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gpg: Improve check for already compressed packets.

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* common/miscellaneous.c (is_openpgp_compressed_packet): New.
(is_file_compressed): Rerad 2 more bytes and call new function.

--

Note that this does not yet allow to detect compressed data piped to
gpg.  This requires a proper read-ahead in iobuf.c which is
complicated due to the auto-removal of filter functions.  Thus such an
read-ahead needs to be done in the I/O backend of iobuf.

Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2017-03-24 11:51:44 +01:00
parent 2c237c1362
commit 0b3770c421
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
1 changed files with 57 additions and 6 deletions
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63
common/miscellaneous.c
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@ -318,6 +318,50 @@ make_printable_string (const void *p, size_t n, int delim )
}
/* Check whether (BUF,LEN) is valid header for an OpenPGP compressed
* packet. LEN should be at least 6. */
static int
is_openpgp_compressed_packet (unsigned char *buf, size_t len)
{
int c, ctb, pkttype;
int lenbytes;
ctb = *buf++; len--;
if (!(ctb & 0x80))
return 0; /* Invalid packet. */
if ((ctb & 0x40)) /* New style (OpenPGP) CTB. */
{
pkttype = (ctb & 0x3f);
if (!len)
return 0; /* Expected first length octet missing. */
c = *buf++; len--;
if (c < 192)
;
else if (c < 224)
{
if (!len)
return 0; /* Expected second length octet missing. */
}
else if (c == 255)
{
if (len < 4)
return 0; /* Expected length octets missing */
}
}
else /* Old style CTB. */
{
pkttype = (ctb>>2)&0xf;
lenbytes = ((ctb&3)==3)? 0 : (1<<(ctb & 3));
if (len < lenbytes)
return 0; /* Not enough length bytes. */
}
return (pkttype == 8);
}
/*
* Check if the file is compressed.
*/
@ -325,8 +369,9 @@ int
is_file_compressed (const char *s, int *ret_rc)
{
iobuf_t a;
byte buf[4];
int i, rc = 0;
byte buf[6];
int i;
int rc = 0;
int overflow;
struct magic_compress_s {
@ -347,12 +392,12 @@ is_file_compressed (const char *s, int *ret_rc)
return 0;
}
if ( iobuf_get_filelength( a, &overflow ) < 4 && !overflow) {
if ( iobuf_get_filelength( a, &overflow ) < 6 && !overflow) {
*ret_rc = 0;
goto leave;
}
if ( iobuf_read( a, buf, 4 ) == -1 ) {
if ( iobuf_read( a, buf, 6 ) == -1 ) {
*ret_rc = a->error;
goto leave;
}
@ -361,11 +406,17 @@ is_file_compressed (const char *s, int *ret_rc)
if ( !memcmp( buf, magic[i].magic, magic[i].len ) ) {
*ret_rc = 0;
rc = 1;
break;
goto leave;
}
}
leave:
if (is_openpgp_compressed_packet (buf, 6))
{
*ret_rc = 0;
rc = 1;
}
leave:
iobuf_close( a );
return rc;
}