From b7bd5fa604c994660fd4718e503484a65973a5c2 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <nat.lasseter@york.ac.uk>
Date: Mon, 21 Nov 2022 17:52:09 +0000
Subject: Add default issuer option

---
 Readme.textile |  4 ++--
 twofa          | 36 +++++++++++++++++++++++++++++++-----
 2 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/Readme.textile b/Readme.textile
index d824368..5f4825e 100644
--- a/Readme.textile
+++ b/Readme.textile
@@ -32,11 +32,11 @@ p. If a HOTP code is requested, the file will be canoncalised.
 
 p. Each issuer should appear on it's own line with the following format:
 
-bc. Method Issuer Secret [TDC [Length [Hash]]]
+bc. [*]Method Issuer Secret [TDC [Length [Hash]]]
 
 h4. Required fields
 
-- Method := The OTP type, currently @totp@ or @hotp@.
+- Method := The OTP type, currently @totp@ or @hotp@. Optionally, prefixing the method with an asterisk specifies this is the default issuer to be used if one is not specified on the command line.
 - Issuer := Human name to identify this issuer.
 - Secret := The BASE32 shared secret.
 
diff --git a/twofa b/twofa
index 487b094..d5e2526 100755
--- a/twofa
+++ b/twofa
@@ -31,6 +31,12 @@ def fatal(msg)
 end
 
 class Secrets
+  class MultipleDefaultException < StandardError
+    def initialize
+      super("Multiple default issuers specified in config file")
+    end
+  end
+
   class Secret
     def initialize(method, secret, tdc, dig, hsh)
       @method = method
@@ -76,25 +82,37 @@ class Secrets
 
   def initialize(arr)
     @secrets = {}
+    @default = nil
+
     arr.each do |secretline|
       m, i, s, tc, d, h = secretline.split
+
+      if m[0] == ?*
+        raise MultipleDefaultException.new unless @default.nil?
+        m = m[1..-1]
+        @default = i
+      end
+
       case m
       when 'totp'
         tc = tc&.to_i || 30
       when 'hotp'
         tc = tc&.to_i || 0
       end
+
       @secrets[i] = Secret.new(m, s, tc, d&.to_i || 6, h || "sha1")
     end
   end
 
+  attr_reader :default
+
   def [](issuer)
     @secrets[issuer]
   end
 
   def puts
     @secrets.map do |i, s|
-      "#{s.method} #{i} #{s.puts}"
+      "#{i == @default ? ?* : ''}#{s.method} #{i} #{s.puts}"
     end
   end
 end
@@ -118,12 +136,20 @@ end
 TWOFAFILE = opts[:twofa_file]
 fatal("No 2fa issuers file at #{File.absolute_path(TWOFAFILE)}") unless File.exist?(TWOFAFILE)
 
-SECRETS = Secrets.new(File.readlines(TWOFAFILE).map(&:strip))
+begin
+  SECRETS = Secrets.new(File.readlines(TWOFAFILE).map(&:strip))
+rescue Secrets::MultipleDefaultException => e
+  fatal(e.message)
+end
 
-ISSUER = ARGV.shift&.strip&.downcase
-fatal("Specify issuer") if ISSUER.nil?
+issuer = ARGV.shift&.strip
+if issuer.nil?
+  issuer = SECRETS.default
+  fatal("Specify issuer") if issuer.nil?
+  puts "Using default issuer: #{issuer}"
+end
 
-sec = SECRETS[ISSUER]
+sec = SECRETS[issuer]
 fatal("No such issuer") if sec.nil?
 
 case sec.method
-- 
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