Hi,
This patch set adds AEAD and RNG support to the AF_ALG interface
exported by the kernel crypto API. By extending AF_ALG with AEAD and RNG
support, all cipher types the kernel crypto API allows access to are
now accessible from userspace.
Both, AEAD and RNG implementations are stand-alone and do not depend
other AF_ALG interfaces (like hash or skcipher).
The AEAD implementation uses the same approach as provided with
skcipher by offering the following interfaces:
* sendmsg and recvmsg interfaces allowing multiple
invocations supporting a threaded user space. To support
multi-threaded user space, kernel-side buffering
is implemented similarly to skcipher.
* splice / vmsplice interfaces allowing a zero-copy
invocation
The RNG interface only implements the recvmsg interface as
zero-copy is not applicable.
The new AEAD and RNG interfaces are fully tested with the test application
provided at [1]. That test application exercises all newly added user space
interfaces. The testing covers:
* use of the sendmsg/recvmsg interface
* use of the splice / vmsplice interface
* invocation of all AF_ALG types (aead, rng, skcipher, hash)
* using all types of operation (encryption, decryption, keyed MD,
MD, random numbers, AEAD decryption with positive and negative
authentication verification)
* stress testing by running all tests for 30 minutes in an
endless loop
* test execution on 64 bit and 32 bit
[1] http://www.chronox.de/libkcapi.html
Changes v2:
* rebase to current cryptodev-2.6 tree
* use memzero_explicit to zeroize AEAD associated data
* use sizeof for determining length of AEAD associated data
* update algif_rng.c covering all suggestions from Daniel Borkmann
<[email protected]>
* addition of patch 9: add digestsize interface for hashes
* addition of patch to update documentation covering the userspace interface
* change numbers of getsockopt options: separate them from sendmsg interface
definitions
Changes v3:
* remove getsockopt interface
* AEAD: associated data is set prepended to the plain/ciphertext
* AEAD: allowing arbitrary associated data lengths
* remove setkey patch as protection was already in the existing code
Changes v4:
* stand-alone implementation of AEAD
* testing of all interfaces offered by AEAD
* stress testing of AEAD and RNG
Changes v5:
* AEAD: add outer while(size) loop in aead_sendmsg to ensure all data is
copied into the kernel (reporter Herbert Xu)
* AEAD: aead_sendmsg bug fix: change size -= len; to size -= plen;
* AF_ALG / AEAD: add aead_setauthsize and associated extension to
struct af_alg_type as well as alg_setsockopt (reporter Herbert Xu)
* RNG: rng_recvmsg: use 128 byte stack variable for output of RNG instead
of ctx->result (reporter Herbert Xu)
* RNG / AF_ALG: allow user space to seed RNG via setsockopt
* RNG: rng_recvmsg bug fix: use genlen as result variable for
crypto_rng_get_bytes as previously no negative errors were obtained
* AF_ALG: alg_setop: zeroize buffer before free
Changes v6:
* AEAD/RNG: port to 3.19-rc1 with the iov_iter handling
* RNG: use the setkey interface to obtain the seed and drop the patch adding
a separate reseeding interface
* extract the zeroization patch for alg_setkey into a stand-alone patch
submission
* fix bug in aead_sufficient_data (reporter Herbert Xu)
* testing of all interfaces with test application provided with libkcapi version
0.6.2
Changes v7:
* AEAD: aead_recvmsg: change error code from ENOMEM to EINVAL
* AEAD: drop aead_readable/aead_sufficient_data and only use ctx->more to decide
whether the read side shall become active. This change requires that the
patch for crypto_aead_decrypt ensuring that the ciphertext contains the
authentication tag was added -- see https://lkml.org/lkml/2014/12/30/200.
Otherwise, user space can trigger a kernel crash.
* RNG: patch dropped as it was applied
* AEAD: port Kconfig/Makefile patch forward to current code base
Changes v8:
* Removed check for aead_assoclen in aead_sendmsg
* Fix endless loop bug in aead_sendmsg (check for sgl->cur > ALG_MAX_PAGES in
while condition removed -- this condition is checked within the loop already)
* Resurrect aead_sufficient_data and call it in aead_sendmsg, aead_sendpage to
notify caller about wrong invocation
* Re-add aead_sufficient_data to aead_recvmsg to verify user input data before
using them to ensure the kernel protects against malicious parameters
* Allow arbitrary size of AD (i.e. up to the maximum buffer size of
ALG_MAX_PAGES)
* When aead_recvmsg receives an error from decryption, release all pages if the
error is EBADMSG -- this error implies that a proper decryption was performed
but the integrity of the message is lost. This error is considered to be a
valid decryption result.
* Add test cases for sendmsg and splice interface to test large AD sizes (in
case of sendmsg, use 65504 bytes AD and 32 bytes plaintext; in case of splice
use 15 pages AD and 32 bytes in the 16th page for plaintext). See [1] for
updated test case.
Stephan Mueller (2):
crypto: AF_ALG: add AEAD support
crypto: AF_ALG: enable AEAD interface compilation
crypto/Kconfig | 9 +
crypto/Makefile | 1 +
crypto/algif_aead.c | 666 ++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 676 insertions(+)
create mode 100644 crypto/algif_aead.c
--
2.1.0
This patch adds the AEAD support for AF_ALG.
The implementation is based on algif_skcipher, but contains heavy
modifications to streamline the interface for AEAD uses.
To use AEAD, the user space consumer has to use the salg_type named
"aead".
The AEAD implementation includes some overhead to calculate the size of
the ciphertext, because the AEAD implementation of the kernel crypto API
makes implied assumption on the location of the authentication tag. When
performing an encryption, the tag will be added to the created
ciphertext (note, the tag is placed adjacent to the ciphertext). For
decryption, the caller must hand in the ciphertext with the tag appended
to the ciphertext. Therefore, the selection of the used memory
needs to add/subtract the tag size from the source/destination buffers
depending on the encryption type. The code is provided with comments
explaining when and how that operation is performed.
A fully working example using all aspects of AEAD is provided at
http://www.chronox.de/libkcapi.html
Signed-off-by: Stephan Mueller <[email protected]>
---
crypto/algif_aead.c | 666 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 666 insertions(+)
create mode 100644 crypto/algif_aead.c
diff --git a/crypto/algif_aead.c b/crypto/algif_aead.c
new file mode 100644
index 0000000..34bf4a0
--- /dev/null
+++ b/crypto/algif_aead.c
@@ -0,0 +1,666 @@
+/*
+ * algif_aeadr: User-space interface for AEAD algorithms
+ *
+ * Copyright (C) 2014, Stephan Mueller <[email protected]>
+ *
+ * This file provides the user-space API for AEAD ciphers.
+ *
+ * This file is derived from algif_skcipher.c.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include <crypto/scatterwalk.h>
+#include <crypto/if_alg.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/net.h>
+#include <net/sock.h>
+
+struct aead_sg_list {
+ unsigned int cur;
+ struct scatterlist sg[ALG_MAX_PAGES];
+};
+
+struct aead_ctx {
+ struct aead_sg_list tsgl;
+ struct af_alg_sgl rsgl;
+
+ void *iv;
+
+ struct af_alg_completion completion;
+
+ unsigned long used;
+
+ unsigned int len;
+ bool more;
+ bool merge;
+ bool enc;
+
+ size_t aead_assoclen;
+ struct aead_request aead_req;
+};
+
+static inline int aead_sndbuf(struct sock *sk)
+{
+ struct alg_sock *ask = alg_sk(sk);
+ struct aead_ctx *ctx = ask->private;
+
+ return max_t(int, max_t(int, sk->sk_sndbuf & PAGE_MASK, PAGE_SIZE) -
+ ctx->used, 0);
+}
+
+static inline bool aead_writable(struct sock *sk)
+{
+ return PAGE_SIZE <= aead_sndbuf(sk);
+}
+
+static inline bool aead_sufficient_data(struct aead_ctx *ctx)
+{
+ unsigned as = crypto_aead_authsize(crypto_aead_reqtfm(&ctx->aead_req));
+
+ return (ctx->used >= (ctx->aead_assoclen + (ctx->enc ? 0 : as)));
+}
+
+static void aead_put_sgl(struct sock *sk)
+{
+ struct alg_sock *ask = alg_sk(sk);
+ struct aead_ctx *ctx = ask->private;
+ struct aead_sg_list *sgl = &ctx->tsgl;
+ struct scatterlist *sg = sgl->sg;
+ unsigned int i;
+
+ for (i = 0; i < sgl->cur; i++) {
+ if (!sg_page(sg + i))
+ continue;
+
+ put_page(sg_page(sg + i));
+ sg_assign_page(sg + i, NULL);
+ }
+ sgl->cur = 0;
+ ctx->used = 0;
+ ctx->more = 0;
+ ctx->merge = 0;
+}
+
+static int aead_wait_for_wmem(struct sock *sk, unsigned flags)
+{
+ long timeout;
+ DEFINE_WAIT(wait);
+ int err = -ERESTARTSYS;
+
+ if (flags & MSG_DONTWAIT)
+ return -EAGAIN;
+
+ set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
+
+ for (;;) {
+ if (signal_pending(current))
+ break;
+ prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+ timeout = MAX_SCHEDULE_TIMEOUT;
+ if (sk_wait_event(sk, &timeout, aead_writable(sk))) {
+ err = 0;
+ break;
+ }
+ }
+ finish_wait(sk_sleep(sk), &wait);
+
+ return err;
+}
+
+static void aead_wmem_wakeup(struct sock *sk)
+{
+ struct socket_wq *wq;
+
+ if (!aead_writable(sk))
+ return;
+
+ rcu_read_lock();
+ wq = rcu_dereference(sk->sk_wq);
+ if (wq_has_sleeper(wq))
+ wake_up_interruptible_sync_poll(&wq->wait, POLLIN |
+ POLLRDNORM |
+ POLLRDBAND);
+ sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
+ rcu_read_unlock();
+}
+
+static int aead_wait_for_data(struct sock *sk, unsigned flags)
+{
+ struct alg_sock *ask = alg_sk(sk);
+ struct aead_ctx *ctx = ask->private;
+ long timeout;
+ DEFINE_WAIT(wait);
+ int err = -ERESTARTSYS;
+
+ if (flags & MSG_DONTWAIT) {
+ return -EAGAIN;
+ }
+
+ set_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
+
+ for (;;) {
+ if (signal_pending(current))
+ break;
+ prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+ timeout = MAX_SCHEDULE_TIMEOUT;
+ if (sk_wait_event(sk, &timeout, !ctx->more)) {
+ err = 0;
+ break;
+ }
+ }
+ finish_wait(sk_sleep(sk), &wait);
+
+ clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
+
+ return err;
+}
+
+static void aead_data_wakeup(struct sock *sk)
+{
+ struct alg_sock *ask = alg_sk(sk);
+ struct aead_ctx *ctx = ask->private;
+ struct socket_wq *wq;
+
+ if (ctx->more)
+ return;
+
+ rcu_read_lock();
+ wq = rcu_dereference(sk->sk_wq);
+ if (wq_has_sleeper(wq))
+ wake_up_interruptible_sync_poll(&wq->wait, POLLOUT |
+ POLLRDNORM |
+ POLLRDBAND);
+ sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
+ rcu_read_unlock();
+}
+
+static int aead_sendmsg(struct kiocb *unused, struct socket *sock,
+ struct msghdr *msg, size_t size)
+{
+ struct sock *sk = sock->sk;
+ struct alg_sock *ask = alg_sk(sk);
+ struct aead_ctx *ctx = ask->private;
+ unsigned ivsize =
+ crypto_aead_ivsize(crypto_aead_reqtfm(&ctx->aead_req));
+ struct aead_sg_list *sgl = &ctx->tsgl;
+ struct af_alg_control con = {};
+ long copied = 0;
+ bool enc = 0;
+ bool init = 0;
+ int err = -EINVAL;
+
+ if (msg->msg_controllen) {
+ err = af_alg_cmsg_send(msg, &con);
+ if (err)
+ return err;
+
+ init = 1;
+ switch (con.op) {
+ case ALG_OP_ENCRYPT:
+ enc = 1;
+ break;
+ case ALG_OP_DECRYPT:
+ enc = 0;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (con.iv && con.iv->ivlen != ivsize)
+ return -EINVAL;
+ }
+
+ lock_sock(sk);
+ if (!ctx->more && ctx->used)
+ goto unlock;
+
+ if (init) {
+ ctx->enc = enc;
+ if (con.iv)
+ memcpy(ctx->iv, con.iv->iv, ivsize);
+
+ ctx->aead_assoclen = con.aead_assoclen;
+ }
+
+ while (size) {
+ unsigned long len = size;
+ struct scatterlist *sg = NULL;
+
+ if (ctx->merge) {
+ sg = sgl->sg + sgl->cur - 1;
+ len = min_t(unsigned long, len,
+ PAGE_SIZE - sg->offset - sg->length);
+ err = memcpy_from_msg(page_address(sg_page(sg)) +
+ sg->offset + sg->length,
+ msg, len);
+ if (err)
+ goto unlock;
+
+ sg->length += len;
+ ctx->merge = (sg->offset + sg->length) &
+ (PAGE_SIZE - 1);
+
+ ctx->used += len;
+ copied += len;
+ size -= len;
+ }
+
+ if (!aead_writable(sk)) {
+ /*
+ * If there is more data to be expected, but we cannot
+ * write more data, forcefully define that we do not
+ * expect more data to invoke the AEAD operation. This
+ * prevents a deadlock in user space.
+ */
+ ctx->more = 0;
+ err = aead_wait_for_wmem(sk, msg->msg_flags);
+ if (err)
+ goto unlock;
+ }
+
+ len = min_t(unsigned long, size, aead_sndbuf(sk));
+ while (len) {
+ int plen = 0;
+
+ if (sgl->cur >= ALG_MAX_PAGES) {
+ err = -E2BIG;
+ goto unlock;
+ }
+
+ sg = sgl->sg + sgl->cur;
+ plen = min_t(int, len, PAGE_SIZE);
+
+ sg_assign_page(sg, alloc_page(GFP_KERNEL));
+ err = -ENOMEM;
+ if (!sg_page(sg))
+ goto unlock;
+
+ err = memcpy_from_msg(page_address(sg_page(sg)),
+ msg, plen);
+ if (err) {
+ __free_page(sg_page(sg));
+ sg_assign_page(sg, NULL);
+ goto unlock;
+ }
+
+ sg->length = plen;
+ len -= plen;
+ ctx->used += plen;
+ copied += plen;
+ sgl->cur++;
+ size -= plen;
+ ctx->merge = plen & (PAGE_SIZE - 1);
+ }
+ }
+
+ err = 0;
+
+ ctx->more = msg->msg_flags & MSG_MORE;
+ if (!ctx->more && !aead_sufficient_data(ctx))
+ err = -EINVAL;
+
+unlock:
+ aead_data_wakeup(sk);
+ release_sock(sk);
+
+ return err ?: copied;
+}
+
+static ssize_t aead_sendpage(struct socket *sock, struct page *page,
+ int offset, size_t size, int flags)
+{
+ struct sock *sk = sock->sk;
+ struct alg_sock *ask = alg_sk(sk);
+ struct aead_ctx *ctx = ask->private;
+ struct aead_sg_list *sgl = &ctx->tsgl;
+ int err = -EINVAL;
+
+ if (flags & MSG_SENDPAGE_NOTLAST)
+ flags |= MSG_MORE;
+
+ if (sgl->cur >= ALG_MAX_PAGES)
+ return -E2BIG;
+
+ lock_sock(sk);
+ if (!ctx->more && ctx->used)
+ goto unlock;
+
+ if (!size)
+ goto done;
+
+ if (!aead_writable(sk)) {
+ /* see aead_sendmsg why more is set to 0 */
+ ctx->more = 0;
+ err = aead_wait_for_wmem(sk, flags);
+ if (err)
+ goto unlock;
+ }
+
+ ctx->merge = 0;
+
+ get_page(page);
+ sg_set_page(sgl->sg + sgl->cur, page, size, offset);
+ sgl->cur++;
+ ctx->used += size;
+
+ err = 0;
+
+done:
+ ctx->more = flags & MSG_MORE;
+ if (!ctx->more && !aead_sufficient_data(ctx))
+ err = -EINVAL;
+
+unlock:
+ aead_data_wakeup(sk);
+ release_sock(sk);
+
+ return err ?: size;
+}
+
+static int aead_recvmsg(struct kiocb *unused, struct socket *sock,
+ struct msghdr *msg, size_t ignored, int flags)
+{
+ struct sock *sk = sock->sk;
+ struct alg_sock *ask = alg_sk(sk);
+ struct aead_ctx *ctx = ask->private;
+ unsigned bs = crypto_aead_blocksize(crypto_aead_reqtfm(&ctx->aead_req));
+ unsigned as = crypto_aead_authsize(crypto_aead_reqtfm(&ctx->aead_req));
+ struct aead_sg_list *sgl = &ctx->tsgl;
+ struct scatterlist *sg = sgl->sg;
+ struct scatterlist assoc[ALG_MAX_PAGES];
+ size_t assoclen = 0;
+ unsigned int i = 0;
+ int err = -EAGAIN;
+ unsigned long used = 0;
+ unsigned long outlen = 0;
+
+ /*
+ * Require exactly one IOV block as the AEAD operation is a one shot
+ * due to the authentication tag.
+ */
+ if (msg->msg_iter.nr_segs != 1)
+ return -ENOMSG;
+
+ lock_sock(sk);
+ /*
+ * AEAD memory structure: For encryption, the tag is appended to the
+ * ciphertext which implies that the memory allocated for the ciphertext
+ * must be increased by the tag length. For decryption, the tag
+ * is expected to be concatenated to the ciphertext. The plaintext
+ * therefore has a memory size of the ciphertext minus the tag length.
+ *
+ * The memory structure for cipher operation has the following
+ * structure:
+ * AEAD encryption input: assoc data || plaintext
+ * AEAD encryption output: cipherntext || auth tag
+ * AEAD decryption input: assoc data || ciphertext || auth tag
+ * AEAD decryption output: plaintext
+ */
+
+ if (ctx->more) {
+ err = aead_wait_for_data(sk, flags);
+ if (err)
+ goto unlock;
+ }
+
+ used = ctx->used;
+
+ err = -EINVAL;
+
+ /*
+ * Make sure sufficient data is present -- note, the same check is
+ * is also present in sendmsg/sendpage. The checks in sendpage/sendmsg
+ * shall provide an information to the data sender that something is
+ * wrong, but they are irrelevant to maintain the kernel integrity.
+ * We need this check here too in case user space decides to not honor
+ * the error message in sendmsg/sendpage and still call recvmsg. This
+ * check here protects the kernel integrity.
+ */
+ if (!aead_sufficient_data(ctx))
+ goto unlock;
+
+ /*
+ * The cipher operation input data is reduced by the associated data
+ * length as this data is processed separately later on.
+ */
+ used -= ctx->aead_assoclen;
+
+ if (ctx->enc) {
+ /* round up output buffer to multiple of block size */
+ outlen = ((used + bs - 1) / bs * bs);
+ /* add the size needed for the auth tag to be created */
+ outlen += as;
+ } else {
+ /* output data size is input without the authentication tag */
+ outlen = used - as;
+ /* round up output buffer to multiple of block size */
+ outlen = ((outlen + bs - 1) / bs * bs);
+ }
+
+ /* ensure output buffer is sufficiently large */
+ if (msg->msg_iter.iov->iov_len < outlen)
+ goto unlock;
+
+ outlen = af_alg_make_sg(&ctx->rsgl, msg->msg_iter.iov->iov_base,
+ outlen, 1);
+ err = outlen;
+ if (err < 0)
+ goto unlock;
+
+ err = -EINVAL;
+ sg_init_table(assoc, ALG_MAX_PAGES);
+ assoclen = ctx->aead_assoclen;
+ /*
+ * Split scatterlist into two: first part becomes AD, second part
+ * is plaintext / ciphertext. The first part is assigned to assoc
+ * scatterlist. When this loop finishes, sg points to the start of the
+ * plaintext / ciphertext.
+ */
+ for(i = 0; i < ctx->tsgl.cur; i++) {
+ sg = sgl->sg + i;
+ if (sg->length <= assoclen) {
+ /* AD is larger than one page */
+ sg_set_page(assoc + i, sg_page(sg),
+ sg->length, sg->offset);
+ assoclen -= sg->length;
+ if (i >= ctx->tsgl.cur)
+ goto unlock;
+ } else if (!assoclen) {
+ /* current page is to start of plaintext / ciphertext */
+ if (i)
+ /* AD terminates at page boundary */
+ sg_mark_end(assoc + i - 1);
+ else
+ /* AD size is zero */
+ sg_mark_end(assoc);
+ break;
+ } else {
+ /* AD does not terminate at page boundary */
+ sg_set_page(assoc + i, sg_page(sg),
+ assoclen, sg->offset);
+ sg_mark_end(assoc + i);
+ /* plaintext / ciphertext starts after AD */
+ sg->length -= assoclen;
+ sg->offset += assoclen;
+ break;
+ }
+ }
+
+ aead_request_set_assoc(&ctx->aead_req, assoc, ctx->aead_assoclen);
+ aead_request_set_crypt(&ctx->aead_req, sg, ctx->rsgl.sg, used, ctx->iv);
+
+ err = af_alg_wait_for_completion(ctx->enc ?
+ crypto_aead_encrypt(&ctx->aead_req) :
+ crypto_aead_decrypt(&ctx->aead_req),
+ &ctx->completion);
+
+ af_alg_free_sg(&ctx->rsgl);
+
+ if (err) {
+ /* EBADMSG implies a valid cipher operation took place */
+ if (err == -EBADMSG)
+ aead_put_sgl(sk);
+ goto unlock;
+ }
+
+ aead_put_sgl(sk);
+
+ err = 0;
+
+unlock:
+ aead_wmem_wakeup(sk);
+ release_sock(sk);
+
+ return err ? err : outlen;
+}
+
+static unsigned int aead_poll(struct file *file, struct socket *sock,
+ poll_table *wait)
+{
+ struct sock *sk = sock->sk;
+ struct alg_sock *ask = alg_sk(sk);
+ struct aead_ctx *ctx = ask->private;
+ unsigned int mask;
+
+ sock_poll_wait(file, sk_sleep(sk), wait);
+ mask = 0;
+
+ if (!ctx->more)
+ mask |= POLLIN | POLLRDNORM;
+
+ if (aead_writable(sk))
+ mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
+
+ return mask;
+}
+
+static struct proto_ops algif_aead_ops = {
+ .family = PF_ALG,
+
+ .connect = sock_no_connect,
+ .socketpair = sock_no_socketpair,
+ .getname = sock_no_getname,
+ .ioctl = sock_no_ioctl,
+ .listen = sock_no_listen,
+ .shutdown = sock_no_shutdown,
+ .getsockopt = sock_no_getsockopt,
+ .mmap = sock_no_mmap,
+ .bind = sock_no_bind,
+ .accept = sock_no_accept,
+ .setsockopt = sock_no_setsockopt,
+
+ .release = af_alg_release,
+ .sendmsg = aead_sendmsg,
+ .sendpage = aead_sendpage,
+ .recvmsg = aead_recvmsg,
+ .poll = aead_poll,
+};
+
+static void *aead_bind(const char *name, u32 type, u32 mask)
+{
+ return crypto_alloc_aead(name, type, mask);
+}
+
+static void aead_release(void *private)
+{
+ crypto_free_aead(private);
+}
+
+static int aead_setauthsize(void *private, unsigned int authsize)
+{
+ return crypto_aead_setauthsize(private, authsize);
+}
+
+static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
+{
+ return crypto_aead_setkey(private, key, keylen);
+}
+
+static void aead_sock_destruct(struct sock *sk)
+{
+ struct alg_sock *ask = alg_sk(sk);
+ struct aead_ctx *ctx = ask->private;
+ unsigned int ivlen = crypto_aead_ivsize(
+ crypto_aead_reqtfm(&ctx->aead_req));
+
+ aead_put_sgl(sk);
+ sock_kzfree_s(sk, ctx->iv, ivlen);
+ sock_kfree_s(sk, ctx, ctx->len);
+ af_alg_release_parent(sk);
+}
+
+static int aead_accept_parent(void *private, struct sock *sk)
+{
+ struct aead_ctx *ctx;
+ struct alg_sock *ask = alg_sk(sk);
+ unsigned int len = sizeof(*ctx) + crypto_aead_reqsize(private);
+ unsigned int ivlen = crypto_aead_ivsize(private);
+
+ ctx = sock_kmalloc(sk, len, GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+ memset(ctx, 0, len);
+
+ ctx->iv = sock_kmalloc(sk, ivlen, GFP_KERNEL);
+ if (!ctx->iv) {
+ sock_kfree_s(sk, ctx, len);
+ return -ENOMEM;
+ }
+ memset(ctx->iv, 0, ivlen);
+
+ ctx->len = len;
+ ctx->used = 0;
+ ctx->more = 0;
+ ctx->merge = 0;
+ ctx->enc = 0;
+ ctx->tsgl.cur = 0;
+ ctx->aead_assoclen = 0;
+ af_alg_init_completion(&ctx->completion);
+ sg_init_table(ctx->tsgl.sg, ALG_MAX_PAGES);
+
+ ask->private = ctx;
+
+ aead_request_set_tfm(&ctx->aead_req, private);
+ aead_request_set_callback(&ctx->aead_req, CRYPTO_TFM_REQ_MAY_BACKLOG,
+ af_alg_complete, &ctx->completion);
+
+ sk->sk_destruct = aead_sock_destruct;
+
+ return 0;
+}
+
+static const struct af_alg_type algif_type_aead = {
+ .bind = aead_bind,
+ .release = aead_release,
+ .setkey = aead_setkey,
+ .setauthsize = aead_setauthsize,
+ .accept = aead_accept_parent,
+ .ops = &algif_aead_ops,
+ .name = "aead",
+ .owner = THIS_MODULE
+};
+
+static int __init algif_aead_init(void)
+{
+ return af_alg_register_type(&algif_type_aead);
+}
+
+static void __exit algif_aead_exit(void)
+{
+ int err = af_alg_unregister_type(&algif_type_aead);
+ BUG_ON(err);
+}
+
+module_init(algif_aead_init);
+module_exit(algif_aead_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Stephan Mueller <[email protected]>");
+MODULE_DESCRIPTION("AEAD kernel crypto API user space interface");
--
2.1.0
On Wed, Jan 07, 2015 at 04:51:38PM +0100, Stephan Mueller wrote:
>
> + if (!aead_writable(sk)) {
> + /*
> + * If there is more data to be expected, but we cannot
> + * write more data, forcefully define that we do not
> + * expect more data to invoke the AEAD operation. This
> + * prevents a deadlock in user space.
> + */
> + ctx->more = 0;
We should return EMSGSIZE here. Also we should clear out the
existing data so that the socket may be reused again.
> + ctx->more = msg->msg_flags & MSG_MORE;
> + if (!ctx->more && !aead_sufficient_data(ctx))
> + err = -EINVAL;
Ditto, we should discard the data that's queued up. Also perhaps
use EBADMSG instead of EINVAL.
> + /*
> + * Require exactly one IOV block as the AEAD operation is a one shot
> + * due to the authentication tag.
> + */
> + if (msg->msg_iter.nr_segs != 1)
> + return -ENOMSG;
Why does the receive buffer have to be contiguous?
Cheers,
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Am Donnerstag, 8. Januar 2015, 22:09:31 schrieb Herbert Xu:
Hi Herbert,
> On Wed, Jan 07, 2015 at 04:51:38PM +0100, Stephan Mueller wrote:
> > + if (!aead_writable(sk)) {
> > + /*
> > + * If there is more data to be expected, but we cannot
> > + * write more data, forcefully define that we do not
> > + * expect more data to invoke the AEAD operation. This
> > + * prevents a deadlock in user space.
> > + */
> > + ctx->more = 0;
>
> We should return EMSGSIZE here. Also we should clear out the
> existing data so that the socket may be reused again.
Is this really wise considering that we want to support a threaded caller? For
example, one thread sends data and another reads data. For some reason, the
reading thread is throttled or slower than the sender. Now, with the current
solution, the sender is put on hold (i.e. throttled) until the reader can
catch up. I.e. we have an automated synchronization between sender/receiver.
Thus, when we remove the wait here and return an error, the sender will be
shut down and there is no synchronization of the reader/writer any more.
Note, the same applies to the very similar code in aead_sendpage too.
>
> > + ctx->more = msg->msg_flags & MSG_MORE;
> > + if (!ctx->more && !aead_sufficient_data(ctx))
> > + err = -EINVAL;
>
> Ditto, we should discard the data that's queued up. Also perhaps
> use EBADMSG instead of EINVAL.
Agreed that we should clear out the buffer. I will provide that in the next
release for both, the sendmsg and sendpage implementations.
However, I am not sure whether using EBADMSG is a good idea. The error of
EBADMSG in the kernel crypto API is only used for integrity errors of AEAD
ciphers. But our error case here has nothing to do with the integrity error.
I would be fine with any other error number -- EMSGSIZE as you suggested
above?
>
> > + /*
> > + * Require exactly one IOV block as the AEAD operation is a one shot
> > + * due to the authentication tag.
> > + */
> > + if (msg->msg_iter.nr_segs != 1)
> > + return -ENOMSG;
>
> Why does the receive buffer have to be contiguous?
I thought for quite some time about how we can use multiple iovecs. But I
found no satisfactory solution. The solution I see is described below.
If we consider the skcipher implementation, the code iterates over the iovecs
as the outermost loop. In each loop iteration the cipher operation is
triggered.
Now in case of AEAD, all provided data the kernel received has to be operated
on with exactly one cipher invocation. Looking at skcipher, that would mean
that we only perform one loop iteration, i.e. processing exactly one iovec.
A possible solution would be that I use an array of struct af_alg_sgl and
iterate over that array for each iovec. Something like the following:
struct aead_ctx {
...
struct af_alg_sgl rsgl[ALG_MAX_PAGES];
for(i = 0; i < ALG_MAX_PAGES; i++) {
af_alg_make_sg(rsgl[i], iov[i])
scatterwalk_sg_chain(rsgl[i-1].sg rsgl[i]);
}
But my concern is that with the array of rsgl we occupy a sizable amount of
memory as af_alg_sgl again defines arrays of entries.
Do you think whether such approach makes sense? If yes, which limit to the
number of rsgl should we apply -- is ALG_MAX_PAGES good?
--
Ciao
Stephan
On Fri, Jan 09, 2015 at 04:30:45AM +0100, Stephan Mueller wrote:
> Am Donnerstag, 8. Januar 2015, 22:09:31 schrieb Herbert Xu:
>
> Hi Herbert,
>
> > On Wed, Jan 07, 2015 at 04:51:38PM +0100, Stephan Mueller wrote:
> > > + if (!aead_writable(sk)) {
> > > + /*
> > > + * If there is more data to be expected, but we cannot
> > > + * write more data, forcefully define that we do not
> > > + * expect more data to invoke the AEAD operation. This
> > > + * prevents a deadlock in user space.
> > > + */
> > > + ctx->more = 0;
> >
> > We should return EMSGSIZE here. Also we should clear out the
> > existing data so that the socket may be reused again.
>
> Is this really wise considering that we want to support a threaded caller? For
> example, one thread sends data and another reads data. For some reason, the
> reading thread is throttled or slower than the sender. Now, with the current
> solution, the sender is put on hold (i.e. throttled) until the reader can
> catch up. I.e. we have an automated synchronization between sender/receiver.
>
> Thus, when we remove the wait here and return an error, the sender will be
> shut down and there is no synchronization of the reader/writer any more.
>
> Note, the same applies to the very similar code in aead_sendpage too.
No, if we're in this case then something seriously wrong has
happened. IOW the application writer has screwed up. We're
not able to carry out the wish of user-space because of resource
limits on the socket. Attempting to continue at this point will
only cause confusion.
So we should loudly declare that there was an error.
> > > + ctx->more = msg->msg_flags & MSG_MORE;
> > > + if (!ctx->more && !aead_sufficient_data(ctx))
> > > + err = -EINVAL;
> >
> > Ditto, we should discard the data that's queued up. Also perhaps
> > use EBADMSG instead of EINVAL.
>
> Agreed that we should clear out the buffer. I will provide that in the next
> release for both, the sendmsg and sendpage implementations.
>
> However, I am not sure whether using EBADMSG is a good idea. The error of
> EBADMSG in the kernel crypto API is only used for integrity errors of AEAD
> ciphers. But our error case here has nothing to do with the integrity error.
>
> I would be fine with any other error number -- EMSGSIZE as you suggested
> above?
Sure.
> Do you think whether such approach makes sense? If yes, which limit to the
> number of rsgl should we apply -- is ALG_MAX_PAGES good?
Yes I think your solution in v10 is fine. The current kernel
AEAD interface isn't the best but we're stuck with it for the
time being so this is the best we can do.
Cheers,
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Am Dienstag, 20. Januar 2015, 14:00:17 schrieb Herbert Xu:
Hi Herbert,
>On Fri, Jan 09, 2015 at 04:30:45AM +0100, Stephan Mueller wrote:
>> Am Donnerstag, 8. Januar 2015, 22:09:31 schrieb Herbert Xu:
>>
>> Hi Herbert,
>>
>> > On Wed, Jan 07, 2015 at 04:51:38PM +0100, Stephan Mueller wrote:
>> > > + if (!aead_writable(sk)) {
>> > > + /*
>> > > + * If there is more data to be expected,
but we cannot
>> > > + * write more data, forcefully define
that we do not
>> > > + * expect more data to invoke the AEAD
operation. This
>> > > + * prevents a deadlock in user space.
>> > > + */
>> > > + ctx->more = 0;
>> >
>> > We should return EMSGSIZE here. Also we should clear out the
>> > existing data so that the socket may be reused again.
>>
>> Is this really wise considering that we want to support a threaded
>> caller? For example, one thread sends data and another reads data.
>> For some reason, the reading thread is throttled or slower than the
>> sender. Now, with the current solution, the sender is put on hold
>> (i.e. throttled) until the reader can catch up. I.e. we have an
>> automated synchronization between sender/receiver.
>>
>> Thus, when we remove the wait here and return an error, the sender
>> will be shut down and there is no synchronization of the
>> reader/writer any more.
>>
>> Note, the same applies to the very similar code in aead_sendpage too.
>
>No, if we're in this case then something seriously wrong has
>happened. IOW the application writer has screwed up. We're
>not able to carry out the wish of user-space because of resource
>limits on the socket. Attempting to continue at this point will
>only cause confusion.
>
>So we should loudly declare that there was an error.
Ok. Your suggestion implies that it needs to be removed in aead_sendmsg
and aead_sendpage. That in turn implies aead_wait_for_wmem can go as
well.
Also, my previous suggestion with MSG_TRUNC can be removed as well.
I will do that with my next installment.
Ciao
Stephan