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, 344 insertions, 0 deletions

diff --git a/backport/compat/verification/mbedtls/asn1.h b/backport/compat/verification/mbedtls/asn1.h
new file mode 100644
index 00000000..bc6b48b8
--- /dev/null
+++ b/backport/compat/verification/mbedtls/asn1.h
@@ -0,0 +1,344 @@
+/**
+ * \file asn1.h
+ *
+ * \brief Generic ASN.1 parsing
+ *
+ *  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_ASN1_H
+#define MBEDTLS_ASN1_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#include <stddef.h>
+
+#if defined(MBEDTLS_BIGNUM_C)
+#include "bignum.h"
+#endif
+
+/**
+ * \addtogroup asn1_module
+ * \{
+ */
+
+/**
+ * \name ASN1 Error codes
+ * These error codes are OR'ed to X509 error codes for
+ * higher error granularity.
+ * ASN1 is a standard to specify data structures.
+ * \{
+ */
+#define MBEDTLS_ERR_ASN1_OUT_OF_DATA                      -0x0060  /**< Out of data when parsing an ASN1 data structure. */
+#define MBEDTLS_ERR_ASN1_UNEXPECTED_TAG                   -0x0062  /**< ASN1 tag was of an unexpected value. */
+#define MBEDTLS_ERR_ASN1_INVALID_LENGTH                   -0x0064  /**< Error when trying to determine the length or invalid length. */
+#define MBEDTLS_ERR_ASN1_LENGTH_MISMATCH                  -0x0066  /**< Actual length differs from expected length. */
+#define MBEDTLS_ERR_ASN1_INVALID_DATA                     -0x0068  /**< Data is invalid. (not used) */
+#define MBEDTLS_ERR_ASN1_ALLOC_FAILED                     -0x006A  /**< Memory allocation failed */
+#define MBEDTLS_ERR_ASN1_BUF_TOO_SMALL                    -0x006C  /**< Buffer too small when writing ASN.1 data structure. */
+
+/* \} name */
+
+/**
+ * \name DER constants
+ * These constants comply with DER encoded the ANS1 type tags.
+ * DER encoding uses hexadecimal representation.
+ * An example DER sequence is:\n
+ * - 0x02 -- tag indicating INTEGER
+ * - 0x01 -- length in octets
+ * - 0x05 -- value
+ * Such sequences are typically read into \c ::mbedtls_x509_buf.
+ * \{
+ */
+#define MBEDTLS_ASN1_BOOLEAN                 0x01
+#define MBEDTLS_ASN1_INTEGER                 0x02
+#define MBEDTLS_ASN1_BIT_STRING              0x03
+#define MBEDTLS_ASN1_OCTET_STRING            0x04
+#define MBEDTLS_ASN1_NULL                    0x05
+#define MBEDTLS_ASN1_OID                     0x06
+#define MBEDTLS_ASN1_UTF8_STRING             0x0C
+#define MBEDTLS_ASN1_SEQUENCE                0x10
+#define MBEDTLS_ASN1_SET                     0x11
+#define MBEDTLS_ASN1_PRINTABLE_STRING        0x13
+#define MBEDTLS_ASN1_T61_STRING              0x14
+#define MBEDTLS_ASN1_IA5_STRING              0x16
+#define MBEDTLS_ASN1_UTC_TIME                0x17
+#define MBEDTLS_ASN1_GENERALIZED_TIME        0x18
+#define MBEDTLS_ASN1_UNIVERSAL_STRING        0x1C
+#define MBEDTLS_ASN1_BMP_STRING              0x1E
+#define MBEDTLS_ASN1_PRIMITIVE               0x00
+#define MBEDTLS_ASN1_CONSTRUCTED             0x20
+#define MBEDTLS_ASN1_CONTEXT_SPECIFIC        0x80
+/* \} name */
+/* \} addtogroup asn1_module */
+
+/** Returns the size of the binary string, without the trailing \\0 */
+#define MBEDTLS_OID_SIZE(x) (sizeof(x) - 1)
+
+/**
+ * Compares an mbedtls_asn1_buf structure to a reference OID.
+ *
+ * Only works for 'defined' oid_str values (MBEDTLS_OID_HMAC_SHA1), you cannot use a
+ * 'unsigned char *oid' here!
+ */
+#define MBEDTLS_OID_CMP(oid_str, oid_buf)                                   \
+        ( ( MBEDTLS_OID_SIZE(oid_str) != (oid_buf)->len ) ||                \
+          memcmp( (oid_str), (oid_buf)->p, (oid_buf)->len) != 0 )
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \name Functions to parse ASN.1 data structures
+ * \{
+ */
+
+/**
+ * Type-length-value structure that allows for ASN1 using DER.
+ */
+typedef struct mbedtls_asn1_buf
+{
+    int tag;                /**< ASN1 type, e.g. MBEDTLS_ASN1_UTF8_STRING. */
+    size_t len;             /**< ASN1 length, in octets. */
+    unsigned char *p;       /**< ASN1 data, e.g. in ASCII. */
+}
+mbedtls_asn1_buf;
+
+/**
+ * Container for ASN1 bit strings.
+ */
+typedef struct mbedtls_asn1_bitstring
+{
+    size_t len;                 /**< ASN1 length, in octets. */
+    unsigned char unused_bits;  /**< Number of unused bits at the end of the string */
+    unsigned char *p;           /**< Raw ASN1 data for the bit string */
+}
+mbedtls_asn1_bitstring;
+
+/**
+ * Container for a sequence of ASN.1 items
+ */
+typedef struct mbedtls_asn1_sequence
+{
+    mbedtls_asn1_buf buf;                   /**< Buffer containing the given ASN.1 item. */
+    struct mbedtls_asn1_sequence *next;    /**< The next entry in the sequence. */
+}
+mbedtls_asn1_sequence;
+
+/**
+ * Container for a sequence or list of 'named' ASN.1 data items
+ */
+typedef struct mbedtls_asn1_named_data
+{
+    mbedtls_asn1_buf oid;                   /**< The object identifier. */
+    mbedtls_asn1_buf val;                   /**< The named value. */
+    struct mbedtls_asn1_named_data *next;  /**< The next entry in the sequence. */
+    unsigned char next_merged;      /**< Merge next item into the current one? */
+}
+mbedtls_asn1_named_data;
+
+/**
+ * \brief       Get the length of an ASN.1 element.
+ *              Updates the pointer to immediately behind the length.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param len   The variable that will receive the value
+ *
+ * \return      0 if successful, MBEDTLS_ERR_ASN1_OUT_OF_DATA on reaching
+ *              end of data, MBEDTLS_ERR_ASN1_INVALID_LENGTH if length is
+ *              unparseable.
+ */
+int mbedtls_asn1_get_len( unsigned char **p,
+                  const unsigned char *end,
+                  size_t *len );
+
+/**
+ * \brief       Get the tag and length of the tag. Check for the requested tag.
+ *              Updates the pointer to immediately behind the tag and length.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param len   The variable that will receive the length
+ * \param tag   The expected tag
+ *
+ * \return      0 if successful, MBEDTLS_ERR_ASN1_UNEXPECTED_TAG if tag did
+ *              not match requested tag, or another specific ASN.1 error code.
+ */
+int mbedtls_asn1_get_tag( unsigned char **p,
+                  const unsigned char *end,
+                  size_t *len, int tag );
+
+/**
+ * \brief       Retrieve a boolean ASN.1 tag and its value.
+ *              Updates the pointer to immediately behind the full tag.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param val   The variable that will receive the value
+ *
+ * \return      0 if successful or a specific ASN.1 error code.
+ */
+int mbedtls_asn1_get_bool( unsigned char **p,
+                   const unsigned char *end,
+                   int *val );
+
+/**
+ * \brief       Retrieve an integer ASN.1 tag and its value.
+ *              Updates the pointer to immediately behind the full tag.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param val   The variable that will receive the value
+ *
+ * \return      0 if successful or a specific ASN.1 error code.
+ */
+int mbedtls_asn1_get_int( unsigned char **p,
+                  const unsigned char *end,
+                  int *val );
+
+/**
+ * \brief       Retrieve a bitstring ASN.1 tag and its value.
+ *              Updates the pointer to immediately behind the full tag.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param bs    The variable that will receive the value
+ *
+ * \return      0 if successful or a specific ASN.1 error code.
+ */
+int mbedtls_asn1_get_bitstring( unsigned char **p, const unsigned char *end,
+                        mbedtls_asn1_bitstring *bs);
+
+/**
+ * \brief       Retrieve a bitstring ASN.1 tag without unused bits and its
+ *              value.
+ *              Updates the pointer to the beginning of the bit/octet string.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param len   Length of the actual bit/octect string in bytes
+ *
+ * \return      0 if successful or a specific ASN.1 error code.
+ */
+int mbedtls_asn1_get_bitstring_null( unsigned char **p, const unsigned char *end,
+                             size_t *len );
+
+/**
+ * \brief       Parses and splits an ASN.1 "SEQUENCE OF <tag>"
+ *              Updated the pointer to immediately behind the full sequence tag.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param cur   First variable in the chain to fill
+ * \param tag   Type of sequence
+ *
+ * \return      0 if successful or a specific ASN.1 error code.
+ */
+int mbedtls_asn1_get_sequence_of( unsigned char **p,
+                          const unsigned char *end,
+                          mbedtls_asn1_sequence *cur,
+                          int tag);
+
+#if defined(MBEDTLS_BIGNUM_C)
+/**
+ * \brief       Retrieve a MPI value from an integer ASN.1 tag.
+ *              Updates the pointer to immediately behind the full tag.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param X     The MPI that will receive the value
+ *
+ * \return      0 if successful or a specific ASN.1 or MPI error code.
+ */
+int mbedtls_asn1_get_mpi( unsigned char **p,
+                  const unsigned char *end,
+                  mbedtls_mpi *X );
+#endif /* MBEDTLS_BIGNUM_C */
+
+/**
+ * \brief       Retrieve an AlgorithmIdentifier ASN.1 sequence.
+ *              Updates the pointer to immediately behind the full
+ *              AlgorithmIdentifier.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param alg   The buffer to receive the OID
+ * \param params The buffer to receive the params (if any)
+ *
+ * \return      0 if successful or a specific ASN.1 or MPI error code.
+ */
+int mbedtls_asn1_get_alg( unsigned char **p,
+                  const unsigned char *end,
+                  mbedtls_asn1_buf *alg, mbedtls_asn1_buf *params );
+
+/**
+ * \brief       Retrieve an AlgorithmIdentifier ASN.1 sequence with NULL or no
+ *              params.
+ *              Updates the pointer to immediately behind the full
+ *              AlgorithmIdentifier.
+ *
+ * \param p     The position in the ASN.1 data
+ * \param end   End of data
+ * \param alg   The buffer to receive the OID
+ *
+ * \return      0 if successful or a specific ASN.1 or MPI error code.
+ */
+int mbedtls_asn1_get_alg_null( unsigned char **p,
+                       const unsigned char *end,
+                       mbedtls_asn1_buf *alg );
+
+/**
+ * \brief       Find a specific named_data entry in a sequence or list based on
+ *              the OID.
+ *
+ * \param list  The list to seek through
+ * \param oid   The OID to look for
+ * \param len   Size of the OID
+ *
+ * \return      NULL if not found, or a pointer to the existing entry.
+ */
+mbedtls_asn1_named_data *mbedtls_asn1_find_named_data( mbedtls_asn1_named_data *list,
+                                       const char *oid, size_t len );
+
+/**
+ * \brief       Free a mbedtls_asn1_named_data entry
+ *
+ * \param entry The named data entry to free
+ */
+void mbedtls_asn1_free_named_data( mbedtls_asn1_named_data *entry );
+
+/**
+ * \brief       Free all entries in a mbedtls_asn1_named_data list
+ *              Head will be set to NULL
+ *
+ * \param head  Pointer to the head of the list of named data entries to free
+ */
+void mbedtls_asn1_free_named_data_list( mbedtls_asn1_named_data **head );
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* asn1.h */