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sunrpc: trim off trailing checksum before returning decrypted or integrity authenticated buffer

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When GSSAPI integrity signatures are in use, or when we're using GSSAPI
privacy with the v2 token format, there is a trailing checksum on the
xdr_buf that is returned.

It's checked during the authentication stage, and afterward nothing
cares about it. Ordinarily, it's not a problem since the XDR code
generally ignores it, but it will be when we try to compute a checksum
over the buffer to help prevent XID collisions in the duplicate reply
cache.

Fix the code to trim off the checksums after verifying them. Note that
in unwrap_integ_data, we must avoid trying to reverify the checksum if
the request was deferred since it will no longer be present when it's
revisited.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
This commit is contained in:
Jeff Layton 2013-02-06 08:28:55 -05:00 committed by J. Bruce Fields
parent de0b65ca55
commit 4c190e2f91
4 changed files with 52 additions and 2 deletions
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1
include/linux/sunrpc/xdr.h
View file

@ -152,6 +152,7 @@ xdr_adjust_iovec(struct kvec *iov, __be32 *p)
extern void xdr_shift_buf(struct xdr_buf *, size_t);
extern void xdr_buf_from_iov(struct kvec *, struct xdr_buf *);
extern int xdr_buf_subsegment(struct xdr_buf *, struct xdr_buf *, unsigned int, unsigned int);
extern void xdr_buf_trim(struct xdr_buf *, unsigned int);
extern int xdr_buf_read_netobj(struct xdr_buf *, struct xdr_netobj *, unsigned int);
extern int read_bytes_from_xdr_buf(struct xdr_buf *, unsigned int, void *, unsigned int);
extern int write_bytes_to_xdr_buf(struct xdr_buf *, unsigned int, void *, unsigned int);

2
net/sunrpc/auth_gss/gss_krb5_wrap.c
View file

@ -574,6 +574,8 @@ gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;
buf->len -= GSS_KRB5_TOK_HDR_LEN + headskip;
/* Trim off the checksum blob */
xdr_buf_trim(buf, GSS_KRB5_TOK_HDR_LEN + tailskip);
return GSS_S_COMPLETE;
}

10
net/sunrpc/auth_gss/svcauth_gss.c
View file

@ -817,13 +817,17 @@ read_u32_from_xdr_buf(struct xdr_buf *buf, int base, u32 *obj)
* The server uses base of head iovec as read pointer, while the
* client uses separate pointer. */
static int
unwrap_integ_data(struct xdr_buf *buf, u32 seq, struct gss_ctx *ctx)
unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct gss_ctx *ctx)
{
int stat = -EINVAL;
u32 integ_len, maj_stat;
struct xdr_netobj mic;
struct xdr_buf integ_buf;
/* Did we already verify the signature on the original pass through? */
if (rqstp->rq_deferred)
return 0;
integ_len = svc_getnl(&buf->head[0]);
if (integ_len & 3)
return stat;
@ -846,6 +850,8 @@ unwrap_integ_data(struct xdr_buf *buf, u32 seq, struct gss_ctx *ctx)
goto out;
if (svc_getnl(&buf->head[0]) != seq)
goto out;
/* trim off the mic at the end before returning */
xdr_buf_trim(buf, mic.len + 4);
stat = 0;
out:
kfree(mic.data);
@ -1190,7 +1196,7 @@ svcauth_gss_accept(struct svc_rqst *rqstp, __be32 *authp)
/* placeholders for length and seq. number: */
svc_putnl(resv, 0);
svc_putnl(resv, 0);
if (unwrap_integ_data(&rqstp->rq_arg,
if (unwrap_integ_data(rqstp, &rqstp->rq_arg,
gc->gc_seq, rsci->mechctx))
goto garbage_args;
break;

41
net/sunrpc/xdr.c
View file

@ -879,6 +879,47 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
}
EXPORT_SYMBOL_GPL(xdr_buf_subsegment);
/**
* xdr_buf_trim - lop at most "len" bytes off the end of "buf"
* @buf: buf to be trimmed
* @len: number of bytes to reduce "buf" by
*
* Trim an xdr_buf by the given number of bytes by fixing up the lengths. Note
* that it's possible that we'll trim less than that amount if the xdr_buf is
* too small, or if (for instance) it's all in the head and the parser has
* already read too far into it.
*/
void xdr_buf_trim(struct xdr_buf *buf, unsigned int len)
{
size_t cur;
unsigned int trim = len;
if (buf->tail[0].iov_len) {
cur = min_t(size_t, buf->tail[0].iov_len, trim);
buf->tail[0].iov_len -= cur;
trim -= cur;
if (!trim)
goto fix_len;
}
if (buf->page_len) {
cur = min_t(unsigned int, buf->page_len, trim);
buf->page_len -= cur;
trim -= cur;
if (!trim)
goto fix_len;
}
if (buf->head[0].iov_len) {
cur = min_t(size_t, buf->head[0].iov_len, trim);
buf->head[0].iov_len -= cur;
trim -= cur;
}
fix_len:
buf->len -= (len - trim);
}
EXPORT_SYMBOL_GPL(xdr_buf_trim);
static void __read_bytes_from_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigned int len)
{
unsigned int this_len;