krb5/krb/preauth.c

/*
 * 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>

static krb5_error_code obtain_enc_ts_padata
    (krb5_context,
     krb5_pa_data *,
     krb5_etype_info,
     krb5_keyblock *,
     krb5_error_code ( * )(krb5_context,
                   const krb5_enctype,
                   krb5_data *,
                   krb5_const_pointer,
                   krb5_keyblock **),
     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 *,
     krb5_error_code ( * )(krb5_context,
                   const krb5_enctype,
                   krb5_data *,
                   krb5_const_pointer,
                   krb5_keyblock **),
     krb5_const_pointer,
     krb5_error_code ( * )(krb5_context,
                   const krb5_keyblock *,
                   krb5_const_pointer,
                   krb5_kdc_rep * ),
     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 *,
     krb5_error_code ( * )(krb5_context,
                   const krb5_enctype,
                   krb5_data *,
                   krb5_const_pointer,
                   krb5_keyblock **),
     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);

/* some typedef's 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 *);

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)))
        return(retval);
    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)
    krb5_xfree(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;

    krb5_xfree(scratch);
    scratch = 0;

    retval = 0;

cleanup:
    if (scratch)
    krb5_free_data(context, scratch);
    if (enc_data.ciphertext.data)
    krb5_xfree(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);
      krb5_xfree(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;
    char *prompt1, *p;
    char *sep1 = ": [";
    char *sep2 = "]\n";
    char *sep3 = ": ";

    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:
     */
    p = prompt1 = malloc(label_len + strlen(sep1) +
             challenge_len + strlen(sep2) +
             prompt_len+ strlen(sep3) + 1);
    if (p == NULL)
    return NULL;
    if (challenge_len) {
    strncpy(p, label, label_len); p += label_len;
    strcpy(p, sep1); p += strlen(sep1);
    strncpy(p, challenge, challenge_len); p += challenge_len;
    strcpy(p, sep2); p += strlen(sep2);
    }
    strncpy(p, prompt, prompt_len); p += prompt_len;
    strcpy(p, sep3); /* p += strlen(sep3); */
    return prompt1;
}

/*
 * 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;
    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;

    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) {
      return KRB5_SAM_UNSUPPORTED;
    }

    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);
      sam_response.sam_patimestamp = enc_sam_response_enc.sam_timestamp;
    }
    if (retval)
      return retval;
    if (sam_challenge->sam_flags & KRB5_SAM_SEND_ENCRYPTED_SAD) {
      /* encrypt passcode in key by stuffing it here */
      unsigned int pcsize = 256;
      char *passcode = malloc(pcsize+1);
      if (passcode == NULL)
    return ENOMEM;
      prompt = handle_sam_labels(sam_challenge);
      if (prompt == NULL) {
    free(passcode);
    return ENOMEM;
      }
      retval = krb5_read_password(context, prompt, 0, passcode, &pcsize);
      free(prompt);

      if (retval) {
    free(passcode);
    return retval;
      }
      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)
    return ENOMEM;
      retval = sam_get_pass_from_user(context, etype_info, key_proc,
                      key_seed, request, &sam_use_key,
                      prompt);
      free(prompt);
      if (retval)
    return retval;
      enc_sam_response_enc.sam_sad.length = 0;
    } else {
      /* what *was* it? */
      return KRB5_SAM_UNSUPPORTED;
    }

    /* 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)
      return retval;

    if ((retval = krb5_encrypt_data(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)
    return retval;

    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;
    scratch = 0;        /* so we don't free it! */

    *out_padata = pa;

    retval = 0;

cleanup:
    if (scratch)
    krb5_free_data(context, scratch);
    if (sam_challenge)
        krb5_xfree(sam_challenge);
    return retval;
}