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https://github.com/ipxe/ipxe
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3f8937d2f3
Simplify the ASN.1 code by assuming that all objects are fully accessible via pointer dereferences. This allows the concept of "additional data beyond the end of the cursor" to be removed, and simplifies parsing of all ASN.1 image formats. Signed-off-by: Michael Brown <mcb30@ipxe.org>
141 lines
3.6 KiB
C
141 lines
3.6 KiB
C
/*
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* Copyright (C) 2016 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*
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* You can also choose to distribute this program under the terms of
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* the Unmodified Binary Distribution Licence (as given in the file
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* COPYING.UBDL), provided that you have satisfied its requirements.
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <stdlib.h>
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#include <errno.h>
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#include <assert.h>
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#include <ipxe/asn1.h>
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#include <ipxe/der.h>
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#include <ipxe/image.h>
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/** @file
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*
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* DER-encoded ASN.1 data
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*
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*/
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/**
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* Extract ASN.1 object from DER data
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*
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* @v data DER data
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* @v len Length of DER data
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* @v offset Offset within data
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* @v cursor ASN.1 cursor to fill in
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* @ret next Offset to next object, or negative error
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*
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* The caller is responsible for eventually calling free() on the
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* allocated ASN.1 cursor.
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*/
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int der_asn1 ( const void *data, size_t len, size_t offset,
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struct asn1_cursor **cursor ) {
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size_t remaining;
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void *raw;
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/* Sanity check */
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assert ( offset <= len );
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remaining = ( len - offset );
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/* Allocate cursor and data buffer */
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*cursor = malloc ( sizeof ( **cursor ) + remaining );
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if ( ! *cursor )
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return -ENOMEM;
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raw = ( ( ( void * ) *cursor ) + sizeof ( **cursor ) );
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/* Populate cursor and data buffer */
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(*cursor)->data = raw;
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(*cursor)->len = remaining;
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memcpy ( raw, ( data + offset ), remaining );
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/* Shrink cursor */
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asn1_shrink_any ( *cursor );
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return ( offset + (*cursor)->len );
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}
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/**
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* Probe DER image
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*
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* @v image DER image
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* @ret rc Return status code
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*/
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static int der_image_probe ( struct image *image ) {
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struct asn1_cursor cursor;
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int rc;
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/* Prepare cursor */
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cursor.data = image->data;
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cursor.len = image->len;
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/* Check that image begins with an ASN.1 sequence object */
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if ( ( rc = asn1_skip ( &cursor, ASN1_SEQUENCE ) ) != 0 ) {
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DBGC ( image, "DER %s is not valid ASN.1: %s\n",
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image->name, strerror ( rc ) );
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return rc;
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}
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/* Check that image comprises a single well-formed ASN.1 object */
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if ( cursor.len ) {
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DBGC ( image, "DER %s is not single ASN.1\n", image->name );
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return -ENOEXEC;
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}
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return 0;
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}
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/**
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* Extract ASN.1 object from DER image
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*
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* @v image DER image
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* @v offset Offset within image
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* @v cursor ASN.1 cursor to fill in
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* @ret next Offset to next image, or negative error
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*
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* The caller is responsible for eventually calling free() on the
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* allocated ASN.1 cursor.
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*/
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static int der_image_asn1 ( struct image *image, size_t offset,
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struct asn1_cursor **cursor ) {
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int next;
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int rc;
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/* Extract ASN.1 object */
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if ( ( next = der_asn1 ( image->data, image->len, offset,
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cursor ) ) < 0 ) {
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rc = next;
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DBGC ( image, "DER %s could not extract ASN.1: %s\n",
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image->name, strerror ( rc ) );
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return rc;
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}
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return next;
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}
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/** DER image type */
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struct image_type der_image_type __image_type ( PROBE_NORMAL ) = {
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.name = "DER",
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.probe = der_image_probe,
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.asn1 = der_image_asn1,
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};
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