Adding upstream version 4.2.2.upstream/4.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 471 insertions, 0 deletions

diff --git a/epan/dissectors/packet-ssyncp.c b/epan/dissectors/packet-ssyncp.c
new file mode 100644
index 00000000..c5d1e09b
--- /dev/null
+++ b/epan/dissectors/packet-ssyncp.c
@@ -0,0 +1,471 @@
+/* packet-ssyncp.c
+ * Routines for dissecting mosh's State Synchronization Protocol
+ * Copyright 2020 Google LLC
+ *
+ * Wireshark - Network traffic analyzer
+ * By Gerald Combs <gerald@wireshark.org>
+ * Copyright 1998 Gerald Combs
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+/*
+ * State Synchronization Protocol is the protocol used by mosh:
+ * <https://mosh.org/mosh-paper-draft.pdf>
+ *
+ * The protocol name is abbreviated as SSyncP to avoid conflict with the
+ * "Scripting Service Protocol".
+ *
+ * The protocol is based on UDP, with a plaintext header followed by an
+ * encrypted payload. For now we just support decrypting a single connection at
+ * a time, using the MOSH_KEY dumped from the environment variables
+ * (`cat /proc/$pid/environ | tr '\0' '\n' | grep MOSH_KEY` on Linux).
+ * Note that to display the embedded protobuf properly, you'll have to add
+ * src/protobufs/ from mosh's source code to the ProtoBuf search path.
+ * For now we stop decoding after reaching the first level of protobufs; in
+ * them, a second layer of protobufs is sometimes embedded (e.g. for
+ * transmitting screen contents and such). Implementing that is left as an
+ * exercise for the reader.
+ */
+
+#include <config.h>
+
+#include <epan/packet.h>   /* Should be first Wireshark include (other than config.h) */
+#include <epan/conversation.h>
+#include <epan/wmem_scopes.h>
+#include <epan/proto_data.h>
+#include <epan/prefs.h>
+#include <epan/expert.h>
+#include <wsutil/report_message.h>
+#include <wsutil/wsgcrypt.h>
+
+void proto_reg_handoff_ssyncp(void);
+void proto_register_ssyncp(void);
+
+static dissector_handle_t ssyncp_handle;
+
+static int proto_ssyncp = -1;
+static int hf_ssyncp_direction = -1;
+static int hf_ssyncp_seq = -1;
+static int hf_ssyncp_encrypted = -1;
+static int hf_ssyncp_seq_delta = -1;
+static int hf_ssyncp_timestamp = -1;
+static int hf_ssyncp_timestamp_reply = -1;
+static int hf_ssyncp_frag_seq = -1;
+static int hf_ssyncp_frag_final = -1;
+static int hf_ssyncp_frag_idx = -1;
+static int hf_ssyncp_rtt_to_server = -1;
+static int hf_ssyncp_rtt_to_client = -1;
+
+/* Initialize the subtree pointers */
+static gint ett_ssyncp = -1;
+static gint ett_ssyncp_decrypted = -1;
+
+static expert_field ei_ssyncp_fragmented = EI_INIT;
+static expert_field ei_ssyncp_bad_key = EI_INIT;
+
+static const char *pref_ssyncp_key;
+static char ssyncp_raw_aes_key[16];
+static gboolean have_ssyncp_key;
+
+static dissector_handle_t dissector_protobuf;
+
+typedef struct _ssyncp_conv_info_t {
+    /* last sequence numbers per direction */
+    guint64 last_seq[2];
+    /* for each direction, have we seen any traffic yet? */
+    gboolean seen_packet[2];
+
+    guint16 clock_offset[2];
+    gboolean clock_seen[2];
+} ssyncp_conv_info_t;
+
+typedef struct _ssyncp_packet_info_t {
+    gboolean first_packet;
+    gint64 seq_delta;
+    gboolean have_rtt_estimate;
+    gint16 rtt_estimate;
+} ssyncp_packet_info_t;
+
+#define SSYNCP_IV_PAD 4
+#define SSYNCP_SEQ_LEN 8
+#define SSYNCP_DATAGRAM_HEADER_LEN (SSYNCP_SEQ_LEN + 2 + 2) /* 64-bit IV and two 16-bit timestamps */
+#define SSYNCP_TRANSPORT_HEADER_LEN (8 + 2)
+#define SSYNCP_AUTHTAG_LEN 16 /* 128-bit auth tag */
+
+/*
+ * We only match on 60001, which mosh uses for its first connection.
+ * If there are more connections in the range 60002-61000, the user will have to
+ * mark those as ssyncp traffic manually - we'd have too many false positives
+ * otherwise.
+ */
+#define SSYNCP_UDP_PORT 60001
+
+static int
+dissect_ssyncp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
+        void *data _U_)
+{
+    /* Check that we have at least a datagram plus an OCB auth tag. */
+    if (tvb_reported_length(tvb) < SSYNCP_DATAGRAM_HEADER_LEN + SSYNCP_TRANSPORT_HEADER_LEN + SSYNCP_AUTHTAG_LEN)
+        return 0;
+
+    guint64 direction_and_seq = tvb_get_guint64(tvb, 0, ENC_BIG_ENDIAN);
+    guint direction = direction_and_seq >> 63;
+    guint64 seq = direction_and_seq & ~(1ULL << 63);
+
+    /* Heuristic: The 63-bit sequence number starts from zero and increments
+     * from there. Even if you send 1000 packets per second over 10 years, you
+     * won't reach 2^35. So check that the sequence number is not outrageously
+     * high.
+     */
+    if (seq > (1ULL << 35))
+        return 0;
+
+    /* On the first pass, track the previous sequence numbers per direction,
+     * compute deltas between sequence numbers, and save those deltas.
+     * On subsequent passes, use the computed deltas.
+     */
+    ssyncp_packet_info_t *ssyncp_pinfo;
+    ssyncp_conv_info_t *ssyncp_info = NULL;
+    if (pinfo->fd->visited) {
+        ssyncp_pinfo = (ssyncp_packet_info_t *)p_get_proto_data(wmem_file_scope(), pinfo, proto_ssyncp, 0);
+    } else {
+        conversation_t *conversation = find_or_create_conversation(pinfo);
+        ssyncp_info = (ssyncp_conv_info_t *)conversation_get_proto_data(conversation, proto_ssyncp);
+        if (!ssyncp_info) {
+            ssyncp_info = wmem_new(wmem_file_scope(), ssyncp_conv_info_t);
+            conversation_add_proto_data(conversation, proto_ssyncp, ssyncp_info);
+            ssyncp_info->seen_packet[0] = FALSE;
+            ssyncp_info->seen_packet[1] = FALSE;
+            ssyncp_info->clock_seen[0] = FALSE;
+            ssyncp_info->clock_seen[1] = FALSE;
+        }
+
+        ssyncp_pinfo = wmem_new(wmem_file_scope(), ssyncp_packet_info_t);
+        ssyncp_pinfo->first_packet = !ssyncp_info->seen_packet[direction];
+        if (ssyncp_pinfo->first_packet) {
+            ssyncp_info->seen_packet[direction] = TRUE;
+        } else {
+            ssyncp_pinfo->seq_delta = seq - ssyncp_info->last_seq[direction];
+        }
+        ssyncp_pinfo->have_rtt_estimate = FALSE;
+        p_add_proto_data(wmem_file_scope(), pinfo, proto_ssyncp, 0, ssyncp_pinfo);
+
+        ssyncp_info->last_seq[direction] = seq;
+    }
+
+    /*** COLUMN DATA ***/
+
+    col_set_str(pinfo->cinfo, COL_PROTOCOL, "ssyncp");
+
+    col_clear(pinfo->cinfo, COL_INFO);
+
+    char *direction_str = direction ? "Server->Client" : "Client->Server";
+    col_set_str(pinfo->cinfo, COL_INFO, direction_str);
+
+    /*** PROTOCOL TREE ***/
+
+    /* create display subtree for the protocol */
+    proto_item *ti = proto_tree_add_item(tree, proto_ssyncp, tvb, 0, -1, ENC_NA);
+
+    proto_tree *ssyncp_tree = proto_item_add_subtree(ti, ett_ssyncp);
+
+    /* Add an item to the subtree, see section 1.5 of README.dissector for more
+     * information. */
+    proto_tree_add_item(ssyncp_tree, hf_ssyncp_direction, tvb,
+            0, 1, ENC_BIG_ENDIAN);
+    proto_tree_add_item(ssyncp_tree, hf_ssyncp_seq, tvb,
+            0, 8, ENC_BIG_ENDIAN);
+#ifdef GCRY_OCB_BLOCK_LEN
+    proto_item *encrypted_item =
+#endif
+       proto_tree_add_item(ssyncp_tree, hf_ssyncp_encrypted,
+            tvb, 8, -1, ENC_NA);
+
+    if (!ssyncp_pinfo->first_packet) {
+        proto_item *delta_item =
+                proto_tree_add_int64(ssyncp_tree, hf_ssyncp_seq_delta, tvb, 0, 0,
+                        ssyncp_pinfo->seq_delta);
+        proto_item_set_generated(delta_item);
+    }
+
+    unsigned char *decrypted = NULL;
+    guint decrypted_len = 0;
+
+    /* avoid build failure on ancient libgcrypt without OCB support */
+#ifdef GCRY_OCB_BLOCK_LEN
+    if (have_ssyncp_key) {
+        gcry_error_t gcry_err;
+
+        /* try to decrypt the rest of the packet */
+        gcry_cipher_hd_t gcry_hd;
+        gcry_err = gcry_cipher_open(&gcry_hd, GCRY_CIPHER_AES128, GCRY_CIPHER_MODE_OCB, 0);
+        if (gcry_err_code(gcry_err)) {
+            /* this shouldn't happen (even if the packet is garbage) */
+            report_failure("ssyncp: unable to initialize cipher???");
+            return tvb_captured_length(tvb);
+        }
+        gcry_err = gcry_cipher_setkey(gcry_hd, ssyncp_raw_aes_key, sizeof(ssyncp_raw_aes_key));
+        if (gcry_err_code(gcry_err)) {
+            /* this shouldn't happen (even if the packet is garbage) */
+            report_failure("ssyncp: unable to set key???");
+            gcry_cipher_close(gcry_hd);
+            return tvb_captured_length(tvb);
+        }
+        char nonce[SSYNCP_IV_PAD + SSYNCP_SEQ_LEN];
+        memset(nonce, 0, SSYNCP_IV_PAD);
+        tvb_memcpy(tvb, nonce + SSYNCP_IV_PAD, 0, SSYNCP_SEQ_LEN);
+        gcry_err = gcry_cipher_setiv(gcry_hd, nonce, sizeof(nonce));
+        if (gcry_err_code(gcry_err)) {
+            /* this shouldn't happen (even if the packet is garbage) */
+            report_failure("ssyncp: unable to set iv???");
+            gcry_cipher_close(gcry_hd);
+            return tvb_captured_length(tvb);
+        }
+        decrypted_len = tvb_captured_length(tvb) - SSYNCP_SEQ_LEN - SSYNCP_AUTHTAG_LEN;
+        decrypted = (unsigned char *)tvb_memdup(pinfo->pool, tvb,
+                    SSYNCP_SEQ_LEN, decrypted_len);
+        gcry_cipher_final(gcry_hd);
+        gcry_err = gcry_cipher_decrypt(gcry_hd, decrypted, decrypted_len, NULL, 0);
+        if (gcry_err_code(gcry_err)) {
+            /* this shouldn't happen (even if the packet is garbage) */
+            report_failure("ssyncp: unable to decrypt???");
+            gcry_cipher_close(gcry_hd);
+            return tvb_captured_length(tvb);
+        }
+        gcry_err = gcry_cipher_checktag(gcry_hd,
+            tvb_get_ptr(tvb, SSYNCP_SEQ_LEN+decrypted_len, SSYNCP_AUTHTAG_LEN),
+            SSYNCP_AUTHTAG_LEN);
+        if (gcry_err_code(gcry_err) && gcry_err_code(gcry_err) != GPG_ERR_CHECKSUM) {
+            /* this shouldn't happen (even if the packet is garbage) */
+            report_failure("ssyncp: unable to check auth tag???");
+            gcry_cipher_close(gcry_hd);
+            return tvb_captured_length(tvb);
+        }
+        if (gcry_err_code(gcry_err)) {
+            /* if the tag is wrong, the key was wrong and the decrypted data is useless */
+            decrypted = NULL;
+            expert_add_info(pinfo, encrypted_item, &ei_ssyncp_bad_key);
+        }
+        gcry_cipher_close(gcry_hd);
+    }
+#endif
+
+    if (decrypted) {
+        tvbuff_t *decrypted_tvb = tvb_new_child_real_data(tvb, decrypted, decrypted_len, decrypted_len);
+        add_new_data_source(pinfo, decrypted_tvb, "Decrypted data");
+
+        if (!pinfo->fd->visited) {
+            guint16 our_clock16 = ((guint64)pinfo->abs_ts.secs * 1000 + pinfo->abs_ts.nsecs / 1000000) & 0xffff;
+            guint16 sender_ts = tvb_get_guint16(decrypted_tvb, 0, ENC_BIG_ENDIAN);
+            guint16 reply_ts = tvb_get_guint16(decrypted_tvb, 2, ENC_BIG_ENDIAN);
+            ssyncp_info->clock_offset[direction] = sender_ts - our_clock16;
+            ssyncp_info->clock_seen[direction] = TRUE;
+            if (reply_ts != 0xffff && ssyncp_info->clock_seen[1-direction]) {
+                guint16 projected_send_time_our_clock = reply_ts - ssyncp_info->clock_offset[1-direction];
+                ssyncp_pinfo->rtt_estimate = our_clock16 - projected_send_time_our_clock;
+                ssyncp_pinfo->have_rtt_estimate = TRUE;
+            }
+        }
+
+        proto_tree *dec_tree = proto_tree_add_subtree(ssyncp_tree, decrypted_tvb,
+                0, -1, ett_ssyncp_decrypted, NULL, "Decrypted data");
+
+        proto_tree_add_item(dec_tree, hf_ssyncp_timestamp, decrypted_tvb,
+                0, 2, ENC_BIG_ENDIAN);
+        proto_tree_add_item(dec_tree, hf_ssyncp_timestamp_reply, decrypted_tvb,
+                2, 2, ENC_BIG_ENDIAN);
+
+        if (ssyncp_pinfo->have_rtt_estimate) {
+            int rtt_id = direction ? hf_ssyncp_rtt_to_server : hf_ssyncp_rtt_to_client;
+            proto_item *rtt_item = proto_tree_add_int(dec_tree, rtt_id, decrypted_tvb, 2, 2, ssyncp_pinfo->rtt_estimate);
+            proto_item_set_generated(rtt_item);
+        }
+
+        proto_tree_add_item(dec_tree, hf_ssyncp_frag_seq, decrypted_tvb,
+                4, 8, ENC_BIG_ENDIAN);
+        proto_tree_add_item(dec_tree, hf_ssyncp_frag_final, decrypted_tvb,
+                12, 2, ENC_BIG_ENDIAN);
+        proto_item *frag_idx_item = proto_tree_add_item(dec_tree,
+                hf_ssyncp_frag_idx, decrypted_tvb, 12, 2, ENC_BIG_ENDIAN);
+
+        /* TODO actually handle fragmentation; for now just bail out on fragmentation */
+        if (tvb_get_guint16(decrypted_tvb, 12, ENC_BIG_ENDIAN) != 0x8000) {
+            expert_add_info(pinfo, frag_idx_item, &ei_ssyncp_fragmented);
+            return tvb_captured_length(tvb);
+        }
+
+        tvbuff_t *inflated_tvb = tvb_child_uncompress(decrypted_tvb, decrypted_tvb, 14, decrypted_len - 14);
+        if (inflated_tvb == NULL)
+            return tvb_captured_length(tvb);
+        add_new_data_source(pinfo, inflated_tvb, "Inflated data");
+
+        if (dissector_protobuf) {
+            call_dissector_with_data(dissector_protobuf, inflated_tvb, pinfo,
+                    dec_tree, "message,TransportBuffers.Instruction");
+        }
+    }
+
+    return tvb_captured_length(tvb);
+}
+
+/* Register the protocol with Wireshark.
+ *
+ * This format is required because a script is used to build the C function that
+ * calls all the protocol registration.
+ */
+void
+proto_register_ssyncp(void)
+{
+    static const true_false_string direction_name = {
+        "Server->Client",
+        "Client->Server"
+    };
+
+    /* Setup list of header fields  See Section 1.5 of README.dissector for
+     * details. */
+    static hf_register_info hf[] = {
+        { &hf_ssyncp_direction,
+          { "Direction", "ssyncp.direction",
+            FT_BOOLEAN, 8, TFS(&direction_name), 0x80,
+            "Direction of packet", HFILL }
+        },
+        { &hf_ssyncp_seq,
+          { "Sequence number", "ssyncp.seq",
+            FT_UINT64, BASE_HEX, NULL, 0x7fffffffffffffff,
+            "Monotonically incrementing packet sequence number", HFILL }
+        },
+        { &hf_ssyncp_encrypted,
+          { "Encrypted data", "ssyncp.enc_data",
+            FT_BYTES, BASE_NONE, NULL, 0,
+            "Encrypted RTT estimation fields and Transport Layer payload, encrypted with AES-128-OCB",
+            HFILL }
+        },
+        { &hf_ssyncp_seq_delta,
+          { "Sequence number delta", "ssyncp.seq_delta",
+            FT_INT64, BASE_DEC, NULL, 0,
+            "Delta from last sequence number; 1 is normal, 0 is duplicated packet, <0 is reordering, >1 is reordering or packet loss", HFILL }
+        },
+        { &hf_ssyncp_timestamp,
+          { "Truncated timestamp", "ssyncp.timestamp",
+            FT_UINT16, BASE_HEX, NULL, 0,
+            "Low 16 bits of sender's time in milliseconds", HFILL }
+        },
+        { &hf_ssyncp_timestamp_reply,
+          { "Last timestamp received", "ssyncp.timestamp_reply",
+            FT_UINT16, BASE_HEX, NULL, 0,
+            "Low 16 bits of timestamp of last received packet plus time since it was received (for RTT estimation)", HFILL }
+        },
+        { &hf_ssyncp_frag_seq,
+          { "Fragment ID", "ssyncp.frag_seq",
+            FT_UINT64, BASE_HEX, NULL, 0,
+            "Transport-level sequence number, used for fragment reassembly", HFILL }
+        },
+        { &hf_ssyncp_frag_final,
+          { "Final fragment", "ssyncp.frag_final",
+            FT_BOOLEAN, 16, NULL, 0x8000,
+            "Is this the last fragment?", HFILL }
+        },
+        { &hf_ssyncp_frag_idx,
+          { "Fragment Index", "ssyncp.frag_idx",
+            FT_UINT16, BASE_HEX, NULL, 0x7fff,
+            "Index of this fragment in the list of fragments of the transport-level message", HFILL }
+        },
+        { &hf_ssyncp_rtt_to_server,
+          { "RTT estimate to server (in ms)", "ssyncp.rtt_est_to_server",
+            FT_INT16, BASE_DEC, NULL, 0,
+            "Estimated round trip time from point of capture to server", HFILL }
+        },
+        { &hf_ssyncp_rtt_to_client,
+          { "RTT estimate to client (in ms)", "ssyncp.rtt_est_to_client",
+            FT_INT16, BASE_DEC, NULL, 0,
+            "Estimated round trip time from point of capture to client", HFILL }
+        }
+    };
+
+    /* Setup protocol subtree array */
+    static gint *ett[] = {
+        &ett_ssyncp,
+        &ett_ssyncp_decrypted
+    };
+
+    /* Setup protocol expert items */
+    static ei_register_info ei[] = {
+        { &ei_ssyncp_fragmented,
+          { "ssyncp.fragmented", PI_REASSEMBLE, PI_WARN,
+            "SSYNCP-level fragmentation, dissector can't handle that", EXPFILL }
+        },
+        { &ei_ssyncp_bad_key,
+          { "ssyncp.badkey", PI_DECRYPTION, PI_WARN,
+            "Encrypted data could not be decrypted with the provided key", EXPFILL }
+        }
+    };
+
+    /* Register the protocol name and description */
+    proto_ssyncp = proto_register_protocol("State Synchronization Protocol", "SSyncP", "ssyncp");
+
+    /* Register the dissector handle */
+    ssyncp_handle = register_dissector("ssyncp", dissect_ssyncp, proto_ssyncp);
+
+    /* Required function calls to register the header fields and subtrees */
+    proto_register_field_array(proto_ssyncp, hf, array_length(hf));
+    proto_register_subtree_array(ett, array_length(ett));
+
+    expert_module_t *expert_ssyncp = expert_register_protocol(proto_ssyncp);
+    expert_register_field_array(expert_ssyncp, ei, array_length(ei));
+
+    module_t *ssyncp_module = prefs_register_protocol(proto_ssyncp, proto_reg_handoff_ssyncp);
+
+    prefs_register_string_preference(ssyncp_module, "key",
+        "ssyncp MOSH_KEY",
+        "MOSH_KEY AES key (from mosh-{client,server} environment variable)",
+        &pref_ssyncp_key);
+}
+
+void
+proto_reg_handoff_ssyncp(void)
+{
+    static gboolean initialized = FALSE;
+
+    if (!initialized) {
+        dissector_add_uint("udp.port", SSYNCP_UDP_PORT, ssyncp_handle);
+
+        dissector_protobuf = find_dissector("protobuf");
+        if (dissector_protobuf == NULL) {
+            report_failure("unable to find protobuf dissector");
+        }
+
+        initialized = TRUE;
+    }
+
+    have_ssyncp_key = FALSE;
+    if (strlen(pref_ssyncp_key) != 0) {
+        if (strlen(pref_ssyncp_key) != 22) {
+            report_failure("ssyncp: invalid key, must be 22 characters long");
+            return;
+        }
+        char base64_key[25];
+        memcpy(base64_key, pref_ssyncp_key, 22);
+        memcpy(base64_key+22, "==\0", 3);
+        gsize out_len;
+        if (g_base64_decode_inplace(base64_key, &out_len) == NULL || out_len != sizeof(ssyncp_raw_aes_key)) {
+            report_failure("ssyncp: invalid key, base64 decoding (with \"==\" appended) failed");
+            return;
+        }
+        memcpy(ssyncp_raw_aes_key, base64_key, sizeof(ssyncp_raw_aes_key));
+        have_ssyncp_key = TRUE;
+    }
+}
+
+/*
+ * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
+ *
+ * Local variables:
+ * c-basic-offset: 4
+ * tab-width: 8
+ * indent-tabs-mode: nil
+ * End:
+ *
+ * vi: set shiftwidth=4 tabstop=8 expandtab:
+ * :indentSize=4:tabSize=8:noTabs=true:
+ */