Set optional peername when X509_check_host() succeeds.

Pass address of X509_VERIFY_PARAM_ID peername to X509_check_host().
Document modified interface.

apps/apps.c

@@ -2969,7 +2969,8 @@ void print_cert_checks(BIO *bio, X509 *x,
 	if (checkhost)
 		{
 		BIO_printf(bio, "Hostname %s does%s match certificate\n",
-				checkhost, X509_check_host(x, checkhost, 0, 0)
+				checkhost,
+				X509_check_host(x, checkhost, 0, 0, NULL)
 						? "" : " NOT");
 		}
 

crypto/x509/x509_vfy.c

@@ -752,7 +752,8 @@ static int check_hosts(X509 *x, X509_VERIFY_PARAM_ID *id)
 	for (i = 0; i < n; ++i)
 		{
 		name = (unsigned char *)sk_OPENSSL_STRING_value(id->hosts, i);
-		if (X509_check_host(x, name, 0, id->hostflags) > 0)
+		if (X509_check_host(x, name, 0, id->hostflags,
+				    &id->peername) > 0)
 			return 1;
 		}
 	return n == 0;

crypto/x509v3/v3_utl.c

@@ -853,43 +853,50 @@ static int equal_wildcard(const unsigned char *pattern, size_t pattern_len,
 
 static int do_check_string(ASN1_STRING *a, int cmp_type, equal_fn equal,
 				unsigned int flags,
-				const unsigned char *b, size_t blen)
+				const unsigned char *b, size_t blen,
+				char **peername)
 	{
+	int rv = 0;
+
 	if (!a->data || !a->length)
 		return 0;
 	if (cmp_type > 0)
 		{
 		if (cmp_type != a->type)
 			return 0;
 		if (cmp_type == V_ASN1_IA5STRING)
-			return equal(a->data, a->length, b, blen, flags);
-		if (a->length == (int)blen && !memcmp(a->data, b, blen))
-			return 1;
-		else
-			return 0;
+			rv = equal(a->data, a->length, b, blen, flags);
+		else if (a->length == (int)blen && !memcmp(a->data, b, blen))
+			rv = 1;
+		if (rv > 0 && peername)
+			*peername = BUF_strndup((char *)a->data, a->length);
 		}
 	else
 		{
-		int astrlen, rv;
+		int astrlen;
 		unsigned char *astr;
 		astrlen = ASN1_STRING_to_UTF8(&astr, a);
 		if (astrlen < 0)
 			return -1;
 		rv = equal(astr, astrlen, b, blen, flags);
 		OPENSSL_free(astr);
-		return rv;
+		if (rv > 0 && peername)
+			*peername = BUF_strndup((char *)astr, astrlen);
 		}
+	return rv;
 	}
 
 static int do_x509_check(X509 *x, const unsigned char *chk, size_t chklen,
-					unsigned int flags, int check_type)
+					unsigned int flags, int check_type,
+					char **peername)
 	{
 	GENERAL_NAMES *gens = NULL;
 	X509_NAME *name = NULL;
 	int i;
 	int cnid;
 	int alt_type;
 	int san_present = 0;
+	int rv = 0;
 	equal_fn equal;
 
 	/* See below, this flag is internal-only */
@@ -925,7 +932,6 @@ static int do_x509_check(X509 *x, const unsigned char *chk, size_t chklen,
 	gens = X509_get_ext_d2i(x, NID_subject_alt_name, NULL, NULL);
 	if (gens)
 		{
-		int rv = 0;
 		for (i = 0; i < sk_GENERAL_NAME_num(gens); i++)
 			{
 			GENERAL_NAME *gen;
@@ -940,16 +946,14 @@ static int do_x509_check(X509 *x, const unsigned char *chk, size_t chklen,
 				cstr = gen->d.dNSName;
 			else
 				cstr = gen->d.iPAddress;
-			if (do_check_string(cstr, alt_type, equal, flags,
-					    chk, chklen))
-				{
-				rv = 1;
+			/* Positive on success, negative on error! */
+			if ((rv = do_check_string(cstr, alt_type, equal, flags,
+						  chk, chklen, peername)) != 0)
 				break;
-				}
 			}
 		GENERAL_NAMES_free(gens);
-		if (rv)
-			return 1;
+		if (rv != 0)
+			return rv;
 		if (!cnid
 		    || (san_present
 		        && !(flags & X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT)))
@@ -963,14 +967,16 @@ static int do_x509_check(X509 *x, const unsigned char *chk, size_t chklen,
 		ASN1_STRING *str;
 		ne = X509_NAME_get_entry(name, i);
 		str = X509_NAME_ENTRY_get_data(ne);
-		if (do_check_string(str, -1, equal, flags, chk, chklen))
-			return 1;
+		/* Positive on success, negative on error! */
+		if ((rv = do_check_string(str, -1, equal, flags,
+					  chk, chklen, peername)) != 0)
+			return rv;
 		}
 	return 0;
 	}
 
 int X509_check_host(X509 *x, const unsigned char *chk, size_t chklen,
-					unsigned int flags)
+					unsigned int flags, char **peername)
 	{
 	if (chk == NULL)
 		return -2;
@@ -985,7 +991,7 @@ int X509_check_host(X509 *x, const unsigned char *chk, size_t chklen,
 		return -2;
 	if (chklen > 1 && chk[chklen-1] == '\0')
 		--chklen;
-	return do_x509_check(x, chk, chklen, flags, GEN_DNS);
+	return do_x509_check(x, chk, chklen, flags, GEN_DNS, peername);
 	}
 
 int X509_check_email(X509 *x, const unsigned char *chk, size_t chklen,
@@ -1004,15 +1010,15 @@ int X509_check_email(X509 *x, const unsigned char *chk, size_t chklen,
 		return -2;
 	if (chklen > 1 && chk[chklen-1] == '\0')
 		--chklen;
-	return do_x509_check(x, chk, chklen, flags, GEN_EMAIL);
+	return do_x509_check(x, chk, chklen, flags, GEN_EMAIL, NULL);
 	}
 
 int X509_check_ip(X509 *x, const unsigned char *chk, size_t chklen,
 					unsigned int flags)
 	{
 	if (chk == NULL)
 		return -2;
-	return do_x509_check(x, chk, chklen, flags, GEN_IPADD);
+	return do_x509_check(x, chk, chklen, flags, GEN_IPADD, NULL);
 	}
 
 int X509_check_ip_asc(X509 *x, const char *ipasc, unsigned int flags)
@@ -1024,7 +1030,7 @@ int X509_check_ip_asc(X509 *x, const char *ipasc, unsigned int flags)
 	iplen = a2i_ipadd(ipout, ipasc);
 	if (iplen == 0)
 		return -2;
-	return do_x509_check(x, ipout, (size_t)iplen, flags, GEN_IPADD);
+	return do_x509_check(x, ipout, (size_t)iplen, flags, GEN_IPADD, NULL);
 	}
 
 /* Convert IP addresses both IPv4 and IPv6 into an 

crypto/x509v3/v3nametest.c

@@ -276,7 +276,7 @@ static void run_cert(X509 *crt, const char *nameincert,
 		memcpy(name, *pname, namelen);
 
 		ret = X509_check_host(crt, (const unsigned char *)name,
-				      namelen, 0);
+				      namelen, 0, NULL);
 		match = -1;
 		if (ret < 0)
 			{
@@ -295,7 +295,8 @@ static void run_cert(X509 *crt, const char *nameincert,
 		check_message(fn, "host", nameincert, match, *pname);
 
 		ret = X509_check_host(crt, (const unsigned char *)name,
-				      namelen, X509_CHECK_FLAG_NO_WILDCARDS);
+				      namelen, X509_CHECK_FLAG_NO_WILDCARDS,
+				      NULL);
 		match = -1;
 		if (ret < 0)
 			{

crypto/x509v3/x509v3.h

@@ -720,7 +720,7 @@ STACK_OF(OPENSSL_STRING) *X509_get1_ocsp(X509 *x);
 #define _X509_CHECK_FLAG_DOT_SUBDOMAINS 0x8000
 
 int X509_check_host(X509 *x, const unsigned char *chk, size_t chklen,
-					unsigned int flags);
+					unsigned int flags, char **peername);
 int X509_check_email(X509 *x, const unsigned char *chk, size_t chklen,
 					unsigned int flags);
 int X509_check_ip(X509 *x, const unsigned char *chk, size_t chklen,

doc/crypto/X509_check_host.pod

@@ -9,7 +9,7 @@ X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc - X.509 cert
  #include <openssl/x509.h>
 
  int X509_check_host(X509 *, const unsigned char *name,
-                     size_t namelen, unsigned int flags);
+                     size_t namelen, unsigned int flags, char **peername);
  int X509_check_email(X509 *, const unsigned char *address,
                      size_t addresslen, unsigned int flags);
  int X509_check_ip(X509 *, const unsigned char *address,
@@ -32,11 +32,16 @@ characters in the name string or zero in which case the length is
 calculated with strlen(name).  When B<name> starts with a dot (e.g
 ".example.com"), it will be matched by a certificate valid for any
 sub-domain of B<name>, (see also B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS>
-below).  Applications are strongly advised to use
-X509_VERIFY_PARAM_set1_host() in preference to explicitly calling
-L<X509_check_host(3)>, hostname checks are out of scope with the
-DANE-EE(3) certificate usage, and the internal check will be
-suppressed as appropriate when DANE support is added to OpenSSL.
+below).  When the certificate is matched and B<peername> is not
+NULL a pointer to a copy of the matching hostname or CommonName
+from the peer certificate is stored at the address passed in
+B<peername>.  The application is responsible for freeing the peername
+via OPENSSL_free() when it is no longer needed.  Applications are
+advised to use X509_VERIFY_PARAM_set1_host() in preference to
+explicitly calling L<X509_check_host(3)>, hostname checks are out
+of scope with the DANE-EE(3) certificate usage, and the internal
+check will be suppressed as appropriate when DANE support is added
+to OpenSSL.
 
 X509_check_email() checks if the certificate matches the specified
 email address.  Only the mailbox syntax of RFC 822 is supported,