From bc2a23e0e7454fcba9770644055ac4d048db61e5 Mon Sep 17 00:00:00 2001
From: Vasil Velichkov <vvvelichkov@gmail.com>
Date: Tue, 27 Mar 2018 02:37:49 +0300
Subject: [PATCH] Check the gsm0503_xcch_decode return value

- Discard the message when gsm0503_xcch_decode returns -1
- Add automated decrypt test

See https://groups.google.com/d/msg/gr-gsm/9nOkIdrGOck/qTZh47McCQAJ
---
 .travis.yml                                   |  1 +
 lib/decoding/control_channels_decoder_impl.cc |  6 ++-
 tests/fixtures/grgsm_decode_decrypt1_expected | 12 ++++++
 tests/scripts/decrypt.sh                      | 37 +++++++++++++++++++
 4 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 tests/fixtures/grgsm_decode_decrypt1_expected
 create mode 100755 tests/scripts/decrypt.sh

diff --git a/.travis.yml b/.travis.yml
index fde90b4..2d66445 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,3 +20,4 @@ before_install:
 script:
 #  - docker run -it --rm $IMGNAME sh -c 'cd /src/build;make test'
   - docker run -it --rm $IMGNAME /src/tests/scripts/decode.sh
+  - docker run -it --rm $IMGNAME /src/tests/scripts/decrypt.sh
diff --git a/lib/decoding/control_channels_decoder_impl.cc b/lib/decoding/control_channels_decoder_impl.cc
index a6abaa3..bf0d976 100644
--- a/lib/decoding/control_channels_decoder_impl.cc
+++ b/lib/decoding/control_channels_decoder_impl.cc
@@ -105,7 +105,11 @@ namespace gr {
             //convert to soft bits
             ubits2sbits(bursts_u, bursts_s, 116 * 4);
             //decode
-            gsm0503_xcch_decode(result, bursts_s, &n_errors, &n_bits_total);
+            if (-1 == gsm0503_xcch_decode(result, bursts_s, &n_errors, &n_bits_total))
+            {
+                //Possibly an encrypted message
+                return;
+            }
 
             //extract header of the first burst of the four bursts
             pmt::pmt_t first_header_plus_burst = pmt::cdr(d_bursts[0]);
diff --git a/tests/fixtures/grgsm_decode_decrypt1_expected b/tests/fixtures/grgsm_decode_decrypt1_expected
new file mode 100644
index 0000000..378b495
--- /dev/null
+++ b/tests/fixtures/grgsm_decode_decrypt1_expected
@@ -0,0 +1,12 @@
+862210 1331352:  03 03 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
+862242 1332356:  00 01 03 03 49 06 1d 9f 6d 18 10 80 00 00 00 00 00 00 00 00 00 00 00
+862261 1331351:  01 73 35 06 27 00 03 50 18 a0 05 f4 01 5c 57 03 2b 2b 2b 2b 2b 2b 2b
+862312 1331350:  03 20 0d 06 35 11 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
+862344 1332354:  00 00 03 03 2d 06 1e 2b d9 62 f2 20 01 3e 95 78 7b 2b 2b 2b 2b 2b 2b
+862363 1331349:  03 42 45 13 05 1e 02 ea 81 5c 08 11 83 94 03 98 93 92 49 81 2b 2b 2b
+862414 1331348:  01 61 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
+862446 1332352:  00 00 03 03 49 06 1d 9f 6d 18 10 80 00 00 00 00 00 00 00 00 00 00 00
+862465 1331347:  01 81 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
+862516 1331346:  03 84 21 06 2e 0d 02 d5 00 63 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
+862548 1332376:  00 00 03 03 49 06 06 70 00 00 00 00 00 04 15 50 10 00 00 00 00 0a a8
+862567 1331345:  03 03 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
diff --git a/tests/scripts/decrypt.sh b/tests/scripts/decrypt.sh
new file mode 100755
index 0000000..afd12cc
--- /dev/null
+++ b/tests/scripts/decrypt.sh
@@ -0,0 +1,37 @@
+#!/bin/bash
+
+TEST_DIR=`dirname "$0"`
+
+# PYTHONPATH and LD_LIBRARY_PATH are needed on Fedora 26
+export PYTHONPATH=/usr/local/lib64/python2.7/site-packages/:/usr/local/lib64/python2.7/site-packages/grgsm/:$PYTHONPATH
+export LD_LIBRARY_PATH=/usr/local/lib64/:$LD_LIBRARY_PATH
+
+export AP_DECODE="grgsm_decode"
+export CAPFILE="../../test_data/vf_call6_a725_d174_g5_Kc1EF00BAB3BAC7002.cfile"
+export SHORTENED_CAPFILE="tmp.cfile"
+export RESULT_EXPECTED="../fixtures/grgsm_decode_decrypt1_expected"
+export RESULT_OBTAINED="grgsm_decode_test1_result"
+export RUNLINE="$AP_DECODE -c $SHORTENED_CAPFILE -s $((100000000/174)) -m SDCCH8 -t 1 -k 0x1E,0xF0,0x0B,0xAB,0x3B,0xAC,0x70,0x02 -v --ppm -10"
+echo "Testing with:"
+echo "  $RUNLINE"
+gnuradio-companion --version
+
+cd $TEST_DIR
+cat $CAPFILE | head -c -37000000 | head -c 35800000  > $SHORTENED_CAPFILE
+
+$RUNLINE | grep -A 999999 "862210 1331352:  03 03 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b" | tee $RESULT_OBTAINED
+diff -u $RESULT_EXPECTED $RESULT_OBTAINED
+TEST_RESULT=$?
+
+rm $RESULT_OBTAINED
+rm $SHORTENED_CAPFILE
+
+if [ $TEST_RESULT == 0 ]
+then
+  echo "   Result: PASSED"
+  exit 0
+else
+  echo "   Result: FAILED"
+  exit 1
+fi
+