Initial commit.

matter-decode.sh

@@ -0,0 +1,158 @@
+#!/usr/bin/env bash
+#
+# matter-decode.sh — decode a Matter commissioning QR code (MT: URI) from the CLI.
+#
+# This is a bash port of the decode logic in matter-qr-decoder.html (the browser
+# app's camera/QR-scanning feature has no shell equivalent and is intentionally
+# omitted). It decodes the 84-bit payload and prints the same fields the web UI shows.
+#
+# Usage:
+#   ./matter-decode.sh "MT:..."
+#   echo "MT:..." | ./matter-decode.sh
+#
+# A companion file manufacturers.tsv (same directory) maps vendor IDs to names.
+# It is derived from project-chip/connectedhomeip's manufacturers.xml and is
+# optional: without it, all fields still decode — the vendor name line is simply
+# skipped. Regenerate it with:  python3 gen-manufacturers.py  (see that file).
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd -P)"
+
+# Base38 charset, per the Matter spec: 0-9, A-Z, '-', '.' (38 symbols).
+CHARS=( 0 1 2 3 4 5 6 7 8 9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z - . )
+declare -A IDX        # char -> position
+for (( _i=0; _i<${#CHARS[@]}; _i++ )); do IDX["${CHARS[_i]}"]=$_i; done
+# Powers of 38 for the 5-char (3-byte) chunk; 38^0..38^4.
+POW38=( 1 38 1444 54872 2085136 )
+
+BYTES=()             # decoded payload as a byte array, little-endian
+
+# base38_decode STRING -> fills global BYTES.
+# Greedy chunking: 5 chars -> 3 bytes, 4 -> 2, 2 -> 1, matching the reference.
+
+base38_decode() {
+    local s=$1
+    local i=0 len=${#s} j value char idx chunkSize byteCount
+    BYTES=()
+    while (( i < len )); do
+        if   (( i + 5 <= len )); then chunkSize=5; byteCount=3
+        elif (( i + 4 <= len )); then chunkSize=4; byteCount=2
+        elif (( i + 2 <= len )); then chunkSize=2; byteCount=1
+        else
+            echo "Error: Invalid base38 string length" >&2
+            return 1
+        fi
+
+        value=0
+
+        for (( j=0; j<chunkSize; j++ ))
+        do
+            char=${s:i+j:1}
+            idx=${IDX[$char]:-_}        # resolve in param-expansion context;
+            if [[ $idx == _ ]]; then    # avoids an operator-char array key inside $(( ))
+                echo "Error: Invalid character: $char" >&2
+                return 1
+            fi
+            value=$(( value + idx * POW38[j] ))
+        done
+
+        for (( j=0; j<byteCount; j++ ))
+        do
+            BYTES+=( $(( (value >> (8*j)) & 0xFF )) )
+        done
+
+        i=$(( i + chunkSize ))
+
+    done
+}
+
+# extract_bits START COUNT -> prints COUNT bits of BYTES, LSB-first, as a number.
+
+extract_bits() {
+    local start=$1 count=$2 i result=0 bitIndex byteIndex bitOffset bit
+    for (( i=0; i<count; i++ )); do
+        bitIndex=$(( start + i ))
+        byteIndex=$(( bitIndex / 8 ))
+        bitOffset=$(( bitIndex % 8 ))
+
+        if (( byteIndex < ${#BYTES[@]} ))
+        then
+            bit=$(( (BYTES[byteIndex] >> bitOffset) & 1 ))
+            result=$(( result | (bit << i) ))
+        fi
+    done
+
+    printf '%d' "$result"
+}
+
+# get_vendor_name DECID -> prints name if in manufacturers.tsv, else nothing.
+
+get_vendor_name() {
+    local tsv="$SCRIPT_DIR/manufacturers.tsv"
+    [[ -f $tsv ]] || return 0
+    awk -F'\t' -v id="$1" '$1==id { print $2; exit }' "$tsv"
+}
+
+main() {
+    local uri payload
+
+    uri=${1:-}
+
+    [[ -z $uri ]] && uri=$(cat)
+
+    # Trim leading/trailing whitespace
+
+    uri="${uri#"${uri%%[![:space:]]*}"}"
+    uri="${uri%"${uri##*[![:space:]]}"}"
+
+    if [[ $uri != MT:* ]]; then
+        echo 'Error: URI must start with "MT:"' >&2
+        return 1
+    fi
+
+    payload=${uri#MT:}
+
+    [[ -n $payload ]] || { echo 'Error: No data found after "MT:"' >&2; return 1; }
+
+    base38_decode "$payload" || return 1
+
+    local version vendor product customFlow discovery discriminator passcode
+    local cf caps="" vname
+
+    version=$(extract_bits 0 3)
+    vendor=$(extract_bits 3 16)
+    product=$(extract_bits 19 16)
+    customFlow=$(extract_bits 35 2)
+    discovery=$(extract_bits 37 8)
+    discriminator=$(extract_bits 45 12)
+    passcode=$(extract_bits 57 27)
+
+    case $customFlow in
+        0) cf="Standard Commissioning Flow" ;;
+        1) cf="User Intent Commissioning Flow" ;;
+        2) cf="Custom Commissioning Flow" ;;
+        3) cf="Reserved" ;;
+        *) cf="Unknown ($customFlow)" ;;
+    esac
+
+    (( discovery & 0x01 )) && caps="SoftAP"
+    (( discovery & 0x02 )) && caps="${caps:+$caps, }BLE"
+    (( discovery & 0x04 )) && caps="${caps:+$caps, }On IP Network"
+
+    [[ -z $caps ]] && caps="None"
+
+    vname=$(get_vendor_name "$vendor")
+
+    printf 'Version:       %s\n' "$version"
+    printf 'Vendor ID:     %s (0x%04X)' "$vendor" "$vendor"
+    [[ -n $vname ]] && printf '  %s' "$vname"
+    printf '\n'
+    printf 'Product ID:    %s (0x%04X)\n' "$product" "$product"
+    printf 'Custom Flow:   %s\n' "$cf"
+    printf 'Discovery:     %s\n' "$caps"
+    printf 'Discriminator: %s\n' "$discriminator"
+    printf 'Passcode:      %s\n' "$passcode"
+}
+
+main "$@"