backports: add signature verification code

Uh, this was awful. Because the crypto/ things are completely
impossible to backport, I've actually implemented this by using
mbedtls and embedding the relevant functions it has...

The mbedtls code is taken from mbedtls version 2.6.0 and only
minimally modified (mostly to remove <string.h> and similar).

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/backport/compat/verification/mbedtls/md_internal.h b/backport/compat/verification/mbedtls/md_internal.h
new file mode 100644
index 00000000..0a8600b4
--- /dev/null
+++ b/backport/compat/verification/mbedtls/md_internal.h
@@ -0,0 +1,116 @@
+/**
+ * \file md_internal.h
+ *
+ * \brief Message digest wrappers.
+ *
+ * \warning This in an internal header. Do not include directly.
+ *
+ * \author Adriaan de Jong <dejong@fox-it.com>
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: GPL-2.0
+ *
+ *  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
+ *  (at your option) 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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+#ifndef MBEDTLS_MD_WRAP_H
+#define MBEDTLS_MD_WRAP_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#include "md.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Message digest information.
+ * Allows message digest functions to be called in a generic way.
+ */
+struct mbedtls_md_info_t
+{
+    /** Digest identifier */
+    mbedtls_md_type_t type;
+
+    /** Name of the message digest */
+    const char * name;
+
+    /** Output length of the digest function in bytes */
+    int size;
+
+    /** Block length of the digest function in bytes */
+    int block_size;
+
+    /** Digest initialisation function */
+    void (*starts_func)( void *ctx );
+
+    /** Digest update function */
+    void (*update_func)( void *ctx, const unsigned char *input, size_t ilen );
+
+    /** Digest finalisation function */
+    void (*finish_func)( void *ctx, unsigned char *output );
+
+    /** Generic digest function */
+    void (*digest_func)( const unsigned char *input, size_t ilen,
+                         unsigned char *output );
+
+    /** Allocate a new context */
+    void * (*ctx_alloc_func)( void );
+
+    /** Free the given context */
+    void (*ctx_free_func)( void *ctx );
+
+    /** Clone state from a context */
+    void (*clone_func)( void *dst, const void *src );
+
+    /** Internal use only */
+    void (*process_func)( void *ctx, const unsigned char *input );
+};
+
+#if defined(MBEDTLS_MD2_C)
+extern const mbedtls_md_info_t mbedtls_md2_info;
+#endif
+#if defined(MBEDTLS_MD4_C)
+extern const mbedtls_md_info_t mbedtls_md4_info;
+#endif
+#if defined(MBEDTLS_MD5_C)
+extern const mbedtls_md_info_t mbedtls_md5_info;
+#endif
+#if defined(MBEDTLS_RIPEMD160_C)
+extern const mbedtls_md_info_t mbedtls_ripemd160_info;
+#endif
+#if defined(MBEDTLS_SHA1_C)
+extern const mbedtls_md_info_t mbedtls_sha1_info;
+#endif
+#if defined(MBEDTLS_SHA256_C)
+extern const mbedtls_md_info_t mbedtls_sha224_info;
+extern const mbedtls_md_info_t mbedtls_sha256_info;
+#endif
+#if defined(MBEDTLS_SHA512_C)
+extern const mbedtls_md_info_t mbedtls_sha384_info;
+extern const mbedtls_md_info_t mbedtls_sha512_info;
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* MBEDTLS_MD_WRAP_H */