encode.c

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/*
 *   This program is 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 St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * @file src/lib/eap_aka_sim/encode.c
 * @brief Code common to EAP-SIM/AKA/AKA' clients and servers.
 *
 * @copyright 2017 FreeRADIUS server project
 */
 
RCSID("$Id: 428f929758ea6842572001356568e78a2eb0345c $")
 
#include <freeradius-devel/io/test_point.h>
#include <freeradius-devel/server/module.h>
#include <freeradius-devel/tls/base.h>
#include <freeradius-devel/tls/strerror.h>
#include <freeradius-devel/util/dbuff.h>
#include <freeradius-devel/util/rand.h>
#include <freeradius-devel/util/debug.h>
#include <freeradius-devel/util/sha1.h>
 
#include <freeradius-devel/eap/types.h>
#include "base.h"
#include "attrs.h"
#include "crypto_priv.h"
 
#define SIM_MAX_ATTRIBUTE_VALUE_LEN     ((255 * 4) - 2)         /* max length field value less Type + Length fields */
 
/*
 *  EAP-SIM/AKA/AKA' PACKET FORMAT
 *  ---------------- ------ ------
 *
 * EAP Request and Response Packet Format
 * --- ------- --- -------- ------ ------
 *  0              1               2               3
 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |     Code      |  Identifier   |        Length           |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |     Type      |    AT-Type    |   AT-Length   |     value ... |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * With AT-Type/AT-Length/Value... repeating. Length is in units
 * of 32 bits, and includes the Type/Length fields.
 */
 
static ssize_t encode_tlv(fr_dbuff_t *dbuff,
                          fr_da_stack_t *da_stack, unsigned int depth,
                          fr_dcursor_t *cursor, void *encode_ctx);
 
/** Implements the iterator for EAP-AKA
 *
 * @param[in] cursor    to iterate over.
 * @param[in] current   The fr_pair_t cursor->current.  Will be advanced and checked to
 *                      see if it matches the specified fr_dict_t.
 * @param[in] uctx      The fr_dict_t to search for.
 * @return
 *      - Next matching fr_pair_t.
 *      - NULL if not more matching fr_pair_ts could be found.
 */
static void *fr_eap_aka_sim_next_encodable(fr_dcursor_t *cursor, void *current, UNUSED void *uctx)
{
        fr_pair_t       *c = current;
        fr_dict_t       *dict = talloc_get_type_abort(uctx, fr_dict_t);
 
        while ((c = fr_dlist_next(cursor->dlist, c))) {
                PAIR_VERIFY(c);
 
                /*
                 *      Bool attribute presence is 'true' in SIM
                 *      and absence is 'false'
                 */
                if ((c->vp_type == FR_TYPE_BOOL) && (c->vp_bool == false)) continue;
 
                if ((c->da->dict == dict) && (!c->da->flags.internal)) break;
        }
 
        return c;
}
 
/** Add an IV to a packet
 *
 @verbatim
        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |     AT_IV     | Length = 5    |           Reserved            |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                 Initialization Vector                         |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 @endverbatim
 */
static ssize_t encode_iv(fr_dbuff_t *dbuff, void *encode_ctx)
{
        fr_aka_sim_ctx_t        *packet_ctx = encode_ctx;
        uint32_t                iv[4];
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
 
        /*
         *      One IV per packet
         */
        if (packet_ctx->have_iv) return 0;
 
        /*
         *      Generate IV
         */
        iv[0] = fr_rand();
        iv[1] = fr_rand();
        iv[2] = fr_rand();
        iv[3] = fr_rand();
 
        memcpy(packet_ctx->iv, (uint8_t *)&iv[0], sizeof(packet_ctx->iv));      /* ensures alignment */
 
        FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, FR_IV, (4 + AKA_SIM_IV_SIZE) >> 2, 0x00, 0x00);
        FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, packet_ctx->iv, sizeof(packet_ctx->iv));
 
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), "Initialisation vector");
 
        packet_ctx->have_iv = true;
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** encrypt a value with AES-CBC-128
 *
 * encrypts a value using AES-CBC-128, padding the value with AT_PADDING
 * attributes until it matches the block length of the cipher (16).
 *
 * May also write out an AT_IV attribute if this is the first encrypted
 * value being encoded.
 @verbatim
        1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        | AT_ENCR_DATA  | Length        |           Reserved            |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                    Encrypted Data                             .
        .                                                               .
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 @endverbatim
 */
static ssize_t encode_encrypted_value(fr_dbuff_t *dbuff,
                                      uint8_t const *in, size_t inlen, void *encode_ctx)
{
        size_t                  total_len, pad_len, encr_len;
        int                     len = 0;
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        uint8_t                 *encr = NULL;
        fr_aka_sim_ctx_t        *packet_ctx = encode_ctx;
        EVP_CIPHER_CTX          *evp_ctx;
        EVP_CIPHER const        *evp_cipher = EVP_aes_128_cbc();
        size_t                  block_size = EVP_CIPHER_block_size(evp_cipher);
        ssize_t                 slen;
        /*
         *      Needs to be a multiple of 4 else we can't
         *      pad with AT_PADDING correctly as its
         *      length is specified in multiples of 4.
         */
        if (unlikely(inlen % 4)) {
                fr_strerror_printf("%s: Input data length is not a multiple of 4", __FUNCTION__);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        total_len = (inlen + (block_size - 1)) & ~(block_size - 1);     /* Round input length to block size (16) */
        pad_len = (total_len - inlen);          /* How much we need to pad */
 
        /*
         *      Usually in and out will be the same buffer
         */
        if (unlikely(fr_dbuff_start(&work_dbuff) != in)) {
                FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, in, inlen);
        } else {
                FR_DBUFF_EXTEND_LOWAT_OR_RETURN(&work_dbuff, inlen);
                fr_dbuff_advance(&work_dbuff, inlen);
        }
 
        /*
         *      Append an AT_PADDING attribute if required
         */
        if (pad_len != 0) {
                FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, FR_PADDING, (uint8_t)(pad_len >> 2));
                FR_DBUFF_MEMSET_RETURN(&work_dbuff, 0, pad_len - 2);
                FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), pad_len, "Done padding attribute");
        }
 
        if (unlikely(!packet_ctx->k_encr)) {
                fr_strerror_printf("%s: No k_encr set, cannot encrypt attributes", __FUNCTION__);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        evp_ctx = aka_sim_crypto_cipher_ctx();
        if (unlikely(EVP_EncryptInit_ex(evp_ctx, evp_cipher, NULL,
                                        packet_ctx->k_encr, packet_ctx->iv) != 1)) {
                fr_tls_strerror_printf("Failed initialising AES-128-ECB context");
        error:
                talloc_free(encr);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        encr = talloc_array(NULL, uint8_t, total_len);
        if (!encr) {
                fr_strerror_printf("%s: Failed allocating temporary buffer", __FUNCTION__);
                goto error;
        }
 
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), total_len, "plaintext");
 
        /*
         *      By default OpenSSL expects 16 bytes of plaintext
         *      to produce 32 bytes of ciphertext, due to padding
         *      being added if the plaintext is a multiple of 16.
         *
         *      There's no way for OpenSSL to determine if a
         *      16 byte encr was padded or not, so we need to
         *      inform OpenSSL explicitly that there's no padding.
         */
        EVP_CIPHER_CTX_set_padding(evp_ctx, 0);
        if (unlikely(EVP_EncryptUpdate(evp_ctx, encr, &len, fr_dbuff_start(&work_dbuff), total_len) != 1)) {
                fr_tls_strerror_printf("%s: Failed encrypting attribute", __FUNCTION__);
                goto error;
        }
        encr_len = len;
 
        if (unlikely(EVP_EncryptFinal_ex(evp_ctx, encr + encr_len, &len) != 1)) {
                fr_tls_strerror_printf("%s: Failed finalising encrypted attribute", __FUNCTION__);
                goto error;
        }
        encr_len += len;
 
        /*
         *      Ciphertext should be same length as plaintext.
         */
        if (unlikely(encr_len != total_len)) {
                fr_strerror_printf("%s: Invalid plaintext length, expected %zu, got %zu",
                                   __FUNCTION__, total_len, encr_len);
                goto error;
        }
 
        FR_PROTO_HEX_DUMP(encr, encr_len, "ciphertext");
 
        /*
         *      Overwrite the plaintext with our encrypted blob
         */
        fr_dbuff_set_to_start(&work_dbuff);
 
        slen = fr_dbuff_in_memcpy(&work_dbuff, encr, encr_len);
        talloc_free(encr);
        if (slen <= 0) return slen;
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Encodes the data portion of an attribute
 *
 * @return
 *      > 0, Length of the data portion.
 *      = 0, we could not encode anything, skip this attribute (and don't encode the header)
 *      < 0, failure.
 */
static ssize_t encode_value(fr_dbuff_t *dbuff,
                            fr_da_stack_t *da_stack, int depth,
                            fr_dcursor_t *cursor, void *encode_ctx)
{
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_pair_t const         *vp = fr_dcursor_current(cursor);
        fr_dict_attr_t const    *da = da_stack->da[depth];
        fr_aka_sim_ctx_t        *packet_ctx = encode_ctx;
 
        PAIR_VERIFY(vp);
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        if (unlikely(da_stack->da[depth + 1] != NULL)) {
                fr_strerror_printf("%s: Encoding value but not at top of stack", __FUNCTION__);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        if (unlikely(vp->da != da)) {
                fr_strerror_printf("%s: Top of stack does not match vp->da", __FUNCTION__);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        switch (vp->vp_type) {
        case FR_TYPE_STRUCTURAL:
                fr_strerror_printf("%s: Called with structural type %s", __FUNCTION__,
                                   fr_type_to_str(da_stack->da[depth]->type));
                return PAIR_ENCODE_FATAL_ERROR;
 
        default:
                break;
        }
 
        switch (da->attr) {
        /*
         *      Allow manual override of IV - Mostly for testing or debugging
         *
         *      0                   1                   2                   3
         *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      |     AT_IV     | Length = 5    |           Reserved            |
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      |                                                               |
         *      |                 Initialization Vector                         |
         *      |                                                               |
         *      |                                                               |
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_IV:
                if ((vp->da->flags.length && (da->flags.length != vp->vp_length)) ||
                    (vp->vp_length != sizeof(packet_ctx->iv))) {
                        fr_strerror_printf("%s: Attribute \"%s\" needs a value of exactly %zu bytes, "
                                           "but value was %zu bytes", __FUNCTION__,
                                           da->name, (size_t)da->flags.length, vp->vp_length);
                        return PAIR_ENCODE_FATAL_ERROR;
                }
                memcpy(packet_ctx->iv, vp->vp_octets, sizeof(packet_ctx->iv));
                packet_ctx->have_iv = true;
                break;  /* Encode IV */
 
        /*
         *      AT_RES - Special case (RES length is in bits)
         *
         *      0                   1                   2                   3
         *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      |     AT_RES    |    Length     |          RES Length           |
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
         *      |                                                               |
         *      |                             RES                               |
         *      |                                                               |
         *      |                                                               |
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_RES:
                if ((vp->vp_length < 4) || (vp->vp_length > 16)) {
                        fr_strerror_printf("%s: AKA-RES Length must be between 4-16 bytes, got %zu bytes",
                                           __FUNCTION__, vp->vp_length);
                        return PAIR_ENCODE_FATAL_ERROR;
                }
 
                FR_DBUFF_IN_RETURN(&work_dbuff, (uint16_t)(vp->vp_length * 8)); /* RES Length (bits, big endian) */
                FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, vp->vp_octets, vp->vp_length);
                goto done;
 
        /*
         *      AT_CHECKCODE - Special case (Variable length with no length field)
         *
         *      0                   1                   2                   3
         *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      | AT_CHECKCODE  | Length        |           Reserved            |
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      |                                                               |
         *      |                     Checkcode (0 or 20 bytes)                 |
         *      |                                                               |
         *      |                                                               |
         *      |                                                               |
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_CHECKCODE:
                FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, 0x00, 0x00);      /* Reserved */
                FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, vp->vp_octets, vp->vp_length);
                goto done;
 
        default:
                break;
        }
 
        switch (vp->vp_type) {
        /*
         *      In order to represent the string length properly we include a second
         *      16bit length field with the real string length.
         *
         *      The end of the string is padded buff to a multiple of 4.
         *
         *      0                   1                   2                   3
         *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      | AT_<STRING>   | Length        |    Actual <STRING> Length     |
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      |                                                               |
         *      .                           String                              .
         *      .                                                               .
         *      |                                                               |
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_TYPE_STRING:
                if (vp->da->flags.length && (vp->vp_length != vp->da->flags.length)) {
                        fr_strerror_printf("%s: Attribute \"%s\" needs a value of exactly %zu bytes, "
                                           "but value was %zu bytes", __FUNCTION__,
                                           vp->da->name, (size_t)vp->da->flags.length, vp->vp_length);
                        return PAIR_ENCODE_FATAL_ERROR;
                }
 
                FR_DBUFF_IN_RETURN(&work_dbuff, (uint16_t)vp->vp_length);               /* Big endian real string length */
                FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, (uint8_t const *)vp->vp_strvalue, vp->vp_length);
                break;
 
        case FR_TYPE_OCTETS:
                /*
                 *      Fixed length attribute
                 */
                if (vp->da->flags.length) {
                        size_t prefix = fr_aka_sim_octets_prefix_len(vp->da);
                        size_t pad_len;
                        size_t value_len_rounded;
 
                        if (vp->vp_length > vp->da->flags.length) {
                                fr_strerror_printf("%s: Attribute \"%s\" needs a value of <= %zu bytes, "
                                                   "but value was %zu bytes", __FUNCTION__,
                                                   vp->da->name, (size_t)vp->da->flags.length, vp->vp_length);
                                return PAIR_ENCODE_FATAL_ERROR;
                        }
 
                        /*
                         *      Calculate value padding (autopad)
                         */
                        value_len_rounded = ROUND_UP(vp->vp_length, (size_t)vp->da->flags.length);
                        /*
                         *      Zero out reserved bytes
                         */
                        if (prefix) FR_DBUFF_MEMSET_RETURN(&work_dbuff, 0, prefix);
 
                        /*
                         *      Copy in value
                         */
                        FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, vp->vp_octets, vp->vp_length);
 
                        /*
                         *      Pad out the value
                         */
                        pad_len = value_len_rounded - vp->vp_length;
                        if (pad_len) FR_DBUFF_MEMSET_RETURN(&work_dbuff, 0, pad_len);
                /*
                 *      Variable length attribute
                 */
                } else {
                        FR_DBUFF_IN_RETURN(&work_dbuff, (uint16_t)vp->vp_length);       /* Big endian real string length */
                        FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, (uint8_t const *)vp->vp_strvalue, vp->vp_length);
                }
                break;
 
        /*
         *      In SIM/AKA/AKA' we represent truth values
         *      by either including or not including the attribute
         *      in the packet.
         *
         *      0                   1                   2                   3
         *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      |   AT_<BOOL>   | Length = 1    |           Reserved            |
         *      +---------------+---------------+-------------------------------+
         */
        case FR_TYPE_BOOL:
                FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, 0x00, 0x00);      /* reserved bytes */
                break;
 
        /*
         *      Numbers are network byte order.
         *
         *      In the base RFCs only short (16bit) unsigned integers are used.
         *      We add support for more, just for completeness.
         *
         *      0                   1                   2                   3
         *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      |   AT_<SHORT>  | Length = 1    |    Short 1    |    Short 2    |
         *      +---------------+---------------+-------------------------------+
         */
        default:
        {
                ssize_t len = fr_value_box_to_network(&work_dbuff, &vp->data);
                if (len < 0) return len;
                break;
        }
        }
done:
        /*
         *      Rebuilds the TLV stack for encoding the next attribute
         */
        vp = fr_dcursor_next(cursor);
        fr_proto_da_stack_build(da_stack, vp ? vp->da : NULL);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Encodes the data portion of an attribute
 *
 @verbatim
        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        | AT_VERSION_L..| Length        | Actual Version List Length    |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |  Supported Version 1          |  Supported Version 2          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        .                                                               .
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        | Supported Version N           |     Padding                   |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 @endverbatim
 *
 */
static ssize_t encode_array(fr_dbuff_t *dbuff,
                            fr_da_stack_t *da_stack, int depth,
                            fr_dcursor_t *cursor, void *encode_ctx)
{
        size_t                  pad_len;
        size_t                  element_len;
        size_t                  actual_len;
        fr_dbuff_t              len_dbuff = FR_DBUFF(dbuff);
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_dict_attr_t const    *da = da_stack->da[depth];
        fr_assert(da->flags.array);
 
        FR_DBUFF_EXTEND_LOWAT_OR_RETURN(&work_dbuff, 2);
        fr_dbuff_advance(&work_dbuff, 2);
 
        if (unlikely(da->type == FR_TYPE_OCTETS)) {
                if (!da->flags.length) {
                        fr_strerror_printf("Can't encode array type attribute \"%s\" as it does not "
                                           "have a fixed length", da->name);
                        return PAIR_ENCODE_FATAL_ERROR;
                }
                element_len = da->flags.length;
        } else {
                element_len = fr_aka_sim_attr_sizes[da->type][0];
        }
 
        /*
         *      Keep encoding as long as we have space to
         *      encode things.
         */
        while (fr_dbuff_extend_lowat(NULL, &work_dbuff, element_len) >= element_len) {
                fr_pair_t       *vp;
                ssize_t         slen;
 
                slen = encode_value(&work_dbuff, da_stack, depth, cursor, encode_ctx);
                if (slen == PAIR_ENCODE_FATAL_ERROR) return slen;
                if (slen < 0) break;
 
                vp = fr_dcursor_current(cursor);
                if (!vp || (vp->da != da)) break;               /* Stop if we have an attribute of a different type */
        }
 
        actual_len = fr_dbuff_used(&work_dbuff) - 2;    /* Length of the elements we encoded */
        /*
         *      Arrays with an element size which is
         *      a multiple of 4 don't need an
         *      actual_length field, because the number
         *      of elements can be calculated from
         *      the attribute length.
         */
        if (element_len % 4) {
                FR_DBUFF_IN_RETURN(&len_dbuff, (uint16_t) actual_len);
        } else {
                FR_DBUFF_IN_RETURN(&len_dbuff, (uint16_t) 0);
        }
 
        /*
         *      Pad value to multiple of 4
         */
        pad_len = ROUND_UP_POW2(actual_len, 4) - actual_len;
        if (pad_len) FR_DBUFF_MEMSET_RETURN(&work_dbuff, 0, pad_len);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Encode an RFC format attribute header
 *
 * This could be a standard attribute, or a TLV data type.
 * If it's a standard attribute, then vp->da->attr == attribute.
 * Otherwise, attribute may be something else.
 */
static ssize_t encode_rfc(fr_dbuff_t *dbuff, fr_da_stack_t *da_stack, unsigned int depth,
                              fr_dcursor_t *cursor, void *encode_ctx)
{
        size_t                  pad_len;
        fr_dict_attr_t const    *da;
        ssize_t                 slen;
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_dbuff_t              hdr_dbuff = FR_DBUFF(dbuff);
 
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        switch (da_stack->da[depth]->type) {
        case FR_TYPE_STRUCTURAL:
                fr_strerror_printf("%s: Called with structural type %s", __FUNCTION__,
                                   fr_type_to_str(da_stack->da[depth]->type));
                return PAIR_ENCODE_FATAL_ERROR;
 
        default:
                if (((fr_dict_vendor_num_by_da(da_stack->da[depth]) == 0) && (da_stack->da[depth]->attr == 0)) ||
                    (da_stack->da[depth]->attr > 255)) {
                        fr_strerror_printf("%s: Called with non-standard attribute %u", __FUNCTION__,
                                           da_stack->da[depth]->attr);
                        return PAIR_ENCODE_FATAL_ERROR;
                }
                break;
        }
 
        /*
         *      Write out the value to a buffer location
         *      past the AT and Length fields.
         *
         *      Encode value will set reserved bytes to
         *      zero and fill any subfields like actual
         *      length.
         */
        da = da_stack->da[depth];
 
        FR_DBUFF_EXTEND_LOWAT_OR_RETURN(&work_dbuff, 2);
        fr_dbuff_advance(&work_dbuff, 2);
 
        if (da->flags.array) {
                slen = encode_array(&FR_DBUFF_MAX_BIND_CURRENT(&work_dbuff, SIM_MAX_ATTRIBUTE_VALUE_LEN - 2),
                                    da_stack, depth, cursor, encode_ctx);
        } else {
                slen = encode_value(&FR_DBUFF_MAX_BIND_CURRENT(&work_dbuff, SIM_MAX_ATTRIBUTE_VALUE_LEN - 2),
                                    da_stack, depth, cursor, encode_ctx);
        }
        if (slen <= 0) return slen;
 
        /*
         *      Pad value to multiple of 4
         */
        pad_len = ROUND_UP_POW2(fr_dbuff_used(&work_dbuff), 4) - fr_dbuff_used(&work_dbuff);
        if (pad_len) {
                FR_DBUFF_MEMSET_RETURN(&work_dbuff, 0, pad_len);
        }
 
        FR_DBUFF_IN_BYTES_RETURN(&hdr_dbuff, (uint8_t)da->attr,
                                 (uint8_t)(fr_dbuff_used(&work_dbuff) >> 2));
 
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), "Done RFC attribute");
 
        return fr_dbuff_set(dbuff, &work_dbuff);        /* AT + Length + Data */
}
 
static inline ssize_t encode_tlv_internal(fr_dbuff_t *dbuff,
                                          fr_da_stack_t *da_stack, unsigned int depth,
                                          fr_dcursor_t *cursor, void *encode_ctx)
{
        ssize_t                 slen;
        fr_dbuff_t              work_dbuff = FR_DBUFF_MAX(dbuff, SIM_MAX_ATTRIBUTE_VALUE_LEN);
        fr_dbuff_t              value_dbuff;
        fr_dbuff_marker_t       value_start;
        fr_pair_t const         *vp = fr_dcursor_current(cursor);
        fr_dict_attr_t const    *da = da_stack->da[depth];
 
        FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, 0x00, 0x00);
 
        value_dbuff = FR_DBUFF(&work_dbuff);
        fr_dbuff_marker(&value_start, &value_dbuff);
 
        for (;;) {
                FR_PROTO_STACK_PRINT(da_stack, depth);
 
                /*
                 *      This attribute carries sub-TLVs.  The sub-TLVs
                 *      can only carry SIM_MAX_ATTRIBUTE_VALUE_LEN bytes of data.
                 */
 
                /*
                 *      Determine the nested type and call the appropriate encoder
                 */
                if (da_stack->da[depth + 1]->type == FR_TYPE_TLV) {
                        slen = encode_tlv(&work_dbuff, da_stack, depth + 1, cursor, encode_ctx);
                } else {
                        slen = encode_rfc(&work_dbuff, da_stack, depth + 1, cursor, encode_ctx);
                }
 
                if (slen <= 0) {
                        return slen;
                }
 
                /*
                 *      If nothing updated the attribute, stop
                 */
                if (!fr_dcursor_current(cursor) || (vp == fr_dcursor_current(cursor))) {
                        break;
                }
 
                /*
                 *      We can encode multiple sub TLVs, if after
                 *      rebuilding the TLV Stack, the attribute
                 *      at this depth is the same.
                 */
                if ((da != da_stack->da[depth]) || (da_stack->depth < da->depth)) {
                        break;
                }
                vp = fr_dcursor_current(cursor);
        }
 
        /*
         *      encrypt the contents of the TLV using AES-CBC-128
         *      or another encryption algorithm.
         */
        if (fr_aka_sim_flag_encrypted(da)) {
                ssize_t value_len = fr_dbuff_used(&work_dbuff) - 2;
 
                slen = encode_encrypted_value(&value_dbuff, fr_dbuff_current(&value_start),
                                              value_len, encode_ctx);
                if (slen < 0) return PAIR_ENCODE_FATAL_ERROR;
 
#ifdef __COVERITY__
                /*
                 *      Coverity as it stands doesn't see that value_len >= 0 because
                 *      work_dbuff has at least the two zero bytes in it, and thus thinks
                 *      (size_t) slen - value_len will be some huge size_t value. This
                 *      check should pacify it.
                 */
                if (value_len < 0) return -1;
#endif
                FR_DBUFF_EXTEND_LOWAT_OR_RETURN(&work_dbuff, (size_t)slen - value_len);
                fr_dbuff_advance(&work_dbuff, (size_t)slen - value_len);
        }
 
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), "Done TLV");
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
static ssize_t encode_tlv(fr_dbuff_t *dbuff,
                              fr_da_stack_t *da_stack, unsigned int depth,
                              fr_dcursor_t *cursor, void *encode_ctx)
{
        unsigned int            total_len;
        ssize_t                 len;
        fr_dict_attr_t const    *da;
        fr_dbuff_t              tl_dbuff;
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_dcursor_t            *my_cursor = cursor;
        fr_dcursor_t            child_cursor;
 
        PAIR_VERIFY(fr_dcursor_current(cursor));
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        if (da_stack->da[depth]->type != FR_TYPE_TLV) {
                fr_strerror_printf("%s: Expected type \"tlv\" got \"%s\"", __FUNCTION__,
                                   fr_type_to_str(da_stack->da[depth]->type));
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        if (!da_stack->da[depth + 1]) {
                fr_pair_t *vp;
 
                vp = fr_dcursor_current(cursor);
                if ((vp->vp_type != FR_TYPE_TLV) || (fr_pair_list_num_elements(&vp->vp_group) == 0)) {
                        fr_strerror_printf("%s: Can't encode empty TLV", __FUNCTION__);
                        return PAIR_ENCODE_FATAL_ERROR;
                }
 
                fr_assert(vp->da == da_stack->da[depth]);
 
                vp = fr_pair_dcursor_child_iter_init(&child_cursor, &vp->vp_group, cursor);
                my_cursor = &child_cursor;
 
                fr_proto_da_stack_build(da_stack, vp->da);
        }
 
        /*
         *      Add the IV before the TLV
         *      The ASCII art in the RFCs the attributes in
         *      this order.
         */
        if (fr_aka_sim_flag_encrypted(da_stack->da[depth])) {
                len = encode_iv(&work_dbuff, encode_ctx);
                if (len < 0) return len;
        }
        tl_dbuff = FR_DBUFF(&work_dbuff);
 
        FR_DBUFF_EXTEND_LOWAT_OR_RETURN(&work_dbuff, 2);
        fr_dbuff_advance(&work_dbuff, 2);
 
        da = da_stack->da[depth];
        len = encode_tlv_internal(&FR_DBUFF_MAX_BIND_CURRENT(&work_dbuff, SIM_MAX_ATTRIBUTE_VALUE_LEN - 2),
                                  da_stack, depth, my_cursor, encode_ctx);
        if (len <= 0) return len;
 
        if (my_cursor != cursor) fr_dcursor_next(cursor);
 
        /*
         *      Round attr + len + data length out to a multiple
         *      of four, and setup the attribute header and
         *      length field in the buffer.
         */
        total_len = ROUND_UP_POW2(len + 2, 4);
        FR_DBUFF_IN_BYTES_RETURN(&tl_dbuff, (uint8_t)da->attr, (uint8_t)(total_len >> 2));
 
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), "Done TLV attribute");
 
        return fr_dbuff_set(dbuff, &work_dbuff);        /* AT_IV + AT_*(TLV) - Can't use total_len, doesn't include IV */
}
 
ssize_t fr_aka_sim_encode_pair(fr_dbuff_t *dbuff, fr_dcursor_t *cursor, void *encode_ctx)
{
        fr_pair_t const         *vp;
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_dbuff_marker_t       m;
        ssize_t                 slen;
 
        fr_da_stack_t           da_stack;
 
        fr_dbuff_marker(&m, &work_dbuff);
        if (!cursor) return PAIR_ENCODE_FATAL_ERROR;
 
        vp = fr_dcursor_current(cursor);
        if (!vp) return 0;
 
        PAIR_VERIFY(vp);
 
        if (vp->da->depth > FR_DICT_MAX_TLV_STACK) {
                fr_strerror_printf("%s: Attribute depth %u exceeds maximum nesting depth %d",
                                   __FUNCTION__, vp->da->depth, FR_DICT_MAX_TLV_STACK);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        if (vp->da->attr == FR_MAC) {
                fr_dcursor_next(cursor);
                return 0;
        }
        /*
         *      Nested structures of attributes can't be longer than
         *      4 * 255 bytes, so each call to an encode function can
         *      only use 4 * 255 bytes of buffer space at a time.
         */
 
        /*
         *      Do more work to set up the stack for the complex case.
         */
        fr_proto_da_stack_build(&da_stack, vp->da);
        FR_PROTO_STACK_PRINT(&da_stack, 0);
 
        if (da_stack.da[0]->type == FR_TYPE_TLV) {
                slen = encode_tlv(&FR_DBUFF_MAX_BIND_CURRENT(&work_dbuff, SIM_MAX_ATTRIBUTE_VALUE_LEN + 2),
                                  &da_stack, 0, cursor, encode_ctx);
        } else {
                slen = encode_rfc(&FR_DBUFF_MAX_BIND_CURRENT(&work_dbuff, SIM_MAX_ATTRIBUTE_VALUE_LEN + 2),
                                  &da_stack, 0, cursor, encode_ctx);
        }
        if (slen < 0) return slen;
 
        /*
         *      We couldn't do it, so we didn't do anything.
         */
        if (fr_dcursor_current(cursor) == vp) {
                fr_strerror_printf("%s: Nested attribute structure too large to encode", __FUNCTION__);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
ssize_t fr_aka_sim_encode(request_t *request, fr_pair_list_t *to_encode, void *encode_ctx)
{
        fr_pair_t               *vp;
 
        uint8_t                 *buff;
        ssize_t                 slen;
        fr_dbuff_t              dbuff;
        fr_dbuff_marker_t       hmac;
        fr_dbuff_uctx_talloc_t  tctx;
 
        bool                    do_hmac = false;
 
        unsigned char           subtype;
        fr_dcursor_t            cursor;
        fr_aka_sim_ctx_t        *packet_ctx = encode_ctx;
        eap_packet_t            *eap_packet = packet_ctx->eap_packet;
 
        /*
         *      Encoded_msg is now an EAP-SIM message.
         *      It might be too big for putting into an
         *      EAP packet.
         */
        vp = fr_pair_find_by_child_num_idx(to_encode, fr_dict_root(dict_eap_aka_sim), FR_SUBTYPE, 0);
        if (!vp) {
                REDEBUG("Missing subtype attribute");
                return PAIR_ENCODE_FATAL_ERROR;
        }
        subtype = vp->vp_uint16;
 
        /*
         *      Group attributes with similar lineages together
         */
        fr_pair_list_sort(to_encode, fr_pair_cmp_by_parent_num);
        if (fr_pair_dcursor_iter_init(&cursor, to_encode, fr_eap_aka_sim_next_encodable, dict_eap_aka_sim) == vp) {
                fr_dcursor_next(&cursor);       /* Skip subtype if it came out first */
        }
 
        /*
         *      Will we need to generate a HMAC?
         */
        if (fr_pair_find_by_child_num_idx(to_encode, fr_dict_root(dict_eap_aka_sim), FR_MAC, 0)) do_hmac = true;
 
        /*
         *      Fast path, we just need to encode a subtype
         */
        if (!do_hmac && !fr_dcursor_current(&cursor)) {
                MEM(buff = talloc_array(eap_packet, uint8_t, 3));
 
                buff[0] = subtype;      /* SIM or AKA subtype */
                buff[1] = 0;            /* Reserved (0) */
                buff[2] = 0;            /* Reserved (1) */
 
                eap_packet->type.length = 3;
                eap_packet->type.data = buff;
 
                FR_PROTO_HEX_DUMP(buff, eap_packet->type.length, "sim packet");
 
                return 0;
        }
        fr_dcursor_head(&cursor);       /* Reset */
 
        fr_dbuff_init_talloc(NULL, &dbuff, &tctx, 512, 1024);
 
        FR_DBUFF_IN_BYTES_RETURN(&dbuff, subtype, 0x00, 0x00);
 
        /*
         *      Add space in the packet for AT_MAC
         */
        if (do_hmac) {
                FR_DBUFF_IN_BYTES_RETURN(&dbuff, FR_MAC, AKA_SIM_MAC_SIZE >> 2, 0x00, 0x00);
                fr_dbuff_marker(&hmac, &dbuff);
                FR_DBUFF_MEMSET_RETURN(&dbuff, 0, 16);
        }
 
        /*
         *      Encode all the things...
         */
        (void)fr_dcursor_head(&cursor);
        while (fr_dcursor_current(&cursor)) {
                slen = fr_aka_sim_encode_pair(&dbuff, &cursor, packet_ctx);
                if (slen < 0) {
                error:
                        talloc_free(fr_dbuff_buff(&dbuff));
                        return PAIR_ENCODE_FATAL_ERROR;
                }
                fr_assert(fr_dbuff_used(&dbuff) > 0);   /* We messed up a check somewhere in the encoder */
        }
 
        eap_packet->type.length = fr_dbuff_used(&dbuff);
        eap_packet->type.data = fr_dbuff_buff(&dbuff);
 
        /*
         *      Calculate a SHA1-HMAC over the complete EAP packet
         */
        if (do_hmac) {
                slen = fr_aka_sim_crypto_sign_packet(fr_dbuff_current(&hmac), eap_packet, false,
                                                     packet_ctx->hmac_md,
                                                     packet_ctx->k_aut, packet_ctx->k_aut_len,
                                                     packet_ctx->hmac_extra, packet_ctx->hmac_extra_len);
                if (slen < 0) goto error;
                FR_PROTO_HEX_DUMP(fr_dbuff_current(&hmac) - 4, AKA_SIM_MAC_SIZE, "hmac attribute");
        }
        FR_PROTO_HEX_DUMP(eap_packet->type.data, eap_packet->type.length, "sim packet");
 
        /*
         *      Shrink buffer to the correct size
         */
        if (eap_packet->type.length != talloc_array_length(eap_packet->type.data)) {
                uint8_t *realloced;
 
                realloced = talloc_realloc(eap_packet, eap_packet->type.data, uint8_t, eap_packet->type.length);
                if (!realloced) goto error;
 
                eap_packet->type.data = realloced;
        }
 
        return fr_dbuff_used(&dbuff);
}
 
/*
 *      Test ctx data
 */
static int _test_ctx_free(UNUSED fr_aka_sim_ctx_t *ctx)
{
        fr_aka_sim_free();
 
        return 0;
}
 
static fr_aka_sim_ctx_t *test_ctx_init(TALLOC_CTX *ctx, uint8_t const *k_encr, size_t k_encr_len)
{
        fr_aka_sim_ctx_t        *test_ctx;
 
        test_ctx = talloc_zero(ctx, fr_aka_sim_ctx_t);
        test_ctx->k_encr = talloc_memdup(test_ctx, k_encr, k_encr_len);
        test_ctx->k_aut = talloc_zero_array(test_ctx, uint8_t, 16);
        test_ctx->k_aut_len = 16;
 
        talloc_set_destructor(test_ctx, _test_ctx_free);
 
        if (fr_aka_sim_init() < 0) {
                talloc_free(test_ctx);
                return NULL;
        }
 
        return test_ctx;
}
 
/*
 *      Test ctx data
 */
static int encode_test_ctx_sim(void **out, TALLOC_CTX *ctx, UNUSED fr_dict_t const *dict,
                               UNUSED fr_dict_attr_t const *root_da)
{
        fr_aka_sim_ctx_t        *test_ctx;
        static uint8_t          k_encr[] = { 0x00, 0x01, 0x02, 0x03, 0x04 ,0x05, 0x06, 0x07,
                                             0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f };
 
        test_ctx = test_ctx_init(ctx, k_encr, sizeof(k_encr));
        if (!test_ctx) return -1;
 
        test_ctx->have_iv = true;       /* Ensures IV is all zeros */
 
        *out = test_ctx;
 
        return 0;
}
 
static int encode_test_ctx_aka(void **out, TALLOC_CTX *ctx, UNUSED fr_dict_t const *dict,
                               UNUSED fr_dict_attr_t const *root_da)
{
        fr_aka_sim_ctx_t        *test_ctx;
        static uint8_t          k_encr[] = { 0x00, 0x01, 0x02, 0x03, 0x04 ,0x05, 0x06, 0x07,
                                             0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f };
 
        test_ctx = test_ctx_init(ctx, k_encr, sizeof(k_encr));
        if (!test_ctx) return -1;
 
        test_ctx->have_iv = true;       /* Ensures IV is all zeros */
 
        *out = test_ctx;
 
        return 0;
}
 
static int encode_test_ctx_sim_rfc4186(void **out, TALLOC_CTX *ctx, UNUSED fr_dict_t const *dict,
                                       UNUSED fr_dict_attr_t const *root_da)
{
        fr_aka_sim_ctx_t        *test_ctx;
        static uint8_t          k_encr[] = { 0x53, 0x6e, 0x5e, 0xbc, 0x44 ,0x65, 0x58, 0x2a,
                                             0xa6, 0xa8, 0xec, 0x99, 0x86, 0xeb, 0xb6, 0x20 };
 
        test_ctx = test_ctx_init(ctx, k_encr, sizeof(k_encr));
        if (!test_ctx) return -1;
 
        *out = test_ctx;
 
        return 0;
}
 
/*
 *      Test points
 */
extern fr_test_point_pair_encode_t sim_tp_encode;
fr_test_point_pair_encode_t sim_tp_encode = {
        .test_ctx       = encode_test_ctx_sim,
        .func           = fr_aka_sim_encode_pair,
        .next_encodable = fr_eap_aka_sim_next_encodable,
};
 
extern fr_test_point_pair_encode_t aka_tp_encode;
fr_test_point_pair_encode_t aka_tp_encode = {
        .test_ctx       = encode_test_ctx_aka,
        .func           = fr_aka_sim_encode_pair,
        .next_encodable = fr_eap_aka_sim_next_encodable,
};
 
extern fr_test_point_pair_encode_t sim_tp_encode_rfc4186;
fr_test_point_pair_encode_t sim_tp_encode_rfc4186 = {
        .test_ctx       = encode_test_ctx_sim_rfc4186,
        .func           = fr_aka_sim_encode_pair,
        .next_encodable = fr_eap_aka_sim_next_encodable,
};