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gpg: Do not allow creation of user ids larger than our parser allows.

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* g10/parse-packet.c: Move max packet lengths constants to ...
* g10/packet.h: ... here.
* g10/build-packet.c (do_user_id): Return an error if too data is too
large.
* g10/keygen.c (write_uid): Return an error for too large data.
--

This can lead to keyring corruption becuase we expect that our parser
is abale to parse packts created by us.  Test case is

  gpg --batch --passphrase 'abc' -v  \
      --quick-gen-key $(yes 'a'| head -4000|tr -d '\n')

GnuPG-bug-id: 4532
Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2019-05-21 16:25:56 +02:00
parent 6e39541f4f
commit d32963eeb3
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
4 changed files with 31 additions and 21 deletions
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8
g10/build-packet.c
View File

@ -424,15 +424,21 @@ do_user_id( IOBUF out, int ctb, PKT_user_id *uid )
* Without forcing HDRLEN to 2 in this case an indeterminate length
* packet would be written which is not allowed. Note that we are
* always called with a CTB indicating an old packet header format,
* so that forcing a 2 octet header works. */
* so that forcing a 2 octet header works. We also check for the
* maximum allowed packet size by the parser using an arbitrary
* extra 10 bytes for header data. */
if (uid->attrib_data)
{
if (uid->attrib_len > MAX_ATTR_PACKET_LENGTH - 10)
return gpg_error (GPG_ERR_TOO_LARGE);
hdrlen = uid->attrib_len? 0 : 2;
write_header2 (out, ctb, uid->attrib_len, hdrlen);
rc = iobuf_write( out, uid->attrib_data, uid->attrib_len );
}
else
{
if (uid->len > MAX_UID_PACKET_LENGTH - 10)
return gpg_error (GPG_ERR_TOO_LARGE);
hdrlen = uid->len? 0 : 2;
write_header2 (out, ctb, uid->len, hdrlen);
rc = iobuf_write( out, uid->name, uid->len );

19
g10/keygen.c
View File

@ -218,18 +218,22 @@ print_status_key_not_created (const char *handle)
static void
write_uid( KBNODE root, const char *s )
static gpg_error_t
write_uid (kbnode_t root, const char *s)
{
PACKET *pkt = xmalloc_clear(sizeof *pkt );
size_t n = strlen(s);
PACKET *pkt = xmalloc_clear (sizeof *pkt);
size_t n = strlen (s);
if (n > MAX_UID_PACKET_LENGTH - 10)
return gpg_error (GPG_ERR_INV_USER_ID);
pkt->pkttype = PKT_USER_ID;
pkt->pkt.user_id = xmalloc_clear (sizeof *pkt->pkt.user_id + n);
pkt->pkt.user_id->len = n;
pkt->pkt.user_id->ref = 1;
strcpy(pkt->pkt.user_id->name, s);
add_kbnode( root, new_kbnode( pkt ) );
strcpy (pkt->pkt.user_id->name, s);
add_kbnode (root, new_kbnode (pkt));
return 0;
}
static void
@ -4751,7 +4755,8 @@ do_generate_keypair (ctrl_t ctrl, struct para_data_s *para,
if (!err && (s = get_parameter_value (para, pUSERID)))
{
write_uid (pub_root, s );
err = write_uid (pub_root, s );
if (!err)
err = write_selfsigs (ctrl, pub_root, pri_psk,
get_parameter_uint (para, pKEYUSAGE), timestamp,
cache_nonce);

5
g10/packet.h
View File

@ -33,6 +33,11 @@
#define DEBUG_PARSE_PACKET 1
/* Maximum length of packets to avoid excessive memory allocation. */
#define MAX_KEY_PACKET_LENGTH (256 * 1024)
#define MAX_UID_PACKET_LENGTH ( 2 * 1024)
#define MAX_COMMENT_PACKET_LENGTH ( 64 * 1024)
#define MAX_ATTR_PACKET_LENGTH ( 16 * 1024*1024)
/* Constants to allocate static MPI arrays. */
#define PUBKEY_MAX_NPKEY OPENPGP_MAX_NPKEY

6
g10/parse-packet.c
View File

@ -38,12 +38,6 @@
#include "../common/mbox-util.h"
/* Maximum length of packets to avoid excessive memory allocation. */
#define MAX_KEY_PACKET_LENGTH (256 * 1024)
#define MAX_UID_PACKET_LENGTH ( 2 * 1024)
#define MAX_COMMENT_PACKET_LENGTH ( 64 * 1024)
#define MAX_ATTR_PACKET_LENGTH ( 16 * 1024*1024)
static int mpi_print_mode;
static int list_mode;
static estream_t listfp;