static krb5_error_code
pac_checksum(krb5_context context,
const krb5_keyblock *key,
uint32_t *cksumtype,
size_t *cksumsize)
{
krb5_cksumtype cktype;
krb5_error_code ret;
krb5_crypto crypto = NULL;
ret = krb5_crypto_init(context, key, 0, &crypto);
if (ret)
return ret;
ret = krb5_crypto_get_checksum_type(context, crypto, &cktype);
krb5_crypto_destroy(context, crypto);
if (ret)
return ret;
if (krb5_checksum_is_keyed(context, cktype) == FALSE) {
*cksumtype = CKSUMTYPE_HMAC_MD5;
*cksumsize = 16;
}
ret = krb5_checksumsize(context, cktype, cksumsize);
if (ret)
return ret;
*cksumtype = (uint32_t)cktype;
return 0;
}
KRB5_LIB_FUNCTION krb5_boolean KRB5_LIB_CALL
krb5_c_is_keyed_cksum(krb5_cksumtype ctype)
{
return krb5_checksum_is_keyed(NULL, ctype);
}
static krb5_error_code
tgs_check_authenticator(krb5_context context,
krb5_kdc_configuration *config,
krb5_auth_context ac,
KDC_REQ_BODY *b,
const char **e_text,
krb5_keyblock *key)
{
krb5_authenticator auth;
size_t len;
unsigned char *buf;
size_t buf_size;
krb5_error_code ret;
krb5_crypto crypto;
krb5_auth_con_getauthenticator(context, ac, &auth);
if(auth->cksum == NULL){
kdc_log(context, config, 0, "No authenticator in request");
ret = KRB5KRB_AP_ERR_INAPP_CKSUM;
goto out;
}
/*
* according to RFC1510 it doesn't need to be keyed,
* but according to the latest draft it needs to.
*/
if (
#if 0
!krb5_checksum_is_keyed(context, auth->cksum->cksumtype)
||
#endif
!krb5_checksum_is_collision_proof(context, auth->cksum->cksumtype)) {
kdc_log(context, config, 0, "Bad checksum type in authenticator: %d",
auth->cksum->cksumtype);
ret = KRB5KRB_AP_ERR_INAPP_CKSUM;
goto out;
}
/* XXX should not re-encode this */
ASN1_MALLOC_ENCODE(KDC_REQ_BODY, buf, buf_size, b, &len, ret);
if(ret){
kdc_log(context, config, 0, "Failed to encode KDC-REQ-BODY: %s",
krb5_get_err_text(context, ret));
goto out;
}
if(buf_size != len) {
free(buf);
kdc_log(context, config, 0, "Internal error in ASN.1 encoder");
*e_text = "KDC internal error";
ret = KRB5KRB_ERR_GENERIC;
goto out;
}
ret = krb5_crypto_init(context, key, 0, &crypto);
if (ret) {
free(buf);
kdc_log(context, config, 0, "krb5_crypto_init failed: %s",
krb5_get_err_text(context, ret));
goto out;
}
ret = krb5_verify_checksum(context,
crypto,
KRB5_KU_TGS_REQ_AUTH_CKSUM,
buf,
len,
auth->cksum);
free(buf);
krb5_crypto_destroy(context, crypto);
if(ret){
kdc_log(context, config, 0,
"Failed to verify authenticator checksum: %s",
krb5_get_err_text(context, ret));
}
out:
free_Authenticator(auth);
free(auth);
return ret;
}
krb5_error_code KRB5_LIB_FUNCTION
krb5_rd_safe(krb5_context context,
krb5_auth_context auth_context,
const krb5_data *inbuf,
krb5_data *outbuf,
krb5_replay_data *outdata)
{
krb5_error_code ret;
KRB_SAFE safe;
size_t len;
krb5_data_zero(outbuf);
if ((auth_context->flags &
(KRB5_AUTH_CONTEXT_RET_TIME | KRB5_AUTH_CONTEXT_RET_SEQUENCE)))
{
if (outdata == NULL) {
krb5_set_error_message(context, KRB5_RC_REQUIRED,
N_("rd_safe: need outdata "
"to return data", ""));
return KRB5_RC_REQUIRED; /* XXX better error, MIT returns this */
}
/* if these fields are not present in the safe-part, silently
return zero */
memset(outdata, 0, sizeof(*outdata));
}
ret = decode_KRB_SAFE (inbuf->data, inbuf->length, &safe, &len);
if (ret)
return ret;
if (safe.pvno != 5) {
ret = KRB5KRB_AP_ERR_BADVERSION;
krb5_clear_error_message (context);
goto failure;
}
if (safe.msg_type != krb_safe) {
ret = KRB5KRB_AP_ERR_MSG_TYPE;
krb5_clear_error_message (context);
goto failure;
}
if (!krb5_checksum_is_keyed(context, safe.cksum.cksumtype)
|| !krb5_checksum_is_collision_proof(context, safe.cksum.cksumtype)) {
ret = KRB5KRB_AP_ERR_INAPP_CKSUM;
krb5_clear_error_message (context);
goto failure;
}
/* check sender address */
if (safe.safe_body.s_address
&& auth_context->remote_address
&& !krb5_address_compare (context,
auth_context->remote_address,
safe.safe_body.s_address)) {
ret = KRB5KRB_AP_ERR_BADADDR;
krb5_clear_error_message (context);
goto failure;
}
/* check receiver address */
if (safe.safe_body.r_address
&& auth_context->local_address
&& !krb5_address_compare (context,
auth_context->local_address,
safe.safe_body.r_address)) {
ret = KRB5KRB_AP_ERR_BADADDR;
krb5_clear_error_message (context);
goto failure;
}
/* check timestamp */
if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_TIME) {
krb5_timestamp sec;
krb5_timeofday (context, &sec);
if (safe.safe_body.timestamp == NULL ||
safe.safe_body.usec == NULL ||
abs(*safe.safe_body.timestamp - sec) > context->max_skew) {
ret = KRB5KRB_AP_ERR_SKEW;
krb5_clear_error_message (context);
goto failure;
}
}
/* XXX - check replay cache */
/* check sequence number. since MIT krb5 cannot generate a sequence
number of zero but instead generates no sequence number, we accept that
*/
if (auth_context->flags & KRB5_AUTH_CONTEXT_DO_SEQUENCE) {
if ((safe.safe_body.seq_number == NULL
&& auth_context->remote_seqnumber != 0)
|| (safe.safe_body.seq_number != NULL
&& *safe.safe_body.seq_number !=
auth_context->remote_seqnumber)) {
ret = KRB5KRB_AP_ERR_BADORDER;
krb5_clear_error_message (context);
goto failure;
}
auth_context->remote_seqnumber++;
}
ret = verify_checksum (context, auth_context, &safe);
if (ret)
goto failure;
outbuf->length = safe.safe_body.user_data.length;
outbuf->data = malloc(outbuf->length);
if (outbuf->data == NULL && outbuf->length != 0) {
ret = ENOMEM;
krb5_set_error_message(context, ret, N_("malloc: out of memory", ""));
krb5_data_zero(outbuf);
goto failure;
}
memcpy (outbuf->data, safe.safe_body.user_data.data, outbuf->length);
if ((auth_context->flags &
(KRB5_AUTH_CONTEXT_RET_TIME | KRB5_AUTH_CONTEXT_RET_SEQUENCE))) {
if(safe.safe_body.timestamp)
outdata->timestamp = *safe.safe_body.timestamp;
if(safe.safe_body.usec)
outdata->usec = *safe.safe_body.usec;
if(safe.safe_body.seq_number)
outdata->seq = *safe.safe_body.seq_number;
}
failure:
free_KRB_SAFE (&safe);
return ret;
}
static krb5_error_code
verify_checksum(krb5_context context,
const struct PAC_INFO_BUFFER *sig,
const krb5_data *data,
void *ptr, size_t len,
const krb5_keyblock *key)
{
krb5_storage *sp = NULL;
uint32_t type;
krb5_error_code ret;
Checksum cksum;
memset(&cksum, 0, sizeof(cksum));
sp = krb5_storage_from_mem((char *)data->data + sig->offset_lo,
sig->buffersize);
if (sp == NULL)
return krb5_enomem(context);
krb5_storage_set_flags(sp, KRB5_STORAGE_BYTEORDER_LE);
CHECK(ret, krb5_ret_uint32(sp, &type), out);
cksum.cksumtype = type;
cksum.checksum.length =
sig->buffersize - krb5_storage_seek(sp, 0, SEEK_CUR);
cksum.checksum.data = malloc(cksum.checksum.length);
if (cksum.checksum.data == NULL) {
ret = krb5_enomem(context);
goto out;
}
ret = krb5_storage_read(sp, cksum.checksum.data, cksum.checksum.length);
if (ret != cksum.checksum.length) {
ret = EINVAL;
krb5_set_error_message(context, ret, "PAC checksum missing checksum");
goto out;
}
if (!krb5_checksum_is_keyed(context, cksum.cksumtype)) {
ret = EINVAL;
krb5_set_error_message(context, ret, "Checksum type %d not keyed",
cksum.cksumtype);
goto out;
}
/* If the checksum is HMAC-MD5, the checksum type is not tied to
* the key type, instead the HMAC-MD5 checksum is applied blindly
* on whatever key is used for this connection, avoiding issues
* with unkeyed checksums on des-cbc-md5 and des-cbc-crc. See
* http://comments.gmane.org/gmane.comp.encryption.kerberos.devel/8743
* for the same issue in MIT, and
* http://blogs.msdn.com/b/openspecification/archive/2010/01/01/verifying-the-server-signature-in-kerberos-privilege-account-certificate.aspx
* for Microsoft's explaination */
if (cksum.cksumtype == CKSUMTYPE_HMAC_MD5) {
Checksum local_checksum;
memset(&local_checksum, 0, sizeof(local_checksum));
ret = HMAC_MD5_any_checksum(context, key, ptr, len,
KRB5_KU_OTHER_CKSUM, &local_checksum);
if (ret != 0 || krb5_data_ct_cmp(&local_checksum.checksum, &cksum.checksum) != 0) {
ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
krb5_set_error_message(context, ret,
N_("PAC integrity check failed for "
"hmac-md5 checksum", ""));
}
krb5_data_free(&local_checksum.checksum);
} else {
krb5_crypto crypto = NULL;
ret = krb5_crypto_init(context, key, 0, &crypto);
if (ret)
goto out;
ret = krb5_verify_checksum(context, crypto, KRB5_KU_OTHER_CKSUM,
ptr, len, &cksum);
krb5_crypto_destroy(context, crypto);
}
free(cksum.checksum.data);
krb5_storage_free(sp);
return ret;
out:
if (cksum.checksum.data)
free(cksum.checksum.data);
if (sp)
krb5_storage_free(sp);
return ret;
}