When comparing MAC hashes, AEAD authentication tags, or other hash
values in the context of authentication or integrity checking, it
is important not to leak timing information to a potential attacker,
i.e. when communication happens over a network.

Bytewise memory comparisons (such as memcmp) are usually optimized so
that they return a nonzero value as soon as a mismatch is found. E.g,
on x86_64/i5 for 512 bytes this can be ~50 cyc for a full mismatch
and up to ~850 cyc for a full match (cold). This early-return behavior
can leak timing information as a side channel, allowing an attacker to
iteratively guess the correct result.

This patch adds a new method crypto_memneq ("memory not equal to each
other") to the crypto API that compares memory areas of the same length
in roughly "constant time" (cache misses could change the timing, but
since they don't reveal information about the content of the strings
being compared, they are effectively benign). Iow, best and worst case
behaviour take the same amount of time to complete (in contrast to
memcmp).

Note that crypto_memneq (unlike memcmp) can only be used to test for
equality or inequality, NOT for lexicographical order. This, however,
is not an issue for its use-cases within the crypto API.

We tried to locate all of the places in the crypto API where memcmp was
being used for authentication or integrity checking, and convert them
over to crypto_memneq.

crypto_memneq is declared noinline, placed in its own source file,
and compiled with optimizations that might increase code size disabled
("Os") because a smart compiler (or LTO) might notice that the return
value is always compared against zero/nonzero, and might then
reintroduce the same early-return optimization that we are trying to
avoid.

Using #pragma or __attribute__ optimization annotations of the code
for disabling optimization was avoided as it seems to be considered
broken or unmaintained for long time in GCC [1]. Therefore, we work
around that by specifying the compile flag for memneq.o directly in
the Makefile. We found that this seems to be most appropriate.

As we use ("Os"), this patch also provides a loop-free "fast-path" for
frequently used 16 byte digests. Similarly to kernel library string
functions, leave an option for future even further optimized architecture
specific assembler implementations.

This was a joint work of James Yonan and Daniel Borkmann. Also thanks
for feedback from Florian Weimer on this and earlier proposals [2].

  [1] http://gcc.gnu.org/ml/gcc/2012-07/msg00211.html
  [2] https://lkml.org/lkml/2013/2/10/131Signed-off-by: NJames Yonan <james@openvpn.net>
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Cc: Florian Weimer <fw@deneb.enyo.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Replace PTR_ERR followed by ERR_PTR by ERR_CAST, to be more concise.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression err,x;
@@
-       err = PTR_ERR(x);
        if (IS_ERR(x))
-                return ERR_PTR(err);
+                return ERR_CAST(x);
// </smpl>
Signed-off-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

The authenc code doesn't deal with zero-length associated data
correctly and ends up constructing a zero-length sg entry which
causes a crash when it's fed into the crypto system.

This patch fixes this by avoiding the code-path that triggers
the SG construction if we have no associated data.

This isn't the most optimal fix as it means that we'll end up
using the fallback code-path even when we could still execute
the digest function.  However, this isn't a big deal as nobody
but the test path would supply zero-length associated data.
Reported-by: NRomain Francoise <romain@orebokech.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Tested-by: NRomain Francoise <romain@orebokech.com>

Use scatterwalk_crypto_chain in favor of locally defined chaining functions.
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Use ERR_CAST(x) rather than ERR_PTR(PTR_ERR(x)).  The former makes more
clear what is the purpose of the operation, which otherwise looks like a
no-op.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
type T;
T x;
identifier f;
@@

T f (...) { <+...
- ERR_PTR(PTR_ERR(x))
+ x
 ...+> }

@@
expression x;
@@

- ERR_PTR(PTR_ERR(x))
+ ERR_CAST(x)
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch (applied against 2.6.34) fixes the calculation of the
length of the ABLKCIPHER decrypt request ("cryptlen") after an
asynchronous hash request has been completed in the AUTHENC interface.
Signed-off-by: NShikhar Khattar <shikhark@gmail.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

When Steffen originally wrote the authenc async hash patch, he
correctly had EINPROGRESS checks in place so that we did not invoke
the original completion handler with it.

Unfortuantely I told him to remove it before the patch was applied.

As only MAY_BACKLOG request completion handlers are required to
handle EINPROGRESS completions, those checks are really needed.

This patch restores them.
Reported-by: NSebastian Andrzej Siewior <sebastian@breakpoint.cc>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

In crypto_authenc_encrypt() we save the IV behind the ablkcipher
request. To save space on the request, we overwrite the ablkcipher
request with a ahash request after encryption. So the IV may be
overwritten by the ahash request. This patch fixes this by placing
the IV in front of the ablkcipher/ahash request.
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

We accidentally assigned the ahash update complete function to
the wrong function pointer in crypto_authenc_verify.
This patch fixes this.
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Signed-off-by: NRichard Hartmann <richih.mailinglist@gmail.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch converts authenc to the new ahash interface.
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Now that there are no more legacy hash implementations we can
remove the reference to crypto_hash.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

As it is if an algorithm with a zero-length IV is used (e.g.,
NULL encryption) with authenc, authenc may generate an SG entry
of length zero, which will trigger a BUG check in the hash layer.

This patch fixes it by skipping the IV SG generation if the IV
size is zero.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch allows shash algorithms to be used through the old hash
interface.  This is a transitional measure so we can convert the
underlying algorithms to shash before converting the users across.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Authenc works in two stages for encryption, it first encrypts and
then computes an ICV.  The context memory of the request is used
by both operations.  The problem is that when an asynchronous
encryption completes, we will compute the ICV and then reread the
context memory of the encryption to get the original request.

It just happens that we have a buffer of 16 bytes in front of the
request pointer, so ICVs of 16 bytes (such as SHA1) do not trigger
the bug.  However, any attempt to uses a larger ICV instantly kills
the machine when the first asynchronous encryption is completed.

This patch fixes this by saving the request pointer before we start
the ICV computation.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

crypto_authenc_givencrypt_done uses req->data as struct aead_givcrypt_request,
while it really points to a struct aead_request, causing this crash:

BUG: unable to handle kernel paging request at 6b6b6b6b
IP: [<dc87517b>] :authenc:crypto_authenc_genicv+0x23/0x109
*pde = 00000000
Oops: 0000 [#1] PREEMPT DEBUG_PAGEALLOC
Modules linked in: hifn_795x authenc esp4 aead xfrm4_mode_tunnel sha1_generic hmac crypto_hash]

Pid: 3074, comm: ping Not tainted (2.6.25 #4)
EIP: 0060:[<dc87517b>] EFLAGS: 00010296 CPU: 0
EIP is at crypto_authenc_genicv+0x23/0x109 [authenc]
EAX: daa04690 EBX: daa046e0 ECX: dab0a100 EDX: daa046b0
ESI: 6b6b6b6b EDI: dc872054 EBP: c033ff60 ESP: c033ff0c
 DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
Process ping (pid: 3074, ti=c033f000 task=db883a80 task.ti=dab6c000)
Stack: 00000000 daa046b0 c0215a3e daa04690 dab0a100 00000000 ffffffff db9fd7f0
       dba208c0 dbbb1720 00000001 daa04720 00000001 c033ff54 c0119ca9 dc852a75
       c033ff60 c033ff60 daa046e0 00000000 00000001 c033ff6c dc87527b 00000001
Call Trace:
 [<c0215a3e>] ? dev_alloc_skb+0x14/0x29
 [<c0119ca9>] ? printk+0x15/0x17
 [<dc87527b>] ? crypto_authenc_givencrypt_done+0x1a/0x27 [authenc]
 [<dc850cca>] ? hifn_process_ready+0x34a/0x352 [hifn_795x]
 [<dc8353c7>] ? rhine_napipoll+0x3f2/0x3fd [via_rhine]
 [<dc851a56>] ? hifn_check_for_completion+0x4d/0xa6 [hifn_795x]
 [<dc851ab9>] ? hifn_tasklet_callback+0xa/0xc [hifn_795x]
 [<c011d046>] ? tasklet_action+0x3f/0x66
 [<c011d230>] ? __do_softirq+0x38/0x7a
 [<c0105a5f>] ? do_softirq+0x3e/0x71
 [<c011d17c>] ? irq_exit+0x2c/0x65
 [<c010e0c0>] ? smp_apic_timer_interrupt+0x5f/0x6a
 [<c01042e4>] ? apic_timer_interrupt+0x28/0x30
 [<dc851640>] ? hifn_handle_req+0x44a/0x50d [hifn_795x]
 ...
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch implements the givencrypt function for authenc.  It simply
calls the givencrypt operation on the underlying cipher instead of encrypt.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch converts the authenc algorithm over to crypto_grab_skcipher
which is a prerequisite for IV generation.

This patch also changes authenc to set its ASYNC status depending on
the ASYNC status of the underlying skcipher.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch merges the common hashing code between encryption and decryption.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch changes setkey to use RTA_OK to check the validity of the
setkey request.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

The ivsize should be fetched from ablkcipher, not blkcipher.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

The scatterwalk infrastructure is used by algorithms so it needs to
move out of crypto for future users that may live in drivers/crypto
or asm/*/crypto.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch changes gcm/authenc to return EBADMSG instead of EINVAL for
ICV mismatches.  This convention has already been adopted by IPsec.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

The previous code incorrectly included the hash in the verification which
also meant that we'd crash and burn when it comes to actually verifying
the hash since we'd go past the end of the SG list.

This patch fixes that by subtracting authsize from cryptlen at the start.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Having enckeylen as a template parameter makes it a pain for hardware
devices that implement ciphers with many key sizes since each one would
have to be registered separately.

Since the authenc algorithm is mainly used for legacy purposes where its
key is going to be constructed out of two separate keys, we can in fact
embed this value into the key itself.

This patch does this by prepending an rtnetlink header to the key that
contains the encryption key length.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

As it is authsize is an algorithm paramter which cannot be changed at
run-time.  This is inconvenient because hardware that implements such
algorithms would have to register each authsize that they support
separately.

Since authsize is a property common to all AEAD algorithms, we can add
a function setauthsize that sets it at run-time, just like setkey.

This patch does exactly that and also changes authenc so that authsize
is no longer a parameter of its template.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Since alignment masks are always one less than a power of two, we can
use binary or to find their maximum.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Up until now we have ablkcipher algorithms have been identified as
type BLKCIPHER with the ASYNC bit set.  This is suboptimal because
ablkcipher refers to two things.  On the one hand it refers to the
top-level ablkcipher interface with requests.  On the other hand it
refers to and algorithm type underneath.

As it is you cannot request a synchronous block cipher algorithm
with the ablkcipher interface on top.  This is a problem because
we want to be able to eventually phase out the blkcipher top-level
interface.

This patch fixes this by making ABLKCIPHER its own type, just as
we have distinct types for HASH and DIGEST.  The type it associated
with the algorithm implementation only.

Which top-level interface is used for synchronous block ciphers is
then determined by the mask that's used.  If it's a specific mask
then the old blkcipher interface is given, otherwise we go with the
new ablkcipher interface.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

It seems that newer versions of gcc have regressed in their abilities to
analyse initialisations.  This patch moves the initialisations up to avoid
the warnings.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

We do not allow spaces in algorithm names or parameters.  Thanks to Joy Latten
for pointing this out.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch adds the authenc algorithm which constructs an AEAD algorithm
from an asynchronous block cipher and a hash.  The construction is done
by concatenating the encrypted result from the cipher with the output
from the hash, as is used by the IPsec ESP protocol.

The authenc algorithm exists as a template with four parameters:

	authenc(auth, authsize, enc, enckeylen).

The authentication algorithm, the authentication size (i.e., truncating
the output of the authentication algorithm), the encryption algorithm,
and the encryption key length.  Both the size field and the key length
field are in bytes.  For example, AES-128 with SHA1-HMAC would be
represented by

	authenc(hmac(sha1), 12, cbc(aes), 16)

The key for the authenc algorithm is the concatenation of the keys for
the authentication algorithm with the encryption algorithm.  For the
above example, if a key of length 36 bytes is given, then hmac(sha1)
would receive the first 20 bytes while the last 16 would be given to
cbc(aes).
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>