path: root/src/lib/krb5/krb/pac_sign.c

/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* lib/krb5/krb/pac_sign.c */
/*
 * Copyright 2008 by the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 *
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 */

#include "k5-int.h"
#include "authdata.h"

/* draft-brezak-win2k-krb-authz-00 */

static krb5_error_code
k5_insert_client_info(krb5_context context,
                      krb5_pac pac,
                      krb5_timestamp authtime,
                      krb5_const_principal principal)
{
    krb5_error_code ret;
    krb5_data client_info;
    char *princ_name_utf8 = NULL;
    unsigned char *princ_name_ucs2 = NULL, *p;
    size_t princ_name_ucs2_len = 0;
    uint64_t nt_authtime;

    /* If we already have a CLIENT_INFO buffer, then just validate it */
    if (k5_pac_locate_buffer(context, pac, KRB5_PAC_CLIENT_INFO,
                             &client_info) == 0) {
        return k5_pac_validate_client(context, pac, authtime, principal);
    }

    ret = krb5_unparse_name_flags(context, principal,
                                  KRB5_PRINCIPAL_UNPARSE_NO_REALM,
                                  &princ_name_utf8);
    if (ret != 0)
        goto cleanup;

    ret = krb5int_utf8s_to_ucs2les(princ_name_utf8,
                                   &princ_name_ucs2,
                                   &princ_name_ucs2_len);
    if (ret != 0)
        goto cleanup;

    client_info.length = PAC_CLIENT_INFO_LENGTH + princ_name_ucs2_len;
    client_info.data = NULL;

    ret = k5_pac_add_buffer(context, pac, KRB5_PAC_CLIENT_INFO,
                            &client_info, TRUE, &client_info);
    if (ret != 0)
        goto cleanup;

    p = (unsigned char *)client_info.data;

    /* copy in authtime converted to a 64-bit NT time */
    k5_seconds_since_1970_to_time(authtime, &nt_authtime);
    store_64_le(nt_authtime, p);
    p += 8;

    /* copy in number of UCS-2 characters in principal name */
    store_16_le(princ_name_ucs2_len, p);
    p += 2;

    /* copy in principal name */
    memcpy(p, princ_name_ucs2, princ_name_ucs2_len);

cleanup:
    if (princ_name_ucs2 != NULL)
        free(princ_name_ucs2);
    krb5_free_unparsed_name(context, princ_name_utf8);

    return ret;
}

static krb5_error_code
k5_insert_checksum(krb5_context context,
                   krb5_pac pac,
                   krb5_ui_4 type,
                   const krb5_keyblock *key,
                   krb5_cksumtype *cksumtype)
{
    krb5_error_code ret;
    size_t len;
    krb5_data cksumdata;

    ret = krb5int_c_mandatory_cksumtype(context, key->enctype, cksumtype);
    if (ret != 0)
        return ret;

    ret = krb5_c_checksum_length(context, *cksumtype, &len);
    if (ret != 0)
        return ret;

    ret = k5_pac_locate_buffer(context, pac, type, &cksumdata);
    if (ret == 0) {
        /*
         * If we're resigning PAC, make sure we can fit checksum
         * into existing buffer
         */
        if (cksumdata.length != PAC_SIGNATURE_DATA_LENGTH + len)
            return ERANGE;

        memset(cksumdata.data, 0, cksumdata.length);
    } else {
        /* Add a zero filled buffer */
        cksumdata.length = PAC_SIGNATURE_DATA_LENGTH + len;
        cksumdata.data = NULL;

        ret = k5_pac_add_buffer(context, pac,
                                type, &cksumdata,
                                TRUE, &cksumdata);
        if (ret != 0)
            return ret;
    }

    /* Encode checksum type into buffer */
    store_32_le((krb5_ui_4)*cksumtype, cksumdata.data);

    return 0;
}

/* in-place encoding of PAC header */
static krb5_error_code
k5_pac_encode_header(krb5_context context, krb5_pac pac)
{
    size_t i;
    unsigned char *p;
    size_t header_len;

    header_len = PACTYPE_LENGTH +
        (pac->pac->cBuffers * PAC_INFO_BUFFER_LENGTH);
    assert(pac->data.length >= header_len);

    p = (unsigned char *)pac->data.data;

    store_32_le(pac->pac->cBuffers, p);
    p += 4;
    store_32_le(pac->pac->Version, p);
    p += 4;

    for (i = 0; i < pac->pac->cBuffers; i++) {
        PAC_INFO_BUFFER *buffer = &pac->pac->Buffers[i];

        store_32_le(buffer->ulType, p);
        p += 4;
        store_32_le(buffer->cbBufferSize, p);
        p += 4;
        store_64_le(buffer->Offset, p);
        p += 8;

        assert((buffer->Offset % PAC_ALIGNMENT) == 0);
        assert(buffer->Offset + buffer->cbBufferSize <= pac->data.length);
        assert(buffer->Offset >= header_len);

        if (buffer->Offset % PAC_ALIGNMENT ||
            buffer->Offset + buffer->cbBufferSize > pac->data.length ||
            buffer->Offset < header_len)
            return ERANGE;
    }

    return 0;
}

krb5_error_code KRB5_CALLCONV
krb5_pac_sign(krb5_context context, krb5_pac pac, krb5_timestamp authtime,
              krb5_const_principal principal, const krb5_keyblock *server_key,
              const krb5_keyblock *privsvr_key, krb5_data *data)
{
    krb5_error_code ret;
    krb5_data server_cksum, privsvr_cksum;
    krb5_cksumtype server_cksumtype, privsvr_cksumtype;
    krb5_crypto_iov iov[2];

    data->length = 0;
    data->data = NULL;

    if (principal != NULL) {
        ret = k5_insert_client_info(context, pac, authtime, principal);
        if (ret != 0)
            return ret;
    }

    /* Create zeroed buffers for both checksums */
    ret = k5_insert_checksum(context, pac, KRB5_PAC_SERVER_CHECKSUM,
                             server_key, &server_cksumtype);
    if (ret != 0)
        return ret;

    ret = k5_insert_checksum(context, pac, KRB5_PAC_PRIVSVR_CHECKSUM,
                             privsvr_key, &privsvr_cksumtype);
    if (ret != 0)
        return ret;

    /* Now, encode the PAC header so that the checksums will include it */
    ret = k5_pac_encode_header(context, pac);
    if (ret != 0)
        return ret;

    /* Generate the server checksum over the entire PAC */
    ret = k5_pac_locate_buffer(context, pac, KRB5_PAC_SERVER_CHECKSUM,
                               &server_cksum);
    if (ret != 0)
        return ret;

    assert(server_cksum.length > PAC_SIGNATURE_DATA_LENGTH);

    iov[0].flags = KRB5_CRYPTO_TYPE_DATA;
    iov[0].data = pac->data;

    iov[1].flags = KRB5_CRYPTO_TYPE_CHECKSUM;
    iov[1].data.data = server_cksum.data + PAC_SIGNATURE_DATA_LENGTH;
    iov[1].data.length = server_cksum.length - PAC_SIGNATURE_DATA_LENGTH;

    ret = krb5_c_make_checksum_iov(context, server_cksumtype,
                                   server_key, KRB5_KEYUSAGE_APP_DATA_CKSUM,
                                   iov, sizeof(iov)/sizeof(iov[0]));
    if (ret != 0)
        return ret;

    /* Generate the privsvr checksum over the server checksum buffer */
    ret = k5_pac_locate_buffer(context, pac, KRB5_PAC_PRIVSVR_CHECKSUM,
                               &privsvr_cksum);
    if (ret != 0)
        return ret;

    assert(privsvr_cksum.length > PAC_SIGNATURE_DATA_LENGTH);

    iov[0].flags = KRB5_CRYPTO_TYPE_DATA;
    iov[0].data.data = server_cksum.data + PAC_SIGNATURE_DATA_LENGTH;
    iov[0].data.length = server_cksum.length - PAC_SIGNATURE_DATA_LENGTH;

    iov[1].flags = KRB5_CRYPTO_TYPE_CHECKSUM;
    iov[1].data.data = privsvr_cksum.data + PAC_SIGNATURE_DATA_LENGTH;
    iov[1].data.length = privsvr_cksum.length - PAC_SIGNATURE_DATA_LENGTH;

    ret = krb5_c_make_checksum_iov(context, privsvr_cksumtype,
                                   privsvr_key, KRB5_KEYUSAGE_APP_DATA_CKSUM,
                                   iov, sizeof(iov)/sizeof(iov[0]));
    if (ret != 0)
        return ret;

    data->data = k5memdup(pac->data.data, pac->data.length, &ret);
    if (data->data == NULL)
        return ret;
    data->length = pac->data.length;

    memset(pac->data.data, 0,
           PACTYPE_LENGTH + (pac->pac->cBuffers * PAC_INFO_BUFFER_LENGTH));

    return 0;
}