/*
Formats a KRB_SAFE message into outbuf.
userdata is formatted as the user data in the message.
sumtype specifies the encryption type; key specifies the key which
might be used to seed the checksum; sender_addr and recv_addr specify
the full addresses (host and port) of the sender and receiver.
The host portion of sender_addr is used to form the addresses used in the
KRB_SAFE message.
The outbuf buffer storage is allocated, and should be freed by the
caller when finished.
returns system errors
*/
static krb5_error_code
krb5_mk_safe_basic(krb5_context context, const krb5_data *userdata,
krb5_key key, krb5_replay_data *replaydata,
krb5_address *local_addr, krb5_address *remote_addr,
krb5_cksumtype sumtype, krb5_data *outbuf)
{
krb5_error_code retval;
krb5_safe safemsg;
krb5_octet zero_octet = 0;
krb5_checksum safe_checksum;
krb5_data *scratch1, *scratch2;
if (!krb5_c_valid_cksumtype(sumtype))
return KRB5_PROG_SUMTYPE_NOSUPP;
if (!krb5_c_is_coll_proof_cksum(sumtype)
|| !krb5_c_is_keyed_cksum(sumtype))
return KRB5KRB_AP_ERR_INAPP_CKSUM;
safemsg.user_data = *userdata;
safemsg.s_address = (krb5_address *) local_addr;
safemsg.r_address = (krb5_address *) remote_addr;
/* We should check too make sure one exists. */
safemsg.timestamp = replaydata->timestamp;
safemsg.usec = replaydata->usec;
safemsg.seq_number = replaydata->seq;
/*
* To do the checksum stuff, we need to encode the message with a
* zero-length zero-type checksum, then checksum the encoding, then
* re-encode with the checksum.
*/
safe_checksum.length = 0;
safe_checksum.checksum_type = 0;
safe_checksum.contents = &zero_octet;
safemsg.checksum = &safe_checksum;
if ((retval = encode_krb5_safe(&safemsg, &scratch1)))
return retval;
if ((retval = krb5_k_make_checksum(context, sumtype, key,
KRB5_KEYUSAGE_KRB_SAFE_CKSUM,
scratch1, &safe_checksum)))
goto cleanup_checksum;
safemsg.checksum = &safe_checksum;
if ((retval = encode_krb5_safe(&safemsg, &scratch2))) {
goto cleanup_checksum;
}
*outbuf = *scratch2;
free(scratch2);
retval = 0;
cleanup_checksum:
free(safe_checksum.contents);
memset(scratch1->data, 0, scratch1->length);
krb5_free_data(context, scratch1);
return retval;
}
krb5_boolean KRB5_CALLCONV
valid_cksumtype(krb5_cksumtype ctype)
{
return krb5_c_valid_cksumtype (ctype);
}
/*
parses a KRB_SAFE message from inbuf, placing the integrity-protected user
data in *outbuf.
key specifies the key to be used for decryption of the message.
outbuf points to allocated storage which the caller should free when finished.
returns system errors, integrity errors
*/
static krb5_error_code
rd_safe_basic(krb5_context context, krb5_auth_context ac,
const krb5_data *inbuf, krb5_key key,
krb5_replay_data *replaydata, krb5_data *outbuf)
{
krb5_error_code retval;
krb5_safe * message;
krb5_data safe_body;
krb5_checksum our_cksum, *his_cksum;
krb5_octet zero_octet = 0;
krb5_data *scratch;
krb5_boolean valid;
struct krb5_safe_with_body swb;
if (!krb5_is_krb_safe(inbuf))
return KRB5KRB_AP_ERR_MSG_TYPE;
if ((retval = decode_krb5_safe_with_body(inbuf, &message, &safe_body)))
return retval;
if (!krb5_c_valid_cksumtype(message->checksum->checksum_type)) {
retval = KRB5_PROG_SUMTYPE_NOSUPP;
goto cleanup;
}
if (!krb5_c_is_coll_proof_cksum(message->checksum->checksum_type) ||
!krb5_c_is_keyed_cksum(message->checksum->checksum_type)) {
retval = KRB5KRB_AP_ERR_INAPP_CKSUM;
goto cleanup;
}
retval = k5_privsafe_check_addrs(context, ac, message->s_address,
message->r_address);
if (retval)
goto cleanup;
/* verify the checksum */
/*
* In order to recreate what was checksummed, we regenerate the message
* without checksum and then have the cryptographic subsystem verify
* the checksum for us. This is because some checksum methods have
* a confounder encrypted as part of the checksum.
*/
his_cksum = message->checksum;
our_cksum.length = 0;
our_cksum.checksum_type = 0;
our_cksum.contents = &zero_octet;
message->checksum = &our_cksum;
swb.body = &safe_body;
swb.safe = message;
retval = encode_krb5_safe_with_body(&swb, &scratch);
message->checksum = his_cksum;
if (retval)
goto cleanup;
retval = krb5_k_verify_checksum(context, key,
KRB5_KEYUSAGE_KRB_SAFE_CKSUM,
scratch, his_cksum, &valid);
(void) memset(scratch->data, 0, scratch->length);
krb5_free_data(context, scratch);
if (!valid) {
/*
* Checksum over only the KRB-SAFE-BODY, like RFC 1510 says, in
* case someone actually implements it correctly.
*/
retval = krb5_k_verify_checksum(context, key,
KRB5_KEYUSAGE_KRB_SAFE_CKSUM,
&safe_body, his_cksum, &valid);
if (!valid) {
retval = KRB5KRB_AP_ERR_MODIFIED;
goto cleanup;
}
}
replaydata->timestamp = message->timestamp;
replaydata->usec = message->usec;
replaydata->seq = message->seq_number;
*outbuf = message->user_data;
message->user_data.data = NULL;
retval = 0;
cleanup:
krb5_free_safe(context, message);
return retval;
}
int
ksm_process_in_msg(struct snmp_secmod_incoming_params *parms)
{
long temp;
krb5_cksumtype cksumtype;
krb5_auth_context auth_context = NULL;
krb5_error_code retcode;
krb5_checksum checksum;
krb5_data ap_req, ivector;
krb5_flags flags;
krb5_keyblock *subkey = NULL;
#ifdef MIT_NEW_CRYPTO
krb5_data input, output;
krb5_boolean valid;
krb5_enc_data in_crypt;
#else /* MIT_NEW_CRYPTO */
krb5_encrypt_block eblock;
#endif /* MIT_NEW_CRYPTO */
krb5_ticket *ticket = NULL;
int retval = SNMPERR_SUCCESS, response = 0;
size_t length =
parms->wholeMsgLen - (u_int) (parms->secParams - parms->wholeMsg);
u_char *current = parms->secParams, type;
size_t cksumlength, blocksize;
long hint;
char *cname;
struct ksm_secStateRef *ksm_state;
struct ksm_cache_entry *entry;
DEBUGMSGTL(("ksm", "Processing has begun\n"));
checksum.contents = NULL;
ap_req.data = NULL;
ivector.length = 0;
ivector.data = NULL;
/*
* First, parse the security parameters (because we need the subkey inside
* of the ticket to do anything
*/
if ((current = asn_parse_sequence(current, &length, &type,
(ASN_UNIVERSAL | ASN_PRIMITIVE |
ASN_OCTET_STR),
"ksm first octet")) == NULL) {
DEBUGMSGTL(("ksm", "Initial security paramter parsing failed\n"));
retval = SNMPERR_ASN_PARSE_ERR;
goto error;
}
if ((current = asn_parse_sequence(current, &length, &type,
(ASN_SEQUENCE | ASN_CONSTRUCTOR),
"ksm sequence")) == NULL) {
DEBUGMSGTL(("ksm",
"Security parameter sequence parsing failed\n"));
retval = SNMPERR_ASN_PARSE_ERR;
goto error;
}
if ((current = asn_parse_int(current, &length, &type, &temp,
sizeof(temp))) == NULL) {
DEBUGMSGTL(("ksm", "Security parameter checksum type parsing"
"failed\n"));
retval = SNMPERR_ASN_PARSE_ERR;
goto error;
}
cksumtype = temp;
#ifdef MIT_NEW_CRYPTO
if (!krb5_c_valid_cksumtype(cksumtype)) {
DEBUGMSGTL(("ksm", "Invalid checksum type (%d)\n", cksumtype));
retval = SNMPERR_KRB5;
snmp_set_detail("Invalid checksum type");
goto error;
}
if (!krb5_c_is_keyed_cksum(cksumtype)) {
DEBUGMSGTL(("ksm", "Checksum type %d is not a keyed checksum\n",
cksumtype));
snmp_set_detail("Checksum is not a keyed checksum");
retval = SNMPERR_KRB5;
goto error;
}
if (!krb5_c_is_coll_proof_cksum(cksumtype)) {
DEBUGMSGTL(("ksm", "Checksum type %d is not a collision-proof "
"checksum\n", cksumtype));
snmp_set_detail("Checksum is not a collision-proof checksum");
retval = SNMPERR_KRB5;
goto error;
}
#else /* ! MIT_NEW_CRYPTO */
if (!valid_cksumtype(cksumtype)) {
DEBUGMSGTL(("ksm", "Invalid checksum type (%d)\n", cksumtype));
retval = SNMPERR_KRB5;
snmp_set_detail("Invalid checksum type");
goto error;
}
if (!is_keyed_cksum(cksumtype)) {
DEBUGMSGTL(("ksm", "Checksum type %d is not a keyed checksum\n",
cksumtype));
snmp_set_detail("Checksum is not a keyed checksum");
retval = SNMPERR_KRB5;
goto error;
}
if (!is_coll_proof_cksum(cksumtype)) {
DEBUGMSGTL(("ksm", "Checksum type %d is not a collision-proof "
"checksum\n", cksumtype));
snmp_set_detail("Checksum is not a collision-proof checksum");
retval = SNMPERR_KRB5;
goto error;
}
#endif /* MIT_NEW_CRYPTO */
checksum.checksum_type = cksumtype;
cksumlength = length;
if ((current = asn_parse_sequence(current, &cksumlength, &type,
(ASN_UNIVERSAL | ASN_PRIMITIVE |
ASN_OCTET_STR), "ksm checksum")) ==
NULL) {
DEBUGMSGTL(("ksm",
"Security parameter checksum parsing failed\n"));
retval = SNMPERR_ASN_PARSE_ERR;
goto error;
}
checksum.contents = malloc(cksumlength);
if (!checksum.contents) {
DEBUGMSGTL(("ksm", "Unable to malloc %d bytes for checksum.\n",
cksumlength));
retval = SNMPERR_MALLOC;
goto error;
}
memcpy(checksum.contents, current, cksumlength);
checksum.length = cksumlength;
checksum.checksum_type = cksumtype;
/*
* Zero out the checksum so the validation works correctly
*/
memset(current, 0, cksumlength);
current += cksumlength;
length = parms->wholeMsgLen - (u_int) (current - parms->wholeMsg);
if ((current = asn_parse_sequence(current, &length, &type,
(ASN_UNIVERSAL | ASN_PRIMITIVE |
ASN_OCTET_STR), "ksm ap_req")) ==
NULL) {
DEBUGMSGTL(("ksm", "KSM security parameter AP_REQ/REP parsing "
"failed\n"));
retval = SNMPERR_ASN_PARSE_ERR;
goto error;
}
ap_req.length = length;
ap_req.data = malloc(length);
if (!ap_req.data) {
DEBUGMSGTL(("ksm",
"KSM unable to malloc %d bytes for AP_REQ/REP.\n",
length));
retval = SNMPERR_MALLOC;
goto error;
}
memcpy(ap_req.data, current, length);
current += length;
length = parms->wholeMsgLen - (u_int) (current - parms->wholeMsg);
if ((current = asn_parse_int(current, &length, &type, &hint,
sizeof(hint))) == NULL) {
DEBUGMSGTL(("ksm",
"KSM security parameter hint parsing failed\n"));
retval = SNMPERR_ASN_PARSE_ERR;
goto error;
}
/*
* Okay! We've got it all! Now try decoding the damn ticket.
*
* But of course there's a WRINKLE! We need to figure out if we're
* processing a AP_REQ or an AP_REP. How do we do that? We're going
* to cheat, and look at the first couple of bytes (which is what
* the Kerberos library routines do anyway).
*
* If there are ever new Kerberos message formats, we'll need to fix
* this here.
*
* If it's a _response_, then we need to get the auth_context
* from our cache.
*/
if (ap_req.length
&& (ap_req.data[0] == 0x6e || ap_req.data[0] == 0x4e)) {
/*
* We need to initalize the authorization context, and set the
* replay cache in it (and initialize the replay cache if we
* haven't already
*/
retcode = krb5_auth_con_init(kcontext, &auth_context);
if (retcode) {
DEBUGMSGTL(("ksm", "krb5_auth_con_init failed: %s\n",
error_message(retcode)));
retval = SNMPERR_KRB5;
snmp_set_detail(error_message(retcode));
goto error;
}
if (!rcache) {
krb5_data server;
server.data = "host";
server.length = strlen(server.data);
retcode = krb5_get_server_rcache(kcontext, &server, &rcache);
if (retcode) {
DEBUGMSGTL(("ksm", "krb5_get_server_rcache failed: %s\n",
error_message(retcode)));
retval = SNMPERR_KRB5;
snmp_set_detail(error_message(retcode));
goto error;
}
}
retcode = krb5_auth_con_setrcache(kcontext, auth_context, rcache);
if (retcode) {
DEBUGMSGTL(("ksm", "krb5_auth_con_setrcache failed: %s\n",
error_message(retcode)));
retval = SNMPERR_KRB5;
snmp_set_detail(error_message(retcode));
goto error;
}
retcode = krb5_rd_req(kcontext, &auth_context, &ap_req, NULL,
keytab, &flags, &ticket);
krb5_auth_con_setrcache(kcontext, auth_context, NULL);
if (retcode) {
DEBUGMSGTL(("ksm", "krb5_rd_req() failed: %s\n",
error_message(retcode)));
retval = SNMPERR_KRB5;
snmp_set_detail(error_message(retcode));
goto error;
}
retcode =
krb5_unparse_name(kcontext, ticket->enc_part2->client, &cname);
if (retcode == 0) {
DEBUGMSGTL(("ksm", "KSM authenticated principal name: %s\n",
cname));
free(cname);
}
/*
* Check to make sure AP_OPTS_MUTUAL_REQUIRED was set
*/
if (!(flags & AP_OPTS_MUTUAL_REQUIRED)) {
DEBUGMSGTL(("ksm",
"KSM MUTUAL_REQUIRED not set in request!\n"));
retval = SNMPERR_KRB5;
snmp_set_detail("MUTUAL_REQUIRED not set in message");
goto error;
}
retcode =
krb5_auth_con_getremotesubkey(kcontext, auth_context, &subkey);
if (retcode) {
DEBUGMSGTL(("ksm", "KSM remote subkey retrieval failed: %s\n",
error_message(retcode)));
retval = SNMPERR_KRB5;
snmp_set_detail(error_message(retcode));
goto error;
}
} else if (ap_req.length && (ap_req.data[0] == 0x6f ||
ap_req.data[0] == 0x4f)) {
/*
* Looks like a response; let's see if we've got that auth_context
* in our cache.
*/
krb5_ap_rep_enc_part *repl = NULL;
response = 1;
entry = ksm_get_cache(parms->pdu->msgid);
if (!entry) {
DEBUGMSGTL(("ksm",
"KSM: Unable to find auth_context for PDU with "
"message ID of %ld\n", parms->pdu->msgid));
retval = SNMPERR_KRB5;
goto error;
}
auth_context = entry->auth_context;
/*
* In that case, let's call the rd_rep function
*/
retcode = krb5_rd_rep(kcontext, auth_context, &ap_req, &repl);
if (repl)
krb5_free_ap_rep_enc_part(kcontext, repl);
if (retcode) {
DEBUGMSGTL(("ksm", "KSM: krb5_rd_rep() failed: %s\n",
error_message(retcode)));
retval = SNMPERR_KRB5;
goto error;
}
DEBUGMSGTL(("ksm", "KSM: krb5_rd_rep() decoded successfully.\n"));
retcode =
krb5_auth_con_getlocalsubkey(kcontext, auth_context, &subkey);
if (retcode) {
DEBUGMSGTL(("ksm", "Unable to retrieve local subkey: %s\n",
error_message(retcode)));
retval = SNMPERR_KRB5;
snmp_set_detail("Unable to retrieve local subkey");
goto error;
}
} else {
DEBUGMSGTL(("ksm", "Unknown Kerberos message type (%02x)\n",
ap_req.data[0]));
retval = SNMPERR_KRB5;
snmp_set_detail("Unknown Kerberos message type");
goto error;
}
#ifdef MIT_NEW_CRYPTO
input.data = (char *) parms->wholeMsg;
input.length = parms->wholeMsgLen;
retcode =
krb5_c_verify_checksum(kcontext, subkey, KSM_KEY_USAGE_CHECKSUM,
&input, &checksum, &valid);
#else /* MIT_NEW_CRYPTO */
retcode = krb5_verify_checksum(kcontext, cksumtype, &checksum,
parms->wholeMsg, parms->wholeMsgLen,
(krb5_pointer) subkey->contents,
subkey->length);
#endif /* MIT_NEW_CRYPTO */
if (retcode) {
DEBUGMSGTL(("ksm", "KSM checksum verification failed: %s\n",
error_message(retcode)));
retval = SNMPERR_KRB5;
snmp_set_detail(error_message(retcode));
goto error;
}
/*
* Don't ask me why they didn't simply return an error, but we have
* to check to see if "valid" is false.
*/
#ifdef MIT_NEW_CRYPTO
if (!valid) {
DEBUGMSGTL(("ksm", "Computed checksum did not match supplied "
"checksum!\n"));
retval = SNMPERR_KRB5;
snmp_set_detail
("Computed checksum did not match supplied checksum");
goto error;
}
#endif /* MIT_NEW_CRYPTO */
/*
* Handle an encrypted PDU. Note that it's an OCTET_STRING of the
* output of whatever Kerberos cryptosystem you're using (defined by
* the encryption type). Note that this is NOT the EncryptedData
* sequence - it's what goes in the "cipher" field of EncryptedData.
*/
if (parms->secLevel == SNMP_SEC_LEVEL_AUTHPRIV) {
if ((current = asn_parse_sequence(current, &length, &type,
(ASN_UNIVERSAL | ASN_PRIMITIVE |
ASN_OCTET_STR), "ksm pdu")) ==
NULL) {
DEBUGMSGTL(("ksm", "KSM sPDU octet decoding failed\n"));
retval = SNMPERR_ASN_PARSE_ERR;
goto error;
}
/*
* The PDU is now pointed at by "current", and the length is in
* "length".
*/
DEBUGMSGTL(("ksm", "KSM starting sPDU decode\n"));
/*
* We need to set up a blank initialization vector for the decryption.
* Use a block of all zero's (which is dependent on the block size
* of the encryption method).
*/
#ifdef MIT_NEW_CRYPTO
retcode = krb5_c_block_size(kcontext, subkey->enctype, &blocksize);
if (retcode) {
DEBUGMSGTL(("ksm",
"Unable to determine crypto block size: %s\n",
error_message(retcode)));
snmp_set_detail(error_message(retcode));
retval = SNMPERR_KRB5;
goto error;
}
#else /* MIT_NEW_CRYPTO */
blocksize =
krb5_enctype_array[subkey->enctype]->system->block_length;
#endif /* MIT_NEW_CRYPTO */
ivector.data = malloc(blocksize);
if (!ivector.data) {
DEBUGMSGTL(("ksm", "Unable to allocate %d bytes for ivector\n",
blocksize));
retval = SNMPERR_MALLOC;
goto error;
}
ivector.length = blocksize;
memset(ivector.data, 0, blocksize);
#ifndef MIT_NEW_CRYPTO
krb5_use_enctype(kcontext, &eblock, subkey->enctype);
retcode = krb5_process_key(kcontext, &eblock, subkey);
if (retcode) {
DEBUGMSGTL(("ksm", "KSM key post-processing failed: %s\n",
error_message(retcode)));
snmp_set_detail(error_message(retcode));
retval = SNMPERR_KRB5;
goto error;
}
#endif /* !MIT_NEW_CRYPTO */
if (length > *parms->scopedPduLen) {
DEBUGMSGTL(("ksm", "KSM not enough room - have %d bytes to "
"decrypt but only %d bytes available\n", length,
*parms->scopedPduLen));
retval = SNMPERR_TOO_LONG;
#ifndef MIT_NEW_CRYPTO
krb5_finish_key(kcontext, &eblock);
#endif /* ! MIT_NEW_CRYPTO */
goto error;
}
#ifdef MIT_NEW_CRYPTO
in_crypt.ciphertext.data = (char *) current;
in_crypt.ciphertext.length = length;
in_crypt.enctype = subkey->enctype;
output.data = (char *) *parms->scopedPdu;
output.length = *parms->scopedPduLen;
retcode =
krb5_c_decrypt(kcontext, subkey, KSM_KEY_USAGE_ENCRYPTION,
&ivector, &in_crypt, &output);
#else /* MIT_NEW_CRYPTO */
retcode = krb5_decrypt(kcontext, (krb5_pointer) current,
*parms->scopedPdu, length, &eblock,
ivector.data);
krb5_finish_key(kcontext, &eblock);
#endif /* MIT_NEW_CRYPTO */
if (retcode) {
DEBUGMSGTL(("ksm", "Decryption failed: %s\n",
error_message(retcode)));
snmp_set_detail(error_message(retcode));
retval = SNMPERR_KRB5;
goto error;
}
*parms->scopedPduLen = length;
} else {
/*
* Clear PDU
*/
*parms->scopedPdu = current;
*parms->scopedPduLen =
parms->wholeMsgLen - (current - parms->wholeMsg);
}
/*
* A HUGE GROSS HACK
*/
*parms->maxSizeResponse = parms->maxMsgSize - 200;
DEBUGMSGTL(("ksm", "KSM processing complete\n"));
/*
* Set the secName to the right value (a hack for now). But that's
* only used for when we're processing a request, not a response.
*/
if (!response) {
retcode = krb5_unparse_name(kcontext, ticket->enc_part2->client,
&cname);
if (retcode) {
DEBUGMSGTL(("ksm", "KSM krb5_unparse_name failed: %s\n",
error_message(retcode)));
snmp_set_detail(error_message(retcode));
retval = SNMPERR_KRB5;
goto error;
}
if (strlen(cname) > *parms->secNameLen + 1) {
DEBUGMSGTL(("ksm",
"KSM: Principal length (%d) is too long (%d)\n",
strlen(cname), parms->secNameLen));
retval = SNMPERR_TOO_LONG;
free(cname);
goto error;
}
strcpy(parms->secName, cname);
*parms->secNameLen = strlen(cname);
free(cname);
/*
* Also, if we're not a response, keep around our auth_context so we
* can encode the reply message correctly
*/
ksm_state = SNMP_MALLOC_STRUCT(ksm_secStateRef);
if (!ksm_state) {
DEBUGMSGTL(("ksm", "KSM unable to malloc memory for "
"ksm_secStateRef\n"));
retval = SNMPERR_MALLOC;
goto error;
}
ksm_state->auth_context = auth_context;
auth_context = NULL;
ksm_state->cksumtype = cksumtype;
*parms->secStateRef = ksm_state;
} else {
/*
* We _still_ have to set the secName in process_in_msg(). Do
* that now with what we were passed in before (we cached it,
* remember?)
*/
memcpy(parms->secName, entry->secName, entry->secNameLen);
*parms->secNameLen = entry->secNameLen;
}
/*
* Just in case
*/
parms->secEngineID = (u_char *) "";
*parms->secEngineIDLen = 0;
auth_context = NULL; /* So we don't try to free it on success */
error:
if (retval == SNMPERR_ASN_PARSE_ERR &&
snmp_increment_statistic(STAT_SNMPINASNPARSEERRS) == 0)
DEBUGMSGTL(("ksm", "Failed to increment statistics.\n"));
if (subkey)
krb5_free_keyblock(kcontext, subkey);
if (checksum.contents)
free(checksum.contents);
if (ivector.data)
free(ivector.data);
if (ticket)
krb5_free_ticket(kcontext, ticket);
if (!response && auth_context)
krb5_auth_con_free(kcontext, auth_context);
if (ap_req.data)
free(ap_req.data);
return retval;
}
