sunrpc: trim off trailing checksum before returning decrypted or integrity authentica...

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>

diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index 224d060..15f9204 100644 (file)
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -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);

diff --git a/net/sunrpc/auth_gss/gss_krb5_wrap.c b/net/sunrpc/auth_gss/gss_krb5_wrap.c
index 107c452..88edec9 100644 (file)
--- a/net/sunrpc/auth_gss/gss_krb5_wrap.c
+++ b/net/sunrpc/auth_gss/gss_krb5_wrap.c
@@ -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;
 }
 

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 73e9573..a5b41e2 100644 (file)
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -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;

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 5605563..75edcfa 100644 (file)
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -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;