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Message-ID: <149748194451.23919.13232256832988154536.stgit@warthog.procyon.org.uk>
Date: Thu, 15 Jun 2017 00:12:24 +0100
From: David Howells <dhowells@...hat.com>
To: netdev@...r.kernel.org
Cc: dhowells@...hat.com, linux-afs@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: [PATCH net] 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@....cn>
Signed-off-by: David Howells <dhowells@...hat.com>
Reviewed-by: Marc Dionne <marc.c.dionne@...istor.com>
Reviewed-by: Dan Carpenter <dan.carpenter@...cle.com>
---
net/rxrpc/key.c | 64 +++++++++++++++++++++++++++++--------------------------
1 file changed, 34 insertions(+), 30 deletions(-)
diff --git a/net/rxrpc/key.c b/net/rxrpc/key.c
index 0a4e28477ad9..54369225766e 100644
--- a/net/rxrpc/key.c
+++ b/net/rxrpc/key.c
@@ -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);
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