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stunnel4/src/verify.c

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/*
* stunnel Universal SSL tunnel
* Copyright (C) 1998-2012 Michal Trojnara <Michal.Trojnara@mirt.net>
*
* 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, see <http://www.gnu.org/licenses>.
*
* Linking stunnel statically or dynamically with other modules is making
* a combined work based on stunnel. Thus, the terms and conditions of
* the GNU General Public License cover the whole combination.
*
* In addition, as a special exception, the copyright holder of stunnel
* gives you permission to combine stunnel with free software programs or
* libraries that are released under the GNU LGPL and with code included
* in the standard release of OpenSSL under the OpenSSL License (or
* modified versions of such code, with unchanged license). You may copy
* and distribute such a system following the terms of the GNU GPL for
* stunnel and the licenses of the other code concerned.
*
* Note that people who make modified versions of stunnel are not obligated
* to grant this special exception for their modified versions; it is their
* choice whether to do so. The GNU General Public License gives permission
* to release a modified version without this exception; this exception
* also makes it possible to release a modified version which carries
* forward this exception.
*/
#include "common.h"
#include "prototypes.h"
/**************************************** prototypes */
/* verify initialization */
static int load_file_lookup(X509_STORE *, char *);
static int add_dir_lookup(X509_STORE *, char *);
/* verify callback */
static int verify_callback(int, X509_STORE_CTX *);
static int cert_check(CLI *c, X509_STORE_CTX *, int);
static int crl_check(CLI *c, X509_STORE_CTX *);
#ifdef HAVE_OSSL_OCSP_H
static int ocsp_check(CLI *c, X509_STORE_CTX *);
static OCSP_RESPONSE *ocsp_get_response(CLI *, OCSP_REQUEST *);
#endif
/* utility functions */
static void log_time(const int, const char *, ASN1_TIME *);
/**************************************** verify initialization */
int verify_init(SERVICE_OPTIONS *section) {
if(section->verify_level<0)
return 0; /* OK - no certificate verification */
if(section->verify_level>=2 && !section->ca_file && !section->ca_dir) {
s_log(LOG_ERR,
"Either CApath or CAfile has to be used for authentication");
return 1; /* FAILED */
}
section->revocation_store=X509_STORE_new();
if(!section->revocation_store) {
sslerror("X509_STORE_new");
return 1; /* FAILED */
}
if(section->ca_file) {
if(!SSL_CTX_load_verify_locations(section->ctx,
section->ca_file, NULL)) {
s_log(LOG_ERR, "Error loading verify certificates from %s",
section->ca_file);
sslerror("SSL_CTX_load_verify_locations");
return 1; /* FAILED */
}
/* list of trusted CAs for the client to choose the right cert */
SSL_CTX_set_client_CA_list(section->ctx,
SSL_load_client_CA_file(section->ca_file));
s_log(LOG_DEBUG, "Loaded verify certificates from %s",
section->ca_file);
if(load_file_lookup(section->revocation_store, section->ca_file))
return 1; /* FAILED */
}
if(section->ca_dir) {
if(!SSL_CTX_load_verify_locations(section->ctx,
NULL, section->ca_dir)) {
s_log(LOG_ERR, "Error setting verify directory to %s",
section->ca_dir);
sslerror("SSL_CTX_load_verify_locations");
return 1; /* FAILED */
}
s_log(LOG_DEBUG, "Verify directory set to %s", section->ca_dir);
add_dir_lookup(section->revocation_store, section->ca_dir);
}
if(section->crl_file)
if(load_file_lookup(section->revocation_store, section->crl_file))
return 1; /* FAILED */
if(section->crl_dir) {
section->revocation_store->cache=0; /* don't cache CRLs */
add_dir_lookup(section->revocation_store, section->crl_dir);
}
SSL_CTX_set_verify(section->ctx, SSL_VERIFY_PEER |
(section->verify_level>=2 ? SSL_VERIFY_FAIL_IF_NO_PEER_CERT : 0),
verify_callback);
if(section->ca_dir && section->verify_level>=3)
s_log(LOG_INFO, "Peer certificate location %s", section->ca_dir);
return 0; /* OK */
}
static int load_file_lookup(X509_STORE *store, char *name) {
X509_LOOKUP *lookup;
lookup=X509_STORE_add_lookup(store, X509_LOOKUP_file());
if(!lookup) {
sslerror("X509_STORE_add_lookup");
return 1; /* FAILED */
}
if(!X509_LOOKUP_load_file(lookup, name, X509_FILETYPE_PEM)) {
s_log(LOG_ERR, "Failed to load %s revocation lookup file", name);
sslerror("X509_LOOKUP_load_file");
return 1; /* FAILED */
}
s_log(LOG_DEBUG, "Loaded %s revocation lookup file", name);
return 0; /* OK */
}
static int add_dir_lookup(X509_STORE *store, char *name) {
X509_LOOKUP *lookup;
lookup=X509_STORE_add_lookup(store, X509_LOOKUP_hash_dir());
if(!lookup) {
sslerror("X509_STORE_add_lookup");
return 1; /* FAILED */
}
if(!X509_LOOKUP_add_dir(lookup, name, X509_FILETYPE_PEM)) {
s_log(LOG_ERR, "Failed to add %s revocation lookup directory", name);
sslerror("X509_LOOKUP_add_dir");
return 1; /* FAILED */
}
s_log(LOG_DEBUG, "Added %s revocation lookup directory", name);
return 0; /* OK */
}
/**************************************** verify callback */
static int verify_callback(int preverify_ok, X509_STORE_CTX *callback_ctx) {
/* our verify callback function */
SSL *ssl;
CLI *c;
X509 *cert;
int depth;
char *subject_name;
/* retrieve application specific data */
ssl=X509_STORE_CTX_get_ex_data(callback_ctx,
SSL_get_ex_data_X509_STORE_CTX_idx());
c=SSL_get_ex_data(ssl, cli_index);
cert=X509_STORE_CTX_get_current_cert(callback_ctx);
depth=X509_STORE_CTX_get_error_depth(callback_ctx);
/* certificate name for logging */
subject_name=X509_NAME_oneline(X509_get_subject_name(cert), NULL, 0);
s_log(LOG_DEBUG, "Starting certificate verification: depth=%d, %s",
depth, subject_name);
if(!cert_check(c, callback_ctx, preverify_ok)) {
s_log(LOG_WARNING, "Certificate check failed: depth=%d, %s",
depth, subject_name);
OPENSSL_free(subject_name);
return 0; /* reject connection */
}
if(!crl_check(c, callback_ctx)) {
s_log(LOG_WARNING, "CRL check failed: depth=%d, %s",
depth, subject_name);
OPENSSL_free(subject_name);
return 0; /* reject connection */
}
#ifdef HAVE_OSSL_OCSP_H
if(c->opt->option.ocsp && !ocsp_check(c, callback_ctx)) {
s_log(LOG_WARNING, "OCSP check failed: depth=%d, %s",
depth, subject_name);
OPENSSL_free(subject_name);
return 0; /* reject connection */
}
#endif /* HAVE_OSSL_OCSP_H */
/* errnum=X509_STORE_CTX_get_error(ctx); */
s_log(LOG_NOTICE, "Certificate accepted: depth=%d, %s",
depth, subject_name);
OPENSSL_free(subject_name);
return 1; /* accept connection */
}
/**************************************** certificate checking */
static int cert_check(CLI *c, X509_STORE_CTX *callback_ctx, int preverify_ok) {
X509_OBJECT obj;
#if OPENSSL_VERSION_NUMBER>=0x0090700fL
ASN1_BIT_STRING *local_key, *peer_key;
#endif
X509 *cert;
int depth;
if(c->opt->verify_level<1) {
s_log(LOG_INFO, "CERT: Verification not enabled");
return 1; /* accept connection */
}
cert=X509_STORE_CTX_get_current_cert(callback_ctx);
depth=X509_STORE_CTX_get_error_depth(callback_ctx);
if(!preverify_ok) {
/* remote site specified a certificate, but it's not correct */
if(c->opt->verify_level>=4 && depth>0) {
s_log(LOG_INFO, "CERT: Invalid CA certificate ignored");
return 1; /* accept connection */
} else {
s_log(LOG_WARNING, "CERT: Verification error: %s",
X509_verify_cert_error_string(
X509_STORE_CTX_get_error(callback_ctx)));
return 0; /* reject connection */
}
}
if(c->opt->verify_level>=3 && depth==0) {
if(X509_STORE_get_by_subject(callback_ctx, X509_LU_X509,
X509_get_subject_name(cert), &obj)!=1) {
s_log(LOG_WARNING,
"CERT: Certificate not found in local repository");
return 0; /* reject connection */
}
#if OPENSSL_VERSION_NUMBER>=0x0090700fL
peer_key=X509_get0_pubkey_bitstr(cert);
local_key=X509_get0_pubkey_bitstr(obj.data.x509);
if(!peer_key || !local_key || peer_key->length!=local_key->length ||
memcmp(peer_key->data, local_key->data, local_key->length)) {
s_log(LOG_WARNING, "CERT: Public keys do not match");
return 0; /* reject connection */
}
#endif
s_log(LOG_INFO, "CERT: Locally installed certificate matched");
}
return 1; /* accept connection */
}
/**************************************** CRL checking */
/* based on BSD-style licensed code of mod_ssl */
static int crl_check(CLI *c, X509_STORE_CTX *callback_ctx) {
X509_STORE_CTX store_ctx;
X509_OBJECT obj;
X509_NAME *subject;
X509_NAME *issuer;
X509 *cert;
X509_CRL *crl;
X509_REVOKED *revoked;
EVP_PKEY *pubkey;
long serial;
int i, n, rc;
char *cp;
ASN1_TIME *last_update=NULL, *next_update=NULL;
/* determine certificate ingredients in advance */
cert=X509_STORE_CTX_get_current_cert(callback_ctx);
subject=X509_get_subject_name(cert);
issuer=X509_get_issuer_name(cert);
/* try to retrieve a CRL corresponding to the _subject_ of
* the current certificate in order to verify it's integrity */
memset((char *)&obj, 0, sizeof obj);
X509_STORE_CTX_init(&store_ctx, c->opt->revocation_store, NULL, NULL);
rc=X509_STORE_get_by_subject(&store_ctx, X509_LU_CRL, subject, &obj);
X509_STORE_CTX_cleanup(&store_ctx);
crl=obj.data.crl;
if(rc>0 && crl) {
cp=X509_NAME_oneline(subject, NULL, 0);
s_log(LOG_INFO, "CRL: issuer: %s", cp);
OPENSSL_free(cp);
last_update=X509_CRL_get_lastUpdate(crl);
next_update=X509_CRL_get_nextUpdate(crl);
log_time(LOG_INFO, "CRL: last update", last_update);
log_time(LOG_INFO, "CRL: next update", next_update);
/* verify the signature on this CRL */
pubkey=X509_get_pubkey(cert);
if(X509_CRL_verify(crl, pubkey)<=0) {
s_log(LOG_WARNING, "CRL: Invalid signature");
X509_STORE_CTX_set_error(callback_ctx,
X509_V_ERR_CRL_SIGNATURE_FAILURE);
X509_OBJECT_free_contents(&obj);
if(pubkey)
EVP_PKEY_free(pubkey);
return 0; /* reject connection */
}
if(pubkey)
EVP_PKEY_free(pubkey);
/* check date of CRL to make sure it's not expired */
if(!next_update) {
s_log(LOG_WARNING, "CRL: Invalid nextUpdate field");
X509_STORE_CTX_set_error(callback_ctx,
X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD);
X509_OBJECT_free_contents(&obj);
return 0; /* reject connection */
}
if(X509_cmp_current_time(next_update)<0) {
s_log(LOG_WARNING, "CRL: CRL Expired - revoking all certificates");
X509_STORE_CTX_set_error(callback_ctx, X509_V_ERR_CRL_HAS_EXPIRED);
X509_OBJECT_free_contents(&obj);
return 0; /* reject connection */
}
X509_OBJECT_free_contents(&obj);
}
/* try to retrieve a CRL corresponding to the _issuer_ of
* the current certificate in order to check for revocation */
memset((char *)&obj, 0, sizeof obj);
X509_STORE_CTX_init(&store_ctx, c->opt->revocation_store, NULL, NULL);
rc=X509_STORE_get_by_subject(&store_ctx, X509_LU_CRL, issuer, &obj);
X509_STORE_CTX_cleanup(&store_ctx);
crl=obj.data.crl;
if(rc>0 && crl) {
/* check if the current certificate is revoked by this CRL */
n=sk_X509_REVOKED_num(X509_CRL_get_REVOKED(crl));
for(i=0; i<n; i++) {
revoked=sk_X509_REVOKED_value(X509_CRL_get_REVOKED(crl), i);
if(ASN1_INTEGER_cmp(revoked->serialNumber,
X509_get_serialNumber(cert)) == 0) {
serial=ASN1_INTEGER_get(revoked->serialNumber);
cp=X509_NAME_oneline(issuer, NULL, 0);
s_log(LOG_WARNING, "CRL: Certificate with serial %ld (0x%lX) "
"revoked per CRL from issuer %s", serial, serial, cp);
OPENSSL_free(cp);
X509_STORE_CTX_set_error(callback_ctx, X509_V_ERR_CERT_REVOKED);
X509_OBJECT_free_contents(&obj);
return 0; /* reject connection */
}
}
X509_OBJECT_free_contents(&obj);
}
return 1; /* accept connection */
}
#ifdef HAVE_OSSL_OCSP_H
/**************************************** OCSP checking */
/* TODO: check OCSP server specified in the certificate */
static int ocsp_check(CLI *c, X509_STORE_CTX *callback_ctx) {
int error, retval=0;
X509 *cert;
X509 *issuer=NULL;
OCSP_CERTID *certID;
OCSP_REQUEST *request=NULL;
OCSP_RESPONSE *response=NULL;
OCSP_BASICRESP *basicResponse=NULL;
ASN1_GENERALIZEDTIME *revoked_at=NULL,
*this_update=NULL, *next_update=NULL;
int status, reason;
/* get current certificate ID */
cert=X509_STORE_CTX_get_current_cert(callback_ctx); /* get current cert */
if(X509_STORE_CTX_get1_issuer(&issuer, callback_ctx, cert)!=1) {
sslerror("OCSP: X509_STORE_CTX_get1_issuer");
goto cleanup;
}
certID=OCSP_cert_to_id(0, cert, issuer);
if(!certID) {
sslerror("OCSP: OCSP_cert_to_id");
goto cleanup;
}
/* build request */
request=OCSP_REQUEST_new();
if(!request) {
sslerror("OCSP: OCSP_REQUEST_new");
goto cleanup;
}
if(!OCSP_request_add0_id(request, certID)) {
sslerror("OCSP: OCSP_request_add0_id");
goto cleanup;
}
OCSP_request_add1_nonce(request, 0, -1);
/* send the request and get a response */
response=ocsp_get_response(c, request);
if(!response)
goto cleanup;
error=OCSP_response_status(response);
if(error!=OCSP_RESPONSE_STATUS_SUCCESSFUL) {
s_log(LOG_WARNING, "OCSP: Responder error: %d: %s",
error, OCSP_response_status_str(error));
goto cleanup;
}
s_log(LOG_DEBUG, "OCSP: Response received");
/* verify the response */
basicResponse=OCSP_response_get1_basic(response);
if(!basicResponse) {
sslerror("OCSP: OCSP_response_get1_basic");
goto cleanup;
}
if(OCSP_check_nonce(request, basicResponse)<=0) {
sslerror("OCSP: OCSP_check_nonce");
goto cleanup;
}
if(OCSP_basic_verify(basicResponse, NULL,
c->opt->revocation_store, c->opt->ocsp_flags)<=0) {
sslerror("OCSP: OCSP_basic_verify");
goto cleanup;
}
if(!OCSP_resp_find_status(basicResponse, certID, &status, &reason,
&revoked_at, &this_update, &next_update)) {
sslerror("OCSP: OCSP_resp_find_status");
goto cleanup;
}
s_log(LOG_NOTICE, "OCSP: Status: %d: %s",
status, OCSP_cert_status_str(status));
log_time(LOG_INFO, "OCSP: This update", this_update);
log_time(LOG_INFO, "OCSP: Next update", next_update);
/* check if the response is valid for at least one minute */
if(!OCSP_check_validity(this_update, next_update, 60, -1)) {
sslerror("OCSP: OCSP_check_validity");
goto cleanup;
}
if(status==V_OCSP_CERTSTATUS_REVOKED) {
if(reason==-1)
s_log(LOG_WARNING, "OCSP: Certificate revoked");
else
s_log(LOG_WARNING, "OCSP: Certificate revoked: %d: %s",
reason, OCSP_crl_reason_str(reason));
log_time(LOG_NOTICE, "OCSP: Revoked at", revoked_at);
goto cleanup;
}
retval=1; /* accept connection */
cleanup:
if(issuer)
X509_free(issuer);
if(request)
OCSP_REQUEST_free(request);
if(response)
OCSP_RESPONSE_free(response);
if(basicResponse)
OCSP_BASICRESP_free(basicResponse);
return retval;
}
static OCSP_RESPONSE *ocsp_get_response(CLI *c, OCSP_REQUEST *req) {
BIO *bio=NULL;
OCSP_REQ_CTX *req_ctx=NULL;
OCSP_RESPONSE *resp=NULL;
int err;
/* connect specified OCSP server (responder) */
c->fd=s_socket(c->opt->ocsp_addr.sa.sa_family, SOCK_STREAM, 0,
1, "OCSP: socket (auth_user)");
if(c->fd<0)
goto cleanup;
if(connect_blocking(c, &c->opt->ocsp_addr, addr_len(&c->opt->ocsp_addr)))
goto cleanup;
bio=BIO_new_fd(c->fd, BIO_NOCLOSE);
if(!bio)
goto cleanup;
s_log(LOG_DEBUG, "OCSP: server connected");
/* OCSP protocol communication loop */
req_ctx=OCSP_sendreq_new(bio, c->opt->ocsp_path, req, -1);
if(!req_ctx) {
sslerror("OCSP: OCSP_sendreq_new");
goto cleanup;
}
while(OCSP_sendreq_nbio(&resp, req_ctx)==-1) {
s_poll_init(c->fds);
s_poll_add(c->fds, c->fd, BIO_should_read(bio), BIO_should_write(bio));
err=s_poll_wait(c->fds, c->opt->timeout_busy, 0);
if(err==-1)
sockerror("OCSP: s_poll_wait");
if(err==0)
s_log(LOG_INFO, "OCSP: s_poll_wait: TIMEOUTbusy exceeded");
if(err<=0)
goto cleanup;
}
/* s_log(LOG_DEBUG, "OCSP: context state: 0x%x", *(int *)req_ctx); */
/* http://www.mail-archive.com/openssl-users@openssl.org/msg61691.html */
if(!resp) {
if(ERR_peek_error())
sslerror("OCSP: OCSP_sendreq_nbio");
else /* OpenSSL error: OCSP_sendreq_nbio does not use OCSPerr */
s_log(LOG_ERR, "OCSP: OCSP_sendreq_nbio: OpenSSL internal error");
}
cleanup:
if(req_ctx)
OCSP_REQ_CTX_free(req_ctx);
if(bio)
BIO_free_all(bio);
if(c->fd>=0) {
closesocket(c->fd);
c->fd=-1; /* avoid double close on cleanup */
}
return resp;
}
#endif /* HAVE_OSSL_OCSP_H */
static void log_time(const int level, const char *txt, ASN1_TIME *t) {
char *cp;
BIO *bio;
int n;
if(!t)
return;
bio=BIO_new(BIO_s_mem());
if(!bio)
return;
ASN1_TIME_print(bio, t);
n=BIO_pending(bio);
cp=str_alloc(n+1);
n=BIO_read(bio, cp, n);
if(n<0) {
BIO_free(bio);
str_free(cp);
return;
}
cp[n]='\0';
BIO_free(bio);
s_log(level, "%s: %s", txt, cp);
str_free(cp);
}
/* end of verify.c */
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