using System; using System.Collections.Generic; using System.IO; using System.Net; using System.Net.Security; using System.Text; using log4net; namespace OpenSim.Framework { /// /// Used for requests to untrusted endpoints that may potentially be /// malicious /// public static class UntrustedHttpWebRequest { /// Setting this to true will allow HTTP connections to localhost private const bool DEBUG = true; private static readonly ILog m_log = LogManager.GetLogger( System.Reflection.MethodBase.GetCurrentMethod().DeclaringType); private static readonly ICollection allowableSchemes = new List { "http", "https" }; /// /// Creates an HttpWebRequest that is hardened against malicious /// endpoints after ensuring the given Uri is safe to retrieve /// /// Web location to request /// A hardened HttpWebRequest if the uri was determined to be safe /// If uri is null /// If uri is unsafe public static HttpWebRequest Create(Uri uri) { return Create(uri, DEBUG, 1000 * 5, 1000 * 20, 10); } /// /// Creates an HttpWebRequest that is hardened against malicious /// endpoints after ensuring the given Uri is safe to retrieve /// /// Web location to request /// True to allow connections to localhost, otherwise false /// Read write timeout, in milliseconds /// Connection timeout, in milliseconds /// Maximum number of allowed redirects /// A hardened HttpWebRequest if the uri was determined to be safe /// If uri is null /// If uri is unsafe public static HttpWebRequest Create(Uri uri, bool allowLoopback, int readWriteTimeoutMS, int timeoutMS, int maximumRedirects) { if (uri == null) throw new ArgumentNullException("uri"); if (!IsUriAllowable(uri, allowLoopback)) throw new ArgumentException("Uri " + uri + " was rejected"); HttpWebRequest httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(uri); httpWebRequest.MaximumAutomaticRedirections = maximumRedirects; httpWebRequest.ReadWriteTimeout = readWriteTimeoutMS; httpWebRequest.Timeout = timeoutMS; httpWebRequest.KeepAlive = false; return httpWebRequest; } public static string PostToUntrustedUrl(Uri url, string data) { try { byte[] requestData = System.Text.Encoding.UTF8.GetBytes(data); HttpWebRequest request = Create(url); request.Method = "POST"; request.ContentLength = requestData.Length; request.ContentType = "application/x-www-form-urlencoded"; using (Stream requestStream = request.GetRequestStream()) requestStream.Write(requestData, 0, requestData.Length); using (WebResponse response = request.GetResponse()) { using (Stream responseStream = response.GetResponseStream()) return responseStream.GetStreamString(); } } catch (Exception ex) { m_log.Warn("POST to untrusted URL " + url + " failed: " + ex.Message); return null; } } public static string GetUntrustedUrl(Uri url) { try { HttpWebRequest request = Create(url); using (WebResponse response = request.GetResponse()) { using (Stream responseStream = response.GetResponseStream()) return responseStream.GetStreamString(); } } catch (Exception ex) { m_log.Warn("GET from untrusted URL " + url + " failed: " + ex.Message); return null; } } /// /// Determines whether a URI is allowed based on scheme and host name. /// No requireSSL check is done here /// /// True to allow loopback addresses to be used /// The URI to test for whether it should be allowed. /// /// true if [is URI allowable] [the specified URI]; otherwise, false. /// private static bool IsUriAllowable(Uri uri, bool allowLoopback) { if (!allowableSchemes.Contains(uri.Scheme)) { m_log.WarnFormat("Rejecting URL {0} because it uses a disallowed scheme.", uri); return false; } // Try to interpret the hostname as an IP address so we can test for internal // IP address ranges. Note that IP addresses can appear in many forms // (e.g. http://127.0.0.1, http://2130706433, http://0x0100007f, http://::1 // So we convert them to a canonical IPAddress instance, and test for all // non-routable IP ranges: 10.*.*.*, 127.*.*.*, ::1 // Note that Uri.IsLoopback is very unreliable, not catching many of these variants. IPAddress hostIPAddress; if (IPAddress.TryParse(uri.DnsSafeHost, out hostIPAddress)) { byte[] addressBytes = hostIPAddress.GetAddressBytes(); // The host is actually an IP address. switch (hostIPAddress.AddressFamily) { case System.Net.Sockets.AddressFamily.InterNetwork: if (!allowLoopback && (addressBytes[0] == 127 || addressBytes[0] == 10)) { m_log.WarnFormat("Rejecting URL {0} because it is a loopback address.", uri); return false; } break; case System.Net.Sockets.AddressFamily.InterNetworkV6: if (!allowLoopback && IsIPv6Loopback(hostIPAddress)) { m_log.WarnFormat("Rejecting URL {0} because it is a loopback address.", uri); return false; } break; default: m_log.WarnFormat("Rejecting URL {0} because it does not use an IPv4 or IPv6 address.", uri); return false; } } else { // The host is given by name. We require names to contain periods to // help make sure it's not an internal address. if (!allowLoopback && !uri.Host.Contains(".")) { m_log.WarnFormat("Rejecting URL {0} because it does not contain a period in the host name.", uri); return false; } } return true; } /// /// Determines whether an IP address is the IPv6 equivalent of "localhost/127.0.0.1". /// /// The ip address to check. /// /// true if this is a loopback IP address; false otherwise. /// private static bool IsIPv6Loopback(IPAddress ip) { if (ip == null) throw new ArgumentNullException("ip"); byte[] addressBytes = ip.GetAddressBytes(); for (int i = 0; i < addressBytes.Length - 1; i++) { if (addressBytes[i] != 0) return false; } if (addressBytes[addressBytes.Length - 1] != 1) return false; return true; } } }