krb5/krb/preauth.c

/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 * Copyright 1995 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.
 *
 */

/*
 * This file contains routines for establishing, verifying, and any other
 * necessary functions, for utilizing the pre-authentication field of the
 * kerberos kdc request, with various hardware/software verification devices.
 */

#include "k5-int.h"
#include <stdio.h>
#include <time.h>

/* some typedefs for the function args to make things look a bit cleaner */

typedef krb5_error_code (*git_key_proc)(
    krb5_context,
    const krb5_enctype,
    krb5_data *,
    krb5_const_pointer,
    krb5_keyblock **);

typedef krb5_error_code (*git_decrypt_proc)(
    krb5_context,
    const krb5_keyblock *,
    krb5_const_pointer,
    krb5_kdc_rep *);

static krb5_error_code obtain_enc_ts_padata(
    krb5_context,
    krb5_pa_data *,
    krb5_etype_info,
    krb5_keyblock *,
    git_key_proc,
    krb5_const_pointer,
    krb5_creds *,
    krb5_kdc_req *,
    krb5_pa_data **);

static krb5_error_code process_pw_salt(
    krb5_context,
    krb5_pa_data *,
    krb5_kdc_req *,
    krb5_kdc_rep *,
    git_key_proc,
    krb5_const_pointer,
    git_decrypt_proc,
    krb5_keyblock **,
    krb5_creds *,
    krb5_int32 *,
    krb5_int32 *);

static krb5_error_code obtain_sam_padata(
    krb5_context,
    krb5_pa_data *,
    krb5_etype_info,
    krb5_keyblock *,
    git_key_proc,
    krb5_const_pointer,
    krb5_creds *,
    krb5_kdc_req *,
    krb5_pa_data **);

static const krb5_preauth_ops preauth_systems[] = {
    {
        KV5M_PREAUTH_OPS,
        KRB5_PADATA_ENC_TIMESTAMP,
        0,
        obtain_enc_ts_padata,
        0,
    },
    {
        KV5M_PREAUTH_OPS,
        KRB5_PADATA_PW_SALT,
        0,
        0,
        process_pw_salt,
    },
    {
        KV5M_PREAUTH_OPS,
        KRB5_PADATA_AFS3_SALT,
        0,
        0,
        process_pw_salt,
    },
    {
        KV5M_PREAUTH_OPS,
        KRB5_PADATA_SAM_CHALLENGE,
        0,
        obtain_sam_padata,
        0,
    },
    { KV5M_PREAUTH_OPS, -1 }
};

static krb5_error_code
find_pa_system(krb5_preauthtype type, const krb5_preauth_ops **Preauth_proc);

krb5_error_code krb5_obtain_padata(krb5_context context, krb5_pa_data **preauth_to_use, git_key_proc key_proc, krb5_const_pointer key_seed, krb5_creds *creds, krb5_kdc_req *request)
{
    krb5_error_code             retval;
    krb5_etype_info             etype_info = 0;
    krb5_pa_data **             pa;
    krb5_pa_data **             send_pa_list;
    krb5_pa_data **             send_pa;
    const krb5_preauth_ops      *ops;
    krb5_keyblock *             def_enc_key = 0;
    krb5_enctype                enctype;
    krb5_data                   salt;
    krb5_data                   scratch;
    int                         size;
    int                         f_salt = 0;

    if (preauth_to_use == NULL)
        return 0;

    for (pa = preauth_to_use, size=0; *pa; pa++, size++) {
        if ((*pa)->pa_type == KRB5_PADATA_ETYPE_INFO) {
            /* XXX use the first one.  Is there another way to disambiguate? */
            if (etype_info)
                continue;

            scratch.length = (*pa)->length;
            scratch.data = (char *) (*pa)->contents;
            retval = decode_krb5_etype_info(&scratch, &etype_info);
            if (retval)
                return retval;
            if (etype_info[0] == NULL) {
                krb5_free_etype_info(context, etype_info);
                etype_info = NULL;
            }
        }
    }

    if ((send_pa_list = malloc((size+1) * sizeof(krb5_pa_data *))) == NULL)
        return ENOMEM;

    send_pa = send_pa_list;
    *send_pa = 0;

    enctype = request->ktype[0];
    salt.data = 0;
    salt.length = SALT_TYPE_NO_LENGTH;
    if (etype_info) {
        enctype = etype_info[0]->etype;
        salt.data = (char *) etype_info[0]->salt;
        if(etype_info[0]->length == KRB5_ETYPE_NO_SALT)
            salt.length = SALT_TYPE_NO_LENGTH; /* XXX */
        else
            salt.length = etype_info[0]->length;
    }
    if (salt.length == SALT_TYPE_NO_LENGTH) {
        /*
         * This will set the salt length
         */
        if ((retval = krb5_principal2salt(context, request->client, &salt)))
            goto cleanup;
        f_salt = 1;
    }

    if ((retval = (*key_proc)(context, enctype, &salt, key_seed,
                              &def_enc_key)))
        goto cleanup;


    for (pa = preauth_to_use; *pa; pa++) {
        if (find_pa_system((*pa)->pa_type, &ops))
            continue;

        if (ops->obtain == 0)
            continue;

        retval = ((ops)->obtain)(context, *pa, etype_info, def_enc_key,
                                 key_proc, key_seed, creds,
                                 request, send_pa);
        if (retval)
            goto cleanup;

        if (*send_pa)
            send_pa++;
        *send_pa = 0;
    }

    retval = 0;

    if (send_pa_list[0]) {
        request->padata = send_pa_list;
        send_pa_list = 0;
    }

cleanup:
    if (etype_info)
        krb5_free_etype_info(context, etype_info);
    if (f_salt)
        free(salt.data);
    if (send_pa_list)
        krb5_free_pa_data(context, send_pa_list);
    if (def_enc_key)
        krb5_free_keyblock(context, def_enc_key);
    return retval;

}

krb5_error_code
krb5_process_padata(krb5_context context, krb5_kdc_req *request, krb5_kdc_rep *as_reply, git_key_proc key_proc, krb5_const_pointer keyseed, git_decrypt_proc decrypt_proc, krb5_keyblock **decrypt_key, krb5_creds *creds, krb5_int32 *do_more)
{
    krb5_error_code             retval = 0;
    const krb5_preauth_ops *    ops;
    krb5_pa_data **             pa;
    krb5_int32                  done = 0;

    *do_more = 0;               /* By default, we don't need to repeat... */
    if (as_reply->padata == 0)
        return 0;

    for (pa = as_reply->padata; *pa; pa++) {
        if (find_pa_system((*pa)->pa_type, &ops))
            continue;

        if (ops->process == 0)
            continue;

        retval = ((ops)->process)(context, *pa, request, as_reply,
                                  key_proc, keyseed, decrypt_proc,
                                  decrypt_key, creds, do_more, &done);
        if (retval)
            goto cleanup;
        if (done)
            break;
    }

cleanup:
    return retval;
}

/*
 * This routine is the "obtain" function for the ENC_TIMESTAMP
 * preauthentication type.  It take the current time and encrypts it
 * in the user's key.
 */
static krb5_error_code
obtain_enc_ts_padata(krb5_context context, krb5_pa_data *in_padata, krb5_etype_info etype_info, krb5_keyblock *def_enc_key, git_key_proc key_proc, krb5_const_pointer key_seed, krb5_creds *creds, krb5_kdc_req *request, krb5_pa_data **out_padata)
{
    krb5_pa_enc_ts              pa_enc;
    krb5_error_code             retval;
    krb5_data *                 scratch;
    krb5_enc_data               enc_data;
    krb5_pa_data *              pa;

    retval = krb5_us_timeofday(context, &pa_enc.patimestamp, &pa_enc.pausec);
    if (retval)
        return retval;

    if ((retval = encode_krb5_pa_enc_ts(&pa_enc, &scratch)) != 0)
        return retval;

    enc_data.ciphertext.data = 0;

    if ((retval = krb5_encrypt_helper(context, def_enc_key,
                                      KRB5_KEYUSAGE_AS_REQ_PA_ENC_TS,
                                      scratch, &enc_data)))
        goto cleanup;

    krb5_free_data(context, scratch);
    scratch = 0;

    if ((retval = encode_krb5_enc_data(&enc_data, &scratch)) != 0)
        goto cleanup;

    if ((pa = malloc(sizeof(krb5_pa_data))) == NULL) {
        retval = ENOMEM;
        goto cleanup;
    }

    pa->magic = KV5M_PA_DATA;
    pa->pa_type = KRB5_PADATA_ENC_TIMESTAMP;
    pa->length = scratch->length;
    pa->contents = (krb5_octet *) scratch->data;

    *out_padata = pa;

    free(scratch);
    scratch = 0;

    retval = 0;

cleanup:
    if (scratch)
        krb5_free_data(context, scratch);
    if (enc_data.ciphertext.data)
        free(enc_data.ciphertext.data);
    return retval;
}

static krb5_error_code
process_pw_salt(krb5_context context, krb5_pa_data *padata, krb5_kdc_req *request, krb5_kdc_rep *as_reply, git_key_proc key_proc, krb5_const_pointer keyseed, git_decrypt_proc decrypt_proc, krb5_keyblock **decrypt_key, krb5_creds *creds, krb5_int32 *do_more, krb5_int32 *done)
{
    krb5_error_code     retval;
    krb5_data           salt;

    if (*decrypt_key != 0)
        return 0;

    salt.data = (char *) padata->contents;
    salt.length =
        (padata->pa_type == KRB5_PADATA_AFS3_SALT)?(SALT_TYPE_AFS_LENGTH):(padata->length);

    if ((retval = (*key_proc)(context, as_reply->enc_part.enctype,
                              &salt, keyseed, decrypt_key))) {
        *decrypt_key = 0;
        return retval;
    }

    return 0;
}

static krb5_error_code
find_pa_system(krb5_preauthtype type, const krb5_preauth_ops **preauth)
{
    const krb5_preauth_ops *ap = preauth_systems;

    while ((ap->type != -1) && (ap->type != type))
        ap++;
    if (ap->type == -1)
        return(KRB5_PREAUTH_BAD_TYPE);
    *preauth = ap;
    return 0;
}


extern const char *krb5_default_pwd_prompt1;

static krb5_error_code
sam_get_pass_from_user(krb5_context context, krb5_etype_info etype_info, git_key_proc key_proc, krb5_const_pointer key_seed, krb5_kdc_req *request, krb5_keyblock **new_enc_key, const char *prompt)
{
    krb5_enctype                enctype;
    krb5_error_code             retval;
    const char *oldprompt;

    /* enctype = request->ktype[0]; */
    enctype = ENCTYPE_DES_CBC_MD5;
/* hack with this first! */
    oldprompt = krb5_default_pwd_prompt1;
    krb5_default_pwd_prompt1 = prompt;
    {
        krb5_data newpw;
        newpw.data = 0; newpw.length = 0;
        /* we don't keep the new password, just the key... */
        retval = (*key_proc)(context, enctype, 0,
                             (krb5_const_pointer)&newpw, new_enc_key);
        free(newpw.data);
    }
    krb5_default_pwd_prompt1 = oldprompt;
    return retval;
}
static
char *handle_sam_labels(krb5_sam_challenge *sc)
{
    char *label = sc->sam_challenge_label.data;
    unsigned int label_len = sc->sam_challenge_label.length;
    char *prompt = sc->sam_response_prompt.data;
    unsigned int prompt_len = sc->sam_response_prompt.length;
    char *challenge = sc->sam_challenge.data;
    unsigned int challenge_len = sc->sam_challenge.length;
    struct k5buf buf;

    if (sc->sam_cksum.length == 0) {
        /* or invalid -- but lets just handle presence now XXX */
        switch (sc->sam_type) {
        case PA_SAM_TYPE_ENIGMA:  /* Enigma Logic */
            label = "Challenge for Enigma Logic mechanism";
            break;
        case PA_SAM_TYPE_DIGI_PATH: /*  Digital Pathways */
        case PA_SAM_TYPE_DIGI_PATH_HEX: /*  Digital Pathways */
            label = "Challenge for Digital Pathways mechanism";
            break;
        case PA_SAM_TYPE_ACTIVCARD_DEC: /*  Digital Pathways */
        case PA_SAM_TYPE_ACTIVCARD_HEX: /*  Digital Pathways */
            label = "Challenge for Activcard mechanism";
            break;
        case PA_SAM_TYPE_SKEY_K0: /*  S/key where  KDC has key 0 */
            label = "Challenge for Enhanced S/Key mechanism";
            break;
        case PA_SAM_TYPE_SKEY:    /*  Traditional S/Key */
            label = "Challenge for Traditional S/Key mechanism";
            break;
        case PA_SAM_TYPE_SECURID: /*  Security Dynamics */
            label = "Challenge for Security Dynamics mechanism";
            break;
        case PA_SAM_TYPE_SECURID_PREDICT: /* predictive Security Dynamics */
            label = "Challenge for Security Dynamics mechanism";
            break;
        }
        prompt = "Passcode";
        label_len = strlen(label);
        prompt_len = strlen(prompt);
    }

    /* example:
       Challenge for Digital Pathways mechanism: [134591]
       Passcode:
    */
    krb5int_buf_init_dynamic(&buf);
    if (challenge_len) {
        krb5int_buf_add_len(&buf, label, label_len);
        krb5int_buf_add(&buf, ": [");
        krb5int_buf_add_len(&buf, challenge, challenge_len);
        krb5int_buf_add(&buf, "]\n");
    }
    krb5int_buf_add_len(&buf, prompt, prompt_len);
    krb5int_buf_add(&buf, ": ");
    return krb5int_buf_data(&buf);
}

/*
 * This routine is the "obtain" function for the SAM_CHALLENGE
 * preauthentication type.  It presents the challenge...
 */
static krb5_error_code
obtain_sam_padata(krb5_context context, krb5_pa_data *in_padata, krb5_etype_info etype_info, krb5_keyblock *def_enc_key, git_key_proc key_proc, krb5_const_pointer key_seed, krb5_creds *creds, krb5_kdc_req *request, krb5_pa_data **out_padata)
{
    krb5_error_code             retval;
    krb5_data *                 scratch = 0;
    krb5_data                   tmpsam;
    krb5_pa_data *              pa;
    krb5_sam_challenge          *sam_challenge = 0;
    krb5_sam_response           sam_response;
    /* these two get encrypted and stuffed in to sam_response */
    krb5_enc_sam_response_enc   enc_sam_response_enc;
    krb5_keyblock *             sam_use_key = 0;
    char *prompt = 0, *passcode = 0;

    sam_response.sam_enc_nonce_or_ts.ciphertext.data = 0;

    tmpsam.length = in_padata->length;
    tmpsam.data = (char *) in_padata->contents;
    retval = decode_krb5_sam_challenge(&tmpsam, &sam_challenge);
    if (retval)
        return retval;

    if (sam_challenge->sam_flags & KRB5_SAM_MUST_PK_ENCRYPT_SAD) {
        retval = KRB5_SAM_UNSUPPORTED;
        goto cleanup;
    }

    enc_sam_response_enc.sam_nonce = sam_challenge->sam_nonce;
    if (!sam_challenge->sam_nonce) {
        retval = krb5_us_timeofday(context,
                                   &enc_sam_response_enc.sam_timestamp,
                                   &enc_sam_response_enc.sam_usec);
        if (retval)
            goto cleanup;
        sam_response.sam_patimestamp = enc_sam_response_enc.sam_timestamp;
    }
    if (sam_challenge->sam_flags & KRB5_SAM_SEND_ENCRYPTED_SAD) {
        /* encrypt passcode in key by stuffing it here */
        unsigned int pcsize = 256;
        passcode = malloc(pcsize + 1);
        if (passcode == NULL) {
            retval = ENOMEM;
            goto cleanup;
        }
        prompt = handle_sam_labels(sam_challenge);
        if (prompt == NULL) {
            retval = ENOMEM;
            goto cleanup;
        }
        retval = krb5_read_password(context, prompt, 0, passcode, &pcsize);
        if (retval)
            goto cleanup;
        enc_sam_response_enc.sam_sad.data = passcode;
        enc_sam_response_enc.sam_sad.length = pcsize;
    } else if (sam_challenge->sam_flags & KRB5_SAM_USE_SAD_AS_KEY) {
        prompt = handle_sam_labels(sam_challenge);
        if (prompt == NULL) {
            retval = ENOMEM;
            goto cleanup;
        }
        retval = sam_get_pass_from_user(context, etype_info, key_proc,
                                        key_seed, request, &sam_use_key,
                                        prompt);
        if (retval)
            goto cleanup;
        enc_sam_response_enc.sam_sad.length = 0;
    } else {
        /* what *was* it? */
        retval = KRB5_SAM_UNSUPPORTED;
        goto cleanup;
    }

    /* so at this point, either sam_use_key is generated from the passcode
     * or enc_sam_response_enc.sam_sad is set to it, and we use
     * def_enc_key instead. */
    /* encode the encoded part of the response */
    if ((retval = encode_krb5_enc_sam_response_enc(&enc_sam_response_enc,
                                                   &scratch)) != 0)
        goto cleanup;

    if ((retval = krb5_encrypt_helper(context,
                                      sam_use_key?sam_use_key:def_enc_key,
                                      0, scratch,
                                      &sam_response.sam_enc_nonce_or_ts)))
        goto cleanup;

    krb5_free_data(context, scratch);
    scratch = 0;

    /* sam_enc_key is reserved for future use */
    sam_response.sam_enc_key.ciphertext.length = 0;

    /* copy things from the challenge */
    sam_response.sam_nonce = sam_challenge->sam_nonce;
    sam_response.sam_flags = sam_challenge->sam_flags;
    sam_response.sam_track_id = sam_challenge->sam_track_id;
    sam_response.sam_type = sam_challenge->sam_type;
    sam_response.magic = KV5M_SAM_RESPONSE;

    if ((retval = encode_krb5_sam_response(&sam_response, &scratch)) != 0)
        goto cleanup;

    if ((pa = malloc(sizeof(krb5_pa_data))) == NULL) {
        retval = ENOMEM;
        goto cleanup;
    }

    pa->magic = KV5M_PA_DATA;
    pa->pa_type = KRB5_PADATA_SAM_RESPONSE;
    pa->length = scratch->length;
    pa->contents = (krb5_octet *) scratch->data;
    free(scratch);
    scratch = NULL;

    *out_padata = pa;

    retval = 0;

cleanup:
    krb5_free_data(context, scratch);
    krb5_free_sam_challenge(context, sam_challenge);
    free(prompt);
    free(passcode);
    free(sam_response.sam_enc_nonce_or_ts.ciphertext.data);
    return retval;
}