It seems there is a bug in the current version of GPG2 (2.0.17) that prevents it
from uncompressing compressed data packets with uncompressed data:
$ gpg2 --list-packets compressed.pgp
:compressed packet: algo=0
gpg: uncompressing failed: Unknown compression algorithm
I have tracked the problem down to an erroneous if in g10/mainproc.c. Patch
below:
- gnupg-2.0.17/g10/mainproc.c 2011-01-09 22:06:16.000000000 +0000
+++ gnupg-2.0.17_patched/g10/mainproc.c 2011-03-18 12:11:35.000000000 +0000
@@ -771,9 +771,7 @@
int rc;
/*printf("zip: compressed data packet\n");*/- if( !zd->algorithm )
- rc=G10ERR_COMPR_ALGO;
- else if( c->sigs_only )
+ if( c->sigs_only )
rc = handle_compressed( c, zd, proc_compressed_cb, c );
else if( c->encrypt_only )
rc = handle_compressed( c, zd, proc_encrypt_cb, c );
By removing that incorrect if statement, gpg2 now correctly handles uncompressed
data.
Note that the if statement is clearly incorrect, the uncompressed algorithm
value is 0 so it would always return an error, and checking for a correct
compression algorithm is already done in the handle_compressed function.
After removing that if, gpg2 correctly handles this data:
$ gpg2 --list-packets compressed.pgp
:compressed packet: algo=0
:literal data packet:
mode u (75), created 3188556365, name="",
raw data: 12 bytes
Hope that you can include this simple patch in an upcoming release.