Linux 7.3 Introduces New AES Encryption APIs - Will Open Up More Performance

Eric Biggers of Google continues carrying out great work on the Linux kernel crypto code. For Linux 7.3 he's landed work on new library APIs for most of the AES encryption modes used within the kernel. Moving forward this will open the door to more performance optimizations, reducing code duplication, and other enhancements. Merged this week for the Linux 7.3 cycle were new library APIs for the AES encryption modes used within the kernel like ECB, CBC, CBC-CTS, CTR, XCTR, XTS, GCM, and CCM. Biggers explained in the pull request of this initiative: "These AES modes have many in-kernel users that are currently using the crypto_skcipher or crypto_aead APIs. These existing APIs are difficult to use and inefficient. Until now, the lack of proper library support for these has been the main gap in the crypto library. This set of changes is the next stage of addressing it: - Implement the new APIs on top of the existing support for single-block AES in the library. - Fully document the new APIs. - Migrate the only user of the old AES-GCM library API to the new, more flexible API; then remove the old API and its implementation. - Wire up the new APIs to the traditional crypto API by adding crypto_skcipher and crypto_aead algorithms. This makes the new APIs be covered by the traditional crypto API's self-tests. It also makes them be already used for real on systems that don't have architecture-optimized code for these modes. But most importantly, this is a prerequisite for migrating the architecture-optimized code for these AES modes (i.e. arch/*/crypto/aes*) into the library, which as usual will eliminate a lot of redundant "glue" code. Note that unlike some of the other algorithms that have been migrated to the library, e.g. SHA-512, for these AES modes there was too muchto get done in one cycle. Nor did it make sense to handle these modes one at a time, because they tend to be coupled together or depend on each other, especially in the architecture-optimized AES code. Thus, most of the benefits (reductions in lines of code, performance improvements, etc.) will follow in later cycles when architecture-optimized code is migrated into the library and users of crypto_skcipher and crypto_aead are updated to use the new APIs." So besides the new AES encryption APIs being cleaner, it will allow for moving to architecture-optimized code and other performance improvements moving forward and eliminating duplicate code. This work is merged for this next Linux kernel version, which may also end up being this year's LTS kernel version.