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/* $OpenBSD: tls_verify.c,v 1.6 2014/12/17 17:51:33 doug Exp $ */
/*
* Copyright (c) 2014 Jeremie Courreges-Anglas <jca@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
#include <openssl/x509v3.h>
#include "tls_internal.h"
int tls_match_hostname(const char *cert_hostname, const char *hostname);
int tls_check_subject_altname(struct tls *ctx, X509 *cert, const char *host);
int tls_check_common_name(struct tls *ctx, X509 *cert, const char *host);
int
tls_match_hostname(const char *cert_hostname, const char *hostname)
{
const char *cert_domain, *domain, *next_dot;
if (strcasecmp(cert_hostname, hostname) == 0)
return 0;
/* Wildcard match? */
if (cert_hostname[0] == '*') {
/*
* Valid wildcards:
* - "*.domain.tld"
* - "*.sub.domain.tld"
* - etc.
* Reject "*.tld".
* No attempt to prevent the use of eg. "*.co.uk".
*/
cert_domain = &cert_hostname[1];
/* Disallow "*" */
if (cert_domain[0] == '\0')
return -1;
/* Disallow "*foo" */
if (cert_domain[0] != '.')
return -1;
/* Disallow "*.." */
if (cert_domain[1] == '.')
return -1;
next_dot = strchr(&cert_domain[1], '.');
/* Disallow "*.bar" */
if (next_dot == NULL)
return -1;
/* Disallow "*.bar.." */
if (next_dot[1] == '.')
return -1;
domain = strchr(hostname, '.');
/* No wildcard match against a hostname with no domain part. */
if (domain == NULL || strlen(domain) == 1)
return -1;
if (strcasecmp(cert_domain, domain) == 0)
return 0;
}
return -1;
}
int
tls_check_subject_altname(struct tls *ctx, X509 *cert, const char *host)
{
STACK_OF(GENERAL_NAME) *altname_stack = NULL;
union { struct in_addr ip4; struct in6_addr ip6; } addrbuf;
int addrlen, type;
int count, i;
int rv = -1;
altname_stack = X509_get_ext_d2i(cert, NID_subject_alt_name,
NULL, NULL);
if (altname_stack == NULL)
return -1;
if (inet_pton(AF_INET, host, &addrbuf) == 1) {
type = GEN_IPADD;
addrlen = 4;
} else if (inet_pton(AF_INET6, host, &addrbuf) == 1) {
type = GEN_IPADD;
addrlen = 16;
} else {
type = GEN_DNS;
addrlen = 0;
}
count = sk_GENERAL_NAME_num(altname_stack);
for (i = 0; i < count; i++) {
GENERAL_NAME *altname;
altname = sk_GENERAL_NAME_value(altname_stack, i);
if (altname->type != type)
continue;
if (type == GEN_DNS) {
unsigned char *data;
int format, len;
format = ASN1_STRING_type(altname->d.dNSName);
if (format == V_ASN1_IA5STRING) {
data = ASN1_STRING_data(altname->d.dNSName);
len = ASN1_STRING_length(altname->d.dNSName);
if (len < 0 || len != strlen(data)) {
tls_set_error(ctx,
"error verifying host '%s': "
"NUL byte in subjectAltName, "
"probably a malicious certificate",
host);
rv = -2;
break;
}
if (tls_match_hostname(data, host) == 0) {
rv = 0;
break;
}
} else {
#ifdef DEBUG
fprintf(stdout, "%s: unhandled subjectAltName "
"dNSName encoding (%d)\n", getprogname(),
format);
#endif
}
} else if (type == GEN_IPADD) {
unsigned char *data;
int datalen;
datalen = ASN1_STRING_length(altname->d.iPAddress);
data = ASN1_STRING_data(altname->d.iPAddress);
if (datalen < 0) {
tls_set_error(ctx,
"Unexpected negative length for an "
"IP address: %d", datalen);
rv = -2;
break;
}
if (datalen == addrlen &&
memcmp(data, &addrbuf, addrlen) == 0) {
rv = 0;
break;
}
}
}
sk_GENERAL_NAME_pop_free(altname_stack, GENERAL_NAME_free);
return rv;
}
int
tls_check_common_name(struct tls *ctx, X509 *cert, const char *host)
{
X509_NAME *name;
char *common_name = NULL;
int common_name_len;
int rv = -1;
union { struct in_addr ip4; struct in6_addr ip6; } addrbuf;
name = X509_get_subject_name(cert);
if (name == NULL)
goto out;
common_name_len = X509_NAME_get_text_by_NID(name, NID_commonName,
NULL, 0);
if (common_name_len < 0)
goto out;
common_name = calloc(common_name_len + 1, 1);
if (common_name == NULL)
goto out;
X509_NAME_get_text_by_NID(name, NID_commonName, common_name,
common_name_len + 1);
/* NUL bytes in CN? */
if (common_name_len != strlen(common_name)) {
tls_set_error(ctx, "error verifying host '%s': "
"NUL byte in Common Name field, "
"probably a malicious certificate.", host);
rv = -2;
goto out;
}
if (inet_pton(AF_INET, host, &addrbuf) == 1 ||
inet_pton(AF_INET6, host, &addrbuf) == 1) {
/*
* We don't want to attempt wildcard matching against IP
* addresses, so perform a simple comparison here.
*/
if (strcmp(common_name, host) == 0)
rv = 0;
else
rv = -1;
goto out;
}
if (tls_match_hostname(common_name, host) == 0)
rv = 0;
out:
free(common_name);
return rv;
}
int
tls_check_hostname(struct tls *ctx, X509 *cert, const char *host)
{
int rv;
rv = tls_check_subject_altname(ctx, cert, host);
if (rv == 0 || rv == -2)
return rv;
return tls_check_common_name(ctx, cert, host);
}
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