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|
/* Copyright (C) 2020-2021 Artifex Software, Inc.
All Rights Reserved.
This software is provided AS-IS with no warranty, either express or
implied.
This software is distributed under license and may not be copied,
modified or distributed except as expressly authorized under the terms
of the license contained in the file LICENSE in this distribution.
Refer to licensing information at http://www.artifex.com or contact
Artifex Software, Inc., 1305 Grant Avenue - Suite 200, Novato,
CA 94945, U.S.A., +1(415)492-9861, for further information.
*/
/* Routines to attempt repair of PDF files in the event of an error */
#include "pdf_int.h"
#include "pdf_stack.h"
#include "strmio.h"
#include "stream.h"
#include "pdf_deref.h"
#include "pdf_dict.h"
#include "pdf_file.h"
#include "pdf_misc.h"
#include "pdf_repair.h"
static int pdfi_repair_add_object(pdf_context *ctx, uint64_t obj, uint64_t gen, gs_offset_t offset)
{
/* Although we can handle object numbers larger than this, on some systems (32-bit Windows)
* memset is limited to a (signed!) integer for the size of memory to clear. We could deal
* with this by clearing the memory in blocks, but really, this is almost certainly a
* corrupted file or something.
*/
if (obj >= 0x7ffffff / sizeof(xref_entry))
return_error(gs_error_rangecheck);
if (ctx->xref_table == NULL) {
ctx->xref_table = (xref_table_t *)gs_alloc_bytes(ctx->memory, sizeof(xref_table_t), "repair xref table");
if (ctx->xref_table == NULL) {
return_error(gs_error_VMerror);
}
memset(ctx->xref_table, 0x00, sizeof(xref_table_t));
ctx->xref_table->xref = (xref_entry *)gs_alloc_bytes(ctx->memory, (obj + 1) * sizeof(xref_entry), "repair xref table");
if (ctx->xref_table->xref == NULL){
gs_free_object(ctx->memory, ctx->xref_table, "failed to allocate xref table entries for repair");
ctx->xref_table = NULL;
return_error(gs_error_VMerror);
}
memset(ctx->xref_table->xref, 0x00, (obj + 1) * sizeof(xref_entry));
ctx->xref_table->ctx = ctx;
ctx->xref_table->type = PDF_XREF_TABLE;
ctx->xref_table->xref_size = obj + 1;
#if REFCNT_DEBUG
ctx->xref_table->UID = ctx->UID++;
dmprintf1(ctx->memory, "Allocated xref table with UID %"PRIi64"\n", ctx->xref_table->UID);
#endif
pdfi_countup(ctx->xref_table);
} else {
if (ctx->xref_table->xref_size < (obj + 1)) {
xref_entry *new_xrefs;
new_xrefs = (xref_entry *)gs_alloc_bytes(ctx->memory, (obj + 1) * sizeof(xref_entry), "read_xref_stream allocate xref table entries");
if (new_xrefs == NULL){
pdfi_countdown(ctx->xref_table);
ctx->xref_table = NULL;
return_error(gs_error_VMerror);
}
memset(new_xrefs, 0x00, (obj + 1) * sizeof(xref_entry));
memcpy(new_xrefs, ctx->xref_table->xref, ctx->xref_table->xref_size * sizeof(xref_entry));
gs_free_object(ctx->memory, ctx->xref_table->xref, "reallocated xref entries");
ctx->xref_table->xref = new_xrefs;
ctx->xref_table->xref_size = obj + 1;
}
}
ctx->xref_table->xref[obj].compressed = false;
ctx->xref_table->xref[obj].free = false;
ctx->xref_table->xref[obj].object_num = obj;
ctx->xref_table->xref[obj].u.uncompressed.generation_num = gen;
ctx->xref_table->xref[obj].u.uncompressed.offset = offset;
return 0;
}
int pdfi_repair_file(pdf_context *ctx)
{
int code = 0;
gs_offset_t offset, saved_offset;
uint64_t object_num = 0, generation_num = 0;
int i;
gs_offset_t outer_saved_offset[3];
if (ctx->repaired) {
pdfi_set_error(ctx, 0, NULL, E_PDF_UNREPAIRABLE, "pdfi_repair_file", (char *)"%% Trying to repair file for second time -- unrepairable");
return_error(gs_error_undefined);
}
saved_offset = pdfi_unread_tell(ctx);
ctx->repaired = true;
pdfi_set_error(ctx, 0, NULL, E_PDF_REPAIRED, "pdfi_repair_file", NULL);
pdfi_clearstack(ctx);
if(ctx->args.pdfdebug)
dmprintf(ctx->memory, "%% Error encountered in opening PDF file, attempting repair\n");
/* First try to locate a %PDF header. If we can't find one, abort this, the file is too broken
* and may not even be a PDF file.
*/
pdfi_seek(ctx, ctx->main_stream, 0, SEEK_SET);
{
char Buffer[10], test[] = "%PDF";
int index = 0;
do {
code = pdfi_read_bytes(ctx, (byte *)&Buffer[index], 1, 1, ctx->main_stream);
if (code < 0)
goto exit;
if (Buffer[index] == test[index])
index++;
else
index = 0;
} while (index < 4 && ctx->main_stream->eof == false);
if (memcmp(Buffer, test, 4) != 0) {
code = gs_note_error(gs_error_undefined);
goto exit;
}
pdfi_unread(ctx, ctx->main_stream, (byte *)Buffer, 4);
pdfi_skip_comment(ctx, ctx->main_stream);
}
if (ctx->main_stream->eof == true) {
code = gs_note_error(gs_error_ioerror);
goto exit;
}
/* First pass, identify all the objects of the form x y obj */
do {
code = pdfi_skip_white(ctx, ctx->main_stream);
if (code < 0) {
if (code != gs_error_VMerror && code != gs_error_ioerror) {
pdfi_clearstack(ctx);
continue;
} else
goto exit;
}
offset = pdfi_unread_tell(ctx);
outer_saved_offset[0] = outer_saved_offset[1] = outer_saved_offset[2] = 0;
do {
outer_saved_offset[0] = outer_saved_offset[1];
outer_saved_offset[1] = outer_saved_offset[2];
outer_saved_offset[2] = pdfi_unread_tell(ctx);
object_num = 0;
code = pdfi_read_token(ctx, ctx->main_stream, 0, 0);
if (code < 0) {
if (code != gs_error_VMerror && code != gs_error_ioerror) {
pdfi_clearstack(ctx);
continue;
} else
goto exit;
}
if (pdfi_count_stack(ctx) > 0) {
if (ctx->stack_top[-1]->type == PDF_KEYWORD) {
pdf_keyword *k = (pdf_keyword *)ctx->stack_top[-1];
pdf_num *n;
if (k->key == TOKEN_OBJ) {
gs_offset_t saved_offset[3];
offset = outer_saved_offset[0];
saved_offset[0] = saved_offset[1] = saved_offset[2] = 0;
if (pdfi_count_stack(ctx) < 3 || ctx->stack_top[-2]->type != PDF_INT || ctx->stack_top[-2]->type != PDF_INT) {
pdfi_clearstack(ctx);
continue;
}
n = (pdf_num *)ctx->stack_top[-3];
object_num = n->value.i;
n = (pdf_num *)ctx->stack_top[-2];
generation_num = n->value.i;
pdfi_clearstack(ctx);
do {
/* move all the saved offsets up by one */
saved_offset[0] = saved_offset[1];
saved_offset[1] = saved_offset[2];
saved_offset[2] = pdfi_unread_tell(ctx);;
code = pdfi_read_token(ctx, ctx->main_stream, 0, 0);
if (code < 0) {
if (code != gs_error_VMerror && code != gs_error_ioerror)
continue;
goto exit;
}
if (code == 0 && ctx->main_stream->eof)
break;
if (ctx->stack_top[-1]->type == PDF_KEYWORD){
pdf_keyword *k = (pdf_keyword *)ctx->stack_top[-1];
if (k->key == TOKEN_OBJ) {
/* Found obj while looking for endobj, store the existing 'obj'
* and start afresh.
*/
code = pdfi_repair_add_object(ctx, object_num, generation_num, offset);
if (pdfi_count_stack(ctx) < 3 || ctx->stack_top[-2]->type != PDF_INT || ctx->stack_top[-2]->type != PDF_INT) {
pdfi_clearstack(ctx);
break;
}
n = (pdf_num *)ctx->stack_top[-3];
object_num = n->value.i;
n = (pdf_num *)ctx->stack_top[-2];
generation_num = n->value.i;
pdfi_clearstack(ctx);
offset = saved_offset[0];
continue;
}
if (k->key == TOKEN_ENDOBJ) {
code = pdfi_repair_add_object(ctx, object_num, generation_num, offset);
if (code < 0)
goto exit;
pdfi_clearstack(ctx);
break;
} else {
if (k->key == TOKEN_STREAM) {
char Buffer[10], test[] = "endstream";
int index = 0;
do {
code = pdfi_read_bytes(ctx, (byte *)&Buffer[index], 1, 1, ctx->main_stream);
if (code < 0) {
if (code != gs_error_VMerror && code != gs_error_ioerror)
continue;
goto exit;
}
if (Buffer[index] == test[index])
index++;
else
index = 0;
} while (index < 9 && ctx->main_stream->eof == false);
do {
code = pdfi_read_token(ctx, ctx->main_stream, 0, 0);
if (code < 0) {
if (code != gs_error_VMerror && code != gs_error_ioerror)
continue;
goto exit;
}
if (ctx->stack_top[-1]->type == PDF_KEYWORD){
pdf_keyword *k = (pdf_keyword *)ctx->stack_top[-1];
if (k->key == TOKEN_ENDOBJ) {
code = pdfi_repair_add_object(ctx, object_num, generation_num, offset);
if (code < 0) {
if (code != gs_error_VMerror && code != gs_error_ioerror)
break;
goto exit;
}
break;
}
}
}while(ctx->main_stream->eof == false);
pdfi_clearstack(ctx);
break;
} else {
pdfi_clearstack(ctx);
}
}
}
} while(1);
break;
} else {
if (k->key == TOKEN_ENDOBJ) {
pdfi_clearstack(ctx);
} else
if (k->key == TOKEN_STARTXREF) {
code = pdfi_read_token(ctx, ctx->main_stream, 0, 0);
if (code < 0 && code != gs_error_VMerror && code != gs_error_ioerror)
continue;
if (code < 0)
goto exit;
pdfi_clearstack(ctx);
} else {
if (k->key == TOKEN_TRAILER) {
code = pdfi_read_bare_object(ctx, ctx->main_stream, 0, 0, 0);
if (code == 0 && ctx->stack_top[-1]->type == PDF_DICT) {
if (ctx->Trailer) {
pdf_dict *d = (pdf_dict *)ctx->stack_top[-1];
bool known = false;
code = pdfi_dict_known(ctx, d, "Root", &known);
if (code == 0 && known) {
pdfi_countdown(ctx->Trailer);
ctx->Trailer = (pdf_dict *)ctx->stack_top[-1];
pdfi_countup(ctx->Trailer);
}
} else {
ctx->Trailer = (pdf_dict *)ctx->stack_top[-1];
pdfi_countup(ctx->Trailer);
}
}
}
pdfi_clearstack(ctx);
}
}
code = pdfi_skip_white(ctx, ctx->main_stream);
if (code < 0) {
if (code != gs_error_VMerror && code != gs_error_ioerror) {
pdfi_clearstack(ctx);
continue;
} else
goto exit;
}
}
if (pdfi_count_stack(ctx) > 0 && ctx->stack_top[-1]->type != PDF_INT)
pdfi_clearstack(ctx);
}
} while (ctx->main_stream->eof == false);
} while(ctx->main_stream->eof == false);
pdfi_seek(ctx, ctx->main_stream, 0, SEEK_SET);
ctx->main_stream->eof = false;
/* Second pass, examine every object we have located to see if its an ObjStm */
if (ctx->xref_table == NULL || ctx->xref_table->xref_size < 1) {
code = gs_note_error(gs_error_syntaxerror);
goto exit;
}
for (i=1;i < ctx->xref_table->xref_size;i++) {
if (ctx->xref_table->xref[i].object_num != 0) {
/* At this stage, all the objects we've found must be uncompressed */
if (ctx->xref_table->xref[i].u.uncompressed.offset > ctx->main_stream_length) {
code = gs_note_error(gs_error_rangecheck);
goto exit;
}
pdfi_seek(ctx, ctx->main_stream, ctx->xref_table->xref[i].u.uncompressed.offset, SEEK_SET);
do {
code = pdfi_read_token(ctx, ctx->main_stream, 0, 0);
if (ctx->main_stream->eof == true || (code < 0 && code != gs_error_ioerror && code != gs_error_VMerror))
break;
if (code < 0)
goto exit;
if (ctx->stack_top[-1]->type == PDF_KEYWORD) {
pdf_keyword *k = (pdf_keyword *)ctx->stack_top[-1];
if (k->key == TOKEN_OBJ){
continue;
}
if (k->key == TOKEN_ENDOBJ) {
if (pdfi_count_stack(ctx) > 1) {
if (ctx->stack_top[-2]->type == PDF_DICT) {
pdf_dict *d = (pdf_dict *)ctx->stack_top[-2];
pdf_obj *o = NULL;
code = pdfi_dict_knownget_type(ctx, d, "Type", PDF_NAME, &o);
if (code < 0) {
pdfi_clearstack(ctx);
goto exit;
}
if (code > 0) {
pdf_name *n = (pdf_name *)o;
if (pdfi_name_is(n, "Catalog")) {
pdfi_countdown(ctx->Root); /* In case it was already set */
ctx->Root = (pdf_dict *)ctx->stack_top[-2];
pdfi_countup(ctx->Root);
}
}
pdfi_countdown(o);
}
}
pdfi_clearstack(ctx);
break;
}
if (k->key == TOKEN_STREAM) {
pdf_dict *d;
pdf_name *n = NULL;
if (pdfi_count_stack(ctx) <= 1) {
pdfi_clearstack(ctx);
break;;
}
d = (pdf_dict *)ctx->stack_top[-2];
if (d->type != PDF_DICT) {
pdfi_clearstack(ctx);
break;;
}
code = pdfi_dict_knownget_type(ctx, d, "Type", PDF_NAME, (pdf_obj **)&n);
if (code < 0) {
if (ctx->args.pdfstoponerror || code == gs_error_VMerror) {
pdfi_clearstack(ctx);
goto exit;
}
}
if (code > 0) {
if (pdfi_name_is(n, "ObjStm")) {
int64_t N, obj_num, offset;
int j;
pdf_c_stream *compressed_stream;
pdf_obj *o;
pdf_stream *stream;
offset = pdfi_unread_tell(ctx);
pdfi_seek(ctx, ctx->main_stream, offset, SEEK_SET);
code = pdfi_obj_dict_to_stream(ctx, d, &stream, true);
if (code == 0)
code = pdfi_filter(ctx, stream, ctx->main_stream, &compressed_stream, false);
pdfi_countdown(stream);
if (code == 0) {
code = pdfi_dict_get_int(ctx, d, "N", &N);
if (code == 0) {
for (j=0;j < N; j++) {
code = pdfi_read_token(ctx, compressed_stream, 0, 0);
if (code == 0) {
o = ctx->stack_top[-1];
if (((pdf_obj *)o)->type == PDF_INT) {
obj_num = ((pdf_num *)o)->value.i;
pdfi_pop(ctx, 1);
code = pdfi_read_token(ctx, compressed_stream, 0, 0);
if (code == 0) {
o = ctx->stack_top[-1];
if (((pdf_obj *)o)->type == PDF_INT) {
offset = ((pdf_num *)o)->value.i;
if (obj_num < 1) {
pdfi_close_file(ctx, compressed_stream);
pdfi_clearstack(ctx);
code = gs_note_error(gs_error_rangecheck);
goto exit;
}
ctx->xref_table->xref[obj_num].compressed = true;
ctx->xref_table->xref[obj_num].free = false;
ctx->xref_table->xref[obj_num].object_num = obj_num;
ctx->xref_table->xref[obj_num].u.compressed.compressed_stream_num = i;
ctx->xref_table->xref[obj_num].u.compressed.object_index = j;
}
}
}
}
}
}
pdfi_close_file(ctx, compressed_stream);
}
if (code < 0) {
if (ctx->args.pdfstoponerror || code == gs_error_VMerror) {
pdfi_clearstack(ctx);
goto exit;
}
}
}
}
pdfi_countdown(n);
pdfi_clearstack(ctx);
break;
}
}
} while (1);
}
}
exit:
pdfi_seek(ctx, ctx->main_stream, saved_offset, SEEK_SET);
ctx->main_stream->eof = false;
return code;
}
|