CVE-2010-1155: Improper Input Validation (CWE-20)
value: Irssi before 0.8.15, when SSL is used, does not verify that the server hostname matches a domain name in the subject's Common Name (CN) field or a Subject Alternative Name field of the X.509 certificate, which allows man-in-the-middle attackers to spoof IRC servers via an arbitrary certificate.
CWE description: The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.
Published: 2010-04-16T19:30Z
Repository: https://github.com/ensc/irssi-proxy
Language: C
Files changed: src/core/network-openssl.c, src/core/network.h, src/core/servers.c
Commit date: 2009-12-28 12:15:18 +0000
Commit message: Check if an SSL certificate matches the hostname of the server we are connecting to

git-svn-id: http://svn.irssi.org/repos/irssi/trunk@5104 dbcabf3a-b0e7-0310-adc4-f8d773084564

Diff: diff --git a/src/core/network-openssl.c b/src/core/network-openssl.c
index 92832ba..5a9c9bc 100644
--- a/src/core/network-openssl.c
+++ b/src/core/network-openssl.c
@@ -24,10 +24,11 @@
 
 #ifdef HAVE_OPENSSL
 
 #include <openssl/crypto.h>
 #include <openssl/x509.h>
+#include <openssl/x509v3.h>
 #include <openssl/pem.h>
 #include <openssl/ssl.h>
 #include <openssl/err.h>
 
 /* ssl i/o channel object */
@@ -37,10 +38,11 @@ typedef struct
 	gint fd;
 	GIOChannel *giochan;
 	SSL *ssl;
 	SSL_CTX *ctx;
 	unsigned int verify:1;
+	const char *hostname;
 } GIOSSLChannel;
 
 static SSL_CTX *ssl_ctx = NULL;
 
 static void irssi_ssl_free(GIOChannel *handle)
@@ -51,11 +53,153 @@ static void irssi_ssl_free(GIOChannel *handle)
 	if (chan->ctx != ssl_ctx)
 		SSL_CTX_free(chan->ctx);
 	g_free(chan);
 }
 
-static gboolean irssi_ssl_verify(SSL *ssl, SSL_CTX *ctx, X509 *cert)
+/* Checks if the given string has internal NUL characters. */
+static gboolean has_internal_nul(const char* str, int len) {
+	/* Remove trailing nul characters. They would give false alarms */
+	while (len > 0 && str[len-1] == 0)
+		len--;
+	return strlen(str) != len;
+}
+
+/* tls_dns_name - Extract valid DNS name from subjectAltName value */
+static const char *tls_dns_name(const GENERAL_NAME * gn)
+{
+	const char *dnsname;
+
+	/* We expect the OpenSSL library to construct GEN_DNS extension objects as
+	   ASN1_IA5STRING values. Check we got the right union member. */
+	if (ASN1_STRING_type(gn->d.ia5) != V_ASN1_IA5STRING) {
+		g_warning("Invalid ASN1 value type in subjectAltName");
+		return NULL;
+	}
+
+	/* Safe to treat as an ASCII string possibly holding a DNS name */
+	dnsname = (char *) ASN1_STRING_data(gn->d.ia5);
+
+	if (has_internal_nul(dnsname, ASN1_STRING_length(gn->d.ia5))) {
+		g_warning("Internal NUL in subjectAltName");
+		return NULL;
+	}
+
+	return dnsname;
+}
+
+/* tls_text_name - extract certificate property value by name */
+static char *tls_text_name(X509_NAME *name, int nid)
+{
+	int     pos;
+	X509_NAME_ENTRY *entry;
+	ASN1_STRING *entry_str;
+	int     utf8_length;
+	unsigned char *utf8_value;
+	char *result;
+
+	if (name == 0 || (pos = X509_NAME_get_index_by_NID(name, nid, -1)) < 0) {
+		return NULL;
+    }
+
+    entry = X509_NAME_get_entry(name, pos);
+    g_return_val_if_fail(entry != NULL, NULL);
+    entry_str = X509_NAME_ENTRY_get_data(entry);
+    g_return_val_if_fail(entry_str != NULL, NULL);
+
+    /* Convert everything into UTF-8. It's up to OpenSSL to do something
+	   reasonable when converting ASCII formats that contain non-ASCII
+	   content. */
+    if ((utf8_length = ASN1_STRING_to_UTF8(&utf8_value, entry_str)) < 0) {
+    	g_warning("Error decoding ASN.1 type=%d", ASN1_STRING_type(entry_str));
+    	return NULL;
+    }
+
+    if (has_internal_nul((char *)utf8_value, utf8_length)) {
+    	g_warning("NUL character in hostname in certificate");
+    	OPENSSL_free(utf8_value);
+    	return NULL;
+    }
+
+    result = g_strdup((char *) utf8_value);
+	OPENSSL_free(utf8_value);
+	return result;
+}
+
+
+/** check if a hostname in the certificate matches the hostname we used for the connection */
+static gboolean match_hostname(const char *cert_hostname, const char *hostname)
+{
+	const char *hostname_left;
+
+	if (!strcasecmp(cert_hostname, hostname)) { /* exact match */
+		return TRUE;
+	} else if (cert_hostname[0] == '*' && cert_hostname[1] == '.' && cert_hostname[2] != 0) { /* wildcard match */
+		/* The initial '*' matches exactly one hostname component */
+		hostname_left = strchr(hostname, '.');
+		if (hostname_left != NULL && ! strcasecmp(hostname_left + 1, cert_hostname + 2)) {
+			return TRUE;
+		}
+	}
+	return FALSE;
+}
+
+/* based on verify_extract_name from tls_client.c in postfix */
+static gboolean irssi_ssl_verify_hostname(X509 *cert, const char *hostname)
+{
+	int gen_index, gen_count;
+	gboolean matched = FALSE, has_dns_name = FALSE;
+	const char *cert_dns_name;
+	char *cert_subject_cn;
+	const GENERAL_NAME *gn;
+	STACK_OF(GENERAL_NAME) * gens;
+
+	/* Verify the dNSName(s) in the peer certificate against the hostname. */
+	gens = X509_get_ext_d2i(cert, NID_subject_alt_name, 0, 0);
+	if (gens) {
+		gen_count = sk_GENERAL_NAME_num(gens);
+		for (gen_index = 0; gen_index < gen_count && !matched; ++gen_index) {
+			gn = sk_GENERAL_NAME_value(gens, gen_index);
+			if (gn->type != GEN_DNS)
+				continue;
+
+			/* Even if we have an invalid DNS name, we still ultimately
+			   ignore the CommonName, because subjectAltName:DNS is
+			   present (though malformed). */
+			has_dns_name = TRUE;
+			cert_dns_name = tls_dns_name(gn);
+			if (cert_dns_name && *cert_dns_name) {
+				matched = match_hostname(cert_dns_name, hostname);
+			}
+    	}
+
+	    /* Free stack *and* member GENERAL_NAME objects */
+	    sk_GENERAL_NAME_pop_free(gens, GENERAL_NAME_free);
+	}
+
+	if (has_dns_name) {
+		if (! matched) {
+			/* The CommonName in the issuer DN is obsolete when SubjectAltName is available. */
+			g_warning("None of the Subject Alt Names in the certificate match hostname '%s'", hostname);
+		}
+		return matched;
+	} else { /* No subjectAltNames, look at CommonName */
+		cert_subject_cn = tls_text_name(X509_get_subject_name(cert), NID_commonName);
+	    if (cert_subject_cn && *cert_subject_cn) {
+	    	matched = match_hostname(cert_subject_cn, hostname);
+	    	if (! matched) {
+				g_warning("SSL certificate common name '%s' doesn't match host name '%s'", cert_subject_cn, hostname);
+	    	}
+	    } else {
+	    	g_warning("No subjectAltNames and no valid common name in certificate");
+	    }
+	    free(cert_subject_cn);
+	}
+
+	return matched;
+}
+
+static gboolean irssi_ssl_verify(SSL *ssl, SSL_CTX *ctx, const char* hostname, X509 *cert)
 {
 	if (SSL_get_verify_result(ssl) != X509_V_OK) {
 		unsigned char md[EVP_MAX_MD_SIZE];
 		unsigned int n;
 		char *str;
@@ -87,10 +231,12 @@ static gboolean irssi_ssl_verify(SSL *ssl, SSL_CTX *ctx, X509 *cert)
 				}
 				g_warning("  MD5 Fingerprint : %s", fp);
 			}
 		}
 		return FALSE;
+	} else if (! irssi_ssl_verify_hostname(cert, hostname)){
+		return FALSE;
 	}
 	return TRUE;
 }
 
 static GIOStatus irssi_ssl_read(GIOChannel *handle, gchar *buf, gsize len, gsize *ret, GError **gerr)
@@ -239,11 +385,11 @@ static gboolean irssi_ssl_init(void)
 
 	return TRUE;
 
 }
 
-static GIOChannel *irssi_ssl_get_iochannel(GIOChannel *handle, const char *mycert, const char *mypkey, const char *cafile, const char *capath, gboolean verify)
+static GIOChannel *irssi_ssl_get_iochannel(GIOChannel *handle, const char *hostname, const char *mycert, const char *mypkey, const char *cafile, const char *capath, gboolean verify)
 {
 	GIOSSLChannel *chan;
 	GIOChannel *gchan;
 	int fd;
 	SSL *ssl;
@@ -324,28 +470,29 @@ static GIOChannel *irssi_ssl_get_iochannel(GIOChannel *handle, const char *mycer
 	chan->fd = fd;
 	chan->giochan = handle;
 	chan->ssl = ssl;
 	chan->ctx = ctx;
 	chan->verify = verify;
+	chan->hostname = hostname;
 
 	gchan = (GIOChannel *)chan;
 	gchan->funcs = &irssi_ssl_channel_funcs;
 	g_io_channel_init(gchan);
 	gchan->is_readable = gchan->is_writeable = TRUE;
 	gchan->use_buffer = FALSE;
 
 	return gchan;
 }
 
-GIOChannel *net_connect_ip_ssl(IPADDR *ip, int port, IPADDR *my_ip, const char *cert, const char *pkey, const char *cafile, const char *capath, gboolean verify)
+GIOChannel *net_connect_ip_ssl(IPADDR *ip, int port, const char* hostname, IPADDR *my_ip, const char *cert, const char *pkey, const char *cafile, const char *capath, gboolean verify)
 {
 	GIOChannel *handle, *ssl_handle;
 
 	handle = net_connect_ip(ip, port, my_ip);
 	if (handle == NULL)
 		return NULL;
-	ssl_handle  = irssi_ssl_get_iochannel(handle, cert, pkey, cafile, capath, verify);
+	ssl_handle  = irssi_ssl_get_iochannel(handle, hostname, cert, pkey, cafile, capath, verify);
 	if (ssl_handle == NULL)
 		g_io_channel_unref(handle);
 	return ssl_handle;
 }
 
@@ -383,11 +530,11 @@ int irssi_ssl_handshake(GIOChannel *handle)
 	cert = SSL_get_peer_certificate(chan->ssl);
 	if (cert == NULL) {
 		g_warning("SSL server supplied no certificate");
 		return -1;
 	}
-	ret = !chan->verify || irssi_ssl_verify(chan->ssl, chan->ctx, cert);
+	ret = !chan->verify || irssi_ssl_verify(chan->ssl, chan->ctx, chan->hostname, cert);
 	X509_free(cert);
 	return ret ? 0 : -1;
 }
 
 #else /* HAVE_OPENSSL */
diff --git a/src/core/network.h b/src/core/network.h
index 65505ea..8583724 100644
--- a/src/core/network.h
+++ b/src/core/network.h
@@ -45,11 +45,11 @@ extern IPADDR ip4_any;
 int net_ip_compare(IPADDR *ip1, IPADDR *ip2);
 
 /* Connect to socket */
 GIOChannel *net_connect(const char *addr, int port, IPADDR *my_ip);
 /* Connect to socket with ip address and SSL*/
-GIOChannel *net_connect_ip_ssl(IPADDR *ip, int port, IPADDR *my_ip, const char *cert, const char *pkey, const char *cafile, const char *capath, gboolean verify);
+GIOChannel *net_connect_ip_ssl(IPADDR *ip, int port, const char* hostname, IPADDR *my_ip, const char *cert, const char *pkey, const char *cafile, const char *capath, gboolean verify);
 int irssi_ssl_handshake(GIOChannel *handle);
 /* Connect to socket with ip address */
 GIOChannel *net_connect_ip(IPADDR *ip, int port, IPADDR *my_ip);
 /* Connect to named UNIX socket */
 GIOChannel *net_connect_unix(const char *path);
diff --git a/src/core/servers.c b/src/core/servers.c
index d5844e7..017a203 100644
--- a/src/core/servers.c
+++ b/src/core/servers.c
@@ -222,11 +222,11 @@ static void server_real_connect(SERVER_REC *server, IPADDR *ip,
 			(IPADDR_IS_V6(ip) ? server->connrec->own_ip6 :
 			 server->connrec->own_ip4);
 		port = server->connrec->proxy != NULL ?
 			server->connrec->proxy_port : server->connrec->port;
 		handle = server->connrec->use_ssl ?
-			net_connect_ip_ssl(ip, port, own_ip, server->connrec->ssl_cert, server->connrec->ssl_pkey,
+			net_connect_ip_ssl(ip, port, server->connrec->address, own_ip, server->connrec->ssl_cert, server->connrec->ssl_pkey,
 server->connrec->ssl_cafile, server->connrec->ssl_capath, server->connrec->ssl_verify) :
 			net_connect_ip(ip, port, own_ip);
 	} else {
 		handle = net_connect_unix(unix_socket);
 	}

Vulnerable code: static gboolean irssi_ssl_verify(SSL *ssl, SSL_CTX *ctx, X509 *cert)
static GIOChannel *irssi_ssl_get_iochannel(GIOChannel *handle, const char *mycert, const char *mypkey, const char *cafile, const char *capath, gboolean verify)
GIOChannel *net_connect_ip_ssl(IPADDR *ip, int port, IPADDR *my_ip, const char *cert, const char *pkey, const char *cafile, const char *capath, gboolean verify)
	ssl_handle  = irssi_ssl_get_iochannel(handle, cert, pkey, cafile, capath, verify);
	ret = !chan->verify || irssi_ssl_verify(chan->ssl, chan->ctx, cert);
GIOChannel *net_connect_ip_ssl(IPADDR *ip, int port, IPADDR *my_ip, const char *cert, const char *pkey, const char *cafile, const char *capath, gboolean verify);
			net_connect_ip_ssl(ip, port, own_ip, server->connrec->ssl_cert, server->connrec->ssl_pkey,
Fixed code: #include <openssl/x509v3.h>
	const char *hostname;
/* Checks if the given string has internal NUL characters. */
static gboolean has_internal_nul(const char* str, int len) {
	/* Remove trailing nul characters. They would give false alarms */
	while (len > 0 && str[len-1] == 0)
		len--;
	return strlen(str) != len;
}

/* tls_dns_name - Extract valid DNS name from subjectAltName value */
static const char *tls_dns_name(const GENERAL_NAME * gn)
{
	const char *dnsname;

	/* We expect the OpenSSL library to construct GEN_DNS extension objects as
	   ASN1_IA5STRING values. Check we got the right union member. */
	if (ASN1_STRING_type(gn->d.ia5) != V_ASN1_IA5STRING) {
		g_warning("Invalid ASN1 value type in subjectAltName");
		return NULL;
	}

	/* Safe to treat as an ASCII string possibly holding a DNS name */
	dnsname = (char *) ASN1_STRING_data(gn->d.ia5);

	if (has_internal_nul(dnsname, ASN1_STRING_length(gn->d.ia5))) {
		g_warning("Internal NUL in subjectAltName");
		return NULL;
	}

	return dnsname;
}

/* tls_text_name - extract certificate property value by name */
static char *tls_text_name(X509_NAME *name, int nid)
{
	int     pos;
	X509_NAME_ENTRY *entry;
	ASN1_STRING *entry_str;
	int     utf8_length;
	unsigned char *utf8_value;
	char *result;

	if (name == 0 || (pos = X509_NAME_get_index_by_NID(name, nid, -1)) < 0) {
		return NULL;
    }

    entry = X509_NAME_get_entry(name, pos);
    g_return_val_if_fail(entry != NULL, NULL);
    entry_str = X509_NAME_ENTRY_get_data(entry);
    g_return_val_if_fail(entry_str != NULL, NULL);

    /* Convert everything into UTF-8. It's up to OpenSSL to do something
	   reasonable when converting ASCII formats that contain non-ASCII
	   content. */
    if ((utf8_length = ASN1_STRING_to_UTF8(&utf8_value, entry_str)) < 0) {
    	g_warning("Error decoding ASN.1 type=%d", ASN1_STRING_type(entry_str));
    	return NULL;
    }

    if (has_internal_nul((char *)utf8_value, utf8_length)) {
    	g_warning("NUL character in hostname in certificate");
    	OPENSSL_free(utf8_value);
    	return NULL;
    }

    result = g_strdup((char *) utf8_value);
	OPENSSL_free(utf8_value);
	return result;
}


/** check if a hostname in the certificate matches the hostname we used for the connection */
static gboolean match_hostname(const char *cert_hostname, const char *hostname)
{
	const char *hostname_left;

	if (!strcasecmp(cert_hostname, hostname)) { /* exact match */
		return TRUE;
	} else if (cert_hostname[0] == '*' && cert_hostname[1] == '.' && cert_hostname[2] != 0) { /* wildcard match */
		/* The initial '*' matches exactly one hostname component */
		hostname_left = strchr(hostname, '.');
		if (hostname_left != NULL && ! strcasecmp(hostname_left + 1, cert_hostname + 2)) {
			return TRUE;
		}
	}
	return FALSE;
}

/* based on verify_extract_name from tls_client.c in postfix */
static gboolean irssi_ssl_verify_hostname(X509 *cert, const char *hostname)
{
	int gen_index, gen_count;
	gboolean matched = FALSE, has_dns_name = FALSE;
	const char *cert_dns_name;
	char *cert_subject_cn;
	const GENERAL_NAME *gn;
	STACK_OF(GENERAL_NAME) * gens;

	/* Verify the dNSName(s) in the peer certificate against the hostname. */
	gens = X509_get_ext_d2i(cert, NID_subject_alt_name, 0, 0);
	if (gens) {
		gen_count = sk_GENERAL_NAME_num(gens);
		for (gen_index = 0; gen_index < gen_count && !matched; ++gen_index) {
			gn = sk_GENERAL_NAME_value(gens, gen_index);
			if (gn->type != GEN_DNS)
				continue;

			/* Even if we have an invalid DNS name, we still ultimately
			   ignore the CommonName, because subjectAltName:DNS is
			   present (though malformed). */
			has_dns_name = TRUE;
			cert_dns_name = tls_dns_name(gn);
			if (cert_dns_name && *cert_dns_name) {
				matched = match_hostname(cert_dns_name, hostname);
			}
    	}

	    /* Free stack *and* member GENERAL_NAME objects */
	    sk_GENERAL_NAME_pop_free(gens, GENERAL_NAME_free);
	}

	if (has_dns_name) {
		if (! matched) {
			/* The CommonName in the issuer DN is obsolete when SubjectAltName is available. */
			g_warning("None of the Subject Alt Names in the certificate match hostname '%s'", hostname);
		}
		return matched;
	} else { /* No subjectAltNames, look at CommonName */
		cert_subject_cn = tls_text_name(X509_get_subject_name(cert), NID_commonName);
	    if (cert_subject_cn && *cert_subject_cn) {
	    	matched = match_hostname(cert_subject_cn, hostname);
	    	if (! matched) {
				g_warning("SSL certificate common name '%s' doesn't match host name '%s'", cert_subject_cn, hostname);
	    	}
	    } else {
	    	g_warning("No subjectAltNames and no valid common name in certificate");
	    }
	    free(cert_subject_cn);
	}

	return matched;
}

static gboolean irssi_ssl_verify(SSL *ssl, SSL_CTX *ctx, const char* hostname, X509 *cert)
	} else if (! irssi_ssl_verify_hostname(cert, hostname)){
		return FALSE;
static GIOChannel *irssi_ssl_get_iochannel(GIOChannel *handle, const char *hostname, const char *mycert, const char *mypkey, const char *cafile, const char *capath, gboolean verify)
	chan->hostname = hostname;
GIOChannel *net_connect_ip_ssl(IPADDR *ip, int port, const char* hostname, IPADDR *my_ip, const char *cert, const char *pkey, const char *cafile, const char *capath, gboolean verify)
	ssl_handle  = irssi_ssl_get_iochannel(handle, hostname, cert, pkey, cafile, capath, verify);
	ret = !chan->verify || irssi_ssl_verify(chan->ssl, chan->ctx, chan->hostname, cert);
GIOChannel *net_connect_ip_ssl(IPADDR *ip, int port, const char* hostname, IPADDR *my_ip, const char *cert, const char *pkey, const char *cafile, const char *capath, gboolean verify);
			net_connect_ip_ssl(ip, port, server->connrec->address, own_ip, server->connrec->ssl_cert, server->connrec->ssl_pkey,