Add getDhparamInfo

README.md

@@ -166,6 +166,17 @@ Where
   * **certificate** is a PEM encoded certificate, CSR or private key
   * **callback** is a callback function with an error object and `{modulus}`
 
+### Get DH parameter information
+
+Use `getDhparamInfo` to get the size and prime of DH parameters.
+
+    pem.getDhparamInfo(dhparam, callback)
+
+Where
+
+  * **dhparam** is a PEM encoded DH parameters string
+  * **callback** is a callback function with an error object and `{size, prime}`
+
 ### Setting openssl location
 
 In some systems the `openssl` executable might not be available by the default name or it is not included in $PATH. In this case you can define the location of the executable yourself as a one time action after you have loaded the pem module:

lib/pem.js

@@ -19,6 +19,7 @@ module.exports.getPublicKey = getPublicKey;
 module.exports.getFingerprint = getFingerprint;
 module.exports.getModulus = getModulus;
 module.exports.getModulusFromProtected = getModulusFromProtected;
+module.exports.getDhparamInfo = getDhparamInfo;
 module.exports.config = config;
 
 // PUBLIC API
@@ -465,6 +466,53 @@ function getModulusFromProtected(key, password, callback){
     });
 }
 
+/**
+ * get the size and prime of DH parameters
+ *
+ * @param {String} DH parameters, PEM encoded
+ * @param {Function} callback Callback function with an error object and {size, prime}
+ */
+function getDhparamInfo(dh, callback) {
+    dh = Buffer.isBuffer(dh) && dh.toString() || dh;
+
+    var params = [
+        'dh',
+        '-text',
+        '-in',
+        '--TMPFILE--'
+    ];
+
+    spawnWrapper(params, dh, function(err, code, stdout) {
+        if (err) {
+            return callback(err);
+        }
+
+        var result = {};
+        var match = stdout.match(/Parameters: \((\d+) bit\)/);
+
+        if (match) {
+            result.size = Number(match[1]);
+        }
+
+        var prime = '';
+        stdout.split('\n').forEach(function (line) {
+            if (/\s+([0-9a-f][0-9a-f]:)+[0-9a-f]?[0-9a-f]?/g.test(line)) {
+                prime += line.trim();
+            }
+        });
+
+        if (prime) {
+            result.prime = prime;
+        }
+
+        if (!match && !prime) {
+            return callback(new Error('No DH info found'));
+        }
+
+        return callback(null, result);
+    });
+}
+
 /**
  * config the pem module
  * @param {Object} options

test/fixtures/test.dh

@@ -0,0 +1,5 @@
+-----BEGIN DH PARAMETERS-----
+MIGHAoGBAMYXwgiuPY6TqxODWXbRRWx6eWoJuGkjKN8RjhBiLxFJzwgpdfONv5iG
+IHHGI8/IfhHI78Mqq+5z3z8L16fuOYnpbaDa2BSUdHZQQmFiCV748lOv9he08UJ5
+qgrFgdgi56V4FdRs2EHJnezvYmviAbIsi8imn+9TVed4DnOmuE1rAgEC
+-----END DH PARAMETERS-----

test/pem.js

@@ -405,6 +405,7 @@ exports['General Tests'] = {
             });
         });
     },
+
     'Get modulus from a protected key': function(test) {
         var certificate = fs.readFileSync('./test/fixtures/test.crt').toString();
         var key = fs.readFileSync('./test/fixtures/test.key').toString();
@@ -425,8 +426,24 @@ exports['General Tests'] = {
                 test.done();
             });
         });
+    },
 
+    'Get DH param info': function(test) {
+        var dh = fs.readFileSync('./test/fixtures/test.dh').toString();
+
+        pem.getDhparamInfo(dh, function(error, data) {
+            var size = data && data.size || 0;
+            var prime = (data && data.prime || '').toString();
+            test.ifError(error);
+            test.ok(size);
+            test.ok(prime);
+            test.ok(fs.readdirSync('./tmp').length === 0);
+            test.equal(typeof size, 'number');
+            test.ok(/([0-9a-f][0-9a-f]:)+[0-9a-f][0-9a-f]$/g.test(prime));
+            test.done();
+        });
     },
+
     'Create and verify wildcard certificate': function(test) {
         var certInfo = {
             commonName: '*.node.ee'