Perform document signing via fz_stream and fz_output

This change achieves two goals. It allows signing to be performed even
when the document is obtained other than from a disk file. It also
reestablishes to a working state signing of file-based documents, a feature
that was broken due to complete_signatures being called after certain
tables, avaialble via the output options object, had been destroyed.

2 files changed, 171 insertions, 79 deletions

diff --git a/source/pdf/pdf-pkcs7.c b/source/pdf/pdf-pkcs7.c
index 7139156f..864e3039 100644
--- a/source/pdf/pdf-pkcs7.c
+++ b/source/pdf/pdf-pkcs7.c
@@ -80,6 +80,92 @@ static const char AdobeCA_p7c[] = {
 #warning detect version of openssl at compile time
 #endif
 
+typedef struct
+{
+	fz_context *ctx;
+	fz_stream *stm;
+} BIO_stream_data;
+
+static int stream_read(BIO *b, char *buf, int size)
+{
+	BIO_stream_data *data = (BIO_stream_data *)BIO_get_data(b);
+	return fz_read(data->ctx, data->stm, buf, size);
+}
+
+static long stream_ctrl(BIO *b, int cmd, long arg1, void *arg2)
+{
+	BIO_stream_data *data = (BIO_stream_data *)BIO_get_data(b);
+	switch (cmd)
+	{
+	case BIO_C_FILE_SEEK:
+		fz_seek(data->ctx, data->stm, arg1, SEEK_SET);
+		return 0;
+	default:
+		return 1;
+	}
+}
+
+static int stream_new(BIO *b)
+{
+	BIO_stream_data *data = (BIO_stream_data *)malloc(sizeof(BIO_stream_data));
+	if (!data)
+		return 0;
+
+	data->ctx = NULL;
+	data->stm = NULL;
+
+	BIO_set_init(b, 1);
+	BIO_set_data(b, data);
+	BIO_clear_flags(b, INT_MAX);
+
+	return 1;
+}
+
+static int stream_free(BIO *b)
+{
+	if (b == NULL)
+		return 0;
+
+	free(BIO_get_data(b));
+	BIO_set_data(b, NULL);
+	BIO_set_init(b, 0);
+	BIO_clear_flags(b, INT_MAX);
+
+	return 1;
+}
+
+static long stream_callback_ctrl(BIO *b, int cmd, bio_info_cb *fp)
+{
+	return 1;
+}
+
+static BIO *BIO_new_stream(fz_context *ctx, fz_stream *stm)
+{
+	static BIO_METHOD *methods = NULL;
+	BIO *bio;
+	BIO_stream_data *data;
+
+	if (!methods)
+	{
+		methods = BIO_meth_new(BIO_TYPE_NONE, "segment reader");
+		if (!methods)
+			return NULL;
+
+		BIO_meth_set_read(methods, stream_read);
+		BIO_meth_set_ctrl(methods, stream_ctrl);
+		BIO_meth_set_create(methods, stream_new);
+		BIO_meth_set_destroy(methods, stream_free);
+		BIO_meth_set_callback_ctrl(methods, stream_callback_ctrl);
+	}
+
+	bio = BIO_new(methods);
+	data = BIO_get_data(bio);
+	data->ctx = ctx;
+	data->stm = stm;
+
+	return bio;
+}
+
 enum
 {
 	SEG_START = 0,
@@ -649,25 +735,25 @@ pdf_designated_name *pdf_signer_designated_name(fz_context *ctx, pdf_signer *sig
 	return (pdf_designated_name *)dn;
 }
 
-void pdf_write_digest(fz_context *ctx, pdf_document *doc, const char *filename, pdf_obj *byte_range, int digest_offset, int digest_length, pdf_signer *signer)
+void pdf_write_digest(fz_context *ctx, fz_output *out, pdf_obj *byte_range, int digest_offset, int digest_length, pdf_signer *signer)
 {
+	fz_stream *in = NULL;
 	BIO *bdata = NULL;
 	BIO *bsegs = NULL;
 	BIO *bp7in = NULL;
 	BIO *bp7 = NULL;
 	PKCS7 *p7 = NULL;
 	PKCS7_SIGNER_INFO *si;
-	FILE *f = NULL;
 
 	int (*brange)[2] = NULL;
 	int brange_len = pdf_array_len(ctx, byte_range)/2;
 
+	fz_var(in);
 	fz_var(bdata);
 	fz_var(bsegs);
 	fz_var(bp7in);
 	fz_var(bp7);
 	fz_var(p7);
-	fz_var(f);
 
 	fz_try(ctx)
 	{
@@ -675,6 +761,8 @@ void pdf_write_digest(fz_context *ctx, pdf_document *doc, const char *filename,
 		int p7_len;
 		int i;
 
+		in = fz_stream_from_output(ctx, out);
+
 		brange = fz_calloc(ctx, brange_len, sizeof(*brange));
 		for (i = 0; i < brange_len; i++)
 		{
@@ -682,10 +770,9 @@ void pdf_write_digest(fz_context *ctx, pdf_document *doc, const char *filename,
 			brange[i][1] = pdf_to_int(ctx, pdf_array_get(ctx, byte_range, 2*i+1));
 		}
 
-		bdata = BIO_new(BIO_s_file());
+		bdata = BIO_new_stream(ctx, in);
 		if (bdata == NULL)
 			fz_throw(ctx, FZ_ERROR_GENERIC, "Failed to create file BIO");
-		BIO_read_filename(bdata, filename);
 
 		bsegs = BIO_new(BIO_f_segments());
 		if (bsegs == NULL)
@@ -729,6 +816,8 @@ void pdf_write_digest(fz_context *ctx, pdf_document *doc, const char *filename,
 		bsegs = NULL;
 		BIO_free(bdata);
 		bdata = NULL;
+		fz_drop_stream(ctx, in);
+		in = NULL;
 
 		bp7 = BIO_new(BIO_s_mem());
 		if (bp7 == NULL || !i2d_PKCS7_bio(bp7, p7))
@@ -738,24 +827,19 @@ void pdf_write_digest(fz_context *ctx, pdf_document *doc, const char *filename,
 		if (p7_len*2 + 2 > digest_length)
 			fz_throw(ctx, FZ_ERROR_GENERIC, "Insufficient space for digest");
 
-		f = fopen(filename, "rb+");
-		if (f == NULL)
-			fz_throw(ctx, FZ_ERROR_GENERIC, "Failed to write digest");
-
-		fseek(f, digest_offset+1, SEEK_SET);
+		fz_seek_output(ctx, out, digest_offset+1, SEEK_SET);
 
 		for (i = 0; i < p7_len; i++)
-			fprintf(f, "%02x", p7_ptr[i]);
+			fz_write_printf(ctx, out, "%02x", p7_ptr[i]);
 	}
 	fz_always(ctx)
 	{
+		fz_drop_stream(ctx, in);
 		PKCS7_free(p7);
 		BIO_free(bsegs);
 		BIO_free(bdata);
 		BIO_free(bp7in);
 		BIO_free(bp7);
-		if (f)
-			fclose(f);
 	}
 	fz_catch(ctx)
 	{
@@ -896,7 +980,7 @@ void pdf_drop_signer(fz_context *ctx, pdf_signer *signer)
 {
 }
 
-void pdf_write_digest(fz_context *ctx, pdf_document *doc, const char *filename, pdf_obj *byte_range, int digest_offset, int digest_length, pdf_signer *signer)
+void pdf_write_digest(fz_context *ctx, fz_output *out, pdf_obj *byte_range, int digest_offset, int digest_length, pdf_signer *signer)
 {
 }
 
diff --git a/source/pdf/pdf-write.c b/source/pdf/pdf-write.c
index b13970b9..28a505f9 100644
--- a/source/pdf/pdf-write.c
+++ b/source/pdf/pdf-write.c
@@ -2624,95 +2624,102 @@ static void presize_unsaved_signature_byteranges(fz_context *ctx, pdf_document *
 	}
 }
 
-static void complete_signatures(fz_context *ctx, pdf_document *doc, pdf_write_state *opts, const char *filename)
+static void complete_signatures(fz_context *ctx, pdf_document *doc, pdf_write_state *opts)
 {
 	pdf_unsaved_sig *usig;
 	char buf[5120];
 	int s;
 	int i;
 	int last_end;
-	FILE *f;
+	fz_stream *stm = NULL;
+	fz_var(stm);
 
-	for (s = 0; s < doc->num_incremental_sections; s++)
+	fz_try(ctx)
 	{
-		pdf_xref *xref = &doc->xref_sections[doc->num_incremental_sections - s - 1];
-
-		if (xref->unsaved_sigs)
+		for (s = 0; s < doc->num_incremental_sections; s++)
 		{
-			pdf_obj *byte_range;
+			pdf_xref *xref = &doc->xref_sections[doc->num_incremental_sections - s - 1];
 
-			f = fopen(filename, "rb+");
-			if (!f)
-				fz_throw(ctx, FZ_ERROR_GENERIC, "Failed to open %s to complete signatures", filename);
-
-			/* Locate the byte ranges and contents in the saved file */
-			for (usig = xref->unsaved_sigs; usig; usig = usig->next)
+			if (xref->unsaved_sigs)
 			{
-				char *bstr, *cstr, *fstr;
-				int pnum = pdf_obj_parent_num(ctx, pdf_dict_getl(ctx, usig->field, PDF_NAME_V, PDF_NAME_ByteRange, NULL));
-				fseek(f, opts->ofs_list[pnum], SEEK_SET);
-				(void)fread(buf, 1, sizeof(buf), f);
-				buf[sizeof(buf)-1] = 0;
+				pdf_obj *byte_range;
 
-				bstr = strstr(buf, "/ByteRange");
-				cstr = strstr(buf, "/Contents");
-				fstr = strstr(buf, "/Filter");
-
-				if (bstr && cstr && fstr && bstr < cstr && cstr < fstr)
+				stm = fz_stream_from_output(ctx, opts->out);
+				/* Locate the byte ranges and contents in the saved file */
+				for (usig = xref->unsaved_sigs; usig; usig = usig->next)
 				{
-					usig->byte_range_start = bstr - buf + 10 + opts->ofs_list[pnum];
-					usig->byte_range_end = cstr - buf + opts->ofs_list[pnum];
-					usig->contents_start = cstr - buf + 9 + opts->ofs_list[pnum];
-					usig->contents_end = fstr - buf + opts->ofs_list[pnum];
+					char *bstr, *cstr, *fstr;
+					int pnum = pdf_obj_parent_num(ctx, pdf_dict_getl(ctx, usig->field, PDF_NAME_V, PDF_NAME_ByteRange, NULL));
+					fz_seek(ctx, stm, opts->ofs_list[pnum], SEEK_SET);
+					(void)fz_read(ctx, stm, (unsigned char *)buf, sizeof(buf));
+					buf[sizeof(buf)-1] = 0;
+
+					bstr = strstr(buf, "/ByteRange");
+					cstr = strstr(buf, "/Contents");
+					fstr = strstr(buf, "/Filter");
+
+					if (bstr && cstr && fstr && bstr < cstr && cstr < fstr)
+					{
+						usig->byte_range_start = bstr - buf + 10 + opts->ofs_list[pnum];
+						usig->byte_range_end = cstr - buf + opts->ofs_list[pnum];
+						usig->contents_start = cstr - buf + 9 + opts->ofs_list[pnum];
+						usig->contents_end = fstr - buf + opts->ofs_list[pnum];
+					}
 				}
-			}
 
-			/* Recreate ByteRange with correct values. Initially store the
-			* recreated object in the first of the unsaved signatures */
-			byte_range = pdf_new_array(ctx, doc, 4);
-			pdf_dict_putl_drop(ctx, xref->unsaved_sigs->field, byte_range, PDF_NAME_V, PDF_NAME_ByteRange, NULL);
+				fz_drop_stream(ctx, stm);
+				stm = NULL;
 
-			last_end = 0;
-			for (usig = xref->unsaved_sigs; usig; usig = usig->next)
-			{
-				pdf_array_push_drop(ctx, byte_range, pdf_new_int(ctx, doc, last_end));
-				pdf_array_push_drop(ctx, byte_range, pdf_new_int(ctx, doc, usig->contents_start - last_end));
-				last_end = usig->contents_end;
-			}
-			pdf_array_push_drop(ctx, byte_range, pdf_new_int(ctx, doc, last_end));
-			pdf_array_push_drop(ctx, byte_range, pdf_new_int(ctx, doc, xref->end_ofs - last_end));
+				/* Recreate ByteRange with correct values. Initially store the
+				* recreated object in the first of the unsaved signatures */
+				byte_range = pdf_new_array(ctx, doc, 4);
+				pdf_dict_putl_drop(ctx, xref->unsaved_sigs->field, byte_range, PDF_NAME_V, PDF_NAME_ByteRange, NULL);
 
-			/* Copy the new ByteRange to the other unsaved signatures */
-			for (usig = xref->unsaved_sigs->next; usig; usig = usig->next)
-				pdf_dict_putl_drop(ctx, usig->field, pdf_copy_array(ctx, byte_range), PDF_NAME_V, PDF_NAME_ByteRange, NULL);
+				last_end = 0;
+				for (usig = xref->unsaved_sigs; usig; usig = usig->next)
+				{
+					pdf_array_push_drop(ctx, byte_range, pdf_new_int(ctx, doc, last_end));
+					pdf_array_push_drop(ctx, byte_range, pdf_new_int(ctx, doc, usig->contents_start - last_end));
+					last_end = usig->contents_end;
+				}
+				pdf_array_push_drop(ctx, byte_range, pdf_new_int(ctx, doc, last_end));
+				pdf_array_push_drop(ctx, byte_range, pdf_new_int(ctx, doc, xref->end_ofs - last_end));
 
-			/* Write the byte range into buf, padding with spaces*/
-			i = pdf_sprint_obj(ctx, buf, sizeof(buf), byte_range, 1);
-			memset(buf+i, ' ', sizeof(buf)-i);
+				/* Copy the new ByteRange to the other unsaved signatures */
+				for (usig = xref->unsaved_sigs->next; usig; usig = usig->next)
+					pdf_dict_putl_drop(ctx, usig->field, pdf_copy_array(ctx, byte_range), PDF_NAME_V, PDF_NAME_ByteRange, NULL);
 
-			/* Write the byte range to the file */
-			for (usig = xref->unsaved_sigs; usig; usig = usig->next)
-			{
-				fseek(f, usig->byte_range_start, SEEK_SET);
-				fwrite(buf, 1, usig->byte_range_end - usig->byte_range_start, f);
-			}
+				/* Write the byte range into buf, padding with spaces*/
+				i = pdf_sprint_obj(ctx, buf, sizeof(buf), byte_range, 1);
+				memset(buf+i, ' ', sizeof(buf)-i);
 
-			fclose(f);
+				/* Write the byte range to the file */
+				for (usig = xref->unsaved_sigs; usig; usig = usig->next)
+				{
+					fz_seek_output(ctx, opts->out, usig->byte_range_start, SEEK_SET);
+					fz_write_data(ctx, opts->out, buf, usig->byte_range_end - usig->byte_range_start);
+				}
 
-			/* Write the digests into the file */
-			for (usig = xref->unsaved_sigs; usig; usig = usig->next)
-				pdf_write_digest(ctx, doc, filename, byte_range, usig->contents_start, usig->contents_end - usig->contents_start, usig->signer);
+				/* Write the digests into the file */
+				for (usig = xref->unsaved_sigs; usig; usig = usig->next)
+					pdf_write_digest(ctx, opts->out, byte_range, usig->contents_start, usig->contents_end - usig->contents_start, usig->signer);
 
-			/* delete the unsaved_sigs records */
-			while ((usig = xref->unsaved_sigs) != NULL)
-			{
-				xref->unsaved_sigs = usig->next;
-				pdf_drop_obj(ctx, usig->field);
-				pdf_drop_signer(ctx, usig->signer);
-				fz_free(ctx, usig);
+				/* delete the unsaved_sigs records */
+				while ((usig = xref->unsaved_sigs) != NULL)
+				{
+					xref->unsaved_sigs = usig->next;
+					pdf_drop_obj(ctx, usig->field);
+					pdf_drop_signer(ctx, usig->signer);
+					fz_free(ctx, usig);
+				}
 			}
 		}
 	}
+	fz_catch(ctx)
+	{
+		fz_drop_stream(ctx, stm);
+		fz_rethrow(ctx);
+	}
 }
 
 static void clean_content_streams(fz_context *ctx, pdf_document *doc, int sanitize, int ascii)
@@ -3054,6 +3061,8 @@ do_pdf_save_document(fz_context *ctx, pdf_document *doc, pdf_write_state *opts,
 			doc->xref_sections[0].end_ofs = fz_tell_output(ctx, opts->out);
 		}
 
+		complete_signatures(ctx, doc, opts);
+
 		doc->dirty = 0;
 	}
 	fz_always(ctx)
@@ -3149,7 +3158,6 @@ void pdf_save_document(fz_context *ctx, pdf_document *doc, const char *filename,
 	{
 		do_pdf_save_document(ctx, doc, &opts, in_opts);
 		fz_close_output(ctx, opts.out);
-		complete_signatures(ctx, doc, &opts, filename);
 	}
 	fz_always(ctx)
 	{