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Fixed EOF detection for encrypted packets.

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The code won't get confused anymore by extra packages following the
encrypted one.
This commit is contained in:
Werner Koch 2009-10-02 12:31:14 +00:00
parent dcae377643
commit 3b7dc7b384
3 changed files with 143 additions and 44 deletions
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12
g10/ChangeLog
View File

@ -1,6 +1,16 @@
2009-10-02 Werner Koch <wk@g10code.com>
* encr-data.c (decode_filter_context_s): Add fields PARTIAL and
LENGTH.
(decrypt_data): Set them. Simplify premature EOF detection.
(mdc_decode_filter): Take fixed length packets in account.
(decode_filter): Ditto. Better EOF detection.
* parse-packet.c (parse_encrypted): Store ed->LEN without the MDC
version byte.
2009-09-30 Werner Koch <wk@g10code.com>
* parse-packet.c (skip_packet, parse_gpg_control) <ist_mode>: Take
* parse-packet.c (skip_packet, parse_gpg_control) <list_mode>: Take
care of premature EOFs.
* gpg.c (main): Remove obsolete GCRYCTL_DISABLE_INTERNAL_LOCKING.

114
g10/encr-data.c
View File

@ -45,6 +45,8 @@ typedef struct decode_filter_context_s
int defer_filled;
int eof_seen;
int refcount;
int partial; /* Working on a partial length packet. */
size_t length; /* If !partial: Remaining bytes in the packet. */
} *decode_filter_ctx_t;
@ -182,6 +184,8 @@ decrypt_data( void *procctx, PKT_encrypted *ed, DEK *dek )
gcry_md_write (dfx->mdc_hash, temp, nprefix+2);
dfx->refcount++;
dfx->partial = ed->is_partial;
dfx->length = ed->len;
if ( ed->mdc_method )
iobuf_push_filter ( ed->buf, mdc_decode_filter, dfx );
else
@ -189,7 +193,7 @@ decrypt_data( void *procctx, PKT_encrypted *ed, DEK *dek )
proc_packets ( procctx, ed->buf );
ed->buf = NULL;
if ( ed->mdc_method && dfx->eof_seen == 2 )
if (dfx->eof_seen > 1 )
rc = gpg_error (GPG_ERR_INV_PACKET);
else if ( ed->mdc_method )
{
@ -235,7 +239,6 @@ decrypt_data( void *procctx, PKT_encrypted *ed, DEK *dek )
/* I think we should merge this with cipher_filter */
static int
mdc_decode_filter (void *opaque, int control, IOBUF a,
byte *buf, size_t *ret_len)
@ -245,6 +248,14 @@ mdc_decode_filter (void *opaque, int control, IOBUF a,
int rc = 0;
int c;
/* Note: We need to distinguish between a partial and a fixed length
packet. The first is the usual case as created by GPG. However
for short messages the format degrades to a fixed length packet
and other implementations might use fixed length as well. Only
looking for the EOF on fixed data works only if the encrypted
packet is not followed by other data. This used to be a long
standing bug which was fixed on 2009-10-02. */
if ( control == IOBUFCTRL_UNDERFLOW && dfx->eof_seen )
{
*ret_len = 0;
@ -253,19 +264,31 @@ mdc_decode_filter (void *opaque, int control, IOBUF a,
else if( control == IOBUFCTRL_UNDERFLOW )
{
assert (a);
assert ( size > 44 );
assert (size > 44); /* Our code requires at least this size. */
/* Get at least 22 bytes and put it somewhere ahead in the buffer. */
/* Get at least 22 bytes and put it ahead in the buffer. */
if (dfx->partial)
{
for (n=22; n < 44; n++)
{
if ( (c = iobuf_get(a)) == -1 )
break;
buf[n] = c;
}
}
else
{
for (n=22; n < 44 && dfx->length; n++, dfx->length--)
{
c = iobuf_get (a);
if (c == -1)
break; /* Premature EOF. */
buf[n] = c;
}
}
if (n == 44)
{
/* We have enough stuff - flush the deferred stuff. */
/* (we asserted that the buffer is large enough) */
if ( !dfx->defer_filled ) /* First time. */
{
memcpy (buf, buf+22, 22);
@ -275,15 +298,37 @@ mdc_decode_filter (void *opaque, int control, IOBUF a,
{
memcpy (buf, dfx->defer, 22);
}
/* Now fill up. */
/* Fill up the buffer. */
if (dfx->partial)
{
for (; n < size; n++ )
{
if ( (c = iobuf_get(a)) == -1 )
{
dfx->eof_seen = 1; /* Normal EOF. */
break;
}
buf[n] = c;
}
/* Move the last 22 bytes back to the defer buffer. */
/* (right, we are wasting 22 bytes of the supplied buffer.) */
}
else
{
for (; n < size && dfx->length; n++, dfx->length--)
{
c = iobuf_get(a);
if (c == -1)
{
dfx->eof_seen = 3; /* Premature EOF. */
break;
}
buf[n] = c;
}
if (!dfx->length)
dfx->eof_seen = 1; /* Normal EOF. */
}
/* Move the trailing 22 bytes back to the defer buffer. We
have at least 44 bytes thus a memmove is not needed. */
n -= 22;
memcpy (dfx->defer, buf+n, 22 );
dfx->defer_filled = 1;
@ -313,7 +358,7 @@ mdc_decode_filter (void *opaque, int control, IOBUF a,
else
{
assert ( dfx->eof_seen );
rc = -1; /* eof */
rc = -1; /* Return EOF. */
}
*ret_len = n;
}
@ -333,22 +378,59 @@ static int
decode_filter( void *opaque, int control, IOBUF a, byte *buf, size_t *ret_len)
{
decode_filter_ctx_t fc = opaque;
size_t n, size = *ret_len;
int rc = 0;
size_t size = *ret_len;
size_t n;
int c, rc = 0;
if ( control == IOBUFCTRL_UNDERFLOW )
if ( control == IOBUFCTRL_UNDERFLOW && fc->eof_seen )
{
*ret_len = 0;
rc = -1;
}
else if ( control == IOBUFCTRL_UNDERFLOW )
{
assert(a);
n = iobuf_read ( a, buf, size );
if ( n == -1 )
n = 0;
if (fc->partial)
{
for (n=0; n < size; n++ )
{
c = iobuf_get(a);
if (c == -1)
{
fc->eof_seen = 1; /* Normal EOF. */
break;
}
buf[n] = c;
}
}
else
{
for (n=0; n < size && fc->length; n++, fc->length--)
{
c = iobuf_get(a);
if (c == -1)
{
fc->eof_seen = 3; /* Premature EOF. */
break;
}
buf[n] = c;
}
if (!fc->length)
fc->eof_seen = 1; /* Normal EOF. */
}
if (n)
{
if (fc->cipher_hd)
gcry_cipher_decrypt (fc->cipher_hd, buf, n, NULL, 0);
}
else
rc = -1; /* EOF */
{
if (!fc->eof_seen)
fc->eof_seen = 1;
rc = -1; /* Return EOF. */
}
*ret_len = n;
}
else if ( control == IOBUFCTRL_FREE )

21
g10/parse-packet.c
View File

@ -2617,16 +2617,11 @@ parse_encrypted (IOBUF inp, int pkttype, unsigned long pktlen,
unsigned long orig_pktlen = pktlen;
ed = pkt->pkt.encrypted = xmalloc (sizeof *pkt->pkt.encrypted);
ed->len = pktlen;
/* We don't know the extralen which is (cipher_blocksize+2) because
the algorithm ist not specified in this packet. However, it is
only important to know this for some sanity checks on the packet
length - it doesn't matter that we can't do it. */
ed->extralen = 0;
/* ed->len is set below. */
ed->extralen = 0; /* Unknown here; only used in build_packet. */
ed->buf = NULL;
ed->new_ctb = new_ctb;
ed->is_partial = partial;
ed->mdc_method = 0;
if (pkttype == PKT_ENCRYPTED_MDC)
{
/* Fixme: add some pktlen sanity checks. */
@ -2645,6 +2640,12 @@ parse_encrypted (IOBUF inp, int pkttype, unsigned long pktlen,
}
ed->mdc_method = DIGEST_ALGO_SHA1;
}
else
ed->mdc_method = 0;
/* A basic sanity check. We need at least an 8 byte IV plus the 2
detection bytes. Note that we don't known the algorithm and thus
we may only check against the minimum blocksize. */
if (orig_pktlen && pktlen < 10)
{
/* Actually this is blocksize+2. */
@ -2653,6 +2654,12 @@ parse_encrypted (IOBUF inp, int pkttype, unsigned long pktlen,
iobuf_skip_rest (inp, pktlen, partial);
goto leave;
}
/* Store the remaining length of the encrypted data (i.e. without
the MDC version number but with the IV etc.). This value is
required during decryption. */
ed->len = pktlen;
if (list_mode)
{
if (orig_pktlen)