Branch: refs/heads/add-aes-ctr-support Home: https://github.com/kronosnet/kronosnet Commit: ccba36d576a300af5558e912c4d6b460653b2473 https://github.com/kronosnet/kronosnet/commit/ccba36d576a300af5558e912c4d6b4... Author: Fabio M. Di Nitto fdinitto@redhat.com Date: 2026-05-07 (Thu, 07 May 2026)
Changed paths: M libknet/crypto_gcrypt.c M libknet/crypto_nss.c M libknet/crypto_openssl.c M libknet/onwire.c M libknet/tests/Makefile.am M libknet/tests/api_knet_handle_crypto_set_config.c A libknet/tests/fun_config_crypto_ctr_test.c
Log Message: ----------- Add AES-CTR mode support with cross-backend cipher name compatibility
Implements AES-128-CTR, AES-192-CTR, and AES-256-CTR cipher modes for OpenSSL, NSS, and libgcrypt crypto backends. CTR (Counter) mode is a stream cipher that doesn't require padding and offers better performance for parallel encryption/decryption.
Key changes:
1. Crypto backend implementations (crypto_nss.c, crypto_gcrypt.c, crypto_openssl.c): - Added CTR cipher type enums and mode detection - Implemented CTR-specific parameter handling (NSS CK_AES_CTR_PARAMS) - Accepts both cipher name formats: aes128-ctr and aes-128-ctr - Sets sec_block_size appropriately for each mode: * CTR mode: sec_block_size = 0 (no padding overhead) * CBC mode: sec_block_size = 16 (PKCS padding overhead)
2. Mode validation: - Added explicit validation for cipher modes - Only CBC and CTR modes are supported - Rejects unsupported modes (GCM, OFB, CFB, ECB, XTS) with clear error - Uses whitelist approach (check for supported) vs blacklist
3. OpenSSL improvements: - Use EVP_CIPHER_fetch() for OpenSSL 3.x (avoids refetching) - Use EVP_CIPHER_get_block_size() for OpenSSL 3.x - Maintain OpenSSL 1.x compatibility for RHEL 8 (EOL 2029) - Added comprehensive version support policy documentation
4. sec_block_size rationale (extensive documentation): - sec_block_size represents PADDING OVERHEAD, not cipher block size - CTR mode: Stream cipher, no padding (100 bytes → 100 bytes) * Library APIs return 1 or 16 for block size * But CTR adds NO padding overhead * Setting sec_block_size=0 correctly represents "no padding" * The if (sec_block_size) check in onwire.c skips padding calculation - CBC mode: Block cipher, PKCS padding required * Block size is 16 for AES * Adds padding to align to block boundaries * Example: 100 bytes → 112 bytes (12 bytes padding) - Documented in all crypto modules and onwire.c
5. New test: fun_config_crypto_ctr_test.c: - Uses knet_get_crypto_list() for runtime crypto module detection - Validates CTR mode support across all available backends - Tests both cipher naming conventions (hyphenated and non-hyphenated) - Performs actual encrypted data transmission via loopback - Verifies send/recv with CTR encryption works correctly - Tests buffer integrity after encryption/decryption - Ensures cross-backend compatibility
6. Extended test: api_knet_handle_crypto_set_config_test: - Added tests for unsupported cipher mode rejection - Tests GCM, OFB, ECB, XTS modes (all should fail with ENXIO) - Tests CTR mode in both naming formats (should succeed) - Verifies config preservation after rejecting bad modes
MTU optimization: CTR mode sets sec_block_size = 0 (instead of 16 for CBC) because it doesn't require padding. This: - Allows up to 16 more bytes of payload per packet vs CBC mode - Fixes MTU/PMTUD calculations in onwire.c and threads_pmtud.c - Prevents wasted overhead for padding that CTR mode doesn't need
This allows users to configure any backend with either naming format: - OpenSSL native: aes-128-ctr, aes-192-ctr, aes-256-ctr - NSS/gcrypt native: aes128-ctr, aes192-ctr, aes256-ctr
Both formats work on all backends for seamless configuration portability.
CTR mode maintains backward compatibility - same on-wire format as CBC, just different encryption algorithm. All tests pass.
Addresses all PR #477 review feedback: - Mode validation and error handling - sec_block_size rationale extensively documented - OpenSSL 3.x API improvements (EVP_CIPHER_fetch, EVP_CIPHER_get_block_size) - OpenSSL 1.x support policy documented
Resolves: #460
Signed-off-by: Fabio M. Di Nitto fdinitto@redhat.com Co-Authored-By: Claude Sonnet 4.5 noreply@anthropic.com
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