summaryrefslogtreecommitdiffstats
path: root/lib/iolog/hostcheck.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--lib/iolog/hostcheck.c400
1 files changed, 400 insertions, 0 deletions
diff --git a/lib/iolog/hostcheck.c b/lib/iolog/hostcheck.c
new file mode 100644
index 0000000..d23514e
--- /dev/null
+++ b/lib/iolog/hostcheck.c
@@ -0,0 +1,400 @@
+/*
+ * Copyright (c) 2020 Laszlo Orban <laszlo.orban@oneidentity.com>
+ *
+ * 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.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#if defined(HAVE_OPENSSL)
+# if defined(HAVE_WOLFSSL)
+# include <wolfssl/options.h>
+# endif
+# include <sys/types.h>
+# include <sys/socket.h>
+# include <netinet/in.h>
+# include <arpa/inet.h>
+# include <stdlib.h>
+# include <string.h>
+# include <netdb.h>
+
+# define NEED_INET_NTOP /* to expose sudo_inet_ntop in sudo_compat.h */
+
+# include "sudo_compat.h"
+# include "sudo_debug.h"
+# include "sudo_util.h"
+# include "hostcheck.h"
+
+#ifndef INET_ADDRSTRLEN
+# define INET_ADDRSTRLEN 16
+#endif
+#ifndef INET6_ADDRSTRLEN
+# define INET6_ADDRSTRLEN 46
+#endif
+
+/**
+ * @brief Checks if given hostname resolves to the given IP address.
+ *
+ * @param hostname hostname to be resolved
+ * @param ipaddr ip address to be checked
+ *
+ * @return 1 if hostname resolves to the given IP address
+ * 0 otherwise
+ */
+static int
+forward_lookup_match(const char *hostname, const char *ipaddr)
+{
+ int rc, ret = 0;
+ struct addrinfo *res = NULL, *p;
+ void *addr;
+ struct sockaddr_in *ipv4;
+#if defined(HAVE_STRUCT_IN6_ADDR)
+ struct sockaddr_in6 *ipv6;
+ char ipstr[INET6_ADDRSTRLEN];
+#else
+ char ipstr[INET_ADDRSTRLEN];
+#endif
+ debug_decl(forward_lookup_match, SUDO_DEBUG_UTIL);
+
+ sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+ "verify %s resolves to %s", hostname, ipaddr);
+
+ if ((rc = getaddrinfo(hostname, NULL, NULL, &res)) != 0) {
+ sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+ "unable to resolve %s: %s", hostname, gai_strerror(rc));
+ goto exit;
+ }
+
+ for (p = res; p != NULL; p = p->ai_next) {
+ if (p->ai_family == AF_INET) {
+ ipv4 = (struct sockaddr_in *)p->ai_addr;
+ addr = &(ipv4->sin_addr);
+#if defined(HAVE_STRUCT_IN6_ADDR)
+ } else if (p->ai_family == AF_INET6) {
+ ipv6 = (struct sockaddr_in6 *)p->ai_addr;
+ addr = &(ipv6->sin6_addr);
+#endif
+ } else {
+ goto exit;
+ }
+
+ if (inet_ntop(p->ai_family, addr, ipstr, sizeof(ipstr)) != 0) {
+ sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+ "comparing %s to %s", ipstr, ipaddr);
+ if (strcmp(ipaddr, ipstr) == 0) {
+ ret = 1;
+ break;
+ }
+ }
+ }
+
+exit:
+ if (res != NULL) {
+ freeaddrinfo(res);
+ }
+ debug_return_int(ret);
+}
+
+/**
+ * @brief Compares the given hostname with a DNS entry in a certificate.
+ *
+ * The certificate DNS name can contain wildcards in the left-most label.
+ * A wildcard can match only one label.
+ * Accepted names:
+ * - foo.bar.example.com
+ * - *.example.com
+ * - *.bar.example.com
+ *
+ * @param hostname peer's name
+ * @param certname_asn1 hostname in the certificate
+ *
+ * @return MatchFound
+ * MatchNotFound
+ */
+static HostnameValidationResult
+validate_name(const char *hostname, ASN1_STRING *certname_asn1)
+{
+ char *certname_s = (char *) ASN1_STRING_get0_data(certname_asn1);
+ int certname_len = ASN1_STRING_length(certname_asn1);
+ int hostname_len = strlen(hostname);
+ debug_decl(validate_name, SUDO_DEBUG_UTIL);
+
+ /* remove last '.' from hostname if exists */
+ if (hostname_len != 0 && hostname[hostname_len - 1] == '.') {
+ --hostname_len;
+ }
+
+ sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+ "comparing %.*s to %.*s in cert", hostname_len, hostname,
+ certname_len, certname_s);
+
+ /* skip the first label if wildcard */
+ if (certname_len > 2 && certname_s[0] == '*' && certname_s[1] == '.') {
+ if (hostname_len != 0) {
+ do {
+ --hostname_len;
+ if (*hostname++ == '.') {
+ break;
+ }
+ } while (hostname_len != 0);
+ }
+ certname_s += 2;
+ certname_len -= 2;
+ }
+ /* Compare expected hostname with the DNS name */
+ if (certname_len != hostname_len) {
+ debug_return_int(MatchNotFound);
+ }
+ if (strncasecmp(hostname, certname_s, hostname_len) != 0) {
+ debug_return_int(MatchNotFound);
+ }
+
+ debug_return_int(MatchFound);
+}
+
+/**
+ * @brief Matches a hostname with the cert's CN.
+ *
+ * @param hostname peer's name
+ * on client side: it is the name where the client is connected to
+ * on server side, it is in fact an IP address of the remote client
+ * @param ipaddr peer's IP address
+ * @param cert peer's X509 certificate
+ * @param resolve if the value is not 0, the function checks that the value of the CN
+ * resolves to the given ipaddr or not.
+ *
+ * @return MatchFound
+ * MatchNotFound
+ * MalformedCertificate
+ * Error
+ */
+static HostnameValidationResult
+matches_common_name(const char *hostname, const char *ipaddr, const X509 *cert, int resolve)
+{
+ X509_NAME_ENTRY *common_name_entry = NULL;
+ ASN1_STRING *common_name_asn1 = NULL;
+ int common_name_loc;
+ debug_decl(matches_common_name, SUDO_DEBUG_UTIL);
+
+ /* 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 *) cert), NID_commonName, -1);
+ if (common_name_loc < 0) {
+ debug_return_int(Error);
+ }
+
+ /* Extract the CN field */
+ common_name_entry = X509_NAME_get_entry(X509_get_subject_name((X509 *) cert), common_name_loc);
+ if (common_name_entry == NULL) {
+ debug_return_int(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) {
+ debug_return_int(Error);
+ }
+ const unsigned char *common_name_str = ASN1_STRING_get0_data(common_name_asn1);
+
+ /* Make sure there isn't an embedded NUL character in the CN */
+ if (memchr(common_name_str, '\0', ASN1_STRING_length(common_name_asn1)) != NULL) {
+ debug_return_int(MalformedCertificate);
+ }
+
+ /* Compare expected hostname with the CN */
+ if (validate_name(hostname, common_name_asn1) == MatchFound) {
+ debug_return_int(MatchFound);
+ }
+
+ int common_name_length = ASN1_STRING_length(common_name_asn1);
+ char *nullterm_common_name = malloc(common_name_length + 1);
+
+ if (nullterm_common_name == NULL) {
+ debug_return_int(Error);
+ }
+
+ memcpy(nullterm_common_name, common_name_str, common_name_length);
+ nullterm_common_name[common_name_length] = '\0';
+
+
+ /* check if hostname in the CN field resolves to the given ip address */
+ if (resolve && forward_lookup_match(nullterm_common_name, ipaddr)) {
+ free(nullterm_common_name);
+ debug_return_int(MatchFound);
+ }
+
+ free(nullterm_common_name);
+ debug_return_int(MatchNotFound);
+}
+
+/**
+ * @brief Matches a hostname or ipaddr with the cert's corresponding SAN field.
+ *
+ * SAN can have different fields. For hostname matching, the GEN_DNS field is used,
+ * for IP address matching, the GEN_IPADD field is used.
+ * Since SAN is an X503 v3 extension, it can happen that the cert does
+ * not contain SAN at all.
+ *
+ * @param hostname remote peer's name
+ * on client side: it is the name where the client is connected to
+ * on server side, it is in fact an IP address of the remote client
+ * @param ipaddr remote peer's IP address
+ * @param cert peer's X509 certificate
+ * @param resolve if the value is not 0, the function checks that the value of the
+ * SAN GEN_DNS resolves to the given ipaddr or not.
+ *
+ * @return MatchFound
+ * MatchNotFound
+ * NoSANPresent
+ * MalformedCertificate
+ * Error
+ */
+static HostnameValidationResult
+matches_subject_alternative_name(const char *hostname, const char *ipaddr, const X509 *cert, int resolve)
+{
+ HostnameValidationResult result = MatchNotFound;
+ int i;
+ int san_names_nb;
+ STACK_OF(GENERAL_NAME) *san_names = NULL;
+ debug_decl(matches_subject_alternative_name, SUDO_DEBUG_UTIL);
+
+ /* Try to extract the names within the SAN extension from the certificate */
+ san_names = X509_get_ext_d2i((X509 *) cert, NID_subject_alt_name, NULL, NULL);
+ if (san_names == NULL) {
+ debug_return_int(NoSANPresent);
+ }
+ 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) {
+ const unsigned char *dns_name = ASN1_STRING_get0_data(current_name->d.dNSName);
+
+ /* Make sure there isn't an embedded NUL character in the DNS name */
+ if (memchr(dns_name, '\0', ASN1_STRING_length(current_name->d.dNSName)) != NULL) {
+ result = MalformedCertificate;
+ break;
+ } else {
+ /* Compare expected hostname with the DNS name */
+ if (validate_name(hostname, current_name->d.dNSName) == MatchFound) {
+ result = MatchFound;
+ break;
+ }
+
+ int dns_name_length = ASN1_STRING_length(current_name->d.dNSName);
+ char *nullterm_dns_name = malloc(dns_name_length + 1);
+
+ if (nullterm_dns_name == NULL) {
+ debug_return_int(Error);
+ }
+
+ memcpy(nullterm_dns_name, dns_name, dns_name_length);
+ nullterm_dns_name[dns_name_length] = '\0';
+
+ if (resolve && forward_lookup_match(nullterm_dns_name, ipaddr)) {
+ free(nullterm_dns_name);
+ result = MatchFound;
+ break;
+ }
+ free(nullterm_dns_name);
+ }
+ } else if (current_name->type == GEN_IPADD) {
+ const unsigned char *san_ip = ASN1_STRING_get0_data(current_name->d.iPAddress);
+#if defined(HAVE_STRUCT_IN6_ADDR)
+ char san_ip_str[INET6_ADDRSTRLEN];
+#else
+ char san_ip_str[INET_ADDRSTRLEN];
+#endif
+
+ /* IPV4 address */
+ if(current_name->d.iPAddress->length == 4) {
+ if (inet_ntop(AF_INET, san_ip, san_ip_str, INET_ADDRSTRLEN) == NULL) {
+ result = MalformedCertificate;
+ break;
+ }
+#if defined(HAVE_STRUCT_IN6_ADDR)
+ /* IPV6 address */
+ } else if (current_name->d.iPAddress->length == 16) {
+ if (inet_ntop(AF_INET6, san_ip, san_ip_str, INET6_ADDRSTRLEN) == NULL) {
+ result = MalformedCertificate;
+ break;
+ }
+# endif
+ } else {
+ result = MalformedCertificate;
+ break;
+ }
+
+ if (strcasecmp(ipaddr, san_ip_str) == 0) {
+ result = MatchFound;
+ break;
+ }
+ }
+ }
+ sk_GENERAL_NAME_pop_free(san_names, GENERAL_NAME_free);
+
+ debug_return_int(result);
+}
+
+/**
+ * @brief Do hostname/IP validation on the given X509 certificate.
+ *
+ * According to RFC 6125 section 6.4.4, first the certificate's SAN field
+ * has to be checked. If there is no SAN field, the certificate's CN field
+ * has to be checked.
+ *
+ * @param cert X509 certificate
+ * @param hostname remote peer's name
+ * on client side: it is the name where the client is connected to
+ * on server side, it is in fact an IP address of the remote client
+ * @param ipaddr remote peer's IP address
+ * @param resolve if the value is not 0, the function checks that the value of the
+ * SAN GEN_DNS or the value of CN resolves to the given ipaddr or not.
+ *
+ * @return MatchFound
+ * MatchNotFound
+ * MalformedCertificate
+ * Error
+ */
+HostnameValidationResult
+validate_hostname(const X509 *cert, const char *hostname, const char *ipaddr, int resolve)
+{
+ HostnameValidationResult res = MatchFound;
+ debug_decl(validate_hostname, SUDO_DEBUG_UTIL);
+
+ /* hostname can be also an ip address, if client connects
+ * to ip instead of FQDN
+ */
+ if((ipaddr == NULL) || (cert == NULL)) {
+ debug_return_int(Error);
+ }
+
+ /* check SAN first if exists */
+ res = matches_subject_alternative_name(hostname, ipaddr, cert, resolve);
+
+ /* According to RFC 6125 section 6.4.4, check CN only,
+ * if no SAN name was provided
+ */
+ if (res == NoSANPresent) {
+ res = matches_common_name(hostname, ipaddr, cert, resolve);
+ }
+
+ debug_return_int(res);
+}
+#endif /* HAVE_OPENSSL */
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-26 20:09:10 +0000