Added derdump.py, a fault-tolerant developer-friendly DER / ASN.1 pretty printer

Fixed a small bug in inputter.c

diff --git a/derdump.py b/derdump.py
new file mode 100755 (executable)
index 0000000..aa31b1d
--- /dev/null
+++ b/derdump.py
@@ -0,0 +1,139 @@
+#!/usr/bin/python
+
+import sys
+
+if len (sys.argv) != 2:
+       print 'Usage: ' + sys.argv [0] + 'file.der'
+       sys.exit (1)
+
+der = open (sys.argv [1], 'r').read (65537)
+ofs = 0
+
+def eof ():
+       global ofs, der
+       return ofs >= len (der)
+
+def read1 ():
+       global ofs, der
+       if eof ():
+               print 'ATTEMPTED READ BEYOND EOF (RETURNING 0x00)'
+               return 0
+       else:
+               ofs = ofs + 1
+               return ord (der [ofs-1])
+
+nesting = []
+
+class2str = {
+       0: 'Universal',
+       1: 'Application',
+       2: 'Contextual',
+       3: 'Private'
+}
+
+pc2str = {
+       0: 'Primitive',
+       1: 'Constructed'
+}
+
+universal2str = {
+       0: 'End-Of-Content',
+       1: 'BOOLEAN',
+       2: 'INTEGER',
+       3: 'BITSTRING',
+       4: 'OCTETSTRING',
+       5: 'NULL',
+       6: 'OID',
+       7: 'Object-Descriptor',
+       8: 'EXTERNAL',
+       9: 'REAL',
+       10: 'ENUMERATED',
+       11: 'EMBEDDED PDV',
+       12: 'UTF8String',
+       13: 'RELATIVE-OID',
+       14: '*****',
+       15: '*****',
+       16: 'SEQUENCE (OF)',
+       17: 'SET (OF)',
+       18: 'NumericString',
+       19: 'PrintableString',
+       20: 'T61String',
+       21: 'VideotexString',
+       22: 'IA5String',
+       23: 'UTCTime',
+       24: 'GeneralizedTime',
+       25: 'GraphicString',
+       26: 'VisibleString',
+       27: 'GeneralString',
+       28: 'UniversalString',
+       29: 'CHARACTER STRING',
+       30: 'BMPString',
+       31: '*****'
+}
+
+while not eof ():
+
+       while nesting != [] and ofs >= nesting [-1]:
+               if ofs > nesting [-1]:
+                       print 'READ OFFSET %d EXCEEDS ENCAPSULATION %d (RETURNING)' % (ofs, nesting [1])
+               ofs = nesting.pop ()
+
+       tag = read1 ()
+       tag_class = (tag & 0xc0) >> 6
+       tag_pc = (tag & 0x20) != 0
+       tag_num = tag & 0x1f
+
+       lenlen = read1 ()
+       if lenlen & 0x80 == 0:
+               leng = lenlen
+               lenlen = 1
+       else:
+               lenlen = lenlen - 0x80 + 1
+               leng = 0
+               i = 1
+               while i < lenlen:
+                       leng <<= 8
+                       leng = leng + read1 ()
+                       i = i + 1
+
+       if tag_class == 0:
+               meaning = universal2str [tag_num]
+       elif tag_class == 1:
+               meaning = '[APPLICATION ' + str (tag_num) + ']'
+       elif tag_class == 2:
+               meaning = '[' + str (tag_num) + ']'
+       else:
+               meaning = '[PRIVATE ' + str (tag_num) + ']'
+
+       print '%s%s: tag 0x%02x %s%d @%d ^%d, %s, %s' % (
+                       '  ' * len (nesting),
+                       meaning, tag,
+                       '#' * lenlen, leng,
+                       ofs - lenlen - 1,
+                       len (nesting),
+                       class2str [tag_class],
+                       pc2str [tag_pc] )
+
+       if tag_pc == 0 and leng > 0:
+               print '  ' * ( len (nesting) + 1 ),
+               cstr = ' == "'
+               while leng > 0:
+                       ch = read1 ()
+                       print '%02x' % ch,
+                       if 32 <= ch <= 127:
+                               cstr = cstr + chr (ch)
+                       else:
+                               cstr = cstr + '.'
+                       leng = leng - 1
+               cstr = cstr + '"'
+               print cstr
+
+       if tag_pc != 0:
+               # print 'Now at', ofs, 'adding', leng, 'pushing', ofs + leng
+               nesting.append (ofs + leng)
+
+while nesting != []:
+       if ofs != nesting [-1]:
+               print 'NESTING NOT ENDED CORRECTLY, OFFSET IS %d INSTEAD OF %d (CONTINUING)' % (ofs, nesting [-1])
+       nesting.pop ()
+

diff --git a/inputter.c b/inputter.c
index e7bff6f..408673d 100644 (file)
--- a/inputter.c
+++ b/inputter.c
@@ -29,7 +29,7 @@ int getbyte (char *output) {
        *output = 0;
 
        if (status == error) {
-               return;
+               return 0;
        }
 
        do {