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Adjust for signed integer passed to OpenPGP card decrypt.

This commit is contained in:
Werner Koch 2011-08-08 10:44:03 +02:00
parent 663768f9af
commit 14e0b60efd
2 changed files with 26 additions and 8 deletions
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5
scd/ChangeLog
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@ -1,3 +1,8 @@
2011-08-08 Werner Koch <wk@g10code.com>
* app-openpgp.c (do_decipher): Take care of accidentally passed
signed integer data with a leading 0.
2011-06-16 Werner Koch <wk@g10code.com>
* app-openpgp.c (send_key_data): Implemented chunked mode.

29
scd/app-openpgp.c
View File

@ -3367,17 +3367,19 @@ do_decipher (app_t app, const char *keyidstr,
rc = verify_chv2 (app, pincb, pincb_arg);
if (!rc)
{
size_t fixuplen;
int fixuplen;
unsigned char *fixbuf = NULL;
int padind = 0;
/* 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. */
cryptogram. Due to internal use of MPIs these 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 a signed conversion was used
we may also encounter one leading zero followed by the correct
length. We fix that as well. */
if (indatalen >= (128-16) && indatalen < 128) /* 1024 bit key. */
fixuplen = 128 - indatalen;
else if (indatalen >= (192-16) && indatalen < 192) /* 1536 bit key. */
@ -3388,10 +3390,16 @@ do_decipher (app_t app, const char *keyidstr,
fixuplen = 384 - indatalen;
else if (indatalen >= (512-16) && indatalen < 512) /* 4096 bit key. */
fixuplen = 512 - indatalen;
else if (!*(const char *)indata && (indatalen == 129
|| indatalen == 193
|| indatalen == 257
|| indatalen == 385
|| indatalen == 513))
fixuplen = -1;
else
fixuplen = 0;
if (fixuplen)
if (fixuplen > 0)
{
/* While we have to prepend stuff anyway, we can also
include the padding byte here so that iso1816_decipher
@ -3408,6 +3416,11 @@ do_decipher (app_t app, const char *keyidstr,
indatalen = fixuplen + indatalen;
padind = -1; /* Already padded. */
}
else if (fixuplen < 0)
{
/* We use the extra leading zero as the padding byte. */
padind = -1;
}
if (app->app_local->cardcap.ext_lc_le && indatalen > 254 )
{