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fwknop/server/incoming_spa.c
Michael Rash 4c3d2188a1 Update to make AES encryption modes selectable 
This is a significant update to allow AES encryption modes to be selected on a
per-key basis.  For now, only ECB and CBC (recommended) modes are supported.
The default is ECB modes in order to maintain backwards compatibility with the
older perl version of fwknop and the Crypt::CBC CPAN module.  This will likely
be changed to use CBC mode by default because of its better security
properties.

In the access.conf file on the server side, there is a new configuration
variable "ENCRYPTION_MODE" that controls the mode for the corresponding AES
key.  On the client side, a new command line argument "--encryption-mode"
controls how the client encrypts SPA packets.
2012-01-24 20:26:21 -05:00

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/*
*****************************************************************************
*
* File: incoming_spa.c
*
* Author: Damien S. Stuart
*
* Purpose: Process an incoming SPA data packet for fwknopd.
*
* Copyright 2010 Damien Stuart (dstuart@dstuart.org)
*
* License (GNU Public License):
*
* 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 2
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*****************************************************************************
*/
#include "fwknopd_common.h"
#include "netinet_common.h"
#if HAVE_SYS_WAIT_H
#include <sys/wait.h>
#endif
#include "incoming_spa.h"
#include "access.h"
#include "extcmd.h"
#include "log_msg.h"
#include "utils.h"
#include "fw_util.h"
#include "fwknopd_errors.h"
#include "replay_cache.h"
/* Validate and in some cases preprocess/reformat the SPA data. Return an
* error code value if there is any indication the data is not valid spa data.
*/
static int
preprocess_spa_data(fko_srv_options_t *opts, const char *src_ip)
{
spa_pkt_info_t *spa_pkt = &(opts->spa_pkt);
char *ndx = (char *)&(spa_pkt->packet_data);
int pkt_data_len = spa_pkt->packet_data_len;
int i;
/* At this point, we can reset the packet data length to 0. This is our
* indicator to the rest of the program that we do not have a current
* spa packet to process (after this one that is).
*/
spa_pkt->packet_data_len = 0;
/* Detect and parse out SPA data from an HTTP request. If the SPA data
* starts with "GET /" and the user agent starts with "Fwknop", then
* assume it is a SPA over HTTP request.
*/
if(strncasecmp(opts->config[CONF_ENABLE_SPA_OVER_HTTP], "N", 1) == 0
&& strncasecmp(ndx, "GET /", 5) == 0
&& strstr(ndx, "User-Agent: Fwknop") != NULL)
{
/* This looks like an HTTP request, so let's see if we are
* configured to accept such request and if so, find the SPA
* data.
*/
/* Now extract, adjust (convert characters translated by the fwknop
* client), and reset the SPA message itself.
*/
strlcpy((char *)spa_pkt->packet_data, ndx+5, pkt_data_len);
for(i=0; i<pkt_data_len; i++)
{
if(isspace(*ndx)) /* The first space marks the end of the req */
{
*ndx = '\0';
break;
}
else if(*ndx == '-') /* Convert '-' to '+' */
*ndx = '+';
else if(*ndx == '_') /* Convert '_' to '/' */
*ndx = '/';
ndx++;
}
}
/* Require base64-encoded data
*/
if(! is_base64(spa_pkt->packet_data, pkt_data_len))
return(SPA_MSG_NOT_SPA_DATA);
/* --DSS: Are there other checks we can do here ??? */
/* If we made it here, we have no reason to assume this is not SPA data
* (at least until we come up with more checks).
*/
return(FKO_SUCCESS);
}
/* Popluate a spa_data struct from an initialized (and populated) FKO context.
*/
static int
get_spa_data_fields(fko_ctx_t ctx, spa_data_t *spdat)
{
int res = FKO_SUCCESS;
res = fko_get_username(ctx, &(spdat->username));
if(res != FKO_SUCCESS)
return(res);
res = fko_get_timestamp(ctx, &(spdat->timestamp));
if(res != FKO_SUCCESS)
return(res);
res = fko_get_version(ctx, &(spdat->version));
if(res != FKO_SUCCESS)
return(res);
res = fko_get_spa_message_type(ctx, &(spdat->message_type));
if(res != FKO_SUCCESS)
return(res);
res = fko_get_spa_message(ctx, &(spdat->spa_message));
if(res != FKO_SUCCESS)
return(res);
res = fko_get_spa_nat_access(ctx, &(spdat->nat_access));
if(res != FKO_SUCCESS)
return(res);
res = fko_get_spa_server_auth(ctx, &(spdat->server_auth));
if(res != FKO_SUCCESS)
return(res);
res = fko_get_spa_client_timeout(ctx, (int *)&(spdat->client_timeout));
if(res != FKO_SUCCESS)
return(res);
return(res);
}
/* Process the SPA packet data
*/
void
incoming_spa(fko_srv_options_t *opts)
{
/* Always a good idea to initialize ctx to null if it will be used
* repeatedly (especially when using fko_new_with_data()).
*/
fko_ctx_t ctx = NULL;
char *spa_ip_demark, *gpg_id;
time_t now_ts;
int res, status, ts_diff, enc_type, found_acc_sip=0, stanza_num=0;
spa_pkt_info_t *spa_pkt = &(opts->spa_pkt);
/* This will hold our pertinent SPA data.
*/
spa_data_t spadat;
/* Loop through all access stanzas looking for a match
*/
acc_stanza_t *acc = opts->acc_stanzas;
inet_ntop(AF_INET, &(spa_pkt->packet_src_ip),
spadat.pkt_source_ip, sizeof(spadat.pkt_source_ip));
/* At this point, we want to validate and (if needed) preprocess the
* SPA data and/or to be reasonably sure we have a SPA packet (i.e
* try to eliminate obvious non-spa packets).
*/
res = preprocess_spa_data(opts, spadat.pkt_source_ip);
if(res != FKO_SUCCESS)
{
if(opts->verbose > 1)
log_msg(LOG_INFO, "preprocess_spa_data() returned error %i: '%s' for incoming packet.",
res, get_errstr(res));
return;
}
while(acc)
{
stanza_num++;
/* Check for a match for the SPA source IP and the access stanza
*/
if(! compare_addr_list(acc->source_list, ntohl(spa_pkt->packet_src_ip)))
{
acc = acc->next;
continue;
}
found_acc_sip = 1;
log_msg(LOG_INFO, "(stanza #%d) SPA Packet from IP: %s received with access source match",
stanza_num, spadat.pkt_source_ip);
if(opts->verbose > 1)
log_msg(LOG_INFO, "SPA Packet: '%s'\n", spa_pkt->packet_data);
/* Make sure this access stanza has not expired
*/
if(acc->access_expire_time > 0)
{
if(acc->expired)
{
acc = acc->next;
continue;
}
else
{
if(time(NULL) > acc->access_expire_time)
{
log_msg(LOG_INFO, "(stanza #%d) Access stanza has expired",
stanza_num);
acc->expired = 1;
acc = acc->next;
continue;
}
}
}
/* Get encryption type and try its decoding routine first (if the key
* for that type is set)
*/
enc_type = fko_encryption_type((char *)spa_pkt->packet_data);
if(enc_type == FKO_ENCRYPTION_RIJNDAEL)
{
if(acc->key != NULL)
res = fko_new_with_data(&ctx,
(char *)spa_pkt->packet_data, acc->key, acc->encryption_mode);
else
{
log_msg(LOG_ERR,
"(stanza #%d) No KEY for RIJNDAEL encrypted messages",
stanza_num
);
acc = acc->next;
continue;
}
}
else if(enc_type == FKO_ENCRYPTION_GPG)
{
/* For GPG we create the new context without decrypting on the fly
* so we can set some GPG parameters first.
*/
if(acc->gpg_decrypt_pw != NULL)
{
res = fko_new_with_data(&ctx, (char *)spa_pkt->packet_data, NULL,
acc->encryption_mode);
if(res != FKO_SUCCESS)
{
log_msg(LOG_WARNING,
"(stanza #%d) Error creating fko context (before decryption): %s",
stanza_num, fko_errstr(res)
);
acc = acc->next;
continue;
}
/* Set whatever GPG parameters we have.
*/
if(acc->gpg_home_dir != NULL)
res = fko_set_gpg_home_dir(ctx, acc->gpg_home_dir);
if(res != FKO_SUCCESS)
{
log_msg(LOG_WARNING,
"(stanza #%d) Error setting GPG keyring path to %s: %s",
stanza_num, acc->gpg_home_dir, fko_errstr(res)
);
acc = acc->next;
continue;
}
if(acc->gpg_decrypt_id != NULL)
fko_set_gpg_recipient(ctx, acc->gpg_decrypt_id);
/* If GPG_REQUIRE_SIG is set for this acc stanza, then set
* the FKO context accordingly and check the other GPG Sig-
* related parameters. This also applies when REMOTE_ID is
* set.
*/
if(acc->gpg_require_sig)
{
fko_set_gpg_signature_verify(ctx, 1);
/* Set whether or not to ignore signature verification errors.
*/
fko_set_gpg_ignore_verify_error(ctx, acc->gpg_ignore_sig_error);
}
else
{
fko_set_gpg_signature_verify(ctx, 0);
fko_set_gpg_ignore_verify_error(ctx, 1);
}
/* Now decrypt the data.
*/
res = fko_decrypt_spa_data(ctx, acc->gpg_decrypt_pw);
}
else
{
log_msg(LOG_ERR,
"(stanza #%d) No GPG_DECRYPT_PW for GPG encrypted messages",
stanza_num
);
acc = acc->next;
continue;
}
}
else
{
log_msg(LOG_ERR, "(stanza #%d) Unable to determing encryption type. Got type=%i.",
stanza_num, enc_type);
acc = acc->next;
continue;
}
/* Do we have a valid FKO context?
*/
if(res != FKO_SUCCESS)
{
log_msg(LOG_WARNING, "(stanza #%d) Error creating fko context: %s",
stanza_num, fko_errstr(res));
if(IS_GPG_ERROR(res))
log_msg(LOG_WARNING, "(stanza #%d) - GPG ERROR: %s",
stanza_num, fko_gpg_errstr(ctx));
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
/* At this point, we assume the SPA data is valid. Now we need to see
* if it meets our access criteria.
*/
if(opts->verbose > 1)
log_msg(LOG_INFO, "(stanza #%d) SPA Decode (res=%i):\n%s",
stanza_num, res, dump_ctx(ctx));
/* First, if this is a GPG message, and GPG_REMOTE_ID list is not empty,
* then we need to make sure this incoming message is signer ID matches
* an entry in the list.
*/
if(enc_type == FKO_ENCRYPTION_GPG && acc->gpg_require_sig)
{
res = fko_get_gpg_signature_id(ctx, &gpg_id);
if(res != FKO_SUCCESS)
{
log_msg(LOG_WARNING, "(stanza #%d) Error pulling the GPG signature ID from the context: %s",
stanza_num, fko_gpg_errstr(ctx));
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
if(opts->verbose)
log_msg(LOG_INFO, "(stanza #%d) Incoming SPA data signed by '%s'.",
stanza_num, gpg_id);
if(acc->gpg_remote_id != NULL && !acc_check_gpg_remote_id(acc, gpg_id))
{
log_msg(LOG_WARNING,
"(stanza #%d) Incoming SPA packet signed by ID: %s, but that ID is not the GPG_REMOTE_ID list.",
stanza_num, gpg_id);
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
}
/* Check for replays if so configured.
*/
if(strncasecmp(opts->config[CONF_ENABLE_DIGEST_PERSISTENCE], "Y", 1) == 0)
{
res = replay_check(opts, ctx);
if(res != 0) /* non-zero means we have seen this packet before. */
{
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
}
/* Populate our spa data struct for future reference.
*/
res = get_spa_data_fields(ctx, &spadat);
/* Figure out what our timeout will be. If it is specified in the SPA
* data, then use that. If not, try the FW_ACCESS_TIMEOUT from the
* access.conf file (if there is one). Otherwise use the default.
*/
if(spadat.client_timeout > 0)
spadat.fw_access_timeout = spadat.client_timeout;
else if(acc->fw_access_timeout > 0)
spadat.fw_access_timeout = acc->fw_access_timeout;
else
spadat.fw_access_timeout = DEF_FW_ACCESS_TIMEOUT;
if(res != FKO_SUCCESS)
{
log_msg(LOG_ERR, "(stanza #%d) Unexpected error pulling SPA data from the context: %s",
stanza_num, fko_errstr(res));
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
/* Check packet age if so configured.
*/
if(strncasecmp(opts->config[CONF_ENABLE_SPA_PACKET_AGING], "Y", 1) == 0)
{
time(&now_ts);
ts_diff = abs(now_ts - spadat.timestamp);
if(ts_diff > atoi(opts->config[CONF_MAX_SPA_PACKET_AGE]))
{
log_msg(LOG_WARNING, "(stanza #%d) SPA data time difference is too great (%i seconds).",
stanza_num, ts_diff);
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
}
/* At this point, we have enough to check the embedded (or packet source)
* IP address against the defined access rights. We start by splitting
* the spa msg source IP from the remainder of the message.
*/
spa_ip_demark = strchr(spadat.spa_message, ',');
if(spa_ip_demark == NULL)
{
log_msg(LOG_WARNING, "(stanza #%d) Error parsing SPA message string: %s",
stanza_num, fko_errstr(res));
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
strlcpy(spadat.spa_message_src_ip, spadat.spa_message, (spa_ip_demark-spadat.spa_message)+1);
strlcpy(spadat.spa_message_remain, spa_ip_demark+1, 1024);
/* If use source IP was requested (embedded IP of 0.0.0.0), make sure it
* is allowed.
*/
if(strcmp(spadat.spa_message_src_ip, "0.0.0.0") == 0)
{
if(acc->require_source_address)
{
log_msg(LOG_WARNING,
"(stanza #%d) Got 0.0.0.0 when valid source IP was required.",
stanza_num
);
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
spadat.use_src_ip = spadat.pkt_source_ip;
}
else
spadat.use_src_ip = spadat.spa_message_src_ip;
/* If REQUIRE_USERNAME is set, make sure the username in this SPA data
* matches.
*/
if(acc->require_username != NULL)
{
if(strcmp(spadat.username, acc->require_username) != 0)
{
log_msg(LOG_WARNING,
"(stanza #%d) Username in SPA data (%s) does not match required username: %s",
stanza_num, spadat.username, acc->require_username
);
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
}
/* Take action based on SPA message type.
*/
if(spadat.message_type == FKO_LOCAL_NAT_ACCESS_MSG
|| spadat.message_type == FKO_CLIENT_TIMEOUT_LOCAL_NAT_ACCESS_MSG
|| spadat.message_type == FKO_NAT_ACCESS_MSG
|| spadat.message_type == FKO_CLIENT_TIMEOUT_NAT_ACCESS_MSG)
{
#if FIREWALL_IPTABLES
if(strncasecmp(opts->config[CONF_ENABLE_IPT_FORWARDING], "Y", 1)!=0)
{
log_msg(LOG_WARNING,
"(stanza #%d) SPA packet from %s requested NAT access, but is not enabled",
stanza_num, spadat.pkt_source_ip
);
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
#else
log_msg(LOG_WARNING,
"(stanza #%d) SPA packet from %s requested unsupported NAT access",
stanza_num, spadat.pkt_source_ip
);
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
#endif
}
/* Command messages.
*/
if(spadat.message_type == FKO_COMMAND_MSG)
{
if(!acc->enable_cmd_exec)
{
log_msg(LOG_WARNING,
"(stanza #%d) SPA Command message are not allowed in the current configuration.",
stanza_num
);
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
else
{
log_msg(LOG_INFO,
"(stanza #%d) Processing SPA Command message: command='%s'.",
stanza_num, spadat.spa_message_remain
);
/* Do we need to become another user? If so, we call
* run_extcmd_as and pass the cmd_exec_uid.
*/
if(acc->cmd_exec_user != NULL && strncasecmp(acc->cmd_exec_user, "root", 4) != 0)
{
if(opts->verbose)
log_msg(LOG_INFO, "(stanza #%d) Setting effective user to %s (UID=%i) before running command.",
stanza_num, acc->cmd_exec_user, acc->cmd_exec_uid);
res = run_extcmd_as(acc->cmd_exec_uid,
spadat.spa_message_remain, NULL, 0, 0);
}
else /* Just run it as we are (root that is). */
res = run_extcmd(spadat.spa_message_remain, NULL, 0, 5);
/* --DSS XXX: I have found that the status (and res for that
* matter) have been unreliable indicators of the
* actual exit status of some commands. Not sure
* why yet. For now, we will take what we get.
*/
status = WEXITSTATUS(res);
if(opts->verbose > 1)
log_msg(LOG_WARNING,
"(stanza #%d) CMD_EXEC: command returned %i",
stanza_num, status);
if(status != 0)
res = SPA_MSG_COMMAND_ERROR;
if(ctx != NULL)
fko_destroy(ctx);
/* we processed the command on a matching access stanza, so we
* don't look for anything else to do with this SPA packet
*/
break;
}
}
/* From this point forward, we have some kind of access message. So
* we first see if access is allowed by checking access against
* restrict_ports and open_ports.
*
* --DSS TODO: We should add BLACKLIST support here as well.
*/
if(! acc_check_port_access(acc, spadat.spa_message_remain))
{
log_msg(LOG_WARNING,
"(stanza #%d) One or more requested protocol/ports was denied per access.conf.",
stanza_num
);
if(ctx != NULL)
fko_destroy(ctx);
acc = acc->next;
continue;
}
/* At this point, we process the SPA request and break out of the
* access stanza loop (first valid access stanza stops us looking
* for others).
*/
process_spa_request(opts, acc, &spadat);
if(ctx != NULL)
fko_destroy(ctx);
break;
}
if(! found_acc_sip)
{
log_msg(LOG_WARNING,
"No access data found for source IP: %s", spadat.pkt_source_ip
);
}
return;
}
/***EOF***/
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