[PATCH 11/17] cifs: Add a function to Hash the contents of an iterator

David Howells
2023-02-16T21:50:34Z

Add a function to push the contents of a BVEC-, KVEC- or XARRAY-type
iterator into a symmetric hash algorithm.

UBUF- and IOBUF-type iterators are not supported on the assumption that
either we're doing buffered I/O, in which case we won't see them, or we're
doing direct I/O, in which case the iterator will have been extracted into
a BVEC-type iterator higher up.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-crypto@vger.kernel.org

Link: https://lore.kernel.org/r/166697257423.61150.12070648579830206483.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/166732029577.3186319.17162612653237909961.stgit@warthog.procyon.org.uk/ # rfc
---
fs/cifs/cifsencrypt.c | 144 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 144 insertions(+)

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index cbc18b4a9cb2..7be589aeb520 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -24,6 +24,150 @@
#include "../smbfs_common/arc4.h"
#include <crypto/aead.h>

+/*
+ * Hash data from a BVEC-type iterator.
+ */
+static int cifs_shash_bvec(const struct iov_iter *iter, ssize_t maxsize,
+ struct shash_desc *shash)
+{
+ const struct bio_vec *bv = iter->bvec;
+ unsigned long start = iter->iov_offset;
+ unsigned int i;
+ void *p;
+ int ret;
+
+ for (i = 0; i < iter->nr_segs; i++) {
+ size_t off, len;
+
+ len = bv[i].bv_len;
+ if (start >= len) {
+ start -= len;
+ continue;
+ }
+
+ len = min_t(size_t, maxsize, len - start);
+ off = bv[i].bv_offset + start;
+
+ p = kmap_local_page(bv[i].bv_page);
+ ret = crypto_shash_update(shash, p + off, len);
+ kunmap_local(p);
+ if (ret < 0)
+ return ret;
+
+ maxsize -= len;
+ if (maxsize <= 0)
+ break;
+ start = 0;
+ }
+
+ return 0;
+}
+
+/*
+ * Hash data from a KVEC-type iterator.
+ */
+static int cifs_shash_kvec(const struct iov_iter *iter, ssize_t maxsize,
+ struct shash_desc *shash)
+{
+ const struct kvec *kv = iter->kvec;
+ unsigned long start = iter->iov_offset;
+ unsigned int i;
+ int ret;
+
+ for (i = 0; i < iter->nr_segs; i++) {
+ size_t len;
+
+ len = kv[i].iov_len;
+ if (start >= len) {
+ start -= len;
+ continue;
+ }
+
+ len = min_t(size_t, maxsize, len - start);
+ ret = crypto_shash_update(shash, kv[i].iov_base + start, len);
+ if (ret < 0)
+ return ret;
+ maxsize -= len;
+
+ if (maxsize <= 0)
+ break;
+ start = 0;
+ }
+
+ return 0;
+}
+
+/*
+ * Hash data from an XARRAY-type iterator.
+ */
+static ssize_t cifs_shash_xarray(const struct iov_iter *iter, ssize_t maxsize,
+ struct shash_desc *shash)
+{
+ struct folio *folios[16], *folio;
+ unsigned int nr, i, j, npages;
+ loff_t start = iter->xarray_start + iter->iov_offset;
+ pgoff_t last, index = start / PAGE_SIZE;
+ ssize_t ret = 0;
+ size_t len, offset, foffset;
+ void *p;
+
+ if (maxsize == 0)
+ return 0;
+
+ last = (start + maxsize - 1) / PAGE_SIZE;
+ do {
+ nr = xa_extract(iter->xarray, (void **)folios, index, last,
+ ARRAY_SIZE(folios), XA_PRESENT);
+ if (nr == 0)
+ return -EIO;
+
+ for (i = 0; i < nr; i++) {
+ folio = folios[i];
+ npages = folio_nr_pages(folio);
+ foffset = start - folio_pos(folio);
+ offset = foffset % PAGE_SIZE;
+ for (j = foffset / PAGE_SIZE; j < npages; j++) {
+ len = min_t(size_t, maxsize, PAGE_SIZE - offset);
+ p = kmap_local_page(folio_page(folio, j));
+ ret = crypto_shash_update(shash, p, len);
+ kunmap_local(p);
+ if (ret < 0)
+ return ret;
+ maxsize -= len;
+ if (maxsize <= 0)
+ return 0;
+ start += len;
+ offset = 0;
+ index++;
+ }
+ }
+ } while (nr == ARRAY_SIZE(folios));
+ return 0;
+}
+
+/*
+ * Pass the data from an iterator into a hash.
+ */
+static int cifs_shash_iter(const struct iov_iter *iter, size_t maxsize,
+ struct shash_desc *shash)
+{
+ if (maxsize == 0)
+ return 0;
+
+ switch (iov_iter_type(iter)) {
+ case ITER_BVEC:
+ return cifs_shash_bvec(iter, maxsize, shash);
+ case ITER_KVEC:
+ return cifs_shash_kvec(iter, maxsize, shash);
+ case ITER_XARRAY:
+ return cifs_shash_xarray(iter, maxsize, shash);
+ default:
+ pr_err("cifs_shash_iter(%u) unsupported\n", iov_iter_type(iter));
+ WARN_ON_ONCE(1);
+ return -EIO;
+ }
+}
+
int __cifs_calc_signature(struct smb_rqst *rqst,
struct TCP_Server_Info *server, char *signature,
struct shash_desc *shash)