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rxrpc: Fix several cases where a padded len isn't checked in ticket decode 

This fixes CVE-2017-7482.

When a kerberos 5 ticket is being decoded so that it can be loaded into an
rxrpc-type key, there are several places in which the length of a
variable-length field is checked to make sure that it's not going to
overrun the available data - but the data is padded to the nearest
four-byte boundary and the code doesn't check for this extra.  This could
lead to the size-remaining variable wrapping and the data pointer going
over the end of the buffer.

Fix this by making the various variable-length data checks use the padded
length.

Reported-by: 石磊 <shilei-c@360.cn>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.c.dionne@auristor.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
zero-colors
David Howells 2017-06-15 00:12:24 +01:00 committed by David S. Miller
parent f8a894b218
commit 5f2f97656a
1 changed files with 34 additions and 30 deletions
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64
net/rxrpc/key.c
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@ -217,7 +217,7 @@ static int rxrpc_krb5_decode_principal(struct krb5_principal *princ,
unsigned int *_toklen)
{
const __be32 *xdr = *_xdr;
unsigned int toklen = *_toklen, n_parts, loop, tmp;
unsigned int toklen = *_toklen, n_parts, loop, tmp, paddedlen;
/* there must be at least one name, and at least #names+1 length
* words */
@ -247,16 +247,16 @@ static int rxrpc_krb5_decode_principal(struct krb5_principal *princ,
toklen -= 4;
if (tmp <= 0 || tmp > AFSTOKEN_STRING_MAX)
return -EINVAL;
if (tmp > toklen)
paddedlen = (tmp + 3) & ~3;
if (paddedlen > toklen)
return -EINVAL;
princ->name_parts[loop] = kmalloc(tmp + 1, GFP_KERNEL);
if (!princ->name_parts[loop])
return -ENOMEM;
memcpy(princ->name_parts[loop], xdr, tmp);
princ->name_parts[loop][tmp] = 0;
tmp = (tmp + 3) & ~3;
toklen -= tmp;
xdr += tmp >> 2;
toklen -= paddedlen;
xdr += paddedlen >> 2;
}
if (toklen < 4)
@ -265,16 +265,16 @@ static int rxrpc_krb5_decode_principal(struct krb5_principal *princ,
toklen -= 4;
if (tmp <= 0 || tmp > AFSTOKEN_K5_REALM_MAX)
return -EINVAL;
if (tmp > toklen)
paddedlen = (tmp + 3) & ~3;
if (paddedlen > toklen)
return -EINVAL;
princ->realm = kmalloc(tmp + 1, GFP_KERNEL);
if (!princ->realm)
return -ENOMEM;
memcpy(princ->realm, xdr, tmp);
princ->realm[tmp] = 0;
tmp = (tmp + 3) & ~3;
toklen -= tmp;
xdr += tmp >> 2;
toklen -= paddedlen;
xdr += paddedlen >> 2;
_debug("%s/...@%s", princ->name_parts[0], princ->realm);
@ -293,7 +293,7 @@ static int rxrpc_krb5_decode_tagged_data(struct krb5_tagged_data *td,
unsigned int *_toklen)
{
const __be32 *xdr = *_xdr;
unsigned int toklen = *_toklen, len;
unsigned int toklen = *_toklen, len, paddedlen;
/* there must be at least one tag and one length word */
if (toklen <= 8)
@ -307,15 +307,17 @@ static int rxrpc_krb5_decode_tagged_data(struct krb5_tagged_data *td,
toklen -= 8;
if (len > max_data_size)
return -EINVAL;
paddedlen = (len + 3) & ~3;
if (paddedlen > toklen)
return -EINVAL;
td->data_len = len;
if (len > 0) {
td->data = kmemdup(xdr, len, GFP_KERNEL);
if (!td->data)
return -ENOMEM;
len = (len + 3) & ~3;
toklen -= len;
xdr += len >> 2;
toklen -= paddedlen;
xdr += paddedlen >> 2;
}
_debug("tag %x len %x", td->tag, td->data_len);
@ -387,7 +389,7 @@ static int rxrpc_krb5_decode_ticket(u8 **_ticket, u16 *_tktlen,
const __be32 **_xdr, unsigned int *_toklen)
{
const __be32 *xdr = *_xdr;
unsigned int toklen = *_toklen, len;
unsigned int toklen = *_toklen, len, paddedlen;
/* there must be at least one length word */
if (toklen <= 4)
@ -399,6 +401,9 @@ static int rxrpc_krb5_decode_ticket(u8 **_ticket, u16 *_tktlen,
toklen -= 4;
if (len > AFSTOKEN_K5_TIX_MAX)
return -EINVAL;
paddedlen = (len + 3) & ~3;
if (paddedlen > toklen)
return -EINVAL;
*_tktlen = len;
_debug("ticket len %u", len);
@ -407,9 +412,8 @@ static int rxrpc_krb5_decode_ticket(u8 **_ticket, u16 *_tktlen,
*_ticket = kmemdup(xdr, len, GFP_KERNEL);
if (!*_ticket)
return -ENOMEM;
len = (len + 3) & ~3;
toklen -= len;
xdr += len >> 2;
toklen -= paddedlen;
xdr += paddedlen >> 2;
}
*_xdr = xdr;
@ -552,7 +556,7 @@ static int rxrpc_preparse_xdr(struct key_preparsed_payload *prep)
{
const __be32 *xdr = prep->data, *token;
const char *cp;
unsigned int len, tmp, loop, ntoken, toklen, sec_ix;
unsigned int len, paddedlen, loop, ntoken, toklen, sec_ix;
size_t datalen = prep->datalen;
int ret;
@ -578,22 +582,21 @@ static int rxrpc_preparse_xdr(struct key_preparsed_payload *prep)
if (len < 1 || len > AFSTOKEN_CELL_MAX)
goto not_xdr;
datalen -= 4;
tmp = (len + 3) & ~3;
if (tmp > datalen)
paddedlen = (len + 3) & ~3;
if (paddedlen > datalen)
goto not_xdr;
cp = (const char *) xdr;
for (loop = 0; loop < len; loop++)
if (!isprint(cp[loop]))
goto not_xdr;
if (len < tmp)
for (; loop < tmp; loop++)
if (cp[loop])
goto not_xdr;
for (; loop < paddedlen; loop++)
if (cp[loop])
goto not_xdr;
_debug("cellname: [%u/%u] '%*.*s'",
len, tmp, len, len, (const char *) xdr);
datalen -= tmp;
xdr += tmp >> 2;
len, paddedlen, len, len, (const char *) xdr);
datalen -= paddedlen;
xdr += paddedlen >> 2;
/* get the token count */
if (datalen < 12)
@ -614,10 +617,11 @@ static int rxrpc_preparse_xdr(struct key_preparsed_payload *prep)
sec_ix = ntohl(*xdr);
datalen -= 4;
_debug("token: [%x/%zx] %x", toklen, datalen, sec_ix);
if (toklen < 20 || toklen > datalen)
paddedlen = (toklen + 3) & ~3;
if (toklen < 20 || toklen > datalen || paddedlen > datalen)
goto not_xdr;
datalen -= (toklen + 3) & ~3;
xdr += (toklen + 3) >> 2;
datalen -= paddedlen;
xdr += paddedlen >> 2;
} while (--loop > 0);