diff options
Diffstat (limited to 'scd/app-openpgp.c')
| -rw-r--r-- | scd/app-openpgp.c | 47 |
1 files changed, 44 insertions, 3 deletions
diff --git a/scd/app-openpgp.c b/scd/app-openpgp.c index bf7c0afc5..5cfec0407 100644 --- a/scd/app-openpgp.c +++ b/scd/app-openpgp.c @@ -1,5 +1,5 @@ /* app-openpgp.c - The OpenPGP card application. - * Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc. + * Copyright (C) 2003, 2004, 2005, 2007 Free Software Foundation, Inc. * * This file is part of GnuPG. * @@ -2456,8 +2456,49 @@ do_decipher (app_t app, const char *keyidstr, rc = verify_chv2 (app, pincb, pincb_arg); if (!rc) - rc = iso7816_decipher (app->slot, indata, indatalen, 0, - outdata, outdatalen); + { + size_t fixuplen; + + /* We might encounter a couple of leading zeroes in the + cryptogram. Due to internal use of MPIs thease leading + zeroes are stripped. However the OpenPGp card expects + exactly 128 bytes for the cryptogram (for a 1k key). Thus we + need to fix it up. We do this for up to 16 leading zero + bytes; a cryptogram with more than this is with a very high + probability anyway broken. */ + if (indatalen >= (128-16) && indatalen < 128) /* 1024 bit key. */ + fixuplen = 128 - indatalen; + else if (indatalen >= (256-16) && indatalen < 256) /* 2048 bit key. */ + fixuplen = 256 - indatalen; + else if (indatalen >= (192-16) && indatalen < 192) /* 1536 bit key. */ + fixuplen = 192 - indatalen; + else + fixuplen = 0; + if (fixuplen) + { + unsigned char *fixbuf; + + /* While we have to prepend stuff anyway, we can also + include the padding byte here so that iso1816_decipher + does not need to do yet another data mangling. */ + fixuplen++; + fixbuf = xtrymalloc (fixuplen + indatalen); + if (!fixbuf) + rc = gpg_error_from_syserror (); + else + { + memset (fixbuf, 0, fixuplen); + memcpy (fixbuf+fixuplen, indata, indatalen); + rc = iso7816_decipher (app->slot, fixbuf, fixuplen+indatalen, -1, + outdata, outdatalen); + xfree (fixbuf); + } + + } + else + rc = iso7816_decipher (app->slot, indata, indatalen, 0, + outdata, outdatalen); + } return rc; } |