[crypto] Add DER image format

Add DER-encoded ASN.1 as an image format.  There is no fixed signature
for DER files.  We treat an image as DER if it comprises a single
valid SEQUENCE object covering the entire length of the image.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/config/config.c

@@ -188,6 +188,9 @@ REQUIRE_OBJECT ( pnm );
 #ifdef IMAGE_PNG
 REQUIRE_OBJECT ( png );
 #endif
+#ifdef IMAGE_DER
+REQUIRE_OBJECT ( der );
+#endif
 
 /*
  * Drag in all requested commands

src/config/general.h

@@ -112,6 +112,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 //#define	IMAGE_SDI		/* SDI image support */
 //#define	IMAGE_PNM		/* PNM image support */
 //#define	IMAGE_PNG		/* PNG image support */
+//#define	IMAGE_DER		/* DER image support */
 
 /*
  * Command-line commands to include

src/image/der.c

@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2016 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdlib.h>
+#include <errno.h>
+#include <assert.h>
+#include <ipxe/asn1.h>
+#include <ipxe/der.h>
+#include <ipxe/uaccess.h>
+#include <ipxe/image.h>
+
+/** @file
+ *
+ * DER-encoded ASN.1 data
+ *
+ */
+
+/**
+ * Extract ASN.1 object from image
+ *
+ * @v image		DER image
+ * @v offset		Offset within image
+ * @v cursor		ASN.1 cursor to fill in
+ * @ret next		Offset to next image, or negative error
+ *
+ * The caller is responsible for eventually calling free() on the
+ * allocated ASN.1 cursor.
+ */
+static int der_asn1 ( struct image *image, size_t offset __unused,
+		      struct asn1_cursor **cursor ) {
+	void *data;
+
+	/* Allocate cursor and data buffer */
+	*cursor = malloc ( sizeof ( **cursor ) + image->len );
+	if ( ! *cursor )
+		return -ENOMEM;
+	data = ( ( ( void * ) *cursor ) + sizeof ( **cursor ) );
+
+	/* Populate cursor and data buffer */
+	(*cursor)->data = data;
+	(*cursor)->len = image->len;
+	copy_from_user ( data, image->data, 0, image->len );
+
+	return image->len;
+}
+
+/**
+ * Probe DER image
+ *
+ * @v image		DER image
+ * @ret rc		Return status code
+ */
+static int der_probe ( struct image *image ) {
+	struct asn1_cursor cursor;
+	uint8_t buf[8];
+	size_t extra;
+	size_t total;
+	int len;
+	int rc;
+
+	/* Sanity check: no realistic DER image can be smaller than this */
+	if ( image->len < sizeof ( buf ) )
+		return -ENOEXEC;
+
+	/* Prepare partial cursor */
+	cursor.data = buf;
+	cursor.len = sizeof ( buf );
+	copy_from_user ( buf, image->data, 0, sizeof ( buf ) );
+	extra = ( image->len - sizeof ( buf ) );
+
+	/* Get length of ASN.1 sequence */
+	len = asn1_start ( &cursor, ASN1_SEQUENCE, extra );
+	if ( len < 0 ) {
+		rc = len;
+		DBGC ( image, "DER %s is not valid ASN.1: %s\n",
+		       image->name, strerror ( rc ) );
+		return rc;
+	}
+
+	/* Add length of tag and length bytes consumed by asn1_start() */
+	total = ( len + ( cursor.data - ( ( void * ) buf ) ) );
+	assert ( total <= image->len );
+
+	/* Check that image comprises a single well-formed ASN.1 object */
+	if ( total != image->len ) {
+		DBGC ( image, "DER %s is not single ASN.1\n", image->name );
+		return -ENOEXEC;
+	}
+
+	return 0;
+}
+
+/** DER image type */
+struct image_type der_image_type __image_type ( PROBE_NORMAL ) = {
+	.name = "DER",
+	.probe = der_probe,
+	.asn1 = der_asn1,
+};

src/include/ipxe/der.h

@@ -0,0 +1,16 @@
+#ifndef _IPXE_DER_H
+#define _IPXE_DER_H
+
+/** @file
+ *
+ * DER image format
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <ipxe/image.h>
+
+extern struct image_type der_image_type __image_type ( PROBE_NORMAL );
+
+#endif /* _IPXE_DER_H */

src/include/ipxe/errfile.h

@@ -276,6 +276,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_embedded	      ( ERRFILE_IMAGE | 0x00050000 )
 #define ERRFILE_pnm		      ( ERRFILE_IMAGE | 0x00060000 )
 #define ERRFILE_png		      ( ERRFILE_IMAGE | 0x00070000 )
+#define ERRFILE_der		      ( ERRFILE_IMAGE | 0x00080000 )
 
 #define ERRFILE_asn1		      ( ERRFILE_OTHER | 0x00000000 )
 #define ERRFILE_chap		      ( ERRFILE_OTHER | 0x00010000 )

src/tests/asn1_test.c

@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2016 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * ASN.1 self-tests
+ *
+ */
+
+/* Forcibly enable assertions */
+#undef NDEBUG
+
+#include <stdlib.h>
+#include <assert.h>
+#include <ipxe/image.h>
+#include <ipxe/asn1.h>
+#include <ipxe/test.h>
+#include "asn1_test.h"
+
+/**
+ * Report ASN.1 test result
+ *
+ * @v test		ASN.1 test
+ * @v file		Test code file
+ * @v line		Test code line
+ */
+void asn1_okx ( struct asn1_test *test, const char *file, unsigned int line ) {
+	struct digest_algorithm *digest = &asn1_test_digest_algorithm;
+	struct asn1_cursor *cursor;
+	uint8_t ctx[digest->ctxsize];
+	uint8_t out[ASN1_TEST_DIGEST_SIZE];
+	unsigned int i;
+	size_t offset;
+	int next;
+
+	/* Sanity check */
+	assert ( sizeof ( out ) == digest->digestsize );
+
+	/* Correct image data pointer */
+	test->image->data = virt_to_user ( ( void * ) test->image->data );
+
+	/* Check that image is detected as correct type */
+	okx ( register_image ( test->image ) == 0, file, line );
+	okx ( test->image->type == test->type, file, line );
+
+	/* Check that all ASN.1 objects can be extracted */
+	for ( offset = 0, i = 0 ; i < test->count ; offset = next, i++ ) {
+
+		/* Extract ASN.1 object */
+		next = image_asn1 ( test->image, offset, &cursor );
+		okx ( next >= 0, file, line );
+		okx ( ( ( size_t ) next ) > offset, file, line );
+		if ( next > 0 ) {
+
+			/* Calculate digest of ASN.1 object */
+			digest_init ( digest, ctx );
+			digest_update ( digest, ctx, cursor->data,
+					cursor->len );
+			digest_final ( digest, ctx, out );
+
+			/* Compare against expected digest */
+			okx ( memcmp ( out, test->expected[i].digest,
+				       sizeof ( out ) ) == 0, file, line );
+
+			/* Free ASN.1 object */
+			free ( cursor );
+		}
+	}
+
+	/* Check that we have reached the end of the image */
+	okx ( offset == test->image->len, file, line );
+
+	/* Unregister image */
+	unregister_image ( test->image );
+}

src/tests/asn1_test.h

@@ -0,0 +1,73 @@
+#ifndef _ASN1_TEST_H
+#define _ASN1_TEST_H
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <ipxe/image.h>
+#include <ipxe/sha1.h>
+#include <ipxe/test.h>
+
+/** Digest algorithm used for ASN.1 tests */
+#define asn1_test_digest_algorithm sha1_algorithm
+
+/** Digest size used for ASN.1 tests */
+#define ASN1_TEST_DIGEST_SIZE SHA1_DIGEST_SIZE
+
+/** An ASN.1 test digest */
+struct asn1_test_digest {
+	/** Digest value */
+	uint8_t digest[ASN1_TEST_DIGEST_SIZE];
+};
+
+/** An ASN.1 test */
+struct asn1_test {
+	/** Image type */
+	struct image_type *type;
+	/** Source image */
+	struct image *image;
+	/** Expected digests of ASN.1 objects */
+	struct asn1_test_digest *expected;
+	/** Number of ASN.1 objects */
+	unsigned int count;
+};
+
+/**
+ * Define an ASN.1 test
+ *
+ * @v _name		Test name
+ * @v _type		Test image file type
+ * @v _file		Test image file data
+ * @v ...		Expected ASN.1 object digests
+ * @ret test		ASN.1 test
+ */
+#define ASN1( _name, _type, _file, ... )				\
+	static const char _name ## __file[] = _file;			\
+	static struct image _name ## __image = {			\
+		.refcnt = REF_INIT ( ref_no_free ),			\
+		.name = #_name,						\
+		.data = ( userptr_t ) ( _name ## __file ),		\
+		.len = sizeof ( _name ## __file ),			\
+	};								\
+	static struct asn1_test_digest _name ## _expected[] = {		\
+		__VA_ARGS__						\
+	};								\
+	static struct asn1_test _name = {				\
+		.type = _type,						\
+		.image = & _name ## __image,				\
+		.expected = _name ## _expected,				\
+		.count = ( sizeof ( _name ## _expected ) /		\
+			   sizeof ( _name ## _expected[0] ) ),		\
+	};
+
+extern void asn1_okx ( struct asn1_test *test, const char *file,
+		       unsigned int line );
+
+/**
+ * Report ASN.1 test result
+ *
+ * @v test		ASN.1 test
+ */
+#define asn1_ok( test ) asn1_okx ( test, __FILE__, __LINE__ )
+
+#endif /* _ASN1_TEST_H */