diff --git a/include/polarssl/x509write.h b/include/polarssl/x509write.h
index 6710474..a8e672a 100644
--- a/include/polarssl/x509write.h
+++ b/include/polarssl/x509write.h
@@ -130,13 +130,39 @@
  *                  (e.g. KU_DIGITAL_SIGNATURE | KU_KEY_CERT_SIGN)
  *
  * \param ctx       CSR context to use
- * \param key_usage key usage bitstring to set
+ * \param key_usage key usage flags to set
  *
  * \return          0 if successful, or POLARSSL_ERR_X509WRITE_MALLOC_FAILED
  */
 int x509write_csr_set_key_usage( x509_csr *ctx, unsigned char key_usage );
 
 /**
+ * \brief           Set the Netscape Cert Type flags
+ *                  (e.g. NS_CERT_TYPE_SSL_CLIENT | NS_CERT_TYPE_EMAIL)
+ *
+ * \param ctx           CSR context to use
+ * \param ns_cert_type  Netscape Cert Type flags to set
+ *
+ * \return          0 if successful, or POLARSSL_ERR_X509WRITE_MALLOC_FAILED
+ */
+int x509write_csr_set_ns_cert_type( x509_csr *ctx, unsigned char ns_cert_type );
+
+/**
+ * \brief           Generic function to add to or replace an extension in the CSR
+ *
+ * \param ctx       CSR context to use
+ * \param oid       OID of the extension
+ * \param oid_len   length of the OID
+ * \param val       value of the extension OCTET STRING
+ * \param val_len   length of the value data
+ *
+ * \return          0 if successful, or a POLARSSL_ERR_X509WRITE_MALLOC_FAILED
+ */
+int x509write_csr_set_extension( x509_csr *ctx,
+                                 const char *oid, size_t oid_len,
+                                 const unsigned char *val, size_t val_len );
+
+/**
  * \brief           Free the contents of a CSR context
  *
  * \param ctx       CSR context to free
diff --git a/library/x509write.c b/library/x509write.c
index 0ca7733..f609fb4 100644
--- a/library/x509write.c
+++ b/library/x509write.c
@@ -156,14 +156,14 @@
     return( ret );
 }
 
-int x509write_csr_set_key_usage( x509_csr *ctx, unsigned char key_usage )
+int x509write_csr_set_extension( x509_csr *ctx,
+                                 const char *oid, size_t oid_len,
+                                 const unsigned char *val, size_t val_len )
 {
     asn1_named_data *cur;
-    unsigned char *c;
-    int len;
 
-    if( ( cur = asn1_find_named_data( ctx->extensions, OID_KEY_USAGE,
-                                      OID_SIZE( OID_KEY_USAGE ) ) ) == NULL )
+    if( ( cur = asn1_find_named_data( ctx->extensions, oid,
+                                      oid_len ) ) == NULL )
     {
         cur = polarssl_malloc( sizeof(asn1_named_data) );
         if( cur == NULL )
@@ -171,32 +171,84 @@
 
         memset( cur, 0, sizeof(asn1_named_data) );
 
-        cur->oid.len = OID_SIZE( OID_KEY_USAGE );
-        cur->oid.p = polarssl_malloc( cur->oid.len );
+        cur->oid.len = oid_len;
+        cur->oid.p = polarssl_malloc( oid_len );
         if( cur->oid.p == NULL )
         {
-            free( cur );
+            polarssl_free( cur );
             return( POLARSSL_ERR_X509WRITE_MALLOC_FAILED );
         }
 
-        cur->val.len = 4;
-        cur->val.p = polarssl_malloc( cur->val.len );
+        cur->val.len = val_len;
+        cur->val.p = polarssl_malloc( val_len );
         if( cur->val.p == NULL )
         {
-            free( cur->oid.p );
-            free( cur );
+            polarssl_free( cur->oid.p );
+            polarssl_free( cur );
             return( POLARSSL_ERR_X509WRITE_MALLOC_FAILED );
         }
 
-        memcpy( cur->oid.p, OID_KEY_USAGE, OID_SIZE( OID_KEY_USAGE ) );
+        memcpy( cur->oid.p, oid, oid_len );
 
         cur->next = ctx->extensions;
         ctx->extensions = cur;
     }
 
-    c = cur->val.p + cur->val.len;
-    if( ( len = asn1_write_bitstring( &c, cur->val.p, &key_usage, 6 ) ) < 0 )
-exit(1);
+    if( cur->val.len != val_len )
+    {
+        polarssl_free( cur->val.p );
+
+        cur->val.len = val_len;
+        cur->val.p = polarssl_malloc( val_len );
+        if( cur->val.p == NULL )
+        {
+            polarssl_free( cur->oid.p );
+            polarssl_free( cur );
+            return( POLARSSL_ERR_X509WRITE_MALLOC_FAILED );
+        }
+    }
+
+    memcpy( cur->val.p, val, val_len );
+
+    return( 0 );
+}
+
+int x509write_csr_set_key_usage( x509_csr *ctx, unsigned char key_usage )
+{
+    unsigned char buf[4];
+    unsigned char *c;
+    int ret;
+
+    c = buf + 4;
+
+    if( ( ret = asn1_write_bitstring( &c, buf, &key_usage, 6 ) ) != 4 )
+        return( ret );
+
+    ret = x509write_csr_set_extension( ctx, OID_KEY_USAGE,
+                                       OID_SIZE( OID_KEY_USAGE ),
+                                       buf, 4 );
+    if( ret != 0 )
+        return( ret );
+
+    return( 0 );
+}
+
+int x509write_csr_set_ns_cert_type( x509_csr *ctx, unsigned char ns_cert_type )
+{
+    unsigned char buf[4];
+    unsigned char *c;
+    int ret;
+
+    c = buf + 4;
+
+    if( ( ret = asn1_write_bitstring( &c, buf, &ns_cert_type, 8 ) ) != 4 )
+        return( ret );
+
+    ret = x509write_csr_set_extension( ctx, OID_NS_CERT_TYPE,
+                                       OID_SIZE( OID_NS_CERT_TYPE ),
+                                       buf, 4 );
+    if( ret != 0 )
+        return( ret );
 
     return( 0 );
 }