--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/source/fitz/untar.c	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,354 @@
+// Copyright (C) 2004-2024 Artifex Software, Inc.
+//
+// This file is part of MuPDF.
+//
+// MuPDF is free software: you can redistribute it and/or modify it under the
+// terms of the GNU Affero General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// MuPDF is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+// details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
+//
+// Alternative licensing terms are available from the licensor.
+// For commercial licensing, see <https://www.artifex.com/> or contact
+// Artifex Software, Inc., 39 Mesa Street, Suite 108A, San Francisco,
+// CA 94129, USA, for further information.
+
+#include "mupdf/fitz.h"
+
+#include <string.h>
+#include <limits.h>
+
+#define TYPE_NORMAL_OLD '\0'
+#define TYPE_NORMAL '0'
+#define TYPE_CONTIGUOUS '7'
+#define TYPE_LONG_NAME 'L'
+
+typedef struct
+{
+	char *name;
+	int64_t offset;
+	int size;
+} tar_entry;
+
+typedef struct
+{
+	fz_archive super;
+
+	int count;
+	tar_entry *entries;
+} fz_tar_archive;
+
+static inline int isoctdigit(char c)
+{
+	return c >= '0' && c <= '7';
+}
+
+static inline int64_t otoi(const char *s)
+{
+	int64_t value = 0;
+
+	while (*s && isoctdigit(*s))
+	{
+		value *= 8;
+		value += (*s) - '0';
+		s++;
+	}
+
+	return value;
+}
+
+static void drop_tar_archive(fz_context *ctx, fz_archive *arch)
+{
+	fz_tar_archive *tar = (fz_tar_archive *) arch;
+	int i;
+	for (i = 0; i < tar->count; ++i)
+		fz_free(ctx, tar->entries[i].name);
+	fz_free(ctx, tar->entries);
+}
+
+static int is_zeroed(fz_context *ctx, unsigned char *buf, size_t size)
+{
+	size_t off;
+
+	for (off = 0; off < size; off++)
+		if (buf[off] != 0)
+			return 0;
+
+	return 1;
+}
+
+static void ensure_tar_entries(fz_context *ctx, fz_tar_archive *tar)
+{
+	fz_stream *file = tar->super.file;
+	unsigned char record[512];
+	char *longname = NULL;
+	char name[101];
+	char octsize[13];
+	char typeflag;
+	int64_t offset, blocks, size;
+	size_t n;
+
+	tar->count = 0;
+
+	fz_seek(ctx, file, 0, SEEK_SET);
+
+	while (1)
+	{
+		offset = fz_tell(ctx, file);
+		n = fz_read(ctx, file, record, nelem(record));
+		if (n == 0)
+			break;
+		if (n < nelem(record))
+			fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of data in tar record");
+
+		if (is_zeroed(ctx, record, nelem(record)))
+			continue;
+
+		memcpy(name, record + 0, nelem(name) - 1);
+		name[nelem(name) - 1] = '\0';
+
+		memcpy(octsize, record + 124, nelem(octsize) - 1);
+		octsize[nelem(octsize) - 1] = '\0';
+
+		size = otoi(octsize);
+		if (size > INT_MAX)
+			fz_throw(ctx, FZ_ERROR_FORMAT, "tar archive entry too large");
+
+		typeflag = (char) record[156];
+
+		if (typeflag == TYPE_LONG_NAME)
+		{
+			longname = fz_malloc(ctx, size + 1);
+			fz_try(ctx)
+			{
+				n = fz_read(ctx, file, (unsigned char *) longname, size);
+				if (n < (size_t) size)
+					fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of data in tar long name entry name");
+				longname[size] = '\0';
+			}
+			fz_catch(ctx)
+			{
+				fz_free(ctx, longname);
+				fz_rethrow(ctx);
+			}
+
+			fz_seek(ctx, file, 512 - (size % 512), 1);
+		}
+
+		if (typeflag != TYPE_NORMAL_OLD && typeflag != TYPE_NORMAL &&
+			typeflag != TYPE_CONTIGUOUS && typeflag != TYPE_LONG_NAME)
+			continue;
+
+		blocks = (size + 511) / 512;
+		fz_seek(ctx, file, blocks * 512, 1);
+
+		tar->entries = fz_realloc_array(ctx, tar->entries, tar->count + 1, tar_entry);
+
+		tar->entries[tar->count].offset = offset;
+		tar->entries[tar->count].size = size;
+		if (longname != NULL)
+		{
+			tar->entries[tar->count].name = longname;
+			longname = NULL;
+		}
+		else
+			tar->entries[tar->count].name = fz_strdup(ctx, name);
+
+		tar->count++;
+	}
+}
+
+static tar_entry *lookup_tar_entry(fz_context *ctx, fz_tar_archive *tar, const char *name)
+{
+	int i;
+	for (i = 0; i < tar->count; i++)
+		if (!fz_strcasecmp(name, tar->entries[i].name))
+			return &tar->entries[i];
+	return NULL;
+}
+
+static fz_stream *open_tar_entry(fz_context *ctx, fz_archive *arch, const char *name)
+{
+	fz_tar_archive *tar = (fz_tar_archive *) arch;
+	fz_stream *file = tar->super.file;
+	tar_entry *ent;
+
+	ent = lookup_tar_entry(ctx, tar, name);
+	if (!ent)
+		return NULL;
+
+	fz_seek(ctx, file, ent->offset + 512, 0);
+	return fz_open_null_filter(ctx, file, ent->size, fz_tell(ctx, file));
+}
+
+static fz_buffer *read_tar_entry(fz_context *ctx, fz_archive *arch, const char *name)
+{
+	fz_tar_archive *tar = (fz_tar_archive *) arch;
+	fz_stream *file = tar->super.file;
+	fz_buffer *ubuf;
+	tar_entry *ent;
+
+	ent = lookup_tar_entry(ctx, tar, name);
+	if (!ent)
+		return NULL;
+
+	ubuf = fz_new_buffer(ctx, ent->size);
+
+	fz_try(ctx)
+	{
+		fz_seek(ctx, file, ent->offset + 512, 0);
+		ubuf->len = fz_read(ctx, file, ubuf->data, ent->size);
+		if (ubuf->len != (size_t)ent->size)
+			fz_throw(ctx, FZ_ERROR_FORMAT, "cannot read entire archive entry");
+	}
+	fz_catch(ctx)
+	{
+		fz_drop_buffer(ctx, ubuf);
+		fz_rethrow(ctx);
+	}
+
+	return ubuf;
+}
+
+static int has_tar_entry(fz_context *ctx, fz_archive *arch, const char *name)
+{
+	fz_tar_archive *tar = (fz_tar_archive *) arch;
+	tar_entry *ent = lookup_tar_entry(ctx, tar, name);
+	return ent != NULL;
+}
+
+static const char *list_tar_entry(fz_context *ctx, fz_archive *arch, int idx)
+{
+	fz_tar_archive *tar = (fz_tar_archive *) arch;
+	if (idx < 0 || idx >= tar->count)
+		return NULL;
+	return tar->entries[idx].name;
+}
+
+static int count_tar_entries(fz_context *ctx, fz_archive *arch)
+{
+	fz_tar_archive *tar = (fz_tar_archive *) arch;
+	return tar->count;
+}
+
+static int isoct(unsigned char *d, int n)
+{
+	while (--n > 0)
+	{
+		unsigned char c = *d++;
+		if (c < '0' || c > '7')
+			return 0;
+	}
+	return (*d == 0);
+}
+
+static int
+check_v7(fz_context *ctx, fz_stream *file)
+{
+	unsigned char data[512];
+	size_t n;
+	int i;
+
+	fz_seek(ctx, file, 0, SEEK_SET);
+	n = fz_read(ctx, file, data, nelem(data));
+	if (n != nelem(data))
+		return 0;
+
+	/* Skip over name. */
+	for (i = 0; i < 100 && data[i] != 0; i++);
+
+	/* We want at least 1 byte of name, and a zero terminator. */
+	if (i == 0 || i == 100)
+		return 0;
+
+	/* Skip over a run of zero terminators. */
+	for (; i < 100 && data[i] == 0; i++);
+
+	if (i != 100)
+		return 0;
+
+	return (isoct(data+100, 8) &&
+		isoct(data+108, 8) &&
+		isoct(data+116, 8) &&
+		isoct(data+124, 12) &&
+		isoct(data+136, 12) &&
+		isoct(data+148, 8));
+}
+
+int
+fz_is_tar_archive(fz_context *ctx, fz_stream *file)
+{
+	const unsigned char gnusignature[6] = { 'u', 's', 't', 'a', 'r', ' ' };
+	const unsigned char paxsignature[6] = { 'u', 's', 't', 'a', 'r', '\0' };
+	const unsigned char v7signature[6] = { '\0', '\0', '\0', '\0', '\0', '\0' };
+	unsigned char data[6];
+	size_t n;
+
+	fz_seek(ctx, file, 257, 0);
+	n = fz_read(ctx, file, data, nelem(data));
+	if (n != nelem(data))
+		return 0;
+	if (!memcmp(data, gnusignature, nelem(gnusignature)))
+		return 1;
+	if (!memcmp(data, paxsignature, nelem(paxsignature)))
+		return 1;
+	if (!memcmp(data, v7signature, nelem(v7signature)))
+		return check_v7(ctx, file);
+
+	return 0;
+}
+
+fz_archive *
+fz_open_tar_archive_with_stream(fz_context *ctx, fz_stream *file)
+{
+	fz_tar_archive *tar;
+
+	if (!fz_is_tar_archive(ctx, file))
+		fz_throw(ctx, FZ_ERROR_FORMAT, "cannot recognize tar archive");
+
+	tar = fz_new_derived_archive(ctx, file, fz_tar_archive);
+	tar->super.format = "tar";
+	tar->super.count_entries = count_tar_entries;
+	tar->super.list_entry = list_tar_entry;
+	tar->super.has_entry = has_tar_entry;
+	tar->super.read_entry = read_tar_entry;
+	tar->super.open_entry = open_tar_entry;
+	tar->super.drop_archive = drop_tar_archive;
+
+	fz_try(ctx)
+	{
+		ensure_tar_entries(ctx, tar);
+	}
+	fz_catch(ctx)
+	{
+		fz_drop_archive(ctx, &tar->super);
+		fz_rethrow(ctx);
+	}
+
+	return &tar->super;
+}
+
+fz_archive *
+fz_open_tar_archive(fz_context *ctx, const char *filename)
+{
+	fz_archive *tar = NULL;
+	fz_stream *file;
+
+	file = fz_open_file(ctx, filename);
+
+	fz_try(ctx)
+		tar = fz_open_tar_archive_with_stream(ctx, file);
+	fz_always(ctx)
+		fz_drop_stream(ctx, file);
+	fz_catch(ctx)
+		fz_rethrow(ctx);
+
+	return tar;
+}