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/* vim:set ft=c ts=2 sw=2 sts=2 et cindent: */
/*
* Copyright (C) 2012, iSEC Partners.
* Copyright (C) 2015 Alan Antonuk.
*
* All rights reserved.
*
* 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", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
* USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* Except as contained in this notice, the name of a copyright holder shall
* not be used in advertising or otherwise to promote the sale, use or other
* dealings in this Software without prior written authorization of the
* copyright holder.
*/
/* Originally from:
* https://github.com/iSECPartners/ssl-conservatory
* https://wiki.openssl.org/index.php/Hostname_validation
*/
#include <openssl/x509v3.h>
#include <openssl/ssl.h>
#include "amqp_openssl_hostname_validation.h"
#include "amqp_hostcheck.h"
#define HOSTNAME_MAX_SIZE 255
/**
* Tries to find a match for hostname in the certificate's Common Name field.
*
* Returns AMQP_HVR_MATCH_FOUND if a match was found.
* Returns AMQP_HVR_MATCH_NOT_FOUND if no matches were found.
* Returns AMQP_HVR_MALFORMED_CERTIFICATE if the Common Name had a NUL character embedded in it.
* Returns AMQP_HVR_ERROR if the Common Name could not be extracted.
*/
static amqp_hostname_validation_result amqp_matches_common_name(
const char *hostname, const X509 *server_cert) {
int common_name_loc = -1;
X509_NAME_ENTRY *common_name_entry = NULL;
ASN1_STRING *common_name_asn1 = NULL;
char *common_name_str = NULL;
// Find the position of the CN field in the Subject field of the certificate
common_name_loc = X509_NAME_get_index_by_NID(
X509_get_subject_name((X509 *)server_cert), NID_commonName, -1);
if (common_name_loc < 0) {
return AMQP_HVR_ERROR;
}
// Extract the CN field
common_name_entry = X509_NAME_get_entry(
X509_get_subject_name((X509 *)server_cert), common_name_loc);
if (common_name_entry == NULL) {
return AMQP_HVR_ERROR;
}
// Convert the CN field to a C string
common_name_asn1 = X509_NAME_ENTRY_get_data(common_name_entry);
if (common_name_asn1 == NULL) {
return AMQP_HVR_ERROR;
}
common_name_str = (char *)ASN1_STRING_data(common_name_asn1);
// Make sure there isn't an embedded NUL character in the CN
if ((size_t)ASN1_STRING_length(common_name_asn1) != strlen(common_name_str)) {
return AMQP_HVR_MALFORMED_CERTIFICATE;
}
// Compare expected hostname with the CN
if (amqp_hostcheck(common_name_str, hostname) == AMQP_HCR_MATCH) {
return AMQP_HVR_MATCH_FOUND;
} else {
return AMQP_HVR_MATCH_NOT_FOUND;
}
}
/**
* Tries to find a match for hostname in the certificate's Subject Alternative
* Name extension.
*
* Returns AMQP_HVR_MATCH_FOUND if a match was found.
* Returns AMQP_HVR_MATCH_NOT_FOUND if no matches were found.
* Returns AMQP_HVR_MALFORMED_CERTIFICATE if any of the hostnames had a NUL
* character embedded in it.
* Returns AMQP_HVR_NO_SAN_PRESENT if the SAN extension was not present in the
* certificate.
*/
static amqp_hostname_validation_result amqp_matches_subject_alternative_name(
const char *hostname, const X509 *server_cert) {
amqp_hostname_validation_result result = AMQP_HVR_MATCH_NOT_FOUND;
int i;
int san_names_nb = -1;
STACK_OF(GENERAL_NAME) *san_names = NULL;
// Try to extract the names within the SAN extension from the certificate
san_names =
X509_get_ext_d2i((X509 *)server_cert, NID_subject_alt_name, NULL, NULL);
if (san_names == NULL) {
return AMQP_HVR_NO_SAN_PRESENT;
}
san_names_nb = sk_GENERAL_NAME_num(san_names);
// Check each name within the extension
for (i = 0; i < san_names_nb; i++) {
const GENERAL_NAME *current_name = sk_GENERAL_NAME_value(san_names, i);
if (current_name->type == GEN_DNS) {
// Current name is a DNS name, let's check it
char *dns_name = (char *)ASN1_STRING_data(current_name->d.dNSName);
// Make sure there isn't an embedded NUL character in the DNS name
if ((size_t)ASN1_STRING_length(current_name->d.dNSName) !=
strlen(dns_name)) {
result = AMQP_HVR_MALFORMED_CERTIFICATE;
break;
} else { // Compare expected hostname with the DNS name
if (amqp_hostcheck(dns_name, hostname) == AMQP_HCR_MATCH) {
result = AMQP_HVR_MATCH_FOUND;
break;
}
}
}
}
sk_GENERAL_NAME_pop_free(san_names, GENERAL_NAME_free);
return result;
}
/**
* Validates the server's identity by looking for the expected hostname in the
* server's certificate. As described in RFC 6125, it first tries to find a match
* in the Subject Alternative Name extension. If the extension is not present in
* the certificate, it checks the Common Name instead.
*
* Returns AMQP_HVR_MATCH_FOUND if a match was found.
* Returns AMQP_HVR_MATCH_NOT_FOUND if no matches were found.
* Returns AMQP_HVR_MALFORMED_CERTIFICATE if any of the hostnames had a NUL
* character embedded in it.
* Returns AMQP_HVR_ERROR if there was an error.
*/
amqp_hostname_validation_result amqp_ssl_validate_hostname(
const char *hostname, const X509 *server_cert) {
amqp_hostname_validation_result result;
if ((hostname == NULL) || (server_cert == NULL)) return AMQP_HVR_ERROR;
// First try the Subject Alternative Names extension
result = amqp_matches_subject_alternative_name(hostname, server_cert);
if (result == AMQP_HVR_NO_SAN_PRESENT) {
// Extension was not found: try the Common Name
result = amqp_matches_common_name(hostname, server_cert);
}
return result;
}
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