fcc-unlock: Transition the 14c3 FCC unlock script to use sh

This enables the usage with busybox and strict environments.

This is related to #483 and the previous commit 91ed72aa, 02baf283.

Signed-off-by: Jongmin Kim <jmkim@debian.org>

1 files changed, 30 insertions, 33 deletions

diff --git a/data/dispatcher-fcc-unlock/14c3 b/data/dispatcher-fcc-unlock/14c3
index f4d2f0b4..78f09861 100755
--- a/data/dispatcher-fcc-unlock/14c3
+++ b/data/dispatcher-fcc-unlock/14c3
@@ -1,15 +1,16 @@
-#!/bin/bash
+#!/bin/sh
 
 # SPDX-License-Identifier: CC0-1.0
 # 2023 Thilo-Alexander Ginkel <thilo@ginkel.com>
+# 2025 Jongmin Kim <jmkim@debian.org>
 #
 # Lenovo-shipped Fibocom FM350-GL (14c3:4d75) FCC unlock
 
-if [[ "$FCC_UNLOCK_DEBUG_LOG" == '1' ]]; then
+[ "$FCC_UNLOCK_DEBUG_LOG" = '1' ] && {
     exec 3>&1 4>&2
     trap 'exec 2>&4 1>&3' 0 1 2 3
-    exec 1>>/var/log/mm-fm350-fcc.log 2>&1
-fi
+    exec 1>>'/var/log/mm-fm350-fcc.log' 2>&1
+}
 
 # require program name and at least 2 arguments
 [ $# -lt 2 ] && exit 1
@@ -34,12 +35,12 @@ done
 DEVICE="/dev/$AT_PORT"
 
 at_command() {
-    exec 99<>"$DEVICE"
-    echo -e "$1\r" >&99
-    read answer <&99
-    read answer <&99
+    exec 9<>"$DEVICE"
+    printf "%s\r" "$1" >&9
+    read answer <&9
+    read answer <&9
     echo "$answer"
-    exec 99>&-
+    exec 9>&-
 }
 
 log() {
@@ -50,40 +51,36 @@ error() {
     echo "$1" >&2
 }
 
-VENDOR_ID_HASH="3df8c719"
+VENDOR_ID_HASH='3df8c719'
 
-for i in {1..9}; do
-    log "Requesting challenge from WWAN modem (attempt #${i})"
-    RAW_CHALLENGE=$(at_command "at+gtfcclockgen")
-    CHALLENGE=$(echo "$RAW_CHALLENGE" | grep -o '0x[0-9a-fA-F]\+' | awk '{print $1}')
+i=1
+while [ "$i" -le 9 ]; do
+    log "Requesting challenge from WWAN modem (attempt #$i)"
+    RAW_CHALLENGE="$(at_command 'at+gtfcclockgen')"
+    CHALLENGE="$(echo "$RAW_CHALLENGE" | grep -o '0x[0-9a-fA-F]\+' | awk '{print $1}')"
 
-    if [ -n "$CHALLENGE" ]; then
+    [ -n "$CHALLENGE" ] && {
         log "Got challenge from modem: $CHALLENGE"
-        HEX_CHALLENGE=$(printf "%08x" "$CHALLENGE")
-        COMBINED_CHALLENGE="${HEX_CHALLENGE}$(printf "%.8s" "${VENDOR_ID_HASH}")"
-        RESPONSE_HASH=$(echo "$COMBINED_CHALLENGE" | xxd -r -p | sha256sum | cut -d ' ' -f 1)
-        TRUNCATED_RESPONSE=$(printf "%.8s" "$RESPONSE_HASH")
-        RESPONSE=$(printf "%d" "0x$TRUNCATED_RESPONSE")
+        HEX_CHALLENGE="$(printf '%08x' "$CHALLENGE")"
+        COMBINED_CHALLENGE="$HEX_CHALLENGE$(printf '%.8s' "$VENDOR_ID_HASH")"
+        RESPONSE_HASH="$(echo "$COMBINED_CHALLENGE" | xxd -r -p | sha256sum | cut -d ' ' -f 1)"
+        TRUNCATED_RESPONSE="$(printf '%.8s' "$RESPONSE_HASH")"
+        RESPONSE="$(printf '%d' "0x$TRUNCATED_RESPONSE")"
 
         log "Sending response to WWAN modem: $RESPONSE"
-        UNLOCK_RESPONSE=$(at_command "at+gtfcclockver=$RESPONSE")
+        UNLOCK_RESPONSE="$(at_command "at+gtfcclockver=$RESPONSE")"
 
-        if [[ "$UNLOCK_RESPONSE" == "+GTFCCLOCKVER:"* ]]; then
-            UNLOCK_RESULT=$(echo "$UNLOCK_RESPONSE" | grep -o '[0-9]\+')
-            if [[ "$UNLOCK_RESULT" == "1" ]]; then
+        echo "$UNLOCK_RESPONSE" | grep -q '^+GTFCCLOCKVER:' && {
+            UNLOCK_RESULT="$(echo "$UNLOCK_RESPONSE" | grep -o '[0-9]*')"
+            [ "$UNLOCK_RESULT" = '1' ] && {
                 log "FCC unlock succeeded"
                 exit 0
-            else
-                error "FCC unlock failed. Got result: $UNLOCK_RESULT"
-            fi
-        else
-            error "Unlock failed. Got response: $UNLOCK_RESPONSE"
-        fi
-    else
-        error "Failed to obtain FCC challenge. Got: ${RAW_CHALLENGE}"
-    fi
+            } || error "FCC unlock failed. Got result: $UNLOCK_RESULT"
+        } || error "Unlock failed. Got response: $UNLOCK_RESPONSE"
+    } || error "Failed to obtain FCC challenge. Got: $RAW_CHALLENGE"
 
     sleep 0.5
+    i="$((i + 1))"
 done
 
 exit 2