gss_krb5: Added and improved code comments
Signed-off-by: Steve Dickson <steved@redhat.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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@ -1316,15 +1316,21 @@ gss_wrap_req_priv(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
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inpages = snd_buf->pages + first;
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snd_buf->pages = rqstp->rq_enc_pages;
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snd_buf->page_base -= first << PAGE_CACHE_SHIFT;
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/* Give the tail its own page, in case we need extra space in the
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* head when wrapping: */
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/*
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* Give the tail its own page, in case we need extra space in the
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* head when wrapping:
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*
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* call_allocate() allocates twice the slack space required
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* by the authentication flavor to rq_callsize.
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* For GSS, slack is GSS_CRED_SLACK.
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*/
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if (snd_buf->page_len || snd_buf->tail[0].iov_len) {
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tmp = page_address(rqstp->rq_enc_pages[rqstp->rq_enc_pages_num - 1]);
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memcpy(tmp, snd_buf->tail[0].iov_base, snd_buf->tail[0].iov_len);
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snd_buf->tail[0].iov_base = tmp;
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}
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maj_stat = gss_wrap(ctx->gc_gss_ctx, offset, snd_buf, inpages);
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/* RPC_SLACK_SPACE should prevent this ever happening: */
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/* slack space should prevent this ever happening: */
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BUG_ON(snd_buf->len > snd_buf->buflen);
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status = -EIO;
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/* We're assuming that when GSS_S_CONTEXT_EXPIRED, the encryption was
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@ -285,6 +285,20 @@ gss_verify_mic(struct gss_ctx *context_handle,
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mic_token);
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}
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/*
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* This function is called from both the client and server code.
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* Each makes guarantees about how much "slack" space is available
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* for the underlying function in "buf"'s head and tail while
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* performing the wrap.
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*
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* The client and server code allocate RPC_MAX_AUTH_SIZE extra
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* space in both the head and tail which is available for use by
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* the wrap function.
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*
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* Underlying functions should verify they do not use more than
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* RPC_MAX_AUTH_SIZE of extra space in either the head or tail
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* when performing the wrap.
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*/
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u32
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gss_wrap(struct gss_ctx *ctx_id,
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int offset,
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@ -1315,6 +1315,14 @@ svcauth_gss_wrap_resp_priv(struct svc_rqst *rqstp)
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inpages = resbuf->pages;
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/* XXX: Would be better to write some xdr helper functions for
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* nfs{2,3,4}xdr.c that place the data right, instead of copying: */
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/*
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* If there is currently tail data, make sure there is
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* room for the head, tail, and 2 * RPC_MAX_AUTH_SIZE in
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* the page, and move the current tail data such that
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* there is RPC_MAX_AUTH_SIZE slack space available in
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* both the head and tail.
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*/
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if (resbuf->tail[0].iov_base) {
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BUG_ON(resbuf->tail[0].iov_base >= resbuf->head[0].iov_base
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+ PAGE_SIZE);
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@ -1327,6 +1335,13 @@ svcauth_gss_wrap_resp_priv(struct svc_rqst *rqstp)
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resbuf->tail[0].iov_len);
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resbuf->tail[0].iov_base += RPC_MAX_AUTH_SIZE;
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}
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/*
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* If there is no current tail data, make sure there is
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* room for the head data, and 2 * RPC_MAX_AUTH_SIZE in the
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* allotted page, and set up tail information such that there
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* is RPC_MAX_AUTH_SIZE slack space available in both the
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* head and tail.
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*/
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if (resbuf->tail[0].iov_base == NULL) {
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if (resbuf->head[0].iov_len + 2*RPC_MAX_AUTH_SIZE > PAGE_SIZE)
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return -ENOMEM;
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