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scd:piv: Fix RSA decryption. 

* scd/app-piv.c (do_decipher): Fixup leading zero byte.
--

Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2019-04-04 12:51:21 +02:00
parent 310944aa37
commit 958172cc3a
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
1 changed files with 25 additions and 6 deletions
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31
scd/app-piv.c
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@ -2434,15 +2434,34 @@ do_decipher (app_t app, const char *keyidstr,
/* Check that the ciphertext has the right length; due to internal
* convey mechanism using MPIs leading zero bytes might have been
* lost. Adjust for this. Note that for ECC this actually
* superfluous because the first octet is always '04' to indicate an
* lost. Adjust for this. Unfortunately the ciphertext might have
* also been prefixed with a leading zero to make it a positive
* number; that may be a too long frame and we need to adjust for
* this too. Note that for ECC thoses fixes are not reqquired
* because the first octet is always '04' to indicate an
* uncompressed point. */
if (indatalen > framelen)
{
err = gpg_error (GPG_ERR_INV_VALUE);
log_error ("piv: input of %zu octets too large for mechanism %d\n",
indatalen, mechanism);
goto leave;
if (mechanism == PIV_ALGORITHM_RSA
&& indatalen == framelen + 1 && !*indata)
{
indata_buffer = xtrycalloc (1, framelen);
if (!indata_buffer)
{
err = gpg_error_from_syserror ();
goto leave;
}
memcpy (indata_buffer, indata+1, framelen);
indata = indata_buffer;
indatalen = framelen;
}
else
{
err = gpg_error (GPG_ERR_INV_VALUE);
log_error ("piv: input of %zu octets too large for mechanism %d\n",
indatalen, mechanism);
goto leave;
}
}
if (indatalen < framelen)
{