf
 ALL_DIR += $(OUT)/source/tools
 ALL_DIR += $(OUT)/source/helpers
 ALL_DIR += $(OUT)/source/helpers/mu-threads
+ALL_DIR += $(OUT)/source/helpers/pkcs7
 ALL_DIR += $(OUT)/platform/x11
 ALL_DIR += $(OUT)/platform/x11/curl
 ALL_DIR += $(OUT)/platform/gl
@@ -93,9 +94,12 @@ $(OUT)/%.a :
 $(OUT)/%.exe: $(OUT)/%.o | $(ALL_DIR)
 	$(LINK_CMD)
 
-$(OUT)/source/helpers/%.o : source/helpers/%.c | $(ALL_DIR)
+$(OUT)/source/helpers/mu-threads/%.o : source/helpers/mu-threads/%.c | $(ALL_DIR)
 	$(CC_CMD) $(THREADING_CFLAGS)
 
+$(OUT)/source/helpers/pkcs7/%.o : source/helpers/pkcs7/%.c | $(ALL_DIR)
+	$(CC_CMD)
+
 $(OUT)/source/tools/%.o : source/tools/%.c | $(ALL_DIR)
 	$(CC_CMD) $(THREADING_CFLAGS)
 
@@ -127,6 +131,7 @@ $(OUT)/%.o : %.cpp | $(ALL_DIR)
 FITZ_HDR := include/mupdf/fitz.h $(wildcard include/mupdf/fitz/*.h)
 PDF_HDR := include/mupdf/pdf.h $(wildcard include/mupdf/pdf/*.h)
 THREAD_HDR := include/mupdf/helpers/mu-threads.h
+PKCS7_HDR := $(sort $(wildcard include/mupdf/helpers/pkcs7-*.h))
 
 FITZ_SRC := $(sort $(wildcard source/fitz/*.c))
 PDF_SRC := $(sort $(wildcard source/pdf/*.c))
@@ -136,6 +141,7 @@ CBZ_SRC := $(sort $(wildcard source/cbz/*.c))
 HTML_SRC := $(sort $(wildcard source/html/*.c))
 GPRF_SRC := $(sort $(wildcard source/gprf/*.c))
 THREAD_SRC := $(sort $(wildcard source/helpers/mu-threads/*.c))
+PKCS7_SRC := $(sort $(wildcard source/helpers/pkcs7/*.c))
 
 FITZ_SRC_HDR := $(wildcard source/fitz/*.h)
 PDF_SRC_HDR := $(wildcard source/pdf/*.h) source/pdf/pdf-name-table.h
@@ -152,6 +158,8 @@ CBZ_OBJ := $(CBZ_SRC:%.c=$(OUT)/%.o)
 HTML_OBJ := $(HTML_SRC:%.c=$(OUT)/%.o)
 GPRF_OBJ := $(GPRF_SRC:%.c=$(OUT)/%.o)
 THREAD_OBJ := $(THREAD_SRC:%.c=$(OUT)/%.o)
+PKCS7_OBJ := $(PKCS7_SRC:%.c=$(OUT)/%.o)
+SIGNATURE_OBJ := $(OUT)/platform/x11/pdfapp.o $(OUT)/source/tools/pdfsign.o
 
 $(FITZ_OBJ) : $(FITZ_HDR) $(FITZ_SRC_HDR)
 $(PDF_OBJ) : $(FITZ_HDR) $(PDF_HDR) $(PDF_SRC_HDR)
@@ -163,6 +171,8 @@ $(CBZ_OBJ) : $(FITZ_HDR) $(CBZ_HDR) $(CBZ_SRC_HDR)
 $(HTML_OBJ) : $(FITZ_HDR) $(HTML_HDR) $(HTML_SRC_HDR)
 $(GPRF_OBJ) : $(FITZ_HDR) $(GPRF_HDR) $(GPRF_SRC_HDR)
 $(THREAD_OBJ) : $(THREAD_HDR)
+$(PKCS7_OBJ) : $(FITZ_HDR) $(PDF_HDR) $(PKCS7_HDR)
+$(SIGNATURE_OBJ) : $(PKCS7_HDR)
 
 # --- Generated PDF name tables ---
 
@@ -315,6 +325,9 @@ generate: $(JAVASCRIPT_GEN)
 MUPDF_LIB = $(OUT)/libmupdf.a
 THIRD_LIB = $(OUT)/libmupdfthird.a
 THREAD_LIB = $(OUT)/libmuthreads.a
+ifeq "$(HAVE_LIBCRYPTO)" "yes"
+PKCS7_LIB = $(OUT)/libmupkcs7.a
+endif
 
 MUPDF_OBJ := \
 	$(FITZ_OBJ) \
@@ -341,11 +354,12 @@ THIRD_OBJ := \
 	$(ZLIB_OBJ) \
 	$(LCMS2_OBJ)
 
-THREAD_OBJ := $(THREAD_OBJ)
-
 $(MUPDF_LIB) : $(MUPDF_OBJ)
 $(THIRD_LIB) : $(THIRD_OBJ)
 $(THREAD_LIB) : $(THREAD_OBJ)
+ifeq "$(HAVE_LIBCRYPTO)" "yes"
+$(PKCS7_LIB) : $(PKCS7_OBJ)
+endif
 
 INSTALL_LIBS := $(MUPDF_LIB) $(THIRD_LIB)
 
@@ -356,7 +370,7 @@ MUTOOL_SRC := source/tools/mutool.c source/tools/muconvert.c source/tools/mudraw
 MUTOOL_SRC += $(sort $(wildcard source/tools/pdf*.c))
 MUTOOL_OBJ := $(MUTOOL_SRC:%.c=$(OUT)/%.o)
 $(MUTOOL_OBJ) : $(FITZ_HDR) $(PDF_HDR)
-$(MUTOOL_EXE) : $(MUTOOL_OBJ) $(MUPDF_LIB) $(THIRD_LIB) $(THREAD_LIB)
+$(MUTOOL_EXE) : $(MUTOOL_OBJ) $(MUPDF_LIB) $(THIRD_LIB) $(THREAD_LIB) $(PKCS7_LIB)
 	$(LINK_CMD) $(THREADING_LIBS)
 
 MURASTER_EXE := $(OUT)/muraster
@@ -381,14 +395,14 @@ ifeq "$(HAVE_X11)" "yes"
 MUVIEW_X11_EXE := $(OUT)/mupdf-x11
 MUVIEW_X11_OBJ := $(addprefix $(OUT)/platform/x11/, x11_main.o x11_image.o pdfapp.o)
 $(MUVIEW_X11_OBJ) : $(FITZ_HDR) $(PDF_HDR)
-$(MUVIEW_X11_EXE) : $(MUVIEW_X11_OBJ) $(MUPDF_LIB) $(THIRD_LIB)
+$(MUVIEW_X11_EXE) : $(MUVIEW_X11_OBJ) $(MUPDF_LIB) $(THIRD_LIB) $(PKCS7_LIB)
 	$(LINK_CMD) $(X11_LIBS)
 
 ifeq "$(HAVE_CURL)" "yes"
 MUVIEW_X11_CURL_EXE := $(OUT)/mupdf-x11-curl
 MUVIEW_X11_CURL_OBJ := $(addprefix $(OUT)/platform/x11/curl/, x11_main.o x11_image.o pdfapp.o curl_stream.o)
 $(MUVIEW_X11_CURL_OBJ) : $(FITZ_HDR) $(PDF_HDR)
-$(MUVIEW_X11_CURL_EXE) : $(MUVIEW_X11_CURL_OBJ) $(MUPDF_LIB) $(THIRD_LIB) $(CURL_LIB)
+$(MUVIEW_X11_CURL_EXE) : $(MUVIEW_X11_CURL_OBJ) $(MUPDF_LIB) $(THIRD_LIB) $(CURL_LIB) $(PKCS7_LIB)
 	$(LINK_CMD) $(X11_LIBS) $(CURL_LIBS) $(SYS_CURL_DEPS)
 endif
 endif