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SUNRPC: Fix GSS privacy computation of auth->au_ralign 

When the au_ralign field was added to gss_unwrap_resp_priv, the
wrong calculation was used. Setting au_rslack == au_ralign is
probably correct for kerberos_v1 privacy, but kerberos_v2 privacy
adds additional GSS data after the clear text RPC message.
au_ralign needs to be smaller than au_rslack in that fairly common
case.

When xdr_buf_trim() is restored to gss_unwrap_kerberos_v2(), it does
exactly what I feared it would: it trims off part of the clear text
RPC message. However, that's because rpc_prepare_reply_pages() does
not set up the rq_rcv_buf's tail correctly because au_ralign is too
large.

Fixing the au_ralign computation also corrects the alignment of
rq_rcv_buf->pages so that the client does not have to shift reply
data payloads after they are received.

Fixes: 35e77d21ba ("SUNRPC: Add rpc_auth::au_ralign field")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Chuck Lever 2020-04-18 14:38:19 -04:00
parent 31c9590ae4
commit a7e429a6fa
3 changed files with 19 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/sunrpc/gss_api.h
View File

@ -21,6 +21,7 @@
struct gss_ctx {
struct gss_api_mech *mech_type;
void *internal_ctx_id;
unsigned int slack, align;
};
#define GSS_C_NO_BUFFER ((struct xdr_netobj) 0)

8
net/sunrpc/auth_gss/auth_gss.c
View File

@ -2032,7 +2032,6 @@ gss_unwrap_resp_priv(struct rpc_task *task, struct rpc_cred *cred,
struct xdr_buf *rcv_buf = &rqstp->rq_rcv_buf;
struct kvec *head = rqstp->rq_rcv_buf.head;
struct rpc_auth *auth = cred->cr_auth;
unsigned int savedlen = rcv_buf->len;
u32 offset, opaque_len, maj_stat;
__be32 *p;
@ -2059,10 +2058,9 @@ gss_unwrap_resp_priv(struct rpc_task *task, struct rpc_cred *cred,
*/
xdr_init_decode(xdr, rcv_buf, p, rqstp);
auth->au_rslack = auth->au_verfsize + 2 +
XDR_QUADLEN(savedlen - rcv_buf->len);
auth->au_ralign = auth->au_verfsize + 2 +
XDR_QUADLEN(savedlen - rcv_buf->len);
auth->au_rslack = auth->au_verfsize + 2 + ctx->gc_gss_ctx->slack;
auth->au_ralign = auth->au_verfsize + 2 + ctx->gc_gss_ctx->align;
return 0;
unwrap_failed:
trace_rpcgss_unwrap_failed(task);

19
net/sunrpc/auth_gss/gss_krb5_wrap.c
View File

@ -262,7 +262,8 @@ gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
static u32
gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, int len,
struct xdr_buf *buf)
struct xdr_buf *buf, unsigned int *slack,
unsigned int *align)
{
int signalg;
int sealalg;
@ -280,6 +281,7 @@ gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, int len,
u32 conflen = kctx->gk5e->conflen;
int crypt_offset;
u8 *cksumkey;
unsigned int saved_len = buf->len;
dprintk("RPC: gss_unwrap_kerberos\n");
@ -383,6 +385,10 @@ gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, int len,
if (gss_krb5_remove_padding(buf, blocksize))
return GSS_S_DEFECTIVE_TOKEN;
/* slack must include room for krb5 padding */
*slack = XDR_QUADLEN(saved_len - buf->len);
/* The GSS blob always precedes the RPC message payload */
*align = *slack;
return GSS_S_COMPLETE;
}
@ -489,7 +495,8 @@ gss_wrap_kerberos_v2(struct krb5_ctx *kctx, u32 offset,
static u32
gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, int len,
struct xdr_buf *buf)
struct xdr_buf *buf, unsigned int *slack,
unsigned int *align)
{
time64_t now;
u8 *ptr;
@ -583,6 +590,8 @@ gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, int len,
/* Trim off the trailing "extra count" and checksum blob */
buf->len -= ec + GSS_KRB5_TOK_HDR_LEN + tailskip;
*align = XDR_QUADLEN(GSS_KRB5_TOK_HDR_LEN + headskip);
*slack = *align + XDR_QUADLEN(ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
return GSS_S_COMPLETE;
}
@ -617,9 +626,11 @@ gss_unwrap_kerberos(struct gss_ctx *gctx, int offset,
case ENCTYPE_DES_CBC_RAW:
case ENCTYPE_DES3_CBC_RAW:
case ENCTYPE_ARCFOUR_HMAC:
return gss_unwrap_kerberos_v1(kctx, offset, len, buf);
return gss_unwrap_kerberos_v1(kctx, offset, len, buf,
&gctx->slack, &gctx->align);
case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
return gss_unwrap_kerberos_v2(kctx, offset, len, buf);
return gss_unwrap_kerberos_v2(kctx, offset, len, buf,
&gctx->slack, &gctx->align);
}
}