kerberos_util.c

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/* 
   Unix SMB/CIFS implementation.

   Kerberos utility functions for GENSEC
   
   Copyright (C) Andrew Bartlett <[e-mail]> 2004-2005

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "system/kerberos.h"
#include "auth/kerberos/kerberos.h"
#include "auth/credentials/credentials.h"
#include "auth/credentials/credentials_proto.h"
#include "auth/credentials/credentials_krb5.h"

struct principal_container {
	struct smb_krb5_context *smb_krb5_context;
	krb5_principal principal;
};

static int free_principal(struct principal_container *pc)
{
	/* current heimdal - 0.6.3, which we need anyway, fixes segfaults here */
	krb5_free_principal(pc->smb_krb5_context->krb5_context, pc->principal);

	return 0;
}

static krb5_error_code salt_principal_from_credentials(TALLOC_CTX *parent_ctx, 
						       struct cli_credentials *machine_account, 
						       struct smb_krb5_context *smb_krb5_context,
						       krb5_principal *salt_princ)
{
	krb5_error_code ret;
	char *machine_username;
	char *salt_body;
	char *lower_realm;
	const char *salt_principal;
	struct principal_container *mem_ctx = talloc(parent_ctx, struct principal_container);
	if (!mem_ctx) {
		return ENOMEM;
	}

	salt_principal = cli_credentials_get_salt_principal(machine_account);
	if (salt_principal) {
		ret = krb5_parse_name(smb_krb5_context->krb5_context, salt_principal, salt_princ); 
	} else {
		machine_username = talloc_strdup(mem_ctx, cli_credentials_get_username(machine_account));
		
		if (!machine_username) {
			talloc_free(mem_ctx);
			return ENOMEM;
		}
		
		if (machine_username[strlen(machine_username)-1] == '$') {
			machine_username[strlen(machine_username)-1] = '\0';
		}
		lower_realm = strlower_talloc(mem_ctx, cli_credentials_get_realm(machine_account));
		if (!lower_realm) {
			talloc_free(mem_ctx);
			return ENOMEM;
		}
		
		salt_body = talloc_asprintf(mem_ctx, "%s.%s", machine_username, 
					    lower_realm);
		if (!salt_body) {
			talloc_free(mem_ctx);
		return ENOMEM;
		}
		
		ret = krb5_make_principal(smb_krb5_context->krb5_context, salt_princ, 
					  cli_credentials_get_realm(machine_account), 
					  "host", salt_body, NULL);
	} 

	if (ret == 0) {
		/* This song-and-dance effectivly puts the principal
		 * into talloc, so we can't loose it. */
		mem_ctx->smb_krb5_context = talloc_reference(mem_ctx, smb_krb5_context);
		mem_ctx->principal = *salt_princ;
		talloc_set_destructor(mem_ctx, free_principal);
	}
	return ret;
}

/* Obtain the principal set on this context.  Requires a
 * smb_krb5_context because we are doing krb5 principal parsing with
 * the library routines.  The returned princ is placed in the talloc
 * system by means of a destructor (do *not* free). */

 krb5_error_code principal_from_credentials(TALLOC_CTX *parent_ctx, 
					    struct cli_credentials *credentials, 
					    struct smb_krb5_context *smb_krb5_context,
					    krb5_principal *princ)
{
	krb5_error_code ret;
	const char *princ_string;
	struct principal_container *mem_ctx = talloc(parent_ctx, struct principal_container);
	if (!mem_ctx) {
		return ENOMEM;
	}
	
	princ_string = cli_credentials_get_principal(credentials, mem_ctx);

	/* A NULL here has meaning, as the gssapi server case will
	 * then use the principal from the client */
	if (!princ_string) {
		talloc_free(mem_ctx);
		princ = NULL;
		return 0;
	}

	ret = krb5_parse_name(smb_krb5_context->krb5_context,
			      princ_string, princ);

	if (ret == 0) {
		/* This song-and-dance effectivly puts the principal
		 * into talloc, so we can't loose it. */
		mem_ctx->smb_krb5_context = talloc_reference(mem_ctx, smb_krb5_context);
		mem_ctx->principal = *princ;
		talloc_set_destructor(mem_ctx, free_principal);
	}
	return ret;
}

/**
 * Return a freshly allocated ccache (destroyed by destructor on child
 * of parent_ctx), for a given set of client credentials 
 */

 krb5_error_code kinit_to_ccache(TALLOC_CTX *parent_ctx,
				 struct cli_credentials *credentials,
				 struct smb_krb5_context *smb_krb5_context,
				 krb5_ccache ccache) 
{
	krb5_error_code ret;
	const char *password;
	time_t kdc_time = 0;
	krb5_principal princ;
	int tries;
	TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);

	if (!mem_ctx) {
		return ENOMEM;
	}

	ret = principal_from_credentials(mem_ctx, credentials, smb_krb5_context, &princ);
	if (ret) {
		talloc_free(mem_ctx);
		return ret;
	}

	password = cli_credentials_get_password(credentials);

	tries = 2;
	while (tries--) {
		if (password) {
			ret = kerberos_kinit_password_cc(smb_krb5_context->krb5_context, ccache, 
							 princ, 
							 password, NULL, &kdc_time);
		} else {
			/* No password available, try to use a keyblock instead */
			
			krb5_keyblock keyblock;
			const struct samr_Password *mach_pwd;
			mach_pwd = cli_credentials_get_nt_hash(credentials, mem_ctx);
			if (!mach_pwd) {
				talloc_free(mem_ctx);
				DEBUG(1, ("kinit_to_ccache: No password available for kinit\n"));
				return EINVAL;
			}
			ret = krb5_keyblock_init(smb_krb5_context->krb5_context,
						 ETYPE_ARCFOUR_HMAC_MD5,
						 mach_pwd->hash, sizeof(mach_pwd->hash), 
						 &keyblock);
			
			if (ret == 0) {
				ret = kerberos_kinit_keyblock_cc(smb_krb5_context->krb5_context, ccache, 
								 princ,
								 &keyblock, NULL, &kdc_time);
				krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &keyblock);
			}
		}

		if (ret == KRB5KRB_AP_ERR_SKEW || ret == KRB5_KDCREP_SKEW) {
			/* Perhaps we have been given an invalid skew, so try again without it */
			time_t t = time(NULL);
			krb5_set_real_time(smb_krb5_context->krb5_context, t, 0);
		} else {
			/* not a skew problem */
			break;
		}
	}

	if (ret == KRB5KRB_AP_ERR_SKEW || ret == KRB5_KDCREP_SKEW) {
		DEBUG(1,("kinit for %s failed (%s)\n", 
			 cli_credentials_get_principal(credentials, mem_ctx), 
			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
						    ret, mem_ctx)));
		talloc_free(mem_ctx);
		return ret;
	}

	/* cope with ticket being in the future due to clock skew */
	if ((unsigned)kdc_time > time(NULL)) {
		time_t t = time(NULL);
		int time_offset =(unsigned)kdc_time-t;
		DEBUG(4,("Advancing clock by %d seconds to cope with clock skew\n", time_offset));
		krb5_set_real_time(smb_krb5_context->krb5_context, t + time_offset + 1, 0);
	}
	
	if (ret == KRB5KDC_ERR_PREAUTH_FAILED && cli_credentials_wrong_password(credentials)) {
		ret = kinit_to_ccache(parent_ctx,
				      credentials,
				      smb_krb5_context,
				      ccache); 
	}
	if (ret) {
		DEBUG(1,("kinit for %s failed (%s)\n", 
			 cli_credentials_get_principal(credentials, mem_ctx), 
			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
						    ret, mem_ctx)));
		talloc_free(mem_ctx);
		return ret;
	} 
	talloc_free(mem_ctx);
	return 0;
}

static int free_keytab(struct keytab_container *ktc)
{
	krb5_kt_close(ktc->smb_krb5_context->krb5_context, ktc->keytab);

	return 0;
}

int smb_krb5_open_keytab(TALLOC_CTX *mem_ctx,
			 struct smb_krb5_context *smb_krb5_context, 
			 const char *keytab_name, struct keytab_container **ktc) 
{
	krb5_keytab keytab;
	int ret;
	ret = krb5_kt_resolve(smb_krb5_context->krb5_context, keytab_name, &keytab);
	if (ret) {
		DEBUG(1,("failed to open krb5 keytab: %s\n", 
			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
						    ret, mem_ctx)));
		return ret;
	}

	*ktc = talloc(mem_ctx, struct keytab_container);
	if (!*ktc) {
		return ENOMEM;
	}

	(*ktc)->smb_krb5_context = talloc_reference(*ktc, smb_krb5_context);
	(*ktc)->keytab = keytab;
	talloc_set_destructor(*ktc, free_keytab);

	return 0;
}

static krb5_error_code keytab_add_keys(TALLOC_CTX *parent_ctx,
				       const char *princ_string,
				       krb5_principal princ,
				       krb5_principal salt_princ,
				       int kvno,
				       const char *password_s,
				       struct smb_krb5_context *smb_krb5_context,
				       const char **enctype_strings,
				       krb5_keytab keytab)
{
	int i;
	krb5_error_code ret;
	krb5_data password;
	TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
	if (!mem_ctx) {
		return ENOMEM;
	}

	password.data = discard_const_p(char *, password_s);
	password.length = strlen(password_s);

	for (i=0; enctype_strings[i]; i++) {
		krb5_keytab_entry entry;
		krb5_enctype enctype;
		ret = krb5_string_to_enctype(smb_krb5_context->krb5_context, enctype_strings[i], &enctype);
		if (ret != 0) {
			DEBUG(1, ("Failed to interpret %s as a krb5 encryption type: %s\n",				  
				  enctype_strings[i],
				  smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
							     ret, mem_ctx)));
			talloc_free(mem_ctx);
			return ret;
		}
		ret = create_kerberos_key_from_string(smb_krb5_context->krb5_context, 
						      salt_princ, &password, &entry.keyblock, enctype);
		if (ret != 0) {
			talloc_free(mem_ctx);
			return ret;
		}

                entry.principal = princ;
                entry.vno       = kvno;
		ret = krb5_kt_add_entry(smb_krb5_context->krb5_context, keytab, &entry);
		if (ret != 0) {
			DEBUG(1, ("Failed to add %s entry for %s(kvno %d) to keytab: %s\n",
				  enctype_strings[i],
				  princ_string,
				  kvno,
				  smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
							     ret, mem_ctx)));
			talloc_free(mem_ctx);
			krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
			return ret;
		}

		DEBUG(5, ("Added %s(kvno %d) to keytab (%s)\n", 
			  princ_string, kvno,
			  enctype_strings[i]));
		
		krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
	}
	talloc_free(mem_ctx);
	return 0;
}