keys.c

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/*
 * Copyright (c) 1997 - 2001, 2003 - 2004 Kungliga Tekniska H鰃skolan
 * (Royal Institute of Technology, Stockholm, Sweden). 
 * All rights reserved. 
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions 
 * are met: 
 *
 * 1. Redistributions of source code must retain the above copyright 
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright 
 *    notice, this list of conditions and the following disclaimer in the 
 *    documentation and/or other materials provided with the distribution. 
 *
 * 3. Neither the name of the Institute nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
 * SUCH DAMAGE. 
 */

#include "hdb_locl.h"

RCSID("$Id: keys.c 22071 2007-11-14 20:04:50Z lha $");

/*
 * free all the memory used by (len, keys)
 */

void
hdb_free_keys (krb5_context context, int len, Key *keys)
{
    int i;

    for (i = 0; i < len; i++) {
	free(keys[i].mkvno);
	keys[i].mkvno = NULL;
	if (keys[i].salt != NULL) {
	    free_Salt(keys[i].salt);
	    free(keys[i].salt);
	    keys[i].salt = NULL;
	}
	krb5_free_keyblock_contents(context, &keys[i].key);
    }
    free (keys);
}

/* 
 * for each entry in `default_keys' try to parse it as a sequence
 * of etype:salttype:salt, syntax of this if something like:
 * [(des|des3|etype):](pw-salt|afs3)[:string], if etype is omitted it
 *      means all etypes, and if string is omitted is means the default
 * string (for that principal). Additional special values:
 *	v5 == pw-salt, and
 *	v4 == des:pw-salt:
 *	afs or afs3 == des:afs3-salt
 */

/* the 3 DES types must be first */
static const krb5_enctype all_etypes[] = { 
    ETYPE_DES_CBC_MD5,
    ETYPE_DES_CBC_MD4,
    ETYPE_DES_CBC_CRC,
    ETYPE_AES256_CTS_HMAC_SHA1_96,
    ETYPE_ARCFOUR_HMAC_MD5,
    ETYPE_DES3_CBC_SHA1
};

static krb5_error_code
parse_key_set(krb5_context context, const char *key, 
	      krb5_enctype **ret_enctypes, size_t *ret_num_enctypes, 
	      krb5_salt *salt, krb5_principal principal)
{
    const char *p;
    char buf[3][256];
    int num_buf = 0;
    int i, num_enctypes = 0;
    krb5_enctype e;
    const krb5_enctype *enctypes = NULL;
    krb5_error_code ret;
    
    p = key;

    *ret_enctypes = NULL;
    *ret_num_enctypes = 0;

    /* split p in a list of :-separated strings */
    for(num_buf = 0; num_buf < 3; num_buf++)
	if(strsep_copy(&p, ":", buf[num_buf], sizeof(buf[num_buf])) == -1)
	    break;

    salt->saltvalue.data = NULL;
    salt->saltvalue.length = 0;

    for(i = 0; i < num_buf; i++) {
	if(enctypes == NULL && num_buf > 1) {
	    /* this might be a etype specifier */
	    /* XXX there should be a string_to_etypes handling
	       special cases like `des' and `all' */
	    if(strcmp(buf[i], "des") == 0) {
		enctypes = all_etypes;
		num_enctypes = 3;
	    } else if(strcmp(buf[i], "des3") == 0) {
		e = ETYPE_DES3_CBC_SHA1;
		enctypes = &e;
		num_enctypes = 1;
	    } else {
		ret = krb5_string_to_enctype(context, buf[i], &e);
		if (ret == 0) {
		    enctypes = &e;
		    num_enctypes = 1;
		} else
		    return ret;
	    }
	    continue;
	}
	if(salt->salttype == 0) {
	    /* interpret string as a salt specifier, if no etype
	       is set, this sets default values */
	    /* XXX should perhaps use string_to_salttype, but that
	       interface sucks */
	    if(strcmp(buf[i], "pw-salt") == 0) {
		if(enctypes == NULL) {
		    enctypes = all_etypes;
		    num_enctypes = sizeof(all_etypes)/sizeof(all_etypes[0]);
		}
		salt->salttype = KRB5_PW_SALT;
	    } else if(strcmp(buf[i], "afs3-salt") == 0) {
		if(enctypes == NULL) {
		    enctypes = all_etypes;
		    num_enctypes = 3;
		}
		salt->salttype = KRB5_AFS3_SALT;
	    }
	    continue;
	}

	{
	    /* if there is a final string, use it as the string to
	       salt with, this is mostly useful with null salt for
	       v4 compat, and a cell name for afs compat */
	    salt->saltvalue.data = strdup(buf[i]);
	    if (salt->saltvalue.data == NULL) {
		krb5_set_error_string(context, "out of memory");
		return ENOMEM;
	    }
	    salt->saltvalue.length = strlen(buf[i]);
	}
    }
    
    if(enctypes == NULL || salt->salttype == 0) {
	krb5_set_error_string(context, "bad value for default_keys `%s'", key);
	return EINVAL;
    }
    
    /* if no salt was specified make up default salt */
    if(salt->saltvalue.data == NULL) {
	if(salt->salttype == KRB5_PW_SALT)
	    ret = krb5_get_pw_salt(context, principal, salt);
	else if(salt->salttype == KRB5_AFS3_SALT) {
	    krb5_realm *realm = krb5_princ_realm(context, principal);
	    salt->saltvalue.data = strdup(*realm);
	    if(salt->saltvalue.data == NULL) {
		krb5_set_error_string(context, "out of memory while "
				      "parsing salt specifiers");
		return ENOMEM;
	    }
	    strlwr(salt->saltvalue.data);
	    salt->saltvalue.length = strlen(*realm);
	}
    }

    *ret_enctypes = malloc(sizeof(enctypes[0]) * num_enctypes);
    if (*ret_enctypes == NULL) {
	krb5_free_salt(context, *salt);
	krb5_set_error_string(context, "out of memory");
	return ENOMEM;
    }
    memcpy(*ret_enctypes, enctypes, sizeof(enctypes[0]) * num_enctypes);
    *ret_num_enctypes = num_enctypes;

    return 0;
}

static krb5_error_code
add_enctype_to_key_set(Key **key_set, size_t *nkeyset, 
		       krb5_enctype enctype, krb5_salt *salt)
{
    krb5_error_code ret;
    Key key, *tmp;

    memset(&key, 0, sizeof(key));

    tmp = realloc(*key_set, (*nkeyset + 1) * sizeof((*key_set)[0]));
    if (tmp == NULL)
	return ENOMEM;
    
    *key_set = tmp;

    key.key.keytype = enctype;
    key.key.keyvalue.length = 0;
    key.key.keyvalue.data = NULL;
    
    if (salt) {
	key.salt = malloc(sizeof(*key.salt));
	if (key.salt == NULL) {
	    free_Key(&key);
	    return ENOMEM;
	}
	
	key.salt->type = salt->salttype;
	krb5_data_zero (&key.salt->salt);
	
	ret = krb5_data_copy(&key.salt->salt, 
			     salt->saltvalue.data, 
			     salt->saltvalue.length);
	if (ret) {
	    free_Key(&key);
	    return ret;
	}
    } else
	key.salt = NULL;
    
    (*key_set)[*nkeyset] = key;
    
    *nkeyset += 1;

    return 0;
}


/*
 * Generate the `key_set' from the [kadmin]default_keys statement. If
 * `no_salt' is set, salt is not important (and will not be set) since
 * it's random keys that is going to be created.
 */

krb5_error_code
hdb_generate_key_set(krb5_context context, krb5_principal principal,
		     Key **ret_key_set, size_t *nkeyset, int no_salt)
{
    char **ktypes, **kp;
    krb5_error_code ret;
    Key *k, *key_set;
    int i, j;
    char *default_keytypes[] = {
	"des:pw-salt",
	"aes256-cts-hmac-sha1-96:pw-salt",
	"des3-cbc-sha1:pw-salt",
	"arcfour-hmac-md5:pw-salt",
	NULL
    };
    
    ktypes = krb5_config_get_strings(context, NULL, "kadmin",
				     "default_keys", NULL);
    if (ktypes == NULL)
	ktypes = default_keytypes;

    if (ktypes == NULL)
	abort();

    *ret_key_set = key_set = NULL;
    *nkeyset = 0;

    ret = 0;
 
    for(kp = ktypes; kp && *kp; kp++) {
	const char *p;
	krb5_salt salt;
	krb5_enctype *enctypes;
	size_t num_enctypes;

	p = *kp;
	/* check alias */
	if(strcmp(p, "v5") == 0)
	    p = "pw-salt";
	else if(strcmp(p, "v4") == 0)
	    p = "des:pw-salt:";
	else if(strcmp(p, "afs") == 0 || strcmp(p, "afs3") == 0)
	    p = "des:afs3-salt";
	else if (strcmp(p, "arcfour-hmac-md5") == 0)
	    p = "arcfour-hmac-md5:pw-salt";
	    
	memset(&salt, 0, sizeof(salt));

	ret = parse_key_set(context, p,
			    &enctypes, &num_enctypes, &salt, principal);
	if (ret) {
	    krb5_warn(context, ret, "bad value for default_keys `%s'", *kp);
	    ret = 0;
	    continue;
	}

	for (i = 0; i < num_enctypes; i++) {
	    /* find duplicates */
	    for (j = 0; j < *nkeyset; j++) {

		k = &key_set[j];

		if (k->key.keytype == enctypes[i]) {
		    if (no_salt)
			break;
		    if (k->salt == NULL && salt.salttype == KRB5_PW_SALT)
			break;
		    if (k->salt->type == salt.salttype &&
			k->salt->salt.length == salt.saltvalue.length &&
			memcmp(k->salt->salt.data, salt.saltvalue.data, 
			       salt.saltvalue.length) == 0)
			break;
		}
	    }
	    /* not a duplicate, lets add it */
	    if (j == *nkeyset) {
		ret = add_enctype_to_key_set(&key_set, nkeyset, enctypes[i], 
					     no_salt ? NULL : &salt);
		if (ret) {
		    free(enctypes);
		    krb5_free_salt(context, salt);
		    goto out;
		}
	    }
	}
	free(enctypes);
	krb5_free_salt(context, salt);
    }
    
    *ret_key_set = key_set;

 out:
    if (ktypes != default_keytypes)
	krb5_config_free_strings(ktypes);

    if (ret) {
	krb5_warn(context, ret, 
		  "failed to parse the [kadmin]default_keys values");

	for (i = 0; i < *nkeyset; i++)
	    free_Key(&key_set[i]);
	free(key_set);
    } else if (*nkeyset == 0) {
	krb5_warnx(context, 
		   "failed to parse any of the [kadmin]default_keys values");
	ret = EINVAL; /* XXX */
    }

    return ret;
}


krb5_error_code
hdb_generate_key_set_password(krb5_context context, 
			      krb5_principal principal, 
			      const char *password, 
			      Key **keys, size_t *num_keys) 
{
    krb5_error_code ret;
    int i;

    ret = hdb_generate_key_set(context, principal,
				keys, num_keys, 0);
    if (ret)
	return ret;

    for (i = 0; i < (*num_keys); i++) {
	krb5_salt salt;

	salt.salttype = (*keys)[i].salt->type;
	salt.saltvalue.length = (*keys)[i].salt->salt.length;
	salt.saltvalue.data = (*keys)[i].salt->salt.data;

	ret = krb5_string_to_key_salt (context,
				       (*keys)[i].key.keytype,
				       password,
				       salt,
				       &(*keys)[i].key);

	if(ret)
	    break;
    }

    if(ret) {
	hdb_free_keys (context, *num_keys, *keys);
	return ret;
    }
    return ret;
}