Add test for mbedtls_x509write_crt_set_ext_key_usage, and fix reversed order

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/x509write_crt.c b/library/x509write_crt.c
index c48c32b..d0aaa9f 100644
--- a/library/x509write_crt.c
+++ b/library/x509write_crt.c
@@ -303,18 +303,22 @@
     unsigned char *c = buf + sizeof(buf);
     int ret;
     size_t len = 0;
+    const mbedtls_asn1_sequence *last_ext = 0, *ext;
 
+    /* We need at least one extension: SEQUENCE SIZE (1..MAX) OF KeyPurposeId */
     if( exts == NULL )
         return( MBEDTLS_ERR_X509_BAD_INPUT_DATA );
 
-    while( exts != NULL )
+    /* Iterate over exts backwards, so we write them out in the requested order */
+    while( last_ext != exts )
     {
-        if( exts->buf.tag != MBEDTLS_ASN1_OID )
+        for( ext = exts; ext->next != last_ext; ext = ext->next ) {}
+        if( ext->buf.tag != MBEDTLS_ASN1_OID )
             return( MBEDTLS_ERR_X509_BAD_INPUT_DATA );
-        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( &c, buf, exts->buf.p, exts->buf.len ) );
-        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, exts->buf.len ) );
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( &c, buf, ext->buf.p, ext->buf.len ) );
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, ext->buf.len ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_OID ) );
-        exts = exts->next;
+        last_ext = ext;
     }
 
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
diff --git a/tests/data_files/server1.key_ext_usage.crt b/tests/data_files/server1.key_ext_usage.crt
new file mode 100644
index 0000000..4e7f214
--- /dev/null
+++ b/tests/data_files/server1.key_ext_usage.crt
@@ -0,0 +1,20 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/server1.key_ext_usages.crt b/tests/data_files/server1.key_ext_usages.crt
new file mode 100644
index 0000000..4913643
--- /dev/null
+++ b/tests/data_files/server1.key_ext_usages.crt
@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/suites/test_suite_x509write.data b/tests/suites/test_suite_x509write.data
index 1844e5c..8411557 100644
--- a/tests/suites/test_suite_x509write.data
+++ b/tests/suites/test_suite_x509write.data
@@ -56,87 +56,95 @@
 
 Certificate write check Server1 SHA1
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:-1:"data_files/server1.crt":0:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"data_files/server1.crt":0:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, not before 1970
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"19700210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:-1:"":0:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"19700210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"":0:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, not after 2050
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20500210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:-1:"":0:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20500210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"":0:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, not before 1970, not after 2050
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"19700210144406":"20500210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:-1:"":0:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"19700210144406":"20500210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"":0:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, not before 2050, not after 2059
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20500210144406":"20590210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:-1:"":0:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20500210144406":"20590210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"":0:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, key_usage
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:MBEDTLS_X509_KU_DIGITAL_SIGNATURE | MBEDTLS_X509_KU_NON_REPUDIATION | MBEDTLS_X509_KU_KEY_ENCIPHERMENT:1:0:0:1:-1:"data_files/server1.key_usage.crt":0:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:MBEDTLS_X509_KU_DIGITAL_SIGNATURE | MBEDTLS_X509_KU_NON_REPUDIATION | MBEDTLS_X509_KU_KEY_ENCIPHERMENT:1:"NULL":0:0:1:-1:"data_files/server1.key_usage.crt":0:0:"data_files/test-ca.crt"
+
+Certificate write check Server1 SHA1, one ext_key_usage
+depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20110212144406":"20210212144406":MBEDTLS_MD_SHA1:0:0:"serverAuth":0:0:1:-1:"data_files/server1.key_ext_usage.crt":0:0:"data_files/test-ca.crt"
+
+Certificate write check Server1 SHA1, two ext_key_usages
+depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20110212144406":"20210212144406":MBEDTLS_MD_SHA1:0:0:"codeSigning,timeStamping":0:0:1:-1:"data_files/server1.key_ext_usages.crt":0:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, ns_cert_type
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:MBEDTLS_X509_NS_CERT_TYPE_SSL_SERVER:1:1:-1:"data_files/server1.cert_type.crt":0:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":MBEDTLS_X509_NS_CERT_TYPE_SSL_SERVER:1:1:-1:"data_files/server1.cert_type.crt":0:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, version 1
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:MBEDTLS_X509_CRT_VERSION_1:"data_files/server1.v1.crt":0:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:MBEDTLS_X509_CRT_VERSION_1:"data_files/server1.v1.crt":0:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, CA
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:-1:"data_files/server1.ca.crt":0:1:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"data_files/server1.ca.crt":0:1:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, RSA_ALT
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:0:-1:"data_files/server1.noauthid.crt":1:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:0:-1:"data_files/server1.noauthid.crt":1:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, RSA_ALT, key_usage
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:MBEDTLS_X509_KU_DIGITAL_SIGNATURE | MBEDTLS_X509_KU_NON_REPUDIATION | MBEDTLS_X509_KU_KEY_ENCIPHERMENT:1:0:0:0:-1:"data_files/server1.key_usage_noauthid.crt":1:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:MBEDTLS_X509_KU_DIGITAL_SIGNATURE | MBEDTLS_X509_KU_NON_REPUDIATION | MBEDTLS_X509_KU_KEY_ENCIPHERMENT:1:"NULL":0:0:0:-1:"data_files/server1.key_usage_noauthid.crt":1:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, RSA_ALT, ns_cert_type
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:MBEDTLS_X509_NS_CERT_TYPE_SSL_SERVER:1:0:-1:"data_files/server1.cert_type_noauthid.crt":1:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":MBEDTLS_X509_NS_CERT_TYPE_SSL_SERVER:1:0:-1:"data_files/server1.cert_type_noauthid.crt":1:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, RSA_ALT, version 1
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:0:MBEDTLS_X509_CRT_VERSION_1:"data_files/server1.v1.crt":1:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:0:MBEDTLS_X509_CRT_VERSION_1:"data_files/server1.v1.crt":1:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, RSA_ALT, CA
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:0:-1:"data_files/server1.ca_noauthid.crt":1:1:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:0:-1:"data_files/server1.ca_noauthid.crt":1:1:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, Opaque
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_USE_PSA_CRYPTO
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:-1:"data_files/server1.crt":2:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"data_files/server1.crt":2:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, Opaque, key_usage
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_USE_PSA_CRYPTO
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:MBEDTLS_X509_KU_DIGITAL_SIGNATURE | MBEDTLS_X509_KU_NON_REPUDIATION | MBEDTLS_X509_KU_KEY_ENCIPHERMENT:1:0:0:1:-1:"data_files/server1.key_usage.crt":2:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:MBEDTLS_X509_KU_DIGITAL_SIGNATURE | MBEDTLS_X509_KU_NON_REPUDIATION | MBEDTLS_X509_KU_KEY_ENCIPHERMENT:1:"NULL":0:0:1:-1:"data_files/server1.key_usage.crt":2:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, Opaque, ns_cert_type
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_USE_PSA_CRYPTO
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:MBEDTLS_X509_NS_CERT_TYPE_SSL_SERVER:1:1:-1:"data_files/server1.cert_type.crt":2:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":MBEDTLS_X509_NS_CERT_TYPE_SSL_SERVER:1:1:-1:"data_files/server1.cert_type.crt":2:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, Opaque, version 1
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_USE_PSA_CRYPTO
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:MBEDTLS_X509_CRT_VERSION_1:"data_files/server1.v1.crt":2:0:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:MBEDTLS_X509_CRT_VERSION_1:"data_files/server1.v1.crt":2:0:"data_files/test-ca.crt"
 
 Certificate write check Server1 SHA1, Opaque, CA
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_USE_PSA_CRYPTO
-x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:0:0:1:-1:"data_files/server1.ca.crt":2:1:"data_files/test-ca.crt"
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"data_files/server1.ca.crt":2:1:"data_files/test-ca.crt"
 
 Certificate write check Server5 ECDSA
 depends_on:MBEDTLS_HAS_ALG_SHA_256_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_ECDSA_C:MBEDTLS_ECDSA_DETERMINISTIC:MBEDTLS_ECP_DP_SECP384R1_ENABLED:MBEDTLS_ECP_DP_SECP256R1_ENABLED
-x509_crt_check:"data_files/server5.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca2.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=Polarssl Test EC CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA256:0:0:0:0:1:-1:"data_files/server5.crt":0:0:"data_files/test-ca2.crt"
+x509_crt_check:"data_files/server5.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca2.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=Polarssl Test EC CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA256:0:0:"NULL":0:0:1:-1:"data_files/server5.crt":0:0:"data_files/test-ca2.crt"
 
 Certificate write check Server5 ECDSA, Opaque
 depends_on:MBEDTLS_HAS_ALG_SHA_256_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_ECDSA_C:MBEDTLS_ECDSA_DETERMINISTIC:MBEDTLS_ECP_DP_SECP384R1_ENABLED:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_USE_PSA_CRYPTO
-x509_crt_check:"data_files/server5.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca2.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=Polarssl Test EC CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA256:0:0:0:0:1:-1:"":2:0:"data_files/test-ca2.crt"
+x509_crt_check:"data_files/server5.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca2.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=Polarssl Test EC CA":"1":"20190210144406":"20290210144406":MBEDTLS_MD_SHA256:0:0:"NULL":0:0:1:-1:"":2:0:"data_files/test-ca2.crt"
 
 X509 String to Names #1
 mbedtls_x509_string_to_names:"C=NL,O=Offspark\, Inc., OU=PolarSSL":"C=NL, O=Offspark\, Inc., OU=PolarSSL":0
diff --git a/tests/suites/test_suite_x509write.function b/tests/suites/test_suite_x509write.function
index 9cb3dd4..3242232 100644
--- a/tests/suites/test_suite_x509write.function
+++ b/tests/suites/test_suite_x509write.function
@@ -238,6 +238,7 @@
                      char *issuer_pwd, char *issuer_name,
                      char *serial_str, char *not_before, char *not_after,
                      int md_type, int key_usage, int set_key_usage,
+                     char *ext_key_usage,
                      int cert_type, int set_cert_type, int auth_ident,
                      int ver, char *cert_check_file, int pk_wrap, int is_ca,
                      char *cert_verify_file )
@@ -346,6 +347,24 @@
             TEST_ASSERT( mbedtls_x509write_crt_set_key_usage( &crt, key_usage ) == 0 );
         if( set_cert_type != 0 )
             TEST_ASSERT( mbedtls_x509write_crt_set_ns_cert_type( &crt, cert_type ) == 0 );
+        if( strcmp( ext_key_usage, "NULL" ) != 0 )
+        {
+            mbedtls_asn1_sequence exts[2] = { };
+#define SET_OID(x, oid) \
+    do { x.len = MBEDTLS_OID_SIZE(oid); x.p = (unsigned char*)oid; \
+         x.tag = MBEDTLS_ASN1_OID; } while( 0 )
+            if( strcmp( ext_key_usage, "serverAuth" ) == 0 )
+            {
+              SET_OID( exts[0].buf, MBEDTLS_OID_SERVER_AUTH );
+            }
+            else if( strcmp( ext_key_usage, "codeSigning,timeStamping" ) == 0 )
+            {
+              SET_OID( exts[0].buf, MBEDTLS_OID_CODE_SIGNING );
+              exts[0].next = &exts[1];
+              SET_OID( exts[1].buf, MBEDTLS_OID_TIME_STAMPING );
+            }
+            TEST_ASSERT( mbedtls_x509write_crt_set_ext_key_usage( &crt, exts ) == 0 );
+        }
     }
 
     ret = mbedtls_x509write_crt_pem( &crt, buf, sizeof( buf ),