CVE-2010-1155 (C, published 2010-04-16T19:30Z)
Description: 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.
Severity: MEDIUM (CVSS v3 base score: )
Weakness: CWE-20 \u2014 Improper Input Validation
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.
Repository: https://github.com/ensc/irssi-proxy
Files changed:
src/core/network-openssl.c
src/core/network.h
src/core/servers.c
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


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,