kholia
commented
7 years ago The bug seems to be in Symmetrically_Encrypted_Data_Packet function (affected function). It seems that inappropriate code from Symmetrically_Encrypted_and_MDC_Packet function was inserted into the affected function.
diff --git a/src/gpg2john.c b/src/gpg2john.c
index efd8959..6517e80 100644
--- a/src/gpg2john.c
+++ b/src/gpg2john.c
@@ -934,11 +934,8 @@ Symmetrically_Encrypted_Data_Packet(int len, int first, int partial, char *hash)
if (first) {
cp = hash;
totlen = 0;
- // printf("\tVer %d\n", Getc());
- Getc(); // version (we only read this from the first packet. Not read from rest of the 'partial' packets.
- } else
- ++len; // we want the 'full' length for subsquent partial packets, since the logic is len-1 we simply fake it out.
- totlen += (len-1);
+ }
+ totlen += (len);
switch (mode) {
case SYM_ALG_MODE_NOT_SPECIFIED:
@@ -963,7 +960,7 @@ Symmetrically_Encrypted_Data_Packet(int len, int first, int partial, char *hash)
if (give(len, m_data, sizeof(m_data)) != len)
return;
- cp += print_hex(m_data, len - 1, cp);
+ cp += print_hex(m_data, len, cp);
if (!partial) {
// we only dump the packet out when we get the 'non-partial' packet (i.e. last one).Here is a symmetrically encrypted GPG file which gets cracked only after applying this patch.
I am not sure if this patch solves the problem 100% but it is a start.
Tip: Use pgpdump (gpg2john is based on it) to rule out parsing problems with the original files.
2600box
ghost
frank-dittrich
Setup
OK cases
Not OK
GPG files lacking MDC seem to be run into parsing problems.
If the size and contents of "large" file are varied, gpg2john runs into multiple different problems. These
gpg2johnerror message can also change for different runs ofgpgon the same input file.For other files, the following error message is shown by
gpg2john,Note: Cracking of symmetrically encrypted files lacking MDC is currently not practically possible due to too many false positives involved. See https://github.com/magnumripper/JohnTheRipper/issues/1892 for details.