linux.git/lib/crypto/Kconfig, branch v6.15

crypto: lib/Kconfig - hide library options

2025-03-21T09:33:39+00:00

Any driver that needs these library functions should already be selecting
the corresponding Kconfig symbols, so there is no real point in making
these visible.

The original patch that made these user selectable described problems
with drivers failing to select the code they use, but for consistency
it's better to always use 'select' on a symbol than to mix it with
'depends on'.

Fixes: e56e18985596 ("lib/crypto: add prompts back to crypto libraries")
Signed-off-by: Arnd Bergmann 
Acked-by: Jarkko Sakkinen 
Signed-off-by: Herbert Xu

crypto: lib/chachapoly - Drop dependency on CRYPTO_ALGAPI

2025-03-08T08:24:36+00:00

The ChaCha20-Poly1305 library code uses the sg_miter API to process
input presented via scatterlists, except for the special case where the
digest buffer is not covered entirely by the same scatterlist entry as
the last byte of input. In that case, it uses scatterwalk_map_and_copy()
to access the memory in the input scatterlist where the digest is stored.

This results in a dependency on crypto/scatterwalk.c and therefore on
CONFIG_CRYPTO_ALGAPI, which is unnecessary, as the sg_miter API already
provides this functionality via sg_copy_to_buffer(). So use that
instead, and drop the dependencies on CONFIG_CRYPTO_ALGAPI and
CONFIG_CRYPTO.

Reported-by: Arnd Bergmann 
Acked-by: Eric Biggers 
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Herbert Xu

crypto: lib/Kconfig - Hide arch options from user

2025-03-02T07:21:47+00:00

The ARCH_MAY_HAVE patch missed arm64, mips and s390.  But it may
also lead to arch options being enabled but ineffective because
of modular/built-in conflicts.

As the primary user of all these options wireguard is selecting
the arch options anyway, make the same selections at the lib/crypto
option level and hide the arch options from the user.

Instead of selecting them centrally from lib/crypto, simply set
the default of each arch option as suggested by Eric Biggers.

Change the Crypto API generic algorithms to select the top-level
lib/crypto options instead of the generic one as otherwise there
is no way to enable the arch options (Eric Biggers).  Introduce a
set of INTERNAL options to work around dependency cycles on the
CONFIG_CRYPTO symbol.

Fixes: 1047e21aecdf ("crypto: lib/Kconfig - Fix lib built-in failure when arch is modular")
Reported-by: kernel test robot 
Reported-by: Arnd Bergmann 
Closes: https://lore.kernel.org/oe-kbuild-all/202502232152.JC84YDLp-lkp@intel.com/
Signed-off-by: Herbert Xu

crypto: lib/Kconfig - Fix lib built-in failure when arch is modular

2025-02-22T07:56:03+00:00

The HAVE_ARCH Kconfig options in lib/crypto try to solve the
modular versus built-in problem, but it still fails when the
the LIB option (e.g., CRYPTO_LIB_CURVE25519) is selected externally.

Fix this by introducing a level of indirection with ARCH_MAY_HAVE
Kconfig options, these then go on to select the ARCH_HAVE options
if the ARCH Kconfig options matches that of the LIB option.

Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202501230223.ikroNDr1-lkp@intel.com/
Signed-off-by: Herbert Xu

crypto: lib - implement library version of AES in CFB mode

2024-05-09T19:30:51+00:00

Implement AES in CFB mode using the existing, mostly constant-time
generic AES library implementation. This will be used by the TPM code
to encrypt communications with TPM hardware, which is often a discrete
component connected using sniffable wires or traces.

While a CFB template does exist, using a skcipher is a major pain for
non-performance critical synchronous crypto where the algorithm is known
at compile time and the data is in contiguous buffers with valid kernel
virtual addresses.

Tested-by: James Bottomley 
Reviewed-by: James Bottomley 
Reviewed-by: Jarkko Sakkinen 
Link: https://lore.kernel.org/all/20230216201410.15010-1-James.Bottomley@HansenPartnership.com/
Signed-off-by: Ard Biesheuvel 
Signed-off-by: James Bottomley 
Tested-by: Jarkko Sakkinen 
Signed-off-by: Jarkko Sakkinen

crypto: lib/aesgcm - Provide minimal library implementation

2022-11-11T10:14:59+00:00

Implement a minimal library version of AES-GCM based on the existing
library implementations of AES and multiplication in GF(2^128). Using
these primitives, GCM can be implemented in a straight-forward manner.

GCM has a couple of sharp edges, i.e., the amount of input data
processed with the same initialization vector (IV) should be capped to
protect the counter from 32-bit rollover (or carry), and the size of the
authentication tag should be fixed for a given key. [0]

The former concern is addressed trivially, given that the function call
API uses 32-bit signed types for the input lengths. It is still up to
the caller to avoid IV reuse in general, but this is not something we
can police at the implementation level.

As for the latter concern, let's make the authentication tag size part
of the key schedule, and only permit it to be configured as part of the
key expansion routine.

Note that table based AES implementations are susceptible to known
plaintext timing attacks on the encryption key. The AES library already
attempts to mitigate this to some extent, but given that the counter
mode encryption used by GCM operates exclusively on known plaintext by
construction (the IV and therefore the initial counter value are known
to an attacker), let's take some extra care to mitigate this, by calling
the AES library with interrupts disabled.

[0] https://nvlpubs.nist.gov/nistpubs/legacy/sp/nistspecialpublication800-38d.pdf

Link: https://lore.kernel.org/all/c6fb9b25-a4b6-2e4a-2dd1-63adda055a49@amd.com/
Signed-off-by: Ard Biesheuvel 
Tested-by: Nikunj A Dadhania 
Signed-off-by: Herbert Xu

crypto: move gf128mul library into lib/crypto

2022-11-11T10:14:59+00:00

The gf128mul library does not depend on the crypto API at all, so it can
be moved into lib/crypto. This will allow us to use it in other library
code in a subsequent patch without having to depend on CONFIG_CRYPTO.

While at it, change the Kconfig symbol name to align with other crypto
library implementations. However, the source file name is retained, as
it is reflected in the module .ko filename, and changing this might
break things for users.

Signed-off-by: Ard Biesheuvel 
Signed-off-by: Herbert Xu

crypto: lib - move __crypto_xor into utils

2022-08-19T10:39:34+00:00

CRYPTO_LIB_CHACHA depends on CRYPTO for __crypto_xor, defined in
crypto/algapi.c.  This is a layering violation because the dependencies
should only go in the other direction (crypto/ => lib/crypto/).  Also
the correct dependency would be CRYPTO_ALGAPI, not CRYPTO.  Fix this by
moving __crypto_xor into the utils module in lib/crypto/.

Note that CRYPTO_LIB_CHACHA_GENERIC selected XOR_BLOCKS, which is
unrelated and unnecessary.  It was perhaps thought that XOR_BLOCKS was
needed for __crypto_xor, but that's not the case.

Signed-off-by: Eric Biggers 
Reviewed-by: Jason A. Donenfeld 
Signed-off-by: Herbert Xu

crypto: lib - create utils module and move __crypto_memneq into it

2022-08-19T10:39:33+00:00

As requested at
https://lore.kernel.org/r/YtEgzHuuMts0YBCz@gondor.apana.org.au, move
__crypto_memneq into lib/crypto/ and put it under a new tristate.  The
tristate is CRYPTO_LIB_UTILS, and it builds a module libcryptoutils.  As
more crypto library utilities are being added, this creates a single
place for them to go without cluttering up the main lib directory.

The module's main file will be lib/crypto/utils.c.  However, leave
memneq.c as its own file because of its nonstandard license.

Signed-off-by: Eric Biggers 
Reviewed-by: Jason A. Donenfeld 
Signed-off-by: Herbert Xu

crypto: lib - make the sha1 library optional

2022-07-15T08:43:59+00:00

Since the Linux RNG no longer uses sha1_transform(), the SHA-1 library
is no longer needed unconditionally.  Make it possible to build the
Linux kernel without the SHA-1 library by putting it behind a kconfig
option, and selecting this new option from the kconfig options that gate
the remaining users: CRYPTO_SHA1 for crypto/sha1_generic.c, BPF for
kernel/bpf/core.c, and IPV6 for net/ipv6/addrconf.c.

Unfortunately, since BPF is selected by NET, for now this can only make
a difference for kernels built without networking support.

Signed-off-by: Eric Biggers 
Reviewed-by: Jason A. Donenfeld 
Acked-by: Jakub Kicinski 
Acked-by: Alexei Starovoitov 
Signed-off-by: Herbert Xu