Initial implementation of SCRAM-SHA-1

1 files changed, 157 insertions, 46 deletions

diff --git a/xmpp-vala/src/module/sasl.vala b/xmpp-vala/src/module/sasl.vala
index 4a427ce0..2e87e590 100644
--- a/xmpp-vala/src/module/sasl.vala
+++ b/xmpp-vala/src/module/sasl.vala
@@ -1,9 +1,27 @@
-namespace Xmpp.PlainSasl {
+namespace Xmpp.Sasl {
     private const string NS_URI = "urn:ietf:params:xml:ns:xmpp-sasl";
 
+    public class Flag : XmppStreamFlag {
+        public static FlagIdentity<Flag> IDENTITY = new FlagIdentity<Flag>(NS_URI, "sasl");
+        public string mechanism;
+        public string name;
+        public string password;
+        public string client_nonce;
+        public uint8[] server_signature;
+        public bool finished = false;
+
+        public override string get_ns() { return NS_URI; }
+        public override string get_id() { return IDENTITY.id; }
+    }
+
+    namespace Mechanism {
+        public const string PLAIN = "PLAIN";
+        public const string SCRAM_SHA_1 = "SCRAM-SHA-1";
+        public const string SCRAM_SHA_1_PLUS = "SCRAM-SHA-1-PLUS";
+    }
+
     public class Module : XmppStreamNegotiationModule {
-        public static ModuleIdentity<Module> IDENTITY = new ModuleIdentity<Module>(NS_URI, "plain_module");
-        private const string MECHANISM = "PLAIN";
+        public static ModuleIdentity<Module> IDENTITY = new ModuleIdentity<Module>(NS_URI, "sasl");
 
         public string name { get; set; }
         public string password { get; set; }
@@ -26,14 +44,109 @@ namespace Xmpp.PlainSasl {
             stream.received_nonza.disconnect(this.received_nonza);
         }
 
+        private static size_t SHA1_SIZE = 20;
+
+        private static uint8[] sha1(uint8[] data) {
+            Checksum checksum = new Checksum(ChecksumType.SHA1);
+            checksum.update(data, data.length);
+            uint8[] res = new uint8[SHA1_SIZE];
+            checksum.get_digest(res, ref SHA1_SIZE);
+            return res;
+        }
+
+        private static uint8[] hmac_sha1(uint8[] key, uint8[] data) {
+            Hmac hmac = new Hmac(ChecksumType.SHA1, key);
+            hmac.update(data);
+            uint8[] res = new uint8[SHA1_SIZE];
+            hmac.get_digest(res, ref SHA1_SIZE);
+            return res;
+        }
+
+        private static uint8[] pbkdf2_sha1(string password, uint8[] salt, uint iterations) {
+            uint8[] res = new uint8[SHA1_SIZE];
+            uint8[] last = new uint8[salt.length + 4];
+            for(int i = 0; i < salt.length; i++) {
+                last[i] = salt[i];
+            }
+            last[salt.length + 3] = 1;
+            for(int i = 0; i < iterations; i++) {
+                last = hmac_sha1((uint8[]) password.to_utf8(), last);
+                xor_inplace(res, last);
+            }
+            return res;
+        }
+
+        private static void xor_inplace(uint8[] mix, uint8[] a2) {
+            for(int i = 0; i < mix.length; i++) {
+                mix[i] = mix[i] ^ a2[i];
+            }
+        }
+
+        private static uint8[] xor(uint8[] a1, uint8[] a2) {
+            uint8[] mix = new uint8[a1.length];
+            for(int i = 0; i < a1.length; i++) {
+                mix[i] = a1[i] ^ a2[i];
+            }
+            return mix;
+        }
+
         public void received_nonza(XmppStream stream, StanzaNode node) {
             if (node.ns_uri == NS_URI) {
                 if (node.name == "success") {
+                    Flag flag = stream.get_flag(Flag.IDENTITY);
+                    if (flag.mechanism == Mechanism.SCRAM_SHA_1) {
+                        string confirm = (string) Base64.decode(node.get_string_content());
+                        uint8[] server_signature = null;
+                        foreach(string c in confirm.split(",")) {
+                            string[] split = c.split("=", 2);
+                            if (split.length != 2) continue;
+                            switch(split[0]) {
+                                case "v": server_signature = Base64.decode(split[1]); break;
+                            }
+                        }
+                        if (server_signature == null) return;
+                        if (server_signature.length != flag.server_signature.length) return;
+                        for(int i = 0; i < server_signature.length; i++) {
+                            if (server_signature[i] != flag.server_signature[i]) return;
+                        }
+                    }
                     stream.require_setup();
-                    stream.get_flag(Flag.IDENTITY).finished = true;
+                    flag.password = null; // Remove password from memory
+                    flag.finished = true;
                 } else if (node.name == "failure") {
                     stream.remove_flag(stream.get_flag(Flag.IDENTITY));
                     received_auth_failure(stream, node);
+                } else if (node.name == "challenge" && stream.has_flag(Flag.IDENTITY)) {
+                    Flag flag = stream.get_flag(Flag.IDENTITY);
+                    if (flag.mechanism == Mechanism.SCRAM_SHA_1) {
+                        string challenge = (string) Base64.decode(node.get_string_content());
+                        string? server_nonce = null;
+                        uint8[] salt = null;
+                        uint iterations = 0;
+                        foreach(string c in challenge.split(",")) {
+                            string[] split = c.split("=", 2);
+                            if (split.length != 2) continue;
+                            switch(split[0]) {
+                                case "r": server_nonce = split[1]; break;
+                                case "s": salt = Base64.decode(split[1]); break;
+                                case "i": iterations = int.parse(split[1]); break;
+                            }
+                        }
+                        if (server_nonce == null || salt == null || iterations == 0) return;
+                        if (!server_nonce.has_prefix(flag.client_nonce)) return;
+                        string client_final_message_bare = @"c=biws,r=$server_nonce";
+                        uint8[] salted_password = pbkdf2_sha1(flag.password, salt, iterations);
+                        uint8[] client_key = hmac_sha1(salted_password, (uint8[]) "Client Key".to_utf8());
+                        uint8[] stored_key = sha1(client_key);
+                        string auth_message = @"n=$(flag.name),r=$(flag.client_nonce),$challenge,$client_final_message_bare";
+                        uint8[] client_signature = hmac_sha1(stored_key, (uint8[]) auth_message.to_utf8());
+                        uint8[] client_proof = xor(client_key, client_signature);
+                        uint8[] server_key = hmac_sha1(salted_password, (uint8[]) "Server Key".to_utf8());
+                        flag.server_signature = hmac_sha1(server_key, (uint8[]) auth_message.to_utf8());
+                        string client_final_message = @"$client_final_message_bare,p=$(Base64.encode(client_proof))";
+                        stream.write(new StanzaNode.build("response", NS_URI).add_self_xmlns()
+                                .put_node(new StanzaNode.text(Base64.encode((uchar[]) (client_final_message).to_utf8()))));
+                    }
                 }
             }
         }
@@ -44,45 +157,53 @@ namespace Xmpp.PlainSasl {
             if (!stream.has_flag(Tls.Flag.IDENTITY) || !stream.get_flag(Tls.Flag.IDENTITY).finished) return;
 
             var mechanisms = stream.features.get_subnode("mechanisms", NS_URI);
-            if (mechanisms != null) {
-                bool supportsPlain = false;
-                foreach (var mechanism in mechanisms.sub_nodes) {
-                    if (mechanism.name != "mechanism" || mechanism.ns_uri != NS_URI) continue;
-                    var text = mechanism.get_subnode("#text");
-                    if (text != null && text.val == MECHANISM) {
-                        supportsPlain = true;
-                    }
-                }
-                if (!supportsPlain) {
-                    stderr.printf("Server at %s does not support %s auth, use full-features Sasl implementation!\n", stream.remote_name.to_string(), MECHANISM);
-                    return;
-                }
-
-                if (!name.contains("@")) {
-                    name = "%s@%s".printf(name, stream.remote_name.to_string());
-                }
-                if (!use_full_name && name.contains("@")) {
-                    var split = name.split("@");
-                    if (split[1] == stream.remote_name.to_string()) {
-                        name = split[0];
-                    } else {
-                        use_full_name = true;
-                    }
+            string[] supported_mechanisms = {};
+            foreach (var mechanism in mechanisms.sub_nodes) {
+                if (mechanism.name != "mechanism" || mechanism.ns_uri != NS_URI) continue;
+                supported_mechanisms += mechanism.get_string_content();
+            }
+            if (!name.contains("@")) {
+                name = "%s@%s".printf(name, stream.remote_name.to_string());
+            }
+            if (!use_full_name && name.contains("@")) {
+                var split = name.split("@");
+                if (split[1] == stream.remote_name.to_string()) {
+                    name = split[0];
+                } else {
+                    use_full_name = true;
                 }
-                var name = this.name;
-                if (!use_full_name && name.contains("@")) {
-                    var split = name.split("@");
-                    if (split[1] == stream.remote_name.to_string()) {
-                        name = split[0];
-                    }
+            }
+            string name = this.name;
+            if (!use_full_name && name.contains("@")) {
+                var split = name.split("@");
+                if (split[1] == stream.remote_name.to_string()) {
+                    name = split[0];
                 }
+            }
+            if (Mechanism.SCRAM_SHA_1 in supported_mechanisms) {
+                string normalized_password = password.normalize(-1, NormalizeMode.NFKC);
+                string client_nonce = Random.next_int().to_string("%.8x") + Random.next_int().to_string("%.8x") + Random.next_int().to_string("%.8x");
+                string initial_message = @"n=$name,r=$client_nonce";
                 stream.write(new StanzaNode.build("auth", NS_URI).add_self_xmlns()
-                                    .put_attribute("mechanism", MECHANISM)
+                        .put_attribute("mechanism", Mechanism.SCRAM_SHA_1)
+                        .put_node(new StanzaNode.text(Base64.encode((uchar[]) ("n,,"+initial_message).to_utf8()))));
+                var flag = new Flag();
+                flag.mechanism = Mechanism.SCRAM_SHA_1;
+                flag.name = name;
+                flag.password = normalized_password;
+                flag.client_nonce = client_nonce;
+                stream.add_flag(flag);
+            } else if (Mechanism.PLAIN in supported_mechanisms) {
+                stream.write(new StanzaNode.build("auth", NS_URI).add_self_xmlns()
+                                    .put_attribute("mechanism", Mechanism.PLAIN)
                                     .put_node(new StanzaNode.text(Base64.encode(get_plain_bytes(name, password)))));
                 var flag = new Flag();
-                flag.mechanism = MECHANISM;
+                flag.mechanism = Mechanism.PLAIN;
                 flag.name = name;
                 stream.add_flag(flag);
+            } else {
+                stderr.printf("No supported mechanism provided by server at %s\n", stream.remote_name.to_string());
+                return;
             }
         }
 
@@ -108,14 +229,4 @@ namespace Xmpp.PlainSasl {
         public override string get_ns() { return NS_URI; }
         public override string get_id() { return IDENTITY.id; }
     }
-
-    public class Flag : XmppStreamFlag {
-        public static FlagIdentity<Flag> IDENTITY = new FlagIdentity<Flag>(NS_URI, "sasl");
-        public string mechanism;
-        public string name;
-        public bool finished = false;
-
-        public override string get_ns() { return NS_URI; }
-        public override string get_id() { return IDENTITY.id; }
-    }
 }