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

/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
** set password functions added by Paul W. Nelson, Thursby Software Systems, Inc.
*/
#include <string.h>

#include "k5-int.h"
#include "k5-unicode.h"
#include "int-proto.h"
#include "auth_con.h"


krb5_error_code
krb5int_mk_chpw_req(krb5_context context,
                    krb5_auth_context auth_context,
                    krb5_data *ap_req,
                    char *passwd,
                    krb5_data *packet)
{
    krb5_error_code ret = 0;
    krb5_data clearpw;
    krb5_data cipherpw;
    krb5_replay_data replay;
    char *ptr;

    cipherpw.data = NULL;

    if ((ret = krb5_auth_con_setflags(context, auth_context,
                                      KRB5_AUTH_CONTEXT_DO_SEQUENCE)))
        goto cleanup;

    clearpw.length = strlen(passwd);
    clearpw.data = passwd;

    if ((ret = krb5_mk_priv(context, auth_context,
                            &clearpw, &cipherpw, &replay)))
        goto cleanup;

    packet->length = 6 + ap_req->length + cipherpw.length;
    packet->data = (char *) malloc(packet->length);
    if (packet->data == NULL) {
        ret = ENOMEM;
        goto cleanup;
    }
    ptr = packet->data;

    /* length */

    store_16_be(packet->length, ptr);
    ptr += 2;

    /* version == 0x0001 big-endian */

    *ptr++ = 0;
    *ptr++ = 1;

    /* ap_req length, big-endian */

    store_16_be(ap_req->length, ptr);
    ptr += 2;

    /* ap-req data */

    memcpy(ptr, ap_req->data, ap_req->length);
    ptr += ap_req->length;

    /* krb-priv of password */

    memcpy(ptr, cipherpw.data, cipherpw.length);

cleanup:
    if (cipherpw.data != NULL)  /* allocated by krb5_mk_priv */
        free(cipherpw.data);

    return(ret);
}

/* Decode error_packet as a KRB-ERROR message and retrieve its e-data into
 * *edata_out. */
static krb5_error_code
get_error_edata(krb5_context context, const krb5_data *error_packet,
                krb5_data **edata_out)
{
    krb5_error_code ret;
    krb5_error *krberror = NULL;

    *edata_out = NULL;

    ret = krb5_rd_error(context, error_packet, &krberror);
    if (ret)
        return ret;

    if (krberror->e_data.data == NULL) {
        /* Return a krb5 error code based on the error number. */
        ret = ERROR_TABLE_BASE_krb5 + (krb5_error_code)krberror->error;
        goto cleanup;
    }

    ret = krb5_copy_data(context, &krberror->e_data, edata_out);

cleanup:
    krb5_free_error(context, krberror);
    return ret;
}

/* Decode a reply to produce the clear-text output. */
static krb5_error_code
get_clear_result(krb5_context context, krb5_auth_context auth_context,
                 const krb5_data *packet, krb5_data **clear_out,
                 krb5_boolean *is_error_out)
{
    krb5_error_code ret;
    char *ptr, *end = packet->data + packet->length;
    unsigned int plen, vno, aplen;
    krb5_data ap_rep, cipher, error;
    krb5_ap_rep_enc_part *ap_rep_enc;
    krb5_replay_data replay;
    krb5_key send_subkey = NULL;
    krb5_data clear = empty_data();

    *clear_out = NULL;
    *is_error_out = FALSE;

    /* Check for an unframed KRB-ERROR (expected for RFC 3244 requests; also
     * received from MS AD for version 1 requests). */
    if (krb5_is_krb_error(packet)) {
        *is_error_out = TRUE;
        return get_error_edata(context, packet, clear_out);
    }

    if (packet->length < 6)
        return KRB5KRB_AP_ERR_MODIFIED;

    /* Decode and verify the length. */
    ptr = packet->data;
    plen = (*ptr++ & 0xff);
    plen = (plen << 8) | (*ptr++ & 0xff);
    if (plen != packet->length)
        return KRB5KRB_AP_ERR_MODIFIED;

    /* Decode and verify the version number. */
    vno = (*ptr++ & 0xff);
    vno = (vno << 8) | (*ptr++ & 0xff);
    if (vno != 1 && vno != 0xff80)
        return KRB5KDC_ERR_BAD_PVNO;

    /* Decode and check the AP-REP length. */
    aplen = (*ptr++ & 0xff);
    aplen = (aplen << 8) | (*ptr++ & 0xff);
    if (aplen > end - ptr)
        return KRB5KRB_AP_ERR_MODIFIED;

    /* A zero-length AP-REQ indicates a framed KRB-ERROR response.  (Expected
     * for protocol version 1; specified but unusual for RFC 3244 requests.) */
    if (aplen == 0) {
        *is_error_out = TRUE;
        error = make_data(ptr, end - ptr);
        return get_error_edata(context, &error, clear_out);
    }

    /* We have an AP-REP.  Save send_subkey to later smash recv_subkey. */
    ret = krb5_auth_con_getsendsubkey_k(context, auth_context, &send_subkey);
    if (ret)
        return ret;

    /* Verify the AP-REP. */
    ap_rep = make_data(ptr, aplen);
    ptr += ap_rep.length;
    ret = krb5_rd_rep(context, auth_context, &ap_rep, &ap_rep_enc);
    if (ret)
        goto cleanup;
    krb5_free_ap_rep_enc_part(context, ap_rep_enc);

    /* Smash recv_subkey to be send_subkey, per spec. */
    ret = krb5_auth_con_setrecvsubkey_k(context, auth_context, send_subkey);
    if (ret)
        goto cleanup;

    /* Extract and decrypt the result. */
    cipher = make_data(ptr, end - ptr);
    ret = krb5_rd_priv(context, auth_context, &cipher, &clear, &replay);
    if (ret)
        goto cleanup;

    ret = krb5_copy_data(context, &clear, clear_out);
    if (ret)
        goto cleanup;
    *is_error_out = FALSE;

cleanup:
    krb5_k_free_key(context, send_subkey);
    krb5_free_data_contents(context, &clear);
    return ret;
}

krb5_error_code
krb5int_rd_chpw_rep(krb5_context context, krb5_auth_context auth_context,
                    krb5_data *packet, int *result_code_out,
                    krb5_data *result_data_out)
{
    krb5_error_code ret;
    krb5_data result_data, *clear = NULL;
    krb5_boolean is_error;
    char *ptr;
    int result_code;

    *result_code_out = 0;
    *result_data_out = empty_data();

    ret = get_clear_result(context, auth_context, packet, &clear, &is_error);
    if (ret)
        return ret;

    if (clear->length < 2) {
        ret = KRB5KRB_AP_ERR_MODIFIED;
        goto cleanup;
    }

    /* Decode and check the result code. */
    ptr = clear->data;
    result_code = (*ptr++ & 0xff);
    result_code = (result_code << 8) | (*ptr++ & 0xff);
    if (result_code < KRB5_KPASSWD_SUCCESS ||
        result_code > KRB5_KPASSWD_INITIAL_FLAG_NEEDED) {
        ret = KRB5KRB_AP_ERR_MODIFIED;
        goto cleanup;
    }

    /* Successful replies must not come from errors. */
    if (is_error && result_code == KRB5_KPASSWD_SUCCESS) {
        ret = KRB5KRB_AP_ERR_MODIFIED;
        goto cleanup;
    }

    result_data = make_data(ptr, clear->data + clear->length - ptr);
    ret = krb5int_copy_data_contents(context, &result_data, result_data_out);
    if (ret)
        goto cleanup;
    *result_code_out = result_code;

cleanup:
    krb5_free_data(context, clear);
    return ret;
}

krb5_error_code KRB5_CALLCONV
krb5_chpw_result_code_string(krb5_context context, int result_code,
                             char **code_string)
{
    switch (result_code) {
    case KRB5_KPASSWD_MALFORMED:
        *code_string = _("Malformed request error");
        break;
    case KRB5_KPASSWD_HARDERROR:
        *code_string = _("Server error");
        break;
    case KRB5_KPASSWD_AUTHERROR:
        *code_string = _("Authentication error");
        break;
    case KRB5_KPASSWD_SOFTERROR:
        *code_string = _("Password change rejected");
        break;
    case KRB5_KPASSWD_ACCESSDENIED:
        *code_string = _("Access denied");
        break;
    case KRB5_KPASSWD_BAD_VERSION:
        *code_string = _("Wrong protocol version");
        break;
    case KRB5_KPASSWD_INITIAL_FLAG_NEEDED:
        *code_string = _("Initial password required");
        break;
    case 0:
        *code_string = _("Success");
        break;
    default:
        *code_string = _("Password change failed");
        break;
    }

    return 0;
}

krb5_error_code
krb5int_mk_setpw_req(krb5_context context,
                     krb5_auth_context auth_context,
                     krb5_data *ap_req,
                     krb5_principal targprinc,
                     char *passwd,
                     krb5_data *packet)
{
    krb5_error_code ret;
    krb5_data   cipherpw;
    krb5_data   *encoded_setpw;
    struct krb5_setpw_req req;

    char *ptr;

    cipherpw.data = NULL;
    cipherpw.length = 0;

    if ((ret = krb5_auth_con_setflags(context, auth_context,
                                      KRB5_AUTH_CONTEXT_DO_SEQUENCE)))
        return(ret);

    req.target = targprinc;
    req.password.data = passwd;
    req.password.length = strlen(passwd);
    ret = encode_krb5_setpw_req(&req, &encoded_setpw);
    if (ret) {
        return ret;
    }

    if ((ret = krb5_mk_priv(context, auth_context, encoded_setpw, &cipherpw, NULL)) != 0) {
        krb5_free_data(context, encoded_setpw);
        return(ret);
    }
    krb5_free_data(context, encoded_setpw);


    packet->length = 6 + ap_req->length + cipherpw.length;
    packet->data = (char *) malloc(packet->length);
    if (packet->data  == NULL) {
        ret = ENOMEM;
        goto cleanup;
    }
    ptr = packet->data;
    /*
    ** build the packet -
    */
    /* put in the length */
    store_16_be(packet->length, ptr);
    ptr += 2;
    /* put in the version */
    *ptr++ = (char)0xff;
    *ptr++ = (char)0x80;
    /* the ap_req length is big endian */
    store_16_be(ap_req->length, ptr);
    ptr += 2;
    /* put in the request data */
    memcpy(ptr, ap_req->data, ap_req->length);
    ptr += ap_req->length;
    /*
    ** put in the "private" password data -
    */
    memcpy(ptr, cipherpw.data, cipherpw.length);
    ret = 0;
cleanup:
    if (cipherpw.data)
        krb5_free_data_contents(context, &cipherpw);
    if ((ret != 0) && packet->data) {
        free(packet->data);
        packet->data = NULL;
    }
    return ret;
}

/*
 * Active Directory policy information is communicated in the result string
 * field as a packed 30-byte sequence, starting with two zero bytes (so that
 * the string appears as zero-length when interpreted as UTF-8).  The bytes
 * correspond to the fields in the following structure, with each field in
 * big-endian byte order.
 */
struct ad_policy_info {
    uint16_t zero_bytes;
    uint32_t min_length_password;
    uint32_t password_history;
    uint32_t password_properties; /* see defines below */
    uint64_t expire;              /* in seconds * 10,000,000 */
    uint64_t min_passwordage;     /* in seconds * 10,000,000 */
};

#define AD_POLICY_INFO_LENGTH      30
#define AD_POLICY_TIME_TO_DAYS     (86400ULL * 10000000ULL)

#define AD_POLICY_COMPLEX          0x00000001
#define AD_POLICY_NO_ANON_CHANGE   0x00000002
#define AD_POLICY_NO_CLEAR_CHANGE  0x00000004
#define AD_POLICY_LOCKOUT_ADMINS   0x00000008
#define AD_POLICY_STORE_CLEARTEXT  0x00000010
#define AD_POLICY_REFUSE_CHANGE    0x00000020

/* If buf already contains one or more sentences, add spaces to separate them
 * from the next sentence. */
static void
add_spaces(struct k5buf *buf)
{
    if (k5_buf_len(buf) > 0)
        k5_buf_add(buf, "  ");
}

static krb5_error_code
decode_ad_policy_info(const krb5_data *data, char **msg_out)
{
    struct ad_policy_info policy;
    uint64_t password_days;
    const char *p;
    char *msg;
    struct k5buf buf;

    *msg_out = NULL;
    if (data->length != AD_POLICY_INFO_LENGTH)
        return 0;

    p = data->data;
    policy.zero_bytes = load_16_be(p);
    p += 2;

    /* first two bytes are zeros */
    if (policy.zero_bytes != 0)
        return 0;

    /* Read in the rest of structure */
    policy.min_length_password = load_32_be(p);
    p += 4;
    policy.password_history = load_32_be(p);
    p += 4;
    policy.password_properties = load_32_be(p);
    p += 4;
    policy.expire = load_64_be(p);
    p += 8;
    policy.min_passwordage = load_64_be(p);
    p += 8;

    /* Check that we processed exactly the expected number of bytes. */
    assert(p == data->data + AD_POLICY_INFO_LENGTH);

    k5_buf_init_dynamic(&buf);

    /*
     * Update src/tests/misc/test_chpw_message.c if changing these strings!
     */

    if (policy.password_properties & AD_POLICY_COMPLEX) {
        k5_buf_add(&buf, _("The password must include numbers or symbols.  "
                           "Don't include any part of your name in the "
                           "password."));
    }
    if (policy.min_length_password > 0) {
        add_spaces(&buf);
        k5_buf_add_fmt(&buf, ngettext("The password must contain at least %d "
                                      "character.",
                                      "The password must contain at least %d "
                                      "characters.",
                                      policy.min_length_password),
                       policy.min_length_password);
    }
    if (policy.password_history) {
        add_spaces(&buf);
        k5_buf_add_fmt(&buf, ngettext("The password must be different from "
                                      "the previous password.",
                                      "The password must be different from "
                                      "the previous %d passwords.",
                                      policy.password_history),
                       policy.password_history);
    }
    if (policy.min_passwordage) {
        password_days = policy.min_passwordage / AD_POLICY_TIME_TO_DAYS;
        if (password_days == 0)
            password_days = 1;
        add_spaces(&buf);
        k5_buf_add_fmt(&buf, ngettext("The password can only be changed once "
                                      "a day.",
                                      "The password can only be changed every "
                                      "%d days.", (int)password_days),
                       (int)password_days);
    }

    msg = k5_buf_data(&buf);
    if (msg == NULL)
        return ENOMEM;

    if (*msg != '\0')
        *msg_out = msg;
    else
        free(msg);
    return 0;
}

krb5_error_code KRB5_CALLCONV
krb5_chpw_message(krb5_context context, const krb5_data *server_string,
                  char **message_out)
{
    krb5_error_code ret;
    krb5_data *string;
    char *msg;

    *message_out = NULL;

    /* If server_string contains an AD password policy, construct a message
     * based on that. */
    ret = decode_ad_policy_info(server_string, &msg);
    if (ret == 0 && msg != NULL) {
        *message_out = msg;
        return 0;
    }

    /* If server_string contains a valid UTF-8 string, return that. */
    if (server_string->length > 0 &&
        memchr(server_string->data, 0, server_string->length) == NULL &&
        krb5int_utf8_normalize(server_string, &string,
                               KRB5_UTF8_APPROX) == 0) {
        *message_out = string->data; /* already null terminated */
        free(string);
        return 0;
    }

    /* server_string appears invalid, so try to be helpful. */
    msg = strdup(_("Try a more complex password, or contact your "
                   "administrator."));
    if (msg == NULL)
        return ENOMEM;

    *message_out = msg;
    return 0;
}