Add support for Pushbullet notifications

This commit adds the zed_notify_pushbullet() function and hooks
it into zed_notify(), thereby integrating it with the existing
"notify" ZEDLETs.  This enables ZED to push notifications to your
desktop computer and/or mobile device(s).  It is configured with the
ZED_PUSHBULLET_ACCESS_TOKEN and ZED_PUSHBULLET_CHANNEL_TAG variables
in zed.rc.

  https://www.pushbullet.com/

The Makefile install-data-local target has been replaced with
install-data-hook.  With the "-local" target, there is no particular
guarantee of execution order.  But with the zed.rc now potentially
containing sensitive information (i.e., the Pushbullet access token),
the recommended permissions have changed to 0600.  The "-hook" target
is always executed after the main rule's work is done; thus, the
chmod will always take place after the zed.rc file has been installed.

  https://www.gnu.org/software/automake/manual/automake.html#Extending

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>

cmd/zed/Makefile.am

@@ -62,10 +62,11 @@ zedconfdefaults = \
 	resilver.finish-notify.sh \
 	scrub.finish-notify.sh
 
-install-data-local:
+install-data-hook:
 	$(MKDIR_P) "$(DESTDIR)$(zedconfdir)"
 	for f in $(zedconfdefaults); do \
 	  test -f "$(DESTDIR)$(zedconfdir)/$${f}" -o \
 	       -L "$(DESTDIR)$(zedconfdir)/$${f}" || \
 	    ln -s "$(zedexecdir)/$${f}" "$(DESTDIR)$(zedconfdir)"; \
 	done
+	chmod 0600 "$(DESTDIR)$(zedconfdir)/zed.rc"

cmd/zed/zed.d/zed-functions.sh

@@ -195,6 +195,10 @@ zed_notify()
     [ "${rv}" -eq 0 ] && num_success=$((num_success + 1))
     [ "${rv}" -eq 1 ] && num_failure=$((num_failure + 1))
 
+    zed_notify_pushbullet "${subject}" "${pathname}"; rv=$?
+    [ "${rv}" -eq 0 ] && num_success=$((num_success + 1))
+    [ "${rv}" -eq 1 ] && num_failure=$((num_failure + 1))
+
     [ "${num_success}" -gt 0 ] && return 0
     [ "${num_failure}" -gt 0 ] && return 1
     return 2
@@ -243,6 +247,92 @@ zed_notify_email()
 }
 
 
+# zed_notify_pushbullet (subject, pathname)
+#
+# Send a notification via Pushbullet <https://www.pushbullet.com/>.
+# The access token (ZED_PUSHBULLET_ACCESS_TOKEN) identifies this client to the
+# Pushbullet server.  The optional channel tag (ZED_PUSHBULLET_CHANNEL_TAG) is
+# for pushing to notification feeds that can be subscribed to; if a channel is
+# not defined, push notifications will instead be sent to all devices
+# associated with the account specified by the access token.
+#
+# Requires awk, curl, and sed executables to be installed in the standard PATH.
+#
+# References
+#   https://docs.pushbullet.com/
+#   https://www.pushbullet.com/security
+#
+# Arguments
+#   subject: notification subject
+#   pathname: pathname containing the notification message (OPTIONAL)
+#
+# Globals
+#   ZED_PUSHBULLET_ACCESS_TOKEN
+#   ZED_PUSHBULLET_CHANNEL_TAG
+#
+# Return
+#   0: notification sent
+#   1: notification failed
+#   2: not configured
+#
+zed_notify_pushbullet()
+{
+    local subject="$1"
+    local pathname="${2:-"/dev/null"}"
+    local msg_body
+    local msg_tag
+    local msg_json
+    local msg_out
+    local msg_err
+    local url="https://api.pushbullet.com/v2/pushes"
+
+    [ -n "${ZED_PUSHBULLET_ACCESS_TOKEN}" ] || return 2
+
+    [ -n "${subject}" ] || return 1
+    if [ ! -r "${pathname}" ]; then
+        zed_log_err "pushbullet cannot read \"${pathname}\""
+        return 1
+    fi
+
+    zed_check_cmd "awk" "curl" "sed" || return 1
+
+    # Escape the following characters in the message body for JSON:
+    # newline, backslash, double quote, horizontal tab, vertical tab,
+    # and carriage return.
+    #
+    msg_body="$(awk '{ ORS="\\n" } { gsub(/\\/, "\\\\"); gsub(/"/, "\\\"");
+        gsub(/\t/, "\\t"); gsub(/\f/, "\\f"); gsub(/\r/, "\\r"); print }' \
+        "${pathname}")"
+
+    # Push to a channel if one is configured.
+    #
+    [ -n "${ZED_PUSHBULLET_CHANNEL_TAG}" ] && msg_tag="$(printf \
+        '"channel_tag": "%s", ' "${ZED_PUSHBULLET_CHANNEL_TAG}")"
+
+    # Construct the JSON message for pushing a note.
+    #
+    msg_json="$(printf '{%s"type": "note", "title": "%s", "body": "%s"}' \
+        "${msg_tag}" "${subject}" "${msg_body}")"
+
+    # Send the POST request and check for errors.
+    #
+    msg_out="$(curl -u "${ZED_PUSHBULLET_ACCESS_TOKEN}:" -X POST "${url}" \
+        --header "Content-Type: application/json" --data-binary "${msg_json}" \
+        2>/dev/null)"; rv=$?
+    if [ "${rv}" -ne 0 ]; then
+        zed_log_err "curl exit=${rv}"
+        return 1
+    fi
+    msg_err="$(echo "${msg_out}" \
+        | sed -n -e 's/.*"error" *:.*"message" *: *"\([^"]*\)".*/\1/p')"
+    if [ -n "${msg_err}" ]; then
+        zed_log_err "pushbullet \"${msg_err}"\"
+        return 1
+    fi
+    return 0
+}
+
+
 # zed_rate_limit (tag, [interval])
 #
 # Check whether an event of a given type [tag] has already occurred within the

cmd/zed/zed.d/zed.rc

@@ -1,5 +1,7 @@
 ##
 # zed.rc
+#
+# This file should be owned by root and permissioned 0600.
 ##
 
 ##
@@ -31,6 +33,24 @@
 #
 #ZED_NOTIFY_VERBOSE=0
 
+##
+# Pushbullet access token.
+# This grants full access to your account -- protect it accordingly!
+#   <https://www.pushbullet.com/get-started>
+#   <https://www.pushbullet.com/account>
+# Disabled by default; uncomment to enable.
+#
+#ZED_PUSHBULLET_ACCESS_TOKEN=""
+
+##
+# Pushbullet channel tag for push notification feeds that can be subscribed to.
+#   <https://www.pushbullet.com/my-channel>
+# If not defined, push notifications will instead be sent to all devices
+#   associated with the account specified by the access token.
+# Disabled by default; uncomment to enable.
+#
+#ZED_PUSHBULLET_CHANNEL_TAG=""
+
 ##
 # Default directory for zed state files.
 #