use editconf.py to mangle /etc/postfix/master.cf

* using it to enable the Postfix submission service
* per @mkropat's suggestion in #69, set an option to distinguish submission from regular smpd in syslog by giving submission a new name (doing this here to test that editconf is working right on master.cf)

setup/mail.sh

+#!/bin/bash
 # SMTP/IMAP: Postfix and Dovecot
 ################################
 
@@ -25,8 +26,11 @@ mkdir -p $STORAGE_ROOT/mail
 # POSTFIX
 #########
 
-# Enable the 'submission' port 587 listener.
-sed -i "s/#submission/submission/" /etc/postfix/master.cf
+# Enable the 'submission' port 587 smtpd server, and give it a different
+# name in syslog to distinguish it from the port 25 smtpd server.
+tools/editconf.py /etc/postfix/master.cf -s -w \
+	"submission=inet n       -       -       -       -       smtpd
+	  -o syslog_name=postfix/submission"
 
 # Enable TLS and require it for all user authentication.
 tools/editconf.py /etc/postfix/main.cf \

tools/editconf.py

 #!/usr/bin/python3
+#
+# This is a helper tool for editing configuration files during the setup
+# process. The tool is given new values for settings as command-line
+# arguments. It comments-out existing setting values in the configuration
+# file and adds new values either after their former location or at the
+# end.
+#
+# The configuration file has settings that look like:
+#
+# NAME=VALUE
+#
+# If the -s option is given, then space becomes the delimiter, i.e.:
+#
+# NAME VALUE
+#
+# If the -w option is given, then setting lines continue onto following
+# lines while the lines start with whitespace, e.g.:
+#
+# NAME VAL
+#   UE 
 
 import sys, re
 
 # sanity check
 if len(sys.argv) < 3:
-	print("usage: python3 editconf.py /etc/file.conf [-s] NAME=VAL [NAME=VAL ...]")
+	print("usage: python3 editconf.py /etc/file.conf [-s] [-w] [-t] NAME=VAL [NAME=VAL ...]")
 	sys.exit(1)
 
 # parse command line arguments
@@ -13,39 +33,64 @@ settings = sys.argv[2:]
 
 delimiter = "="
 delimiter_re = r"\s*=\s*"
-if settings[0] == "-s":
-	settings.pop(0)
-	delimiter = " "
-	delimiter_re = r"\s+"
+folded_lines = False
+testing = False
+while settings[0][0] == "-" and settings[0] != "--":
+	opt = settings.pop(0)
+	if opt == "-s":
+		# Space is the delimiter
+		delimiter = " "
+		delimiter_re = r"\s+"
+	elif opt == "-w":
+		folded_lines = True
+	elif opt == "-t":
+		testing = True
+	else:
+		print("Invalid option.")
+		sys.exit(1)
 
 # create the new config file in memory
+
 found = set()
 buf = ""
-for line in open(filename):
+input_lines = list(open(filename))
+
+while len(input_lines) > 0:
+	line = input_lines.pop(0)
+
+	# If this configuration file uses folded lines, append any folded lines
+	# into our input buffer.
+	if folded_lines and line[0] not in ("#", " ", ""):
+		while len(input_lines) > 0 and input_lines[0][0] in " \t":
+			line += input_lines.pop(0)
+
+	# See if this line is for any settings passed on the command line.
 	for i in range(len(settings)):
+		# Check that this line contain this setting from the command-line arguments.
 		name, val = settings[i].split("=", 1)
-		m = re.match("\s*" + re.escape(name) + delimiter_re + "(.*?)\s*$", line)
-		if m:
-			# If this is already the setting, do nothing.
-			if m.group(1) == val:
-				buf += line
-				found.add(i)
-				break
-			
-			# comment-out the existing line
-			buf += "#" + line
-			
-			# if this option oddly appears more than once, don't add the setting again
-			if i in found:
-				break
-			
-			# add the new setting
-			buf += name + delimiter + val + "\n"
-			
-			# note that we've applied this option
+		m = re.match("\s*" + re.escape(name) + delimiter_re + "(.*?)\s*$", line, re.S)
+		if not m: continue
+
+		# If this is already the setting, do nothing.
+		if m.group(1) == val:
+			buf += line
 			found.add(i)
-			
 			break
+		
+		# comment-out the existing line (also comment any folded lines)
+		buf += "#" + line.rstrip().replace("\n", "\n#") + "\n"
+		
+		# if this option oddly appears more than once, don't add the setting again
+		if i in found:
+			break
+		
+		# add the new setting
+		buf += name + delimiter + val + "\n"
+		
+		# note that we've applied this option
+		found.add(i)
+		
+		break
 	else:
 		# If did not match any setting names, pass this line through.
 		buf += line
@@ -56,7 +101,10 @@ for i in range(len(settings)):
 		name, val = settings[i].split("=", 1)
 		buf += name + delimiter + val + "\n"
 
-# Write out the new file.
-with open(filename, "w") as f:
-	f.write(buf)
-	
+if not testing:
+	# Write out the new file.
+	with open(filename, "w") as f:
+		f.write(buf)
+else:
+	# Just print the new file to stdout.
+	print(buf)