callagent: Provide Base64 and Random helper

For the Call-ID of SIP one requires a cryptogragic secure
source of random and the GST random number generator is not. For
Linux use /dev/random for others we don't have a solution yet.

callagent/SIPRandom.st

@@ -0,0 +1,55 @@
+"
+ (C) 2011 by Holger Hans Peter Freyther
+ All Rights Reserved
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Affero General Public License as
+ published by the Free Software Foundation, either version 3 of the
+ License, or (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU Affero General Public License for more details.
+
+ You should have received a copy of the GNU Affero General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+"
+
+Object subclass: SIPBase64 [
+    SIPBase64 class >> encode: aString [
+        ^ (Base64MimeConverter mimeEncode: aString readStream) contents
+    ]
+]
+
+Object subclass: SIPSecureRandom [
+    <comment: 'I try to give some cryptographically secure random numbers'>
+
+    SIPSecureRandom class >> nextByte [
+        <category: 'random'>
+        | file |
+        file := FileDescriptor open: '/dev/random' mode: 'r'.
+        [
+            ^ file next value.
+        ] ensure: [
+            file close.
+        ]
+    ]
+
+    SIPSecureRandom class >> nextInt [
+        <category: 'random'>
+        | file |
+        file := FileDescriptor open: '/dev/random' mode: 'r'.
+        [
+            | data |
+            data := ByteArray new: 4.
+            1 to: data size do: [:each |
+                data at: each put: file next value.
+            ].
+
+            ^ data uintAt: 1
+        ] ensure: [
+            file close.
+        ]
+    ]
+]