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authorJune McEnroe <june@causal.agency>2023-10-11 19:33:38 -0400
committerJune McEnroe <june@causal.agency>2023-10-11 19:33:38 -0400
commit198349012002f8d30013eb23c7d6df6a3c9cc65a (patch)
treebd0567586a018ee4a9d450c2c1de1d10e6f6bd61
parentMerge LibreSSL 3.8.0 (diff)
parentImport LibreSSL 3.8.1 (diff)
downloadlibretls-master.tar.gz
libretls-master.zip
Merge LibreSSL 3.8.1 HEAD 3.8.1 master
-rw-r--r--LIBTLS_VERSION2
-rw-r--r--VERSION2
-rw-r--r--compat/posix_win.c113
-rw-r--r--include/compat/sys/types.h12
-rw-r--r--include/compat/unistd.h4
-rw-r--r--include/tls.h14
-rw-r--r--man/tls_config_set_protocols.312
-rw-r--r--tls.c10
-rw-r--r--tls_config.c6
-rw-r--r--tls_internal.h6
-rw-r--r--tls_signer.c15
-rw-r--r--tls_verify.c101
12 files changed, 204 insertions, 93 deletions
diff --git a/LIBTLS_VERSION b/LIBTLS_VERSION
index 6e2f32a..fd02cce 100644
--- a/LIBTLS_VERSION
+++ b/LIBTLS_VERSION
@@ -1 +1 @@
-27:0:0
+28:0:0
diff --git a/VERSION b/VERSION
index 6641052..1693986 100644
--- a/VERSION
+++ b/VERSION
@@ -1,2 +1,2 @@
-3.8.0
+3.8.1
 
diff --git a/compat/posix_win.c b/compat/posix_win.c
index 30c93cd..b3a4687 100644
--- a/compat/posix_win.c
+++ b/compat/posix_win.c
@@ -148,6 +148,49 @@ wsa_errno(int err)
 	return -1;
 }
 
+/*
+ * Employ a similar trick to cpython (pycore_fileutils.h) where the CRT report
+ * handler is disabled while checking if a descriptor is a socket or a file
+ */
+#if defined _MSC_VER && _MSC_VER >= 1900
+
+#include <crtdbg.h>
+#include <stdlib.h>
+
+static void noop_handler(const wchar_t *expression,	const wchar_t *function,
+    const wchar_t *file, unsigned int line, uintptr_t pReserved)
+{
+	return;
+}
+
+#define BEGIN_SUPPRESS_IPH \
+	_invalid_parameter_handler old_handler = _set_thread_local_invalid_parameter_handler(noop_handler)
+#define END_SUPPRESS_IPH \
+	_set_thread_local_invalid_parameter_handler(old_handler)
+
+#else
+
+#define BEGIN_SUPPRESS_IPH
+#define END_SUPPRESS_IPH
+
+#endif
+
+static int
+is_socket(int fd)
+{
+	intptr_t hd;
+
+	BEGIN_SUPPRESS_IPH;
+	hd = _get_osfhandle(fd);
+	END_SUPPRESS_IPH;
+
+	if (hd == (intptr_t)INVALID_HANDLE_VALUE) {
+		return 1; /* fd is not file descriptor */
+	}
+
+	return 0;
+}
+
 int
 posix_connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen)
 {
@@ -160,24 +203,31 @@ posix_connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen)
 int
 posix_close(int fd)
 {
-	if (closesocket(fd) == SOCKET_ERROR) {
-		int err = WSAGetLastError();
-		return (err == WSAENOTSOCK || err == WSAEBADF ||
-		    err == WSANOTINITIALISED) ?
-			close(fd) : wsa_errno(err);
+	int rc;
+
+	if (is_socket(fd)) {
+		if ((rc = closesocket(fd)) == SOCKET_ERROR) {
+			int err = WSAGetLastError();
+			rc = wsa_errno(err);
+		}
+	} else {
+		rc = close(fd);
 	}
-	return 0;
+	return rc;
 }
 
 ssize_t
 posix_read(int fd, void *buf, size_t count)
 {
-	ssize_t rc = recv(fd, buf, count, 0);
-	if (rc == SOCKET_ERROR) {
-		int err = WSAGetLastError();
-		return (err == WSAENOTSOCK || err == WSAEBADF ||
-		    err == WSANOTINITIALISED) ?
-			read(fd, buf, count) : wsa_errno(err);
+	ssize_t rc;
+
+	if (is_socket(fd)) {
+		if ((rc = recv(fd, buf, count, 0)) == SOCKET_ERROR) {
+			int err = WSAGetLastError();
+			rc = wsa_errno(err);
+		}
+	} else {
+		rc = read(fd, buf, count);
 	}
 	return rc;
 }
@@ -185,12 +235,13 @@ posix_read(int fd, void *buf, size_t count)
 ssize_t
 posix_write(int fd, const void *buf, size_t count)
 {
-	ssize_t rc = send(fd, buf, count, 0);
-	if (rc == SOCKET_ERROR) {
-		int err = WSAGetLastError();
-		return (err == WSAENOTSOCK || err == WSAEBADF ||
-		    err == WSANOTINITIALISED) ?
-			write(fd, buf, count) : wsa_errno(err);
+	ssize_t rc;
+	if (is_socket(fd)) {
+		if ((rc = send(fd, buf, count, 0)) == SOCKET_ERROR) {
+			rc = wsa_errno(WSAGetLastError());
+		}
+	} else {
+		rc = write(fd, buf, count);
 	}
 	return rc;
 }
@@ -199,17 +250,32 @@ int
 posix_getsockopt(int sockfd, int level, int optname,
 	void *optval, socklen_t *optlen)
 {
-	int rc = getsockopt(sockfd, level, optname, (char *)optval, optlen);
-	return rc == 0 ? 0 : wsa_errno(WSAGetLastError());
-
+	int rc;
+	if (is_socket(sockfd)) {
+		rc = getsockopt(sockfd, level, optname, (char *)optval, optlen);
+		if (rc != 0) {
+			rc = wsa_errno(WSAGetLastError());
+		}
+	} else {
+		rc = -1;
+	}
+	return rc;
 }
 
 int
 posix_setsockopt(int sockfd, int level, int optname,
 	const void *optval, socklen_t optlen)
 {
-	int rc = setsockopt(sockfd, level, optname, (char *)optval, optlen);
-	return rc == 0 ? 0 : wsa_errno(WSAGetLastError());
+	int rc;
+	if (is_socket(sockfd)) {
+		rc = setsockopt(sockfd, level, optname, (char *)optval, optlen);
+		if (rc != 0) {
+			rc = wsa_errno(WSAGetLastError());
+		}
+	} else {
+		rc = -1;
+	}
+	return rc;
 }
 
 uid_t getuid(void)
@@ -241,5 +307,4 @@ int gettimeofday(struct timeval * tp, struct timezone * tzp)
 	tp->tv_usec = (long)(system_time.wMilliseconds * 1000);
 	return 0;
 }
-
 #endif
diff --git a/include/compat/sys/types.h b/include/compat/sys/types.h
index 4967843..59664bc 100644
--- a/include/compat/sys/types.h
+++ b/include/compat/sys/types.h
@@ -45,18 +45,6 @@ typedef SSIZE_T ssize_t;
 
 #endif
 
-#if !defined(HAVE_ATTRIBUTE__BOUNDED__) && !defined(__bounded__)
-# define __bounded__(x, y, z)
-#endif
-
-#if !defined(HAVE_ATTRIBUTE__DEAD) && !defined(__dead)
-#ifdef _MSC_VER
-#define __dead      __declspec(noreturn)
-#else
-#define __dead      __attribute__((__noreturn__))
-#endif
-#endif
-
 #ifdef _WIN32
 #define __warn_references(sym,msg)
 #else
diff --git a/include/compat/unistd.h b/include/compat/unistd.h
index 5e6ab1d..2583a6e 100644
--- a/include/compat/unistd.h
+++ b/include/compat/unistd.h
@@ -64,6 +64,10 @@ int getentropy(void *buf, size_t buflen);
 #endif
 #endif
 
+#ifndef HAVE_GETOPT
+#include <getopt.h>
+#endif
+
 #ifndef HAVE_GETPAGESIZE
 int getpagesize(void);
 #endif
diff --git a/include/tls.h b/include/tls.h
index 0c9e497..59b2c4c 100644
--- a/include/tls.h
+++ b/include/tls.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls.h,v 1.62 2022/03/24 15:56:34 tb Exp $ */
+/* $OpenBSD: tls.h,v 1.63 2023/07/02 06:37:27 beck Exp $ */
 /*
  * Copyright (c) 2014 Joel Sing <jsing@openbsd.org>
  *
@@ -36,14 +36,18 @@ typedef SSIZE_T ssize_t;
 
 #define TLS_API	20200120
 
-#define TLS_PROTOCOL_TLSv1_0	(1 << 1)
-#define TLS_PROTOCOL_TLSv1_1	(1 << 2)
+/*
+ * Deprecated versions of TLS. Using these effectively selects
+ * the minimum supported version.
+ */
+#define TLS_PROTOCOL_TLSv1_0	(1 << 3)
+#define TLS_PROTOCOL_TLSv1_1	(1 << 3)
+/* Supported versions of TLS */
 #define TLS_PROTOCOL_TLSv1_2	(1 << 3)
 #define TLS_PROTOCOL_TLSv1_3	(1 << 4)
 
 #define TLS_PROTOCOL_TLSv1 \
-	(TLS_PROTOCOL_TLSv1_0|TLS_PROTOCOL_TLSv1_1|\
-	 TLS_PROTOCOL_TLSv1_2|TLS_PROTOCOL_TLSv1_3)
+	(TLS_PROTOCOL_TLSv1_2|TLS_PROTOCOL_TLSv1_3)
 
 #define TLS_PROTOCOLS_ALL TLS_PROTOCOL_TLSv1
 #define TLS_PROTOCOLS_DEFAULT (TLS_PROTOCOL_TLSv1_2|TLS_PROTOCOL_TLSv1_3)
diff --git a/man/tls_config_set_protocols.3 b/man/tls_config_set_protocols.3
index 7c62493..32b8cce 100644
--- a/man/tls_config_set_protocols.3
+++ b/man/tls_config_set_protocols.3
@@ -1,4 +1,4 @@
-.\" $OpenBSD: tls_config_set_protocols.3,v 1.11 2021/01/02 19:58:44 schwarze Exp $
+.\" $OpenBSD: tls_config_set_protocols.3,v 1.12 2023/07/02 06:37:27 beck Exp $
 .\"
 .\" Copyright (c) 2014 Ted Unangst <tedu@openbsd.org>
 .\" Copyright (c) 2015, 2016 Joel Sing <jsing@openbsd.org>
@@ -16,7 +16,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: January 2 2021 $
+.Dd $Mdocdate: July 2 2023 $
 .Dt TLS_CONFIG_SET_PROTOCOLS 3
 .Os
 .Sh NAME
@@ -76,10 +76,6 @@ Possible values are the bitwise OR of:
 .Pp
 .Bl -item -offset indent -compact
 .It
-.Dv TLS_PROTOCOL_TLSv1_0
-.It
-.Dv TLS_PROTOCOL_TLSv1_1
-.It
 .Dv TLS_PROTOCOL_TLSv1_2
 .It
 .Dv TLS_PROTOCOL_TLSv1_3
@@ -87,7 +83,7 @@ Possible values are the bitwise OR of:
 .Pp
 Additionally, the values
 .Dv TLS_PROTOCOL_TLSv1
-(TLSv1.0, TLSv1.1, TLSv1.2, TLSv1.3),
+(TLSv1.2, TLSv1.3),
 .Dv TLS_PROTOCOLS_ALL
 (all supported protocols) and
 .Dv TLS_PROTOCOLS_DEFAULT
@@ -106,8 +102,6 @@ The protocol string is a comma or colon separated list of keywords.
 Valid keywords are:
 .Pp
 .Bl -tag -width "tlsv1.3" -offset indent -compact
-.It Dv tlsv1.0
-.It Dv tlsv1.1
 .It Dv tlsv1.2
 .It Dv tlsv1.3
 .It Dv all
diff --git a/tls.c b/tls.c
index 18b93ef..d387952 100644
--- a/tls.c
+++ b/tls.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls.c,v 1.96 2023/05/25 07:46:21 op Exp $ */
+/* $OpenBSD: tls.c,v 1.98 2023/07/02 06:37:27 beck Exp $ */
 /*
  * Copyright (c) 2014 Joel Sing <jsing@openbsd.org>
  *
@@ -580,16 +580,12 @@ tls_configure_ssl(struct tls *ctx, SSL_CTX *ssl_ctx)
 
 	SSL_CTX_set_options(ssl_ctx, SSL_OP_NO_SSLv2);
 	SSL_CTX_set_options(ssl_ctx, SSL_OP_NO_SSLv3);
+	SSL_CTX_set_options(ssl_ctx, SSL_OP_NO_TLSv1);
+	SSL_CTX_set_options(ssl_ctx, SSL_OP_NO_TLSv1_1);
 
-	SSL_CTX_clear_options(ssl_ctx, SSL_OP_NO_TLSv1);
-	SSL_CTX_clear_options(ssl_ctx, SSL_OP_NO_TLSv1_1);
 	SSL_CTX_clear_options(ssl_ctx, SSL_OP_NO_TLSv1_2);
 	SSL_CTX_clear_options(ssl_ctx, SSL_OP_NO_TLSv1_3);
 
-	if ((ctx->config->protocols & TLS_PROTOCOL_TLSv1_0) == 0)
-		SSL_CTX_set_options(ssl_ctx, SSL_OP_NO_TLSv1);
-	if ((ctx->config->protocols & TLS_PROTOCOL_TLSv1_1) == 0)
-		SSL_CTX_set_options(ssl_ctx, SSL_OP_NO_TLSv1_1);
 	if ((ctx->config->protocols & TLS_PROTOCOL_TLSv1_2) == 0)
 		SSL_CTX_set_options(ssl_ctx, SSL_OP_NO_TLSv1_2);
 	if ((ctx->config->protocols & TLS_PROTOCOL_TLSv1_3) == 0)
diff --git a/tls_config.c b/tls_config.c
index 864ef29..59c69f0 100644
--- a/tls_config.c
+++ b/tls_config.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls_config.c,v 1.66 2023/05/14 07:26:25 op Exp $ */
+/* $OpenBSD: tls_config.c,v 1.67 2023/07/02 06:37:27 beck Exp $ */
 /*
  * Copyright (c) 2014 Joel Sing <jsing@openbsd.org>
  *
@@ -251,9 +251,9 @@ tls_config_parse_protocols(uint32_t *protocols, const char *protostr)
 		if (strcasecmp(p, "tlsv1") == 0)
 			proto = TLS_PROTOCOL_TLSv1;
 		else if (strcasecmp(p, "tlsv1.0") == 0)
-			proto = TLS_PROTOCOL_TLSv1_0;
+			proto = TLS_PROTOCOL_TLSv1_2;
 		else if (strcasecmp(p, "tlsv1.1") == 0)
-			proto = TLS_PROTOCOL_TLSv1_1;
+			proto = TLS_PROTOCOL_TLSv1_2;
 		else if (strcasecmp(p, "tlsv1.2") == 0)
 			proto = TLS_PROTOCOL_TLSv1_2;
 		else if (strcasecmp(p, "tlsv1.3") == 0)
diff --git a/tls_internal.h b/tls_internal.h
index 7424750..e1dcf35 100644
--- a/tls_internal.h
+++ b/tls_internal.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls_internal.h,v 1.81 2023/04/09 18:26:26 tb Exp $ */
+/* $OpenBSD: tls_internal.h,v 1.83 2023/06/27 18:19:59 tb Exp $ */
 /*
  * Copyright (c) 2014 Jeremie Courreges-Anglas <jca@openbsd.org>
  * Copyright (c) 2014 Joel Sing <jsing@openbsd.org>
@@ -28,6 +28,10 @@
 
 __BEGIN_HIDDEN_DECLS
 
+#ifndef TLS_DEFAULT_CA_FILE
+#define TLS_DEFAULT_CA_FILE	"/etc/ssl/cert.pem"
+#endif
+
 #define TLS_CIPHERS_DEFAULT	TLS_CIPHERS_COMPAT
 #define TLS_CIPHERS_COMPAT	"HIGH:!aNULL"
 #define TLS_CIPHERS_LEGACY	"HIGH:MEDIUM:!aNULL"
diff --git a/tls_signer.c b/tls_signer.c
index 97e5e38..76150fd 100644
--- a/tls_signer.c
+++ b/tls_signer.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls_signer.c,v 1.5 2023/04/09 18:26:26 tb Exp $ */
+/* $OpenBSD: tls_signer.c,v 1.9 2023/06/18 19:12:58 tb Exp $ */
 /*
  * Copyright (c) 2021 Eric Faurot <eric@openbsd.org>
  *
@@ -424,17 +424,26 @@ EC_KEY_METHOD *
 tls_signer_ecdsa_method(void)
 {
 	static EC_KEY_METHOD *ecdsa_method = NULL;
+	const EC_KEY_METHOD *default_method;
+	int (*sign)(int type, const unsigned char *dgst, int dlen,
+	    unsigned char *sig, unsigned int *siglen,
+	    const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey);
+	int (*sign_setup)(EC_KEY *eckey, BN_CTX *ctx_in,
+	    BIGNUM **kinvp, BIGNUM **rp);
 
 	pthread_mutex_lock(&signer_method_lock);
 
 	if (ecdsa_method != NULL)
 		goto out;
 
-	ecdsa_method = EC_KEY_METHOD_new(NULL);
+	default_method = EC_KEY_get_default_method();
+	ecdsa_method = EC_KEY_METHOD_new(default_method);
 	if (ecdsa_method == NULL)
 		goto out;
 
-	EC_KEY_METHOD_set_sign(ecdsa_method, NULL, NULL, tls_ecdsa_do_sign);
+	EC_KEY_METHOD_get_sign(default_method, &sign, &sign_setup, NULL);
+	EC_KEY_METHOD_set_sign(ecdsa_method, sign, sign_setup,
+	    tls_ecdsa_do_sign);
 
  out:
 	pthread_mutex_unlock(&signer_method_lock);
diff --git a/tls_verify.c b/tls_verify.c
index 0cb86f6..c588f02 100644
--- a/tls_verify.c
+++ b/tls_verify.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls_verify.c,v 1.23 2023/05/11 07:35:27 tb Exp $ */
+/* $OpenBSD: tls_verify.c,v 1.28 2023/06/01 07:32:25 tb Exp $ */
 /*
  * Copyright (c) 2014 Jeremie Courreges-Anglas <jca@openbsd.org>
  *
@@ -92,15 +92,21 @@ tls_check_subject_altname(struct tls *ctx, X509 *cert, const char *name,
 	union tls_addr addrbuf;
 	int addrlen, type;
 	int count, i;
-	int rv = 0;
+	int critical = 0;
+	int rv = -1;
 
 	*alt_match = 0;
 	*alt_exists = 0;
 
-	altname_stack = X509_get_ext_d2i(cert, NID_subject_alt_name,
-	    NULL, NULL);
-	if (altname_stack == NULL)
-		return 0;
+	altname_stack = X509_get_ext_d2i(cert, NID_subject_alt_name, &critical,
+	    NULL);
+	if (altname_stack == NULL) {
+		if (critical != -1) {
+			tls_set_errorx(ctx, "error decoding subjectAltName");
+			goto err;
+		}
+		goto done;
+	}
 
 	if (inet_pton(AF_INET, name, &addrbuf) == 1) {
 		type = GEN_IPADD;
@@ -140,8 +146,7 @@ tls_check_subject_altname(struct tls *ctx, X509 *cert, const char *name,
 					    "NUL byte in subjectAltName, "
 					    "probably a malicious certificate",
 					    name);
-					rv = -1;
-					break;
+					goto err;
 				}
 
 				/*
@@ -154,13 +159,12 @@ tls_check_subject_altname(struct tls *ctx, X509 *cert, const char *name,
 					    "error verifying name '%s': "
 					    "a dNSName of \" \" must not be "
 					    "used", name);
-					rv = -1;
-					break;
+					goto err;
 				}
 
 				if (tls_match_name(data, name) == 0) {
 					*alt_match = 1;
-					break;
+					goto done;
 				}
 			} else {
 #ifdef DEBUG
@@ -181,8 +185,7 @@ tls_check_subject_altname(struct tls *ctx, X509 *cert, const char *name,
 				tls_set_errorx(ctx,
 				    "Unexpected negative length for an "
 				    "IP address: %d", datalen);
-				rv = -1;
-				break;
+				goto err;
 			}
 
 			/*
@@ -192,11 +195,15 @@ tls_check_subject_altname(struct tls *ctx, X509 *cert, const char *name,
 			if (datalen == addrlen &&
 			    memcmp(data, &addrbuf, addrlen) == 0) {
 				*alt_match = 1;
-				break;
+				goto done;
 			}
 		}
 	}
 
+ done:
+	rv = 0;
+
+ err:
 	sk_GENERAL_NAME_pop_free(altname_stack, GENERAL_NAME_free);
 	return rv;
 }
@@ -205,10 +212,13 @@ static int
 tls_check_common_name(struct tls *ctx, X509 *cert, const char *name,
     int *cn_match)
 {
+	unsigned char *utf8_bytes = NULL;
 	X509_NAME *subject_name;
 	char *common_name = NULL;
 	union tls_addr addrbuf;
 	int common_name_len;
+	ASN1_STRING *data;
+	int lastpos = -1;
 	int rv = -1;
 
 	*cn_match = 0;
@@ -217,29 +227,65 @@ tls_check_common_name(struct tls *ctx, X509 *cert, const char *name,
 	if (subject_name == NULL)
 		goto done;
 
-	common_name_len = X509_NAME_get_text_by_NID(subject_name,
-	    NID_commonName, NULL, 0);
-	if (common_name_len < 0)
+	lastpos = X509_NAME_get_index_by_NID(subject_name,
+	    NID_commonName, lastpos);
+	if (lastpos == -1)
 		goto done;
-
-	common_name = calloc(common_name_len + 1, 1);
-	if (common_name == NULL) {
-		tls_set_error(ctx, "out of memory");
+	if (lastpos < 0)
+		goto err;
+	if (X509_NAME_get_index_by_NID(subject_name, NID_commonName, lastpos)
+	    != -1) {
+		/*
+		 * Having multiple CN's is possible, and even happened back in
+		 * the glory days of mullets and Hammer pants. In anything like
+		 * a modern TLS cert, CN is as close to deprecated as it gets,
+		 * and having more than one is bad. We therefore fail if we have
+		 * more than one CN fed to us in the subject, treating the
+		 * certificate as hostile.
+		 */
+		tls_set_errorx(ctx, "error verifying name '%s': "
+		    "Certificate subject contains mutiple Common Name fields, "
+		    "probably a malicious or malformed certificate", name);
 		goto err;
 	}
 
-	X509_NAME_get_text_by_NID(subject_name, NID_commonName, common_name,
-	    common_name_len + 1);
-
-	/* NUL bytes in CN? */
-	if (common_name_len < 0 ||
-	    (size_t)common_name_len != strlen(common_name)) {
+	data = X509_NAME_ENTRY_get_data(X509_NAME_get_entry(subject_name,
+	    lastpos));
+	/*
+	 * Fail if we cannot encode the CN bytes as UTF-8.
+	 */
+	if ((common_name_len = ASN1_STRING_to_UTF8(&utf8_bytes, data)) < 0) {
+		tls_set_errorx(ctx, "error verifying name '%s': "
+		    "Common Name field cannot be encoded as a UTF-8 string, "
+		    "probably a malicious certificate", name);
+		goto err;
+	}
+	/*
+	 * Fail if the CN is of invalid length. RFC 5280 specifies that a CN
+	 * must be between 1 and 64 bytes long.
+	 */
+	if (common_name_len < 1 || common_name_len > 64) {
+		tls_set_errorx(ctx, "error verifying name '%s': "
+		    "Common Name field has invalid length, "
+		    "probably a malicious certificate", name);
+		goto err;
+	}
+	/*
+	 * Fail if the resulting text contains a NUL byte.
+	 */
+	if (memchr(utf8_bytes, 0, common_name_len) != NULL) {
 		tls_set_errorx(ctx, "error verifying name '%s': "
 		    "NUL byte in Common Name field, "
 		    "probably a malicious certificate", name);
 		goto err;
 	}
 
+	common_name = strndup(utf8_bytes, common_name_len);
+	if (common_name == NULL) {
+		tls_set_error(ctx, "out of memory");
+		goto err;
+	}
+
 	/*
 	 * We don't want to attempt wildcard matching against IP addresses,
 	 * so perform a simple comparison here.
@@ -258,6 +304,7 @@ tls_check_common_name(struct tls *ctx, X509 *cert, const char *name,
 	rv = 0;
 
  err:
+	free(utf8_bytes);
 	free(common_name);
 	return rv;
 }