kernel/linux.git/Documentation/crypto, branch v6.18.39

crypto: af_alg - Remove zero-copy support from skcipher and aead

2026-07-18T14:53:27+00:00

commit ffdd2bc378953b525aca61902534e753f1f8e734 upstream. The zero-copy support is one of the riskiest aspects of AF_ALG. It allows userspace to request cryptographic operations directly on pagecache pages of files like the 'su' binary. It also allows userspace to concurrently modify the memory which is being operated on, a recipe for TOCTOU vulnerabilities. While zero-copy support is more valuable in other areas of the kernel like the frequently used networking and file I/O code, it has far less value in AF_ALG, which is a niche UAPI. AF_ALG primarily just exists for backwards compatibility with a small set of userspace programs such as 'iwd' that haven't yet been fixed to use userspace crypto code. Originally AF_ALG was intended to be used to access hardware crypto accelerators. However, it isn't an efficient interface for that anyway, and it turned out to be rarely used in this way in practice. Thus, the risks of the zero-copy support in AF_ALG vastly outweigh its benefits. Let's just remove it. This commit removes it from the "skcipher" and "aead" algorithm types. "hash" will be handled separately. This is a soft break, not a hard break. Even after this commit, it still works to use splice() or sendfile() to transfer data to an AF_ALG request socket from a pipe or any file, respectively. What changes is just that the kernel now makes an internal, stable copy of the data before doing the crypto operation. So performance is slightly reduced, but the UAPI isn't broken. And, very importantly, it's much safer. Tested with libkcapi/test.sh. All its test cases still pass. I also verified that this would have prevented the copy.fail exploit as well. I also used a custom test program to verify that sendfile() still works. Fixes: 8ff590903d5f ("crypto: algif_skcipher - User-space interface for skcipher operations") Fixes: 400c40cf78da ("crypto: algif - add AEAD support") Reported-by: Taeyang Lee <0wn@theori.io> Link: https://copy.fail/ Reported-by: Feng Ning Closes: https://lore.kernel.org/r/afYcc-tZFwvZZo76@ans-MacBook-Pro.local Reviewed-by: Demi Marie Obenour Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman

crypto/krb5, rxrpc: Fix lack of pre-decrypt/pre-verify length checks

2026-06-01T15:51:06+00:00

[ Upstream commit 2b50aceafe6606ea52ed42aadd1b4d44a188aade ] Change the krb5 crypto library to provide facilities to precheck the length of the message about to be decrypted or verified. Fix AF_RXRPC to make use of this to validate DATA packets secured with RxGK. Fixes: 9d1d2b59341f ("rxrpc: rxgk: Implement the yfs-rxgk security class (GSSAPI)") Closes: https://sashiko.dev/#/patchset/20260511160753.607296-1-dhowells%40redhat.com Signed-off-by: David Howells cc: Herbert Xu cc: Simon Horman cc: Chuck Lever cc: linux-afs@lists.infradead.org Reviewed-by: Jeffrey Altman Tested-by: Marc Dionne Link: https://patch.msgid.link/20260515230516.2718212-2-dhowells@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

crypto: doc - Add explicit title heading to API docs

2025-09-28T03:54:48+00:00

Documentation for crypto programming interfaces lack explicit title. As such, all its sections become entries in the toctree index. Add the title heading to tidy up toctree. Signed-off-by: Bagas Sanjaya Reviewed-by: Randy Dunlap Tested-by: Randy Dunlap Signed-off-by: Herbert Xu

crypto: engine - remove {prepare,unprepare}_crypt_hardware callbacks

2025-07-18T10:52:00+00:00

The {prepare,unprepare}_crypt_hardware callbacks were added back in 2016 by commit 735d37b5424b ("crypto: engine - Introduce the block request crypto engine framework"), but they were never implemented by any driver. Remove them as they are unused. Since the 'engine->idling' and 'was_busy' flags are no longer needed, remove them as well. Signed-off-by: Ovidiu Panait Signed-off-by: Herbert Xu

crypto: remove obsolete 'comp' compression API

2025-03-21T09:39:06+00:00

The 'comp' compression API has been superseded by the acomp API, which is a bit more cumbersome to use, but ultimately more flexible when it comes to hardware implementations. Now that all the users and implementations have been removed, let's remove the core plumbing of the 'comp' API as well. Signed-off-by: Ard Biesheuvel Signed-off-by: Herbert Xu

crypto/krb5: Add API Documentation

2025-03-02T21:39:03+00:00

Add API documentation for the kerberos crypto library. Signed-off-by: David Howells cc: Herbert Xu cc: "David S. Miller" cc: Chuck Lever cc: Marc Dionne cc: Eric Dumazet cc: Jakub Kicinski cc: Paolo Abeni cc: Simon Horman cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-crypto@vger.kernel.org cc: netdev@vger.kernel.org

crypto: doc - Fix akcipher title reference

2024-10-10T09:08:02+00:00

Stephen reports a documentation build warning for "make htmldocs" introduced by recent commit 6b34562f0cfe ("crypto: akcipher - Drop sign/verify operations"). The commit renamed a paragraph title in a header file, but neglected to amend the title reference in the API documentation. Fix it. Fixes: 6b34562f0cfe ("crypto: akcipher - Drop sign/verify operations") Reported-by: Stephen Rothwell Closes: https://lore.kernel.org/all/20241008172926.0b995ea7@canb.auug.org.au/ Signed-off-by: Lukas Wunner Signed-off-by: Herbert Xu

crypto: ecdsa - Move X9.62 signature size calculation into template

2024-10-05T05:22:04+00:00

software_key_query() returns the maximum signature and digest size for a given key to user space. When it only supported RSA keys, calculating those sizes was trivial as they were always equivalent to the key size. However when ECDSA was added, the function grew somewhat complicated calculations which take the ASN.1 encoding and curve into account. This doesn't scale well and adjusting the calculations is easily forgotten when adding support for new encodings or curves. In fact, when NIST P521 support was recently added, the function was initially not amended: https://lore.kernel.org/all/b749d5ee-c3b8-4cbd-b252-7773e4536e07@linux.ibm.com/ Introduce a ->max_size() callback to struct sig_alg and take advantage of it to move the signature size calculations to ecdsa-x962.c. Introduce a ->digest_size() callback to struct sig_alg and move the maximum ECDSA digest size to ecdsa.c. It is common across ecdsa-x962.c and the upcoming ecdsa-p1363.c and thus inherited by both of them. For all other algorithms, continue using the key size as maximum signature and digest size. Signed-off-by: Lukas Wunner Signed-off-by: Herbert Xu

crypto: sig - Rename crypto_sig_maxsize() to crypto_sig_keysize()

2024-10-05T05:22:04+00:00

crypto_sig_maxsize() is a bit of a misnomer as it doesn't return the maximum signature size, but rather the key size. Rename it as well as all implementations of the ->max_size callback. A subsequent commit introduces a crypto_sig_maxsize() function which returns the actual maximum signature size. While at it, change the return type of crypto_sig_keysize() from int to unsigned int for consistency with crypto_akcipher_maxsize(). None of the callers checks for a negative return value and an error condition can always be indicated by returning zero. Signed-off-by: Lukas Wunner Signed-off-by: Herbert Xu

crypto: akcipher - Drop sign/verify operations

2024-10-05T05:22:04+00:00

A sig_alg backend has just been introduced and all asymmetric sign/verify algorithms have been migrated to it. The sign/verify operations can thus be dropped from akcipher_alg. It is now purely for asymmetric encrypt/decrypt. Move struct crypto_akcipher_sync_data from internal.h to akcipher.c and unexport crypto_akcipher_sync_{prep,post}(): They're no longer used by sig.c but only locally in akcipher.c. In crypto_akcipher_sync_{prep,post}(), drop various NULL pointer checks for data->dst as they were only necessary for the verify operation. In the crypto_sig_*() API calls, remove the forks that were necessary while algorithms were converted from crypto_akcipher to crypto_sig one by one. In struct akcipher_testvec, remove the "params", "param_len" and "algo" elements as they were only needed for the ecrdsa verify operation. Remove corresponding dead code from test_akcipher_one() as well. Signed-off-by: Lukas Wunner Signed-off-by: Herbert Xu