SIMtrace Analyser

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APDU trace analyser for the GSMTAP-SIM format — captures SIM/UICC communication from a UDP GSMTAP stream (or imports PCAP/PCAPNG files), decodes it, and serves an installable web app for browsing. The repository also bundles simtrace2-pysniff, a Python replacement for simtrace2-sniff that captures from Osmocom SIMtrace2 hardware and can feed GSMTAP into this analyser.

Components

• Analysis server + PWA (simtrace-analyser-server) — stores captured traffic in SQLite, decodes it, and serves the PWA (frontend/) plus the HTTP API on a single origin. Three capture modes: a GSMTAP listener, direct SIMtrace2 hardware capture, or disabled (browse existing captures only).
• Capture utility (simtrace2-pysniff) — captures SIMtrace2 hardware traffic and writes it to stdout, GSMTAP (Wireshark), or PCAP files. It is one GSMTAP source of several that the analyser accepts (see also sigrok_iso7816_stream).
• PWA (frontend/) — trace browser with decoded APDU, SIM Toolkit, SMS and SCP80 OTA detail; sessions, PCAP and COMPRION trace import, EN/RU UI.

Features

APDU decoder (server-side, rendered by the PWA):

• Full APDU decode — CLA per ISO 7816-4 / ETSI coding with the logical channel 0-19 (standard channels from b2-b1, the extended channels 4-19 from b4-b1 per TS 102 221 §10.3), secure messaging and command chaining, INS names from a spec table, SFI-aware P1/P2 for READ/UPDATE BINARY and record commands; MANAGE CHANNEL replies show the channel the card assigned
• Status words — full ISO 7816-4 set plus UICC-specific values: 91XX (proactive command pending), 62F1/F2/F3, 63F1/F2 (more data), 9300 (SAT busy), 9850, 9862–64
• SIM Toolkit — SAT (GSM 11.14), CAT (TS 102 223) and USAT (TS 31.111) proactive commands with decoded qualifiers, TERMINAL RESPONSE, ENVELOPE (Menu Selection, Call Control, SMS-PP download…); tolerates known non-compliant legacy-card quirks and preserves unrecognized TLVs
• TERMINAL CAPABILITY (TS 102 221 §11.1.19) — terminal power supply (voltage class, maximum current, clock), extended logical channels, additional interfaces (UICC-CLF) and eUICC device capabilities (SGP.22/SGP.32)
• SMS TPDU — SMS-DELIVER/SUBMIT, SCTS timestamps, UDH information elements
• SCP80 OTA secured packets — SPI bits (ciphering, PoR requirement/mode, RC/CC/DS, counter), KIc/KID algorithm + key set, TAR, CNTR/PCNTR; Response Packet (PoR) decode on GET RESPONSE; optional client-side decryption of ciphered packets — paste the card's 3DES/AES key in the detail view to reveal the real CNTR and secured application data (the key stays in the browser, in-memory only; ciphered on-wire CNTR/PCNTR/RC are ciphertext and labeled as such); the secured application message is decoded as a stream of C-APDUs (SELECT, UPDATE BINARY, …) with full CLA/INS/P1/P2/Lc/Le breakdown — plaintext immediately, or after decryption for ciphered packets
• ATR parse (clock-rate conversion, Fi/Di, T-bitmask, truncated-ATR safe) and FCP/FCI TLV; the historical bytes are decoded as the UICC's COMPACT-TLV objects (TS 102 221 §6.3.1) — card service data, the card capabilities (ISO 7816-4 §8.1.1.2.7 Table 88: the assignment methods and the announced maximum number of logical channels, 8 or more for the extended-capable cards) and the trailing status indicator (LCS/SW)

SIMtrace Analyser PWA (frontend/):

• Trace view with Map/List modes — proactive, TERMINAL RESPONSE, ENVELOPE and AUTH commands get distinctive styling in map view
• Sessions with deep links (#session=N), PCAP import (.pcap/.pcapng/.cap), COMPRION trace import (the Device Manager ISO Protocol Layer text export), search and a multi-select command filter — pick any number of commands and/or the conversation presets (Proactive sessions: FETCH, TERMINAL PROFILE and every command answered with SW 91xx; File operations: SELECT, READ/UPDATE BINARY and READ/UPDATE RECORD, with the GET RESPONSE carrying a selected command's data)
• Installable PWA, dark theme, English/Russian UI

Prerequisites

• Python 3.9+
• PyUSB — pip install pyusb (needed only for capture from SIMtrace2 hardware; GSMTAP/UDP capture and PCAP import work without it)
• libusb — system library, present by default on Linux; on Windows the SIMtrace2 driver must be swapped (see USB Device Access)
• SIMtrace2 hardware running firmware in trace mode (only for direct capture; VID 1d50, PID 60e3, USB class ff, subclass 01). For building and flashing trace firmware, see the upstream SIMtrace2 project.

No other dependencies. PCAP, GSMTAP, and hex dump output use only Python stdlib.

Install

There are two ways to get the analyser: install a release artifact (no git history), or clone the repository for development. Both bundle the same PWA.

From a release (no git history)

Everything is on the latest release.

Wheel (recommended — an isolated install, the PWA is inside the package):

pipx install ./simtrace_analyser-2.7.10-py3-none-any.whl
# or: pip install ./simtrace_analyser-2.7.10-py3-none-any.whl

# then run (the UI is served at http://127.0.0.1:8081/):
simtrace-analyser-server --capture gsmtap

pip can also fetch the wheel straight from the release page (use the version shown there):

pip install https://github.com/anttro/simtrace-analyser/releases/download/v2.7.10/simtrace_analyser-2.7.10-py3-none-any.whl

With the GitHub CLI, download the latest wheel without knowing the version:

gh release download --pattern '*.whl'
pipx install ./simtrace_analyser-*.whl

Source archive — the Source code (zip / tar.gz) assets are the full tree without the git history: unzip, cd into it and use the launchers below (./start.sh on Linux/macOS, start.bat on Windows).

From a git clone (development)

git clone https://github.com/anttro/simtrace-analyser.git
cd simtrace-analyser
./start.sh                  # Linux/macOS; on Windows: start.bat

The launchers add the checkout to PYTHONPATH and run python -m simtrace_analyser, so no install step is needed for browsing and GSMTAP capture; they accept the server's options (./start.sh --capture direct --port 8080). Direct hardware capture needs PyUSB (pip install pyusb).

To get the console scripts (simtrace-analyser-server, simtrace2-pysniff) install the package instead:

pip install -e .
simtrace-analyser-server --capture gsmtap

On Windows the .bat launchers run the python command, so Python 3 has to be on PATH (check with python --version); direct USB capture additionally needs the driver swap described in USB Device Access.

Running

Analysis server + PWA (simtrace-analyser-server)

Stores captured APDU traffic in SQLite and serves it over HTTP, together with the bundled SIMtrace Analyser PWA (frontend/ in a source checkout, bundled into the package on install) on the same origin. Three capture modes:

# Listen for GSMTAP from simtrace2-pysniff (or original simtrace2-sniff):
simtrace-analyser-server --capture gsmtap

# Capture directly from SIMtrace2 hardware (no external tool needed):
simtrace-analyser-server --capture direct

# Browse/analyse existing captures without a capture backend:
simtrace-analyser-server --capture disabled

The server logs its capture liveness to stderr (each line timestamped with the local time): Capture started on begin, a periodic Capture alive: session=N messages=M bytes=B dropped=D heartbeat, and Capture stopped (or ERROR: capture thread stopped on error … if the capture thread died unexpectedly). A mis-framed or non-SIM GSMTAP datagram is dropped and counted (dropped) rather than silently killing the capture; a tpdu packet that is not APDU-shaped at all (shorter than the header, the invalid CLA FF or an ISO-reserved class) is skipped and counted (skipped) — a character-level or mis-sampled stream no longer pollutes the decode. The heartbeat interval defaults to 60 s and is tunable via --log-interval SECONDS.

The GSMTAP listener also accepts the sigrok-iso7816-stream decoder (https://github.com/anttro/sigrok_iso7816_stream) — an FX2-logic-analyzer passive SIM sniffer that emits the same GSMTAP-SIM format on UDP 4729. Its standard PPS request/response sub-types (0x02/0x03) are decoded as PPS, and its custom sub-types for RST/VCC line events (0x10/0x11, added for compatibility with that project) are decoded as RESET ASSERTED / RST de-asserted — ATR follows and VCC ON/OFF timeline markers, and a reset-assert or power-removal correctly invalidates the file-selection tracking. When an RST event carries the measured CLK frequency (decoder v1.9.0+, optional payload extension), the following ATR is annotated with the CLK frequency, data rate and ETU derived from its TA1 Fi/Di (data_rate = clk_hz × D / F); the measurement is consumed by the ATR so a later ATR without a reset gets no stale rate (a late-arriving measurement is backfilled onto the ATR it belongs to). GSMTAP packets carrying the GSMTAP_FLAG_BAD_FCS desync flag (set by that decoder on mis-framed exchanges) are surfaced as a flagged/desynced entry in the capture timeline, so such artefacts are easy to spot when reviewing a capture rather than silently altering the decode.

COMPRION text export import

The Import COMPRION trace button accepts the tab-separated ISO Protocol Layer export of COMPRION's Device Manager — the byte-accurate protocol view (ATR, PPS, APDUs with their return codes). The ISO Application Layer export carries no raw response bytes and is not needed; selecting it answers with a pointer to the Protocol Layer file (the same check runs in the PWA before the upload and on the server for API callers).

Exchanges are re-encoded into the same wire-shaped TPDUs a GSMTAP capture carries (a case-4 exchange becomes the command, a 61 xx status word and a GET RESPONSE with the response data and the final SW), so command/response pairing, FCP/file decoding and the filters behave exactly as for a live capture.

Exact timestamps: the import dialog asks for the ISO Protocol Layer export (required) and, optionally, the matching ISO Application Layer export — two separate pickers, both file names visible, and an error stays in the dialog until it is fixed or cancelled. With both files the Application Layer's per-exchange wall-clock times become the trace's timeline — the session window and the inter-APDU gaps are then exact; without it the timeline is the estimate described below. Before anything is imported the two files are verified to belong to the same session (Session Name, falling back to Working directory; the export timestamps of the two layers differ and are not compared) and their exchange counts must align (the two exports must cover the same set of exchanges) — a mismatch refuses the import instead of mixing sessions. The ATR and the PPS exchange have no Application Layer blocks, so they carry the timestamp of the preceding exchange.

Protocol Layer alone: the Delay column measures only card/line activity — host pauses between APDU bursts are absent — so the timeline keeps the message order and the short-term gaps but is much shorter than the real session. Its unit comes from an assumed 3.8 MHz interface clock (CLK_HZ in simtrace_analyser/comprion.py), which is a scale, not a measurement: the export carries no CLK, and the import deliberately does not invent one (the ATR shows the F/D the file states, with no data-rate/ETU annotation, unlike a capture from the sigrok-iso7816-stream sniffer). The session's wall-clock window is taken from the file's Session Name timestamp when it carries one.

Exchanges larger than 255 bytes (extended-length APDUs) cannot be represented in the stored wire shape and are skipped with a note in the import report.

Files view (per-file tracking)

The Trace tab has a view selector (Map / Stats / Files) in its topbar, right-aligned over the side panel with the panel's width, so it stays visible while the panel scrolls (a drop-down, since three tab captions no longer fit). The Files view is a trace-wide timeline of file operations — every Read and Update row shows the same file name as the Map view (a card-side change appears as a read with a Changed on card! link that opens its details), and clicking a row jumps straight to the APDU in the trace and leaves it highlighted until another one is focused (the APDU list keeps the reader's position: new messages pin the view to the bottom only while the reader is already there, so a jump is never pulled away or un-highlighted by the live poll). Rows that carry a recorded change (a card-side change, or an update that wrote or first observed bytes) also offer Show diff: a modal showing the full file path (MF/EF_ICCID (2FE2), ADF/EF_IMSI (6F07), DF_TELECOM/DF_PHONEBOOK/4FA1, AID …/4F09 — the whole DF chain the trace's selection path spells out, each DF named from the specification dictionary and the AID from the EF.DIR labels when known) and the affected unit — the whole file, or the single record that changed — before and after the change, as hex views (up to 16 bytes per row — a shorter file/record ends its row there instead of padding with --, and the offset column only appears when a view spans more than one row) with the bytes that changed highlighted in one colour and the bytes the operation first observed in another, the changed/new byte counts, the APDU reference and a colour legend below the views that lists only the marks actually shown.

Phonebook files have issuer-assigned FIDs, so the dictionary cannot name them: when the trace carries the card's EF_PBR records, they are decoded (TS 31.102 §4.4.2.1 — the A8/A9/AA type groups and the C0…CC primitive tags, each with its FID and, for a three-byte object, its SFI) and the Files view names the files from the card's own declaration — e.g. DF_TELECOM/DF_PHONEBOOK/EF_PBC (4FA1) — while the declared SFIs feed the DF's SFI→FID map (the 88-less FCP fallback of TS 102 221 §11.1.1.4.8 still applies for other files).

The images come from GET /api/sessions/<id>/files/image?key=…&change=… and are reconstructed from the current image by undoing the later changes (filetrack.FileTracker.change_images) — nothing is duplicated per event. Every value change is recorded, so the values are exact; a byte that was only first observed after the selected change can appear as known in both views.

The data comes from simtrace_analyser/filetrack.py (GET /api/sessions/<id>/files), a single-pass tracker over the decoded session that keeps, keyed by (DF, FID) and across card resets: access counters (select/read/update, successful operations only), a sparse image of the observed contents and the change log. Device-initiated changes are the UPDATE operations seen in the trace; card-initiated ones are inferred when a read returns bytes differing from what the image already knew — bytes never seen before just fill the image (an observation, not a change). Files reached by SFI share the entry of their path/FID accesses: the SFI ↔ FID relations come from the normative tables (TS 102 221 Annex H.1 and the TS 31.102 H.1–H.12 annexes; the ISIM SFI rows come from TS 31.103) and from every surfaced FCP carrying the 88 DO, including the spec's "SFI = the 5 LSBs of the FID" rule when the DO is absent; an SFI used before its relation is learned stays provisional and merges into the resolved entry. A file's DF context follows TS 102 221 §8.4/Table 8.2 (selecting an EF leaves its parent DF current, a path selection included); applications selected by an unknown AID get the AID as their DF identity, named from EF.DIR when the trace surfaced it. Bounds: the image freezes past 64 KB of observed bytes per file (image_truncated) and the change log keeps the last 1000 events per file (changes_total keeps counting). Counters are returned by the API but not shown in this view yet.

File names are DF-scoped: simtrace_analyser/ef_tables.py holds the complete per-DF file tables and SFI lists extracted from the pinned specs (TS 102 221, TS 31.102 including its H.1–H.12 SFI annexes, TS 31.103, TS 51.011), so a FID reused across DFs resolves to the file its DF context names — 4F09 is EF_SUPI_NAI under DF_5GS but EF_PROSE_GC under DF_ProSe, 6F07 is EF_IMSI in the USIM/SIM but EF_IST in the ISIM, 6F4E is EF_EXT4 in DF_TELECOM but EF_EXT5 in the USIM ADF — with the flat table as the fallback when no DF is known. tests/extract_spec_tables.py regenerates the pinned fixture (tests/data/spec_files.json) and --check re-verifies the tables against the PDFs.

Server options:

--host ADDR          HTTP bind address (default: 127.0.0.1)
--port PORT          HTTP server port (default: 8081)
--db FILE            SQLite database path (default: ~/.simtrace-analyser/sessions.db)
--capture MODE       gsmtap | direct | disabled  (default: gsmtap)
--gsmtap-port PORT   UDP port for the GSMTAP listener (default: 4729)
--web-dir PATH       PWA static files directory (default: the PWA bundled in
                     the installed package, or <repo>/frontend from source)

Then open http://127.0.0.1:8081/ in a browser — the PWA is served by the server, so the UI and the API share an origin and no CORS/Private-Network-Access setup is involved. Use --web-dir PATH to serve a different PWA directory (default: the bundled PWA, or <repo>/frontend in a source checkout).

Hosted PWA (landing page)

A standalone copy of the PWA is hosted at https://simtrace.atroshin.ru. It is a pure frontend: point it (Settings → Server URL) at a locally running simtrace-analyser-server.

Browser restriction: when the PWA is served from a public HTTPS host, reaching a local server (http://127.0.0.1:8081) requires two things: the server must send Access-Control-Allow-Private-Network: true (this server does), and the browser must be allowed to access the local network — in Chrome/Edge/Vivaldi: Site settings → Local network access → allow the site (or accept the permission prompt). Without the browser permission, the request to 127.0.0.1 is blocked before any preflight is sent.

Capture utility (simtrace2-pysniff)

Captures SIMtrace2 hardware traffic and writes it to stdout, GSMTAP (Wireshark), or PCAP files. It is the bundled replacement for the original Osmocom simtrace2-sniff.

The ./sniff-start.sh startup script performs a pre-flight USB permission check (prints udev install instructions if the SIMtrace2 device is not writable) and then launches the Python module. On Windows, use sniff-start.bat with the same options (no permission check needed).

./sniff-start.sh
./sniff-start.sh --format timestamp
./sniff-start.sh --gsmtap 127.0.0.1:4729
./sniff-start.sh --pcap trace.pcap --format atr-time

OPTIONS can also be set via environment variables:

FORMAT=timestamp GSMTAP=127.0.0.1 ./sniff-start.sh

Cross-platform module invocation:

python -m simtrace2_pysniff
python -m simtrace2_pysniff --format timestamp --gsmtap 127.0.0.1:4729
python -m simtrace2_pysniff --pcap trace.pcap

If installed via pip install -e ., use the console script directly:

simtrace2-pysniff --format atr-time

USB Device Access

Required for capture from SIMtrace2 hardware (the utility and the server's --capture direct mode); not needed for GSMTAP or PCAP sources.

Linux

A udev rule is required for non-root USB access to the SIMtrace2 device.

sudo cp 70-simtrace2-pysniff.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules
sudo udevadm trigger

Then reconnect the SIMtrace2 USB cable. The rule uses TAG+="uaccess" (systemd-logind ACL) — no group membership or world-writable permissions needed.

Windows

Windows does not ship a libusb-compatible driver for SIMtrace2. Use Zadig to replace the default driver:

1. Download and run Zadig
2. Plug in the SIMtrace2 device
3. Select it in the dropdown (VID 1D50, PID 60E3 — "Osmocom SIMtrace 2")
4. Choose WinUSB (or libusbK) as the replacement driver
5. Click Replace Driver (one-time operation)

After that, python -m simtrace2_pysniff works identically to Linux.

The Windows launchers match their shell counterparts and pass every option through: start.bat --capture direct starts the analyser server and sniff-start.bat the capture utility. Both call the python command, so Python 3 must be on PATH (verify with python --version in a new command prompt).

Utility CLI Options

python -m simtrace2_pysniff [OPTIONS]

  --format, -f FORMAT       Output format (default: hex)
                            hex       — plain hex dump
                            timestamp — TPDU lines prefixed with [HH:MM:SS.mmm]
                            atr-time  — TPDU lines prefixed with [SSSS.mmm] from last ATR
  --gsmtap HOST[:PORT]      Send ATR/TPDU as GSMTAP over UDP (default port 4729)
  --pcap FILE               Write sniffed data to PCAP file for Wireshark
  --output, -o FILE         Write hex dump to file
  --no-stdout               Suppress hex dump to stdout
  --vendor HEX              USB vendor ID (default: 0x1d50)
  --product HEX             USB product ID (default: auto-detect)

Recovery options:
  --no-reconnect            Exit on USB disconnect instead of reconnecting
  --reconnect-delay-min SEC Minimum reconnect delay (default: 1.0)
  --reconnect-delay-max SEC Maximum reconnect delay cap (default: 30.0)
  --backoff-factor N        Exponential backoff multiplier (default: 1.5)
  --inactivity-timeout SEC  Reconnect after N seconds of silence (default: disabled)

Output Formats

• hex (default): plain hex dump — ATR: 3b 9e ..., TPDU: a0 a4 00 00 02 3f 00
• timestamp: TPDU lines prefixed with local time — [14:32:05.123] TPDU: a0 a4 00 00 02 3f 00
• atr-time: TPDU lines prefixed with seconds since last ATR — [0001.234] TPDU: a0 a4 00 00 02 3f 00

Non-TPDU messages (ATR, PPS, card state changes, Fi/Di) print identically in all formats.

• GSMTAP: ATR and APDU messages over UDP (port 4729) to Wireshark
• PCAP: ATR/TPDU messages as Ethernet/IP/UDP/GSMTAP packets, openable in Wireshark

Background / Daemon

SIGHUP is automatically ignored when stdin is not a terminal (i.e. run in background or via a pipe). Foreground terminal sessions still respond to SIGHUP normally.

To run persistently in the background with output to files:

nohup ./sniff-start.sh --output /tmp/sniff.log &> /tmp/sniff-err.log &
# or
FORMAT=timestamp nohup python -m simtrace2_pysniff --output /tmp/sniff.log &> /tmp/sniff-err.log &

Library Usage

from simtrace2_pysniff import SniffSession

session = SniffSession(inactivity_timeout=30.0)
for msg in session.iter_messages():
    print(f"{msg.type}: {msg.data.hex()}")

Recovery

The utility survives hardware resets, cable disconnects, and firmware hangs by default — it reconnects with exponential backoff (1s → 30s cap). Use --inactivity-timeout to also trigger reconnect on silent firmware hangs.

Related

• simtrace2 — the upstream SIMtrace2 hardware/firmware project that the capture utility sniffs from.
• sigrok_iso7816_stream — FX2LP-based passive ISO 7816 sniffer that emits the same GSMTAP-SIM stream on UDP 4729 (accepted by this project's GSMTAP listener).