Fix 700053: Add 'decrypt' option to pdf_save_document.

This option is exposed as the -D flag to mutool clean.

Allow saving a document without encryption.

The next step is to allow saving a document with new encryption, but this
may require a fair amount of rejigging since the PDF write code to keep
separate doc->crypt objects for decryption and encryption.

4 files changed, 51 insertions, 11 deletions

diff --git a/include/mupdf/pdf/document.h b/include/mupdf/pdf/document.h
index 7d2110b7..27e3d4f4 100644
--- a/include/mupdf/pdf/document.h
+++ b/include/mupdf/pdf/document.h
@@ -879,6 +879,7 @@ struct pdf_write_options_s
 	int do_linear; /* Write linearised. */
 	int do_clean; /* Clean content streams. */
 	int do_sanitize; /* Sanitize content streams. */
+	int do_decrypt; /* Save without decryption. */
 	int continue_on_error; /* If set, errors are (optionally) counted and writing continues. */
 	int *errors; /* Pointer to a place to store a count of errors */
 };
diff --git a/platform/gl/gl-annotate.c b/platform/gl/gl-annotate.c
index 48f0555e..155cac24 100644
--- a/platform/gl/gl-annotate.c
+++ b/platform/gl/gl-annotate.c
@@ -39,6 +39,7 @@ static void save_pdf_options(void)
 	ui_checkbox("Compress images", &save_opts.do_compress_images);
 	ui_checkbox("Compress fonts", &save_opts.do_compress_fonts);
 	ui_checkbox("Decompress", &save_opts.do_decompress);
+	ui_checkbox("Decrypt", &save_opts.do_decrypt);
 	ui_checkbox("Garbage collect", &save_opts.do_garbage);
 	ui_checkbox("Linearize", &save_opts.do_linear);
 	ui_checkbox("Clean syntax", &save_opts.do_clean);
diff --git a/source/pdf/pdf-write.c b/source/pdf/pdf-write.c
index 6417e2fa..0fe311c1 100644
--- a/source/pdf/pdf-write.c
+++ b/source/pdf/pdf-write.c
@@ -68,6 +68,7 @@ struct pdf_write_state_s
 	int do_garbage;
 	int do_linear;
 	int do_clean;
+	int do_decrypt;
 
 	int list_len;
 	int *use_list;
@@ -1705,13 +1706,25 @@ static void copystream(fz_context *ctx, pdf_document *doc, pdf_write_state *opts
 			addhexfilter(ctx, doc, obj);
 		}
 
-		pdf_dict_put_int(ctx, obj, PDF_NAME(Length), pdf_encrypted_len(ctx, doc->crypt, num, gen, (int)len));
-
 		fz_write_printf(ctx, opts->out, "%d %d obj\n", num, gen);
-		pdf_print_encrypted_obj(ctx, opts->out, obj, opts->do_tight, doc->crypt, num, gen);
-		fz_write_string(ctx, opts->out, "\nstream\n");
-		pdf_encrypt_data(ctx, doc->crypt, num, gen, write_data, opts->out, data, len);
+
+		if (opts->do_decrypt)
+		{
+			pdf_dict_put_int(ctx, obj, PDF_NAME(Length), len);
+			pdf_print_obj(ctx, opts->out, obj, opts->do_tight);
+			fz_write_string(ctx, opts->out, "\nstream\n");
+			fz_write_data(ctx, opts->out, data, len);
+		}
+		else
+		{
+			pdf_dict_put_int(ctx, obj, PDF_NAME(Length), pdf_encrypted_len(ctx, doc->crypt, num, gen, (int)len));
+			pdf_print_encrypted_obj(ctx, opts->out, obj, opts->do_tight, doc->crypt, num, gen);
+			fz_write_string(ctx, opts->out, "\nstream\n");
+			pdf_encrypt_data(ctx, doc->crypt, num, gen, write_data, opts->out, data, len);
+		}
+
 		fz_write_string(ctx, opts->out, "\nendstream\nendobj\n\n");
+
 	}
 	fz_always(ctx)
 	{
@@ -1769,12 +1782,23 @@ static void expandstream(fz_context *ctx, pdf_document *doc, pdf_write_state *op
 			addhexfilter(ctx, doc, obj);
 		}
 
-		pdf_dict_put_int(ctx, obj, PDF_NAME(Length), pdf_encrypted_len(ctx, doc->crypt, num, gen, (int)len));
-
 		fz_write_printf(ctx, opts->out, "%d %d obj\n", num, gen);
-		pdf_print_encrypted_obj(ctx, opts->out, obj, opts->do_tight, doc->crypt, num, gen);
-		fz_write_string(ctx, opts->out, "\nstream\n");
-		pdf_encrypt_data(ctx, doc->crypt, num, gen, write_data, opts->out, data, len);
+
+		if (opts->do_decrypt)
+		{
+			pdf_dict_put_int(ctx, obj, PDF_NAME(Length), len);
+			pdf_print_obj(ctx, opts->out, obj, opts->do_tight);
+			fz_write_string(ctx, opts->out, "\nstream\n");
+			fz_write_data(ctx, opts->out, data, len);
+		}
+		else
+		{
+			pdf_dict_put_int(ctx, obj, PDF_NAME(Length), pdf_encrypted_len(ctx, doc->crypt, num, gen, (int)len));
+			pdf_print_encrypted_obj(ctx, opts->out, obj, opts->do_tight, doc->crypt, num, gen);
+			fz_write_string(ctx, opts->out, "\nstream\n");
+			pdf_encrypt_data(ctx, doc->crypt, num, gen, write_data, opts->out, data, len);
+		}
+
 		fz_write_string(ctx, opts->out, "\nendstream\nendobj\n\n");
 	}
 	fz_always(ctx)
@@ -2800,6 +2824,7 @@ static void initialise_write_state(fz_context *ctx, pdf_document *doc, const pdf
 	opts->do_garbage = in_opts->do_garbage;
 	opts->do_linear = in_opts->do_linear;
 	opts->do_clean = in_opts->do_clean;
+	opts->do_decrypt = in_opts->do_decrypt;
 	opts->start = 0;
 	opts->main_xref_offset = INT_MIN;
 
@@ -2885,6 +2910,8 @@ pdf_parse_write_options(fz_context *ctx, pdf_write_options *opts, const char *ar
 		opts->do_incremental = fz_option_eq(val, "yes");
 	if (fz_has_option(ctx, args, "continue-on-error", &val))
 		opts->continue_on_error = fz_option_eq(val, "yes");
+	if (fz_has_option(ctx, args, "decrypt", &val))
+		opts->do_decrypt = fz_option_eq(val, "yes");
 	if (fz_has_option(ctx, args, "garbage", &val))
 	{
 		if (fz_option_eq(val, "yes"))
@@ -2966,6 +2993,12 @@ do_pdf_save_document(fz_context *ctx, pdf_document *doc, pdf_write_state *opts,
 	{
 		initialise_write_state(ctx, doc, in_opts, opts);
 
+		/* Remove encryption dictionary if saving without encryption. */
+		if (opts->do_decrypt)
+		{
+			pdf_dict_del(ctx, pdf_trailer(ctx, doc), PDF_NAME(Encrypt));
+		}
+
 		/* Make sure any objects hidden in compressed streams have been loaded */
 		if (!opts->do_incremental)
 		{
@@ -3157,6 +3190,8 @@ void pdf_write_document(fz_context *ctx, pdf_document *doc, fz_output *out, pdf_
 		fz_throw(ctx, FZ_ERROR_GENERIC, "Can't do incremental writes with garbage collection");
 	if (in_opts->do_incremental && in_opts->do_linear)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "Can't do incremental writes with linearisation");
+	if (in_opts->do_incremental && in_opts->do_decrypt)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "Can't do incremental writes with decryption");
 	if (pdf_has_unsaved_sigs(ctx, doc) && !out->as_stream)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "Can't write pdf that has unsaved sigs to a fz_output unless it supports fz_stream_from_output!");
 
@@ -3186,6 +3221,8 @@ void pdf_save_document(fz_context *ctx, pdf_document *doc, const char *filename,
 		fz_throw(ctx, FZ_ERROR_GENERIC, "Can't do incremental writes with garbage collection");
 	if (in_opts->do_incremental && in_opts->do_linear)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "Can't do incremental writes with linearisation");
+	if (in_opts->do_incremental && in_opts->do_decrypt)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "Can't do incremental writes with decryption");
 
 	prepare_for_save(ctx, doc, in_opts);
 
diff --git a/source/tools/pdfclean.c b/source/tools/pdfclean.c
index 6d5a69be..0e7a464a 100644
--- a/source/tools/pdfclean.c
+++ b/source/tools/pdfclean.c
@@ -51,7 +51,7 @@ int pdfclean_main(int argc, char **argv)
 	opts.continue_on_error = 1;
 	opts.errors = &errors;
 
-	while ((c = fz_getopt(argc, argv, "adfgilp:scz")) != -1)
+	while ((c = fz_getopt(argc, argv, "adfgilp:sczD")) != -1)
 	{
 		switch (c)
 		{
@@ -66,6 +66,7 @@ int pdfclean_main(int argc, char **argv)
 		case 'l': opts.do_linear += 1; break;
 		case 'c': opts.do_clean += 1; break;
 		case 's': opts.do_sanitize += 1; break;
+		case 'D': opts.do_decrypt += 1; break;
 		default: usage(); break;
 		}
 	}