Filters definition. Example XOR_encrypt filter.

14 years ago · 0dad87f035
5 changed files with 296 additions and 0 deletions
--- a/Makefile.am
+++ b/Makefile.am
@ -28,6 +28,9 @@ libisofs_libisofs_la_SOURCES = \
 	libisofs/libiso_msgs.c \
 	libisofs/stream.h \
 	libisofs/stream.c \
+	libisofs/filter.h \
+	libisofs/filter.c \
+	libisofs/filters/xor_encrypt.c \
 	libisofs/util.h \
 	libisofs/util.c \
 	libisofs/util_rbtree.c \
--- a/libisofs/filter.c
+++ b/libisofs/filter.c
@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2008 Vreixo Formoso
+ * 
+ * This file is part of the libisofs project; you can redistribute it and/or 
+ * modify it under the terms of the GNU General Public License version 2 as 
+ * published by the Free Software Foundation. See COPYING file for details.
+ */
+
+#include "libisofs.h"
+#include "filter.h"
+#include "node.h"
+
+
+void iso_filter_ref(FilterContext *filter)
+{
+    ++filter->refcount;
+}
+
+void iso_filter_unref(FilterContext *filter)
+{
+    if (--filter->refcount == 0) {
+        filter->free(filter);
+        free(filter);
+    }
+}
+
+int iso_file_add_filter(IsoFile *file, FilterContext *filter, int flag)
+{
+    int ret;
+    IsoStream *original, *filtered;
+    if (file == NULL || filter == NULL) {
+        return ISO_NULL_POINTER;
+    }
+    
+    original = file->stream;
+    ret = filter->get_filter(filter, original, &filtered);
+    if (ret < 0) {
+        return ret;
+    }
+    iso_stream_unref(original);
+    file->stream = filtered;
+    return ISO_SUCCESS;
+}
--- a/libisofs/filter.h
+++ b/libisofs/filter.h
@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2008 Vreixo Formoso
+ * 
+ * This file is part of the libisofs project; you can redistribute it and/or 
+ * modify it under the terms of the GNU General Public License version 2 as 
+ * published by the Free Software Foundation. See COPYING file for details.
+ */
+#ifndef LIBISO_FILTER_H_
+#define LIBISO_FILTER_H_
+
+/*
+ * Definitions of filters.
+ */
+
+/* dev_id for stream identification */
+#define XOR_ENCRYPT_DEV_ID      1
+
+typedef struct filter_context FilterContext;
+
+struct filter_context {
+    int version; /* reserved for future usage, set to 0 */
+    int refcount; 
+    
+    /** filter specific shared data */
+    void *data;
+
+    /** 
+     * Factory method to create a filtered stream from another stream.
+     * 
+     * @param original
+     *      The original stream to be filtered. If the filter needs a ref to
+     *      it (most cases), it should take a ref to it with iso_stream_ref().
+     * @param filtered
+     *      Will be filled with the filtered IsoStream (reference belongs to 
+     *      caller).
+     * @return
+     *      1 on success, < 0 on error
+     */
+    int (*get_filter)(FilterContext *filter, IsoStream *original, 
+                      IsoStream **filtered);
+
+    /**
+     * Free implementation specific data. Should never be called by user.
+     * Use iso_filter_unref() instead.
+     */
+    void (*free)(FilterContext *filter);
+};
+
+/**
+ * 
+ * @param flag
+ *      Reserved for future usage, pass always 0 for now. 
+ *      TODO in a future a different value can mean filter caching, where
+ *      the filter is applied once and the filtered file is stored in a temp
+ *      dir. This prevent filter to be applied several times.
+ */
+int iso_file_add_filter(IsoFile *file, FilterContext *filter, int flag);
+
+void iso_filter_ref(FilterContext *filter);
+void iso_filter_unref(FilterContext *filter);
+
+#endif /*LIBISO_FILTER_H_*/
--- a/libisofs/filters/xor_encrypt.c
+++ b/libisofs/filters/xor_encrypt.c
@ -0,0 +1,187 @@
+/*
+ * Copyright (c) 2008 Vreixo Formoso
+ * 
+ * This file is part of the libisofs project; you can redistribute it and/or 
+ * modify it under the terms of the GNU General Public License version 2 as 
+ * published by the Free Software Foundation. See COPYING file for details.
+ */
+
+#include "../libisofs.h"
+#include "../filter.h"
+#include "../fsource.h"
+
+/*
+ * A simple Filter implementation for example purposes. It encrypts a file
+ * by XORing each byte by a given key.
+ */
+
+static ino_t xor_ino_id = 0;
+
+typedef struct
+{
+    IsoStream *orig;
+    uint8_t key;
+    ino_t id;
+} XorEncryptStreamData;
+
+static
+int xor_encrypt_stream_open(IsoStream *stream)
+{
+    XorEncryptStreamData *data;
+    if (stream == NULL) {
+        return ISO_NULL_POINTER;
+    }
+    data = (XorEncryptStreamData*)stream->data;
+    return iso_stream_open(data->orig);
+}
+
+static
+int xor_encrypt_stream_close(IsoStream *stream)
+{
+    XorEncryptStreamData *data;
+    if (stream == NULL) {
+        return ISO_NULL_POINTER;
+    }
+    data = stream->data;
+    return iso_stream_close(data->orig);
+}
+
+static
+off_t xor_encrypt_stream_get_size(IsoStream *stream)
+{
+    XorEncryptStreamData *data;
+    if (stream == NULL) {
+        return ISO_NULL_POINTER;
+    }
+    data = stream->data;
+    return iso_stream_get_size(data->orig);
+}
+
+static
+int xor_encrypt_stream_read(IsoStream *stream, void *buf, size_t count)
+{
+    int ret, len;
+    XorEncryptStreamData *data;
+    uint8_t *buffer = buf;
+
+    if (stream == NULL) {
+        return ISO_NULL_POINTER;
+    }
+    data = stream->data;
+    ret = iso_stream_read(data->orig, buf, count);
+    if (ret < 0) {
+        return ret;
+    }
+    
+    /* xor */
+    for (len = 0; len < ret; ++len) {
+        buffer[len] = buffer[len] ^ data->key;
+    }
+    
+    return ret;
+}
+
+static
+int xor_encrypt_stream_is_repeatable(IsoStream *stream)
+{
+    /* the filter can't be created if underlying stream is not repeatable */
+    return 1;
+}
+
+static
+void xor_encrypt_stream_get_id(IsoStream *stream, unsigned int *fs_id, 
+                               dev_t *dev_id, ino_t *ino_id)
+{
+    XorEncryptStreamData *data = stream->data;
+    *fs_id = ISO_FILTER_FS_ID;
+    *dev_id = XOR_ENCRYPT_DEV_ID;
+    *ino_id = data->id;
+}
+
+static
+void xor_encrypt_stream_free(IsoStream *stream)
+{
+    XorEncryptStreamData *data = stream->data;
+    iso_stream_unref(data->orig);
+    free(data);
+}
+
+IsoStreamIface xor_encrypt_stream_class = {
+    0,
+    "xorf",
+    xor_encrypt_stream_open,
+    xor_encrypt_stream_close,
+    xor_encrypt_stream_get_size,
+    xor_encrypt_stream_read,
+    xor_encrypt_stream_is_repeatable,
+    xor_encrypt_stream_get_id,
+    xor_encrypt_stream_free
+};
+
+
+static
+void xor_encrypt_filter_free(FilterContext *filter)
+{
+    free(filter->data);
+}
+
+static
+int xor_encrypt_filter_get_filter(FilterContext *filter, IsoStream *original, 
+                  IsoStream **filtered)
+{
+    IsoStream *str;
+    XorEncryptStreamData *data;
+
+    if (filter == NULL || original == NULL || filtered == NULL) {
+        return ISO_NULL_POINTER;
+    }
+
+    str = malloc(sizeof(IsoStream));
+    if (str == NULL) {
+        return ISO_OUT_OF_MEM;
+    }
+    data = malloc(sizeof(XorEncryptStreamData));
+    if (str == NULL) {
+        free(str);
+        return ISO_OUT_OF_MEM;
+    }
+
+    /* fill data */
+    data->key = *((uint8_t*)filter->data);
+    data->id = xor_ino_id++;
+
+    /* get reference to the source */
+    data->orig = original;
+    iso_stream_ref(original);
+    
+    str->refcount = 1;
+    str->data = data;
+    str->class = &xor_encrypt_stream_class;
+
+    *filtered = str;
+    return ISO_SUCCESS;
+}
+
+int create_xor_encrypt_filter(uint8_t key, FilterContext **filter)
+{
+    FilterContext *f;
+    uint8_t *data;
+    
+    f = calloc(1, sizeof(FilterContext));
+    if (f == NULL) {
+        return ISO_OUT_OF_MEM;
+    }
+    data = malloc(sizeof(uint8_t));
+    if (data == NULL) {
+        free(f);
+        return ISO_OUT_OF_MEM;
+    }
+    f->refcount = 1;
+    f->version = 0;
+    *data = key;
+    f->data = data;
+    f->free = xor_encrypt_filter_free;
+    f->get_filter = xor_encrypt_filter_get_filter;
+    
+    return ISO_SUCCESS;
+}
--- a/libisofs/fsource.h
+++ b/libisofs/fsource.h
@ -20,6 +20,7 @@
 #define ISO_IMAGE_FS_ID        2
 #define ISO_ELTORITO_FS_ID     3
 #define ISO_MEM_FS_ID          4
+#define ISO_FILTER_FS_ID       5

 /**
 * Create a new IsoFilesystem to deal with local filesystem.