xlat.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/xlat.c
 * @brief EAP-SIM/EAP-AKA identity detection, creation, and decyption.
 *
 * Implements the encrypted IMSI scheme described in TS 33.402 Release 14,
 * section 14.
 *
 * @copyright 2017 The FreeRADIUS server project
 */
 
#include <freeradius-devel/server/base.h>
#include <freeradius-devel/unlang/xlat_func.h>
 
#include "base.h"
#include "attrs.h"
 
static int aka_sim_xlat_refs = 0;
 
 
static xlat_arg_parser_t const aka_sim_xlat_id_method_xlat_args[] = {
        { .required = true, .single = true, .type = FR_TYPE_STRING },
        XLAT_ARG_PARSER_TERMINATOR
};
 
/** Returns the SIM method EAP-SIM or EAP-AKA hinted at by the user identifier
 *
@verbatim
%aka_sim_id_method(%{id_attr})
@endverbatim
 *
 * @ingroup xlat_functions
 */
static xlat_action_t aka_sim_xlat_id_method_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
                                                 UNUSED xlat_ctx_t const *xctx,
                                                 request_t *request,
                                                 fr_value_box_list_t *in)
{
        char const                      *method;
        fr_aka_sim_id_type_t            type_hint;
        fr_aka_sim_method_hint_t        method_hint;
        fr_value_box_t                  *id = fr_value_box_list_head(in);
        fr_value_box_t                  *vb;
 
        if (fr_aka_sim_id_type(&type_hint, &method_hint, id->vb_strvalue, id->vb_length) < 0) {
                RPEDEBUG2("AKA/SIM Id \"%pV\" has unrecognised format", id);
                return XLAT_ACTION_FAIL;
        }
 
        switch (method_hint) {
        default:
        case AKA_SIM_METHOD_HINT_UNKNOWN:
                return XLAT_ACTION_DONE;
 
        case AKA_SIM_METHOD_HINT_SIM:
                method = fr_dict_enum_name_by_value(attr_eap_aka_sim_method_hint,
                                                     fr_box_uint32(FR_METHOD_HINT_VALUE_SIM));
                break;
 
        case AKA_SIM_METHOD_HINT_AKA:
                method = fr_dict_enum_name_by_value(attr_eap_aka_sim_method_hint,
                                                     fr_box_uint32(FR_METHOD_HINT_VALUE_AKA));
                break;
 
        case AKA_SIM_METHOD_HINT_AKA_PRIME:
                method = fr_dict_enum_name_by_value(attr_eap_aka_sim_method_hint,
                                                     fr_box_uint32(FR_METHOD_HINT_VALUE_AKA_PRIME));
                break;
        }
 
        MEM(vb = fr_value_box_alloc(ctx, FR_TYPE_STRING, NULL));
        fr_value_box_bstrndup(vb, vb, NULL, method, strlen(method), false);
        fr_dcursor_append(out, vb);
 
        return XLAT_ACTION_DONE;
}
 
static xlat_arg_parser_t const aka_sim_xlat_id_type_xlat_args[] = {
        { .required = true, .single = true, .type = FR_TYPE_STRING },
        XLAT_ARG_PARSER_TERMINATOR
};
 
/** Returns the type of identity used
 *
@verbatim
%aka_sim_id_type(%{id_attr})
@endverbatim
 *
 * @ingroup xlat_functions
 */
static xlat_action_t aka_sim_xlat_id_type_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
                                               UNUSED xlat_ctx_t const *xctx,
                                               request_t *request, fr_value_box_list_t *in)
{
        char const                      *type;
        fr_aka_sim_id_type_t            type_hint;
        fr_aka_sim_method_hint_t        method_hint;
        fr_value_box_t                  *id = fr_value_box_list_head(in);
        fr_value_box_t                  *vb;
 
        if (fr_aka_sim_id_type(&type_hint, &method_hint, id->vb_strvalue, id->vb_length) < 0) {
                RPEDEBUG2("AKA/AKA/SIM Id \"%pV\" has unrecognised format", id);
                return XLAT_ACTION_FAIL;
        }
 
        switch (type_hint) {
        default:
        case AKA_SIM_ID_TYPE_UNKNOWN:
                return XLAT_ACTION_DONE;
 
        case AKA_SIM_ID_TYPE_PERMANENT:
                type = fr_dict_enum_name_by_value(attr_eap_aka_sim_identity_type,
                                                  fr_box_uint32(FR_IDENTITY_TYPE_VALUE_PERMANENT));
                break;
 
        case AKA_SIM_ID_TYPE_PSEUDONYM:
                type = fr_dict_enum_name_by_value(attr_eap_aka_sim_identity_type,
                                                  fr_box_uint32(FR_IDENTITY_TYPE_VALUE_PSEUDONYM));
                break;
 
        case AKA_SIM_ID_TYPE_FASTAUTH:
                type = fr_dict_enum_name_by_value(attr_eap_aka_sim_identity_type,
                                                  fr_box_uint32(FR_IDENTITY_TYPE_VALUE_FASTAUTH));
                break;
        }
 
        MEM(vb = fr_value_box_alloc(ctx, FR_TYPE_STRING, NULL));
        fr_value_box_bstrndup(vb, vb, NULL, type, strlen(type), false);
        fr_dcursor_append(out, vb);
 
        return XLAT_ACTION_DONE;
}
 
static xlat_arg_parser_t const aka_sim_id_3gpp_temporary_id_key_index_xlat_args[] = {
        { .required = true, .single = true, .type = FR_TYPE_STRING },
        XLAT_ARG_PARSER_TERMINATOR
};
 
/** Returns the key index from a 3gpp temporary id
 *
@verbatim
%3gpp_temporary_id_key_index(%{id_attr})
@endverbatim
 *
 * @ingroup xlat_functions
 */
static xlat_action_t aka_sim_id_3gpp_temporary_id_key_index_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
                                                                 UNUSED xlat_ctx_t const *xctx,
                                                                 request_t *request, fr_value_box_list_t *in)
{
        fr_value_box_t  *id = fr_value_box_list_head(in);
        fr_value_box_t  *vb;
 
        if (id->vb_length != AKA_SIM_3GPP_PSEUDONYM_LEN) {
                REDEBUG2("3gpp pseudonym incorrect length, expected %u bytes, got %zu bytes",
                         AKA_SIM_3GPP_PSEUDONYM_LEN, id->vb_length);
                return XLAT_ACTION_FAIL;
        }
 
        MEM(vb = fr_value_box_alloc(ctx, FR_TYPE_UINT8, NULL));
        vb->vb_uint8 = fr_aka_sim_id_3gpp_pseudonym_tag(id->vb_strvalue);
        fr_dcursor_append(out, vb);
 
        return XLAT_ACTION_DONE;
}
 
static xlat_arg_parser_t aka_sim_3gpp_temporary_id_decrypt_xlat_args[] = {
        { .required = true, .concat = true, .single = false, .type = FR_TYPE_STRING,
          .func = NULL, .uctx = NULL },
        { .required = true, .concat = true, .single = false, .type = FR_TYPE_OCTETS,
          .func = NULL, .uctx = NULL },
        { .required = false, .concat = false, .single = true, .type = FR_TYPE_BOOL,
          .func = NULL, .uctx = NULL },
        XLAT_ARG_PARSER_TERMINATOR
};
 
/** Decrypt a 3gpp temporary id
 *
 @verbatim
 %3gpp_temporary_id_decrypt(<id> <key>)
 @endverbatim
 *
 * The pseudonym is in the format
 @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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Tag    | KeyID |             Encrypted IMSI
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                                                   |
   |                   Encrypted IMSI (cont)                       |
   |                                                               |
   |                   |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   +-+-+-+-+-+-+-+-+-+-+
 @endverbatim
 *
 * Tag (6 bits) - Used to mark the identity as a temporary pseudonym
 * or re-authentication identity.  The idea of this being 6 bits is
 * so that we can choose values that match base64 sextets, so the
 * first character in the base64 output matches one of the known tags
 * for EAP-SIM/AKA/AKA' identities.
 *
 * Key Indicator (4 bits) - Used to select the appropriate key from
 * multiple keys the server may have used to encrypt IMSIs.
 *
 * Encrypted IMSI (128 bits) - The original IMSI encrypted with
 * AES-128-ECB.
 *
 * @ingroup xlat_functions
 */
static xlat_action_t aka_sim_3gpp_temporary_id_decrypt_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
                                                            UNUSED xlat_ctx_t const *xctx,
                                                            request_t *request, fr_value_box_list_t *in)
{
        uint8_t         tag;
        char            out_tag = '\0', *buff;
 
        char            decrypted[AKA_SIM_IMSI_MAX_LEN + 1];
 
        fr_value_box_t  *id_vb = fr_value_box_list_head(in);
        char const      *id = id_vb->vb_strvalue;
        size_t          id_len = id_vb->vb_length;
 
        fr_value_box_t  *key_vb = fr_value_box_list_next(in, id_vb);
        /* coverity[dereference] */
        uint8_t const   *key = key_vb->vb_octets;
        size_t          key_len = key_vb->vb_length;
 
        fr_value_box_t  *tag_vb = fr_value_box_list_next(in, key_vb);
        bool            include_tag = true;
 
        fr_value_box_t  *vb;
        fr_pair_t       *eap_type;
 
        if (tag_vb) include_tag = tag_vb->vb_bool;
 
        if (id_len != (AKA_SIM_3GPP_PSEUDONYM_LEN)) {
                REDEBUG2("3gpp pseudonym incorrect length, expected %u bytes, got %zu bytes",
                         AKA_SIM_3GPP_PSEUDONYM_LEN, id_len);
        error:
                return XLAT_ACTION_FAIL;
        }
 
        if (key_len != 16) {
                REDEBUG2("Decryption key incorrect length, expected %i bytes, got %zu bytes", 16, key_len);
                goto error;
        }
 
        if (include_tag) {
                /*
                 *      Figure out what tag we should add to the permanent id
                 */
                eap_type = fr_pair_find_by_da(&request->request_pairs, NULL, attr_eap_type);
                if (eap_type) {
                        if (eap_type->vp_uint32 == enum_eap_type_sim->vb_uint32) {
                                out_tag = ID_TAG_SIM_PERMANENT;
                        } else if (eap_type->vp_uint32 == enum_eap_type_aka->vb_uint32) {
                                out_tag = ID_TAG_AKA_PERMANENT;
                        } else if (eap_type->vp_uint32 == enum_eap_type_aka_prime->vb_uint32) {
                                out_tag = ID_TAG_AKA_PRIME_PERMANENT;
                        } else {
                                goto use_existing_tag;
                        }
                } else {
                use_existing_tag:
                        tag = fr_aka_sim_id_3gpp_pseudonym_tag(id);
                        switch (tag) {
                        case ID_TAG_SIM_PSEUDONYM_B64:
                        case ID_TAG_SIM_FASTAUTH_B64:
                                out_tag = ID_TAG_SIM_PERMANENT;
                                break;
 
                        case ID_TAG_AKA_PSEUDONYM_B64:
                        case ID_TAG_AKA_FASTAUTH_B64:
                                out_tag = ID_TAG_AKA_PERMANENT;
                                break;
 
                        case ID_TAG_AKA_PRIME_PSEUDONYM_B64:
                        case ID_TAG_AKA_PRIME_FASTAUTH_B64:
                                out_tag = ID_TAG_AKA_PRIME_PERMANENT;
                                break;
 
                        default:
                                REDEBUG2("Unexpected tag value (%u) in AKA/SIM Id \"%pV\"", tag, fr_box_strvalue_len(id, id_len));
                                goto error;
                        }
                }
        }
 
        RDEBUG2("Decrypting \"%pV\"", fr_box_strvalue_len(id, id_len));
        if (fr_aka_sim_id_3gpp_pseudonym_decrypt(decrypted, id, key) < 0) {
                RPEDEBUG2("Failed decrypting AKA/SIM Id");
                goto error;
        }
 
        /*
         *      Recombine unencrypted IMSI with tag
         */
        MEM(vb = fr_value_box_alloc_null(ctx));
        if (include_tag) {
                MEM(fr_value_box_bstr_alloc(vb, &buff, vb, NULL, AKA_SIM_IMSI_MAX_LEN + 1, false) == 0);
                *buff = out_tag;
                strncpy(buff + 1, decrypted, AKA_SIM_IMSI_MAX_LEN + 1);
        } else {
                MEM(fr_value_box_bstrndup(vb, vb, NULL, decrypted, AKA_SIM_IMSI_MAX_LEN, true) == 0);
        }
        fr_dcursor_append(out, vb);
 
        return XLAT_ACTION_DONE;
}
 
static xlat_arg_parser_t aka_sim_3gpp_temporary_id_encrypt_xlat_args[] = {
        { .required = true, .concat = true, .single = false, .type = FR_TYPE_STRING     },
        { .required = true, .concat = true, .single = false, .type = FR_TYPE_OCTETS     },
        { .required = true, .concat = false, .single = true, .type = FR_TYPE_UINT8      },
        { .required = false, .concat = false, .single = true, .type = FR_TYPE_STRING    },
        XLAT_ARG_PARSER_TERMINATOR
};
 
/** Encrypts a 3gpp pseudonym
 *
@verbatim
%3gpp_temporary_id_encrypt(<id>, <key>, <index>, [(pseudonym|fastauth)])
@endverbatim
 *
 * @ingroup xlat_functions
 */
static xlat_action_t aka_sim_3gpp_temporary_id_encrypt_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
                                                            UNUSED xlat_ctx_t const *xctx,
                                                            request_t *request, fr_value_box_list_t *in)
{
        char                            encrypted[AKA_SIM_3GPP_PSEUDONYM_LEN + 1];
        uint8_t                         tag = 0;
 
        char const                      *id_p, *id_end;
        fr_aka_sim_id_type_t            type_hint;
        fr_aka_sim_method_hint_t        method_hint;
 
        fr_value_box_t                  *id_vb = fr_value_box_list_head(in);
        char const                      *id = id_vb->vb_strvalue;
        size_t                          id_len = id_vb->vb_length;
 
        fr_value_box_t                  *key_vb = fr_value_box_list_next(in, id_vb);
        /* coverity[dereference] */
        uint8_t const                   *key = key_vb->vb_octets;
        size_t                          key_len = key_vb->vb_length;
 
        fr_value_box_t                  *index_vb = fr_value_box_list_next(in, key_vb);
        uint8_t                         key_index = index_vb->vb_uint8;
 
        fr_value_box_t                  *type_vb = fr_value_box_list_next(in, index_vb);
 
        bool                            fastauth = false;
 
        fr_value_box_t                  *vb;
 
        /*
         *      Get the key index
         */
        if (key_index > 15) {
                REDEBUG2("Key index must be between 0-15");
        error:
                return XLAT_ACTION_FAIL;
        }
 
        if (key_len != 16) {
                REDEBUG2("Encryption key incorrect length, expected %i bytes, got %zu bytes", 16, key_len);
                goto error;
        }
 
        /*
         *      Check for the optional type argument
         */
        if (type_vb) {
                fr_dict_enum_value_t const              *type_enum;
 
                type_enum = fr_dict_enum_by_name(attr_eap_aka_sim_identity_type,
                                                 type_vb->vb_strvalue, type_vb->vb_length);
                if (!type_enum) {
                bad_type:
                        REDEBUG2("Bad type %pV, must be one of 'fastauth' or 'pseudonym'", type_vb);
                        goto error;
                }
 
                switch (type_enum->value->vb_uint32) {
                case FR_IDENTITY_TYPE_VALUE_PSEUDONYM:
                        break;
 
                case FR_IDENTITY_TYPE_VALUE_FASTAUTH:
                        fastauth = true;
                        break;
 
                default:
                        goto bad_type;
                }
        }
 
        /*
         *      Determine what type/method hints are in the current ID.
         */
        if (id_len == (AKA_SIM_IMSI_MAX_LEN + 1)) {     /* +1 for ID tag */
                if (fr_aka_sim_id_type(&type_hint, &method_hint, id, id_len) < 0) {
                        RPEDEBUG2("ID \"%pV\" has unrecognised format", fr_box_strvalue_len(id, id_len));
                        goto error;
                }
 
                if (type_hint != AKA_SIM_ID_TYPE_PERMANENT) {
                        REDEBUG2("ID \"%pV\" is not a permanent identity (IMSI)", fr_box_strvalue_len(id, id_len));
                        goto error;
                }
 
                switch (method_hint) {
                case AKA_SIM_METHOD_HINT_SIM:
                        tag = !fastauth ? ID_TAG_SIM_PSEUDONYM_B64 : ID_TAG_SIM_FASTAUTH_B64;
                        break;
 
                case AKA_SIM_METHOD_HINT_AKA:
                        tag = !fastauth ? ID_TAG_AKA_PSEUDONYM_B64 : ID_TAG_AKA_FASTAUTH_B64;
                        break;
 
                case AKA_SIM_METHOD_HINT_AKA_PRIME:
                        tag = !fastauth ? ID_TAG_AKA_PRIME_PSEUDONYM_B64 : ID_TAG_AKA_PRIME_FASTAUTH_B64;
                        break;
 
                case AKA_SIM_METHOD_HINT_UNKNOWN:
                case AKA_SIM_METHOD_HINT_MAX:
                        REDEBUG2("ID \"%pV\" does not contain a method hint", fr_box_strvalue_len(id, id_len));
                        goto error;
                }
 
                id_p = id + 1;
                id_end = (id_p + id_len) - 1;
        /*
         *      ID lacks a hint byte, figure it out from &request.EAP-Type
         */
        } else if ((id_len >= AKA_SIM_IMSI_MIN_LEN) && (id_len <= AKA_SIM_IMSI_MAX_LEN)) {
                fr_pair_t *eap_type;
 
                eap_type = fr_pair_find_by_da(&request->request_pairs, NULL, attr_eap_type);
                if (!eap_type) {
                        REDEBUG("ID does not contain method hint, and no &request.EAP-Type found.  "
                                "Don't know what tag to prepend to encrypted identity");
                        goto error;
                }
 
                if (eap_type->vp_uint32 == enum_eap_type_sim->vb_uint32) {
                        tag = !fastauth ? ID_TAG_SIM_PSEUDONYM_B64 : ID_TAG_SIM_FASTAUTH_B64;
                } else if (eap_type->vp_uint32 == enum_eap_type_aka->vb_uint32) {
                        tag = !fastauth ? ID_TAG_AKA_PSEUDONYM_B64 : ID_TAG_AKA_FASTAUTH_B64;
                } else if (eap_type->vp_uint32 == enum_eap_type_aka_prime->vb_uint32) {
                        tag = !fastauth ? ID_TAG_AKA_PRIME_PSEUDONYM_B64 : ID_TAG_AKA_PRIME_FASTAUTH_B64;
                } else {
                        REDEBUG("&request.EAP-Type does not match a SIM based EAP-Type (SIM, AKA, AKA-Prime)");
                }
 
                id_p = id;
                id_end = id_p + id_len;
        } else {
                REDEBUG2("IMSI incorrect length, expected %u bytes, got %zu bytes", AKA_SIM_IMSI_MAX_LEN + 1,
                         id_len);
                goto error;
 
        }
 
        /*
         *      Encrypt the IMSI
         *
         *      Strip existing tag from the permanent id
         */
        if (fr_aka_sim_id_3gpp_pseudonym_encrypt(encrypted, id_p, id_end - id_p, tag, (uint8_t)key_index, key) < 0) {
                RPEDEBUG2("Failed encrypting SIM ID \"%pV\"", fr_box_strvalue_len(id, id_len));
                return XLAT_ACTION_FAIL;
        }
 
        MEM(vb = fr_value_box_alloc(ctx, FR_TYPE_STRING, NULL));
        fr_value_box_bstrndup(vb, vb, NULL, encrypted, strlen(encrypted), false);
        fr_dcursor_append(out, vb);
 
        return XLAT_ACTION_DONE;
}
 
int fr_aka_sim_xlat_func_register(void)
{
        xlat_t  *xlat;
 
        if (aka_sim_xlat_refs) {
                aka_sim_xlat_refs++;
                return 0;
        }
 
        if (unlikely((xlat = xlat_func_register(NULL, "aka_sim_id_method", aka_sim_xlat_id_method_xlat, FR_TYPE_STRING)) == NULL)) return -1;
        xlat_func_args_set(xlat, aka_sim_xlat_id_method_xlat_args);
        if (unlikely((xlat = xlat_func_register(NULL, "aka_sim_id_type", aka_sim_xlat_id_type_xlat, FR_TYPE_STRING)) == NULL)) return -1;
        xlat_func_args_set(xlat, aka_sim_xlat_id_type_xlat_args);
        if (unlikely((xlat = xlat_func_register(NULL, "3gpp_temporary_id_key_index", aka_sim_id_3gpp_temporary_id_key_index_xlat, FR_TYPE_UINT8)) == NULL)) return -1;
        xlat_func_args_set(xlat, aka_sim_id_3gpp_temporary_id_key_index_xlat_args);
        if (unlikely((xlat = xlat_func_register(NULL, "3gpp_temporary_id_decrypt", aka_sim_3gpp_temporary_id_decrypt_xlat, FR_TYPE_STRING)) == NULL)) return -1;
        xlat_func_args_set(xlat, aka_sim_3gpp_temporary_id_decrypt_xlat_args);
        if (unlikely((xlat = xlat_func_register(NULL, "3gpp_temporary_id_encrypt", aka_sim_3gpp_temporary_id_encrypt_xlat, FR_TYPE_STRING)) == NULL)) return -1;
        xlat_func_args_set(xlat, aka_sim_3gpp_temporary_id_encrypt_xlat_args);
        aka_sim_xlat_refs = 1;
 
        return 0;
}
 
void fr_aka_sim_xlat_func_unregister(void)
{
        if (aka_sim_xlat_refs > 1) {
                aka_sim_xlat_refs--;
                return;
        }
 
        xlat_func_unregister("aka_sim_id_method");
        xlat_func_unregister("aka_sim_id_type");
        xlat_func_unregister("3gpp_temporary_id_key_index");
        xlat_func_unregister("3gpp_temporary_id_decrypt");
        xlat_func_unregister("3gpp_temporary_id_encrypt");
        aka_sim_xlat_refs = 0;
}