signal parsing - better input validation

The helper function we use for signal name mapping does not
check for negative numbers nor invalid (too-high) ones. This
can yield unexpected error messages:

   # podman kill -s -1 foo
   ERRO[0000] unknown signal "18446744073709551615"

This PR introduces a small wrapper for it that:

  1) Strips off a leading dash, allowing '-1' or '-HUP'
     as valid inputs; and
  2) Rejects numbers <1 or >64 (SIGRTMAX)

Also adds a test suite checking signal handling as well as
ensuring that invalid signals are rejected by the command line.

Fixes: #4746

Signed-off-by: Ed Santiago <santiago@redhat.com>

test/system/130-kill.bats

@@ -0,0 +1,92 @@
+#!/usr/bin/env bats   -*- bats -*-
+#
+# tests for podman kill
+#
+
+load helpers
+
+@test "podman kill - test signal handling in containers" {
+    # Start a container that will handle all signals by emitting 'got: N'
+    local -a signals=(1 2 3 4 5 6 8 10 12 13 14 15 16 20 21 22 23 24 25 26 64)
+    run_podman run -d $IMAGE sh -c "for i in ${signals[*]}; do trap \"echo got: \$i\" \$i; done; echo READY; while ! test -e /stop; do sleep 0.05; done;echo DONE"
+    cid="$output"
+
+    # Run 'logs -f' on that container, but run it in the background with
+    # redirection to a named pipe from which we (foreground job) read
+    # and confirm that signals are received. We can't use run_podman here.
+    local fifo=${PODMAN_TMPDIR}/podman-kill-fifo.$(random_string 10)
+    mkfifo $fifo
+    $PODMAN logs -f $cid >$fifo &
+    podman_log_pid=$!
+    # First container emits READY when ready; wait for it.
+    read -t 10 ready <$fifo
+    is "$ready" "READY" "first log message from container"
+
+    # Helper function: send the given signal, verify that it's received.
+    kill_and_check() {
+        local signal=$1
+        local signum=${2:-$1}       # e.g. if signal=HUP, we expect to see '1'
+
+        run_podman kill -s $signal $cid
+        read -t 10 actual <$fifo
+        is "$actual" "got: $signum" "Signal $signal handled by container"
+    }
+
+    # Send signals in random order; make sure each one is received
+    for s in $(fmt --width=2 <<< "${signals[*]}" | sort --random-sort);do
+        kill_and_check $s
+    done
+
+    # Variations: with leading dash; by name, with/without dash or SIG
+    kill_and_check -1        1
+    kill_and_check -INT      2
+    kill_and_check  FPE      8
+    kill_and_check -SIGUSR1 10
+    kill_and_check  SIGUSR2 12
+
+    # Done. Tell the container to stop, and wait for final DONE
+    run_podman exec $cid touch /stop
+    read -t 5 done <$fifo
+    is "$done" "DONE" "final log message from container"
+
+    # Clean up
+    run_podman wait $cid
+    run_podman rm $cid
+    wait $podman_log_pid
+}
+
+@test "podman kill - rejects invalid args" {
+    # These errors are thrown by the imported docker/signal.ParseSignal()
+    local -a bad_signal_names=(0 SIGBADSIG SIG BADSIG %% ! "''" '""' " ")
+    for s in ${bad_signal_names[@]}; do
+        # 'nosuchcontainer' is fine: podman should bail before it gets there
+        run_podman 125 kill -s $s nosuchcontainer
+        is "$output" "Error: Invalid signal: $s" "Error from kill -s $s"
+
+        run_podman 125 pod kill -s $s nosuchpod
+        is "$output" "Error: Invalid signal: $s" "Error from pod kill -s $s"
+    done
+
+    # Special case: these too are thrown by docker/signal.ParseSignal(),
+    # but the dash sign is stripped by our wrapper in utils, so the
+    # error message doesn't include the dash.
+    local -a bad_dash_signals=(-0 -SIGBADSIG -SIG -BADSIG -)
+    for s in ${bad_dash_signals[@]}; do
+        run_podman 125 kill -s $s nosuchcontainer
+        is "$output" "Error: Invalid signal: ${s##-}" "Error from kill -s $s"
+    done
+
+    # This error (signal out of range) is thrown by our wrapper
+    local -a bad_signal_nums=(65 -65 96 999 99999999)
+    for s in ${bad_signal_nums[@]}; do
+        run_podman 125 kill -s $s nosuchcontainer
+        is "$output" "Error: valid signals are 1 through 64" \
+           "Error from kill -s $s"
+    done
+
+    # 'podman create' uses the same parsing code
+    run_podman 125 create --stop-signal=99 $IMAGE
+    is "$output" "Error: valid signals are 1 through 64" "podman create"
+}
+
+# vim: filetype=sh