d27c04bbca
RHEL9 kernels (9.6+) disable RSA signing and decryption in the kernel crypto API for security reasons (CVE-2023-6240). The kernel forcibly overwrites akcipher sign/decrypt callbacks to return -ENOSYS, regardless of what the driver provides. Commit 3709c35c in the RHEL kernel: "crypto: akcipher - Disable signing and decryption" This affects our self-tests which call crypto_akcipher_sign() and crypto_akcipher_decrypt(). On RHEL9, these operations return -ENOSYS even though our driver correctly implements them. Add compile-time checks for RHEL_RELEASE_CODE >= 9.6 to detect this scenario and skip the affected self-tests gracefully. The tests pass since the algorithms are registered correctly; the kernel simply refuses to execute sign/decrypt operations as a matter of policy. Note: encrypt and verify operations are unaffected and continue to be tested normally. Signed-off-by: Sameeh Jubran <sameeh@wolfssl.com>
wolfSSL linuxkm (linux kernel module)
libwolfssl supports building as a linux kernel module (libwolfssl.ko).
When loaded, wolfCrypt and wolfSSL API are made available to the rest of
the kernel, supporting cryptography and TLS in kernel space.
Performing cryptographic operations in kernel space has significant advantages over user space for high throughput network (VPN, IPsec, MACsec, TLS, etc) and filesystem (dm-crypt/LUKS, fscrypt disk encryption) IO processing, with the added benefit that keys can be kept isolated to kernel space. Additionally, when wolfCrypt-FIPS is used, this provides a simple recipe for FIPS-compliant kernels.
Supported features:
- crypto acceleration: AES-NI, AVX, etc.
- kernel crypto API registration (wolfCrypt algs appear as drivers in
/proc/crypto.). CONFIG_CRYPTO_FIPS, and crypto-manager self-tests.- FIPS-compliant patches to
drivers/char/random.c, covering kernels 5.10 to 6.15. - Supports FIPS-compliant WireGuard (https://github.com/wolfssl/wolfguard).
- TLS 1.3 and DTLS 1.3 kernel offload.
Building and Installing
Build linuxkm with:
$ ./configure --enable-linuxkm --with-linux-source=/usr/src/linux
$ make -j module
note: replace /usr/src/linux with a path to your fully configured and built
target kernel source tree.
Assuming you are targeting your native system, install with:
$ sudo make install
$ sudo modprobe libwolfssl
options
| linuxkm option | description |
|---|---|
| --enable-linuxkm-lkcapi-register | Register wolfcrypt algs with linux kernel crypto API. Options are 'all', 'none', or comma separated list of algs. |
| --enable-linuxkm-pie | Enable relocatable object build of module |
| --enable-linuxkm-benchmarks | Run crypto benchmark at module load |
Kernel Patches
The dir linuxkm/patches contains a patch to the linux kernel CRNG. The
CRNG provides the implementation for /dev/random, /dev/urandom, and
getrandom().
The patch updates these two sources
drivers/char/random.cinclude/linux/random.h
to use FIPS-compliant algorithms, instead of chacha and blake2s.
Patches are provided for several kernel versions, ranging from 5.10.x to
6.15.
patch procedure
- Ensure kernel src tree is clean before patching:
cd ~/kernelsrc/
make mrproper
- Verify patches will apply clean with a dry run check:
patch -p1 --dry-run <~/wolfssl-5.8.2/linuxkm/patches/6.12/WOLFSSL_LINUXKM_HAVE_GET_RANDOM_CALLBACKS-6v12.patch
checking file drivers/char/random.c
checking file include/linux/random.h
- Finally patch the kernel:
patch -p1 <~/wolfssl-5.8.2/linuxkm/patches/6.12/WOLFSSL_LINUXKM_HAVE_GET_RANDOM_CALLBACKS-6v12.patch
patching file drivers/char/random.c
patching file include/linux/random.h
- Build kernel.