This series extends BPF's cryptographic capabilities by adding kfuncs for SHA hashing and ECDSA signature verification. These functions enable BPF programs to perform cryptographic operations for use cases such as content verification, integrity checking, and data authentication.
BPF programs increasingly need to verify data integrity and authenticity in networking, security, and observability contexts. While BPF already supports symmetric encryption/decryption, it lacks support for:
1. Cryptographic hashing - needed for content verification, fingerprinting, and preparing message digests for signature operations 2. Asymmetric signature verification - needed to verify signed data without requiring the signing key in the datapath
These capabilities enable use cases such as: - Verifying signed network packets or application data in XDP/TC programs - Implementing integrity checks in tracing and security monitoring - Building zero-trust security models where BPF programs verify credentials - Content-addressed storage and deduplication in BPF-based filesystems
Implementation:
The implementation follows BPF's existing crypto patterns: 1. Uses bpf_dynptr for safe memory access without page fault risks 2. Leverages the kernel's existing crypto library (lib/crypto/sha256.c and crypto/ecdsa.c) rather than reimplementing algorithms 3. Provides context-based API for ECDSA to enable key reuse and support multiple program types (syscall, XDP, TC) 4. Includes comprehensive selftests with NIST test vectors
Patch 1: bpf: Extend bpf_crypto_type with hash operations - Adds hash operation callbacks to bpf_crypto_type structure - Adds hash() and digestsize() function pointers - Must come before crypto module to maintain bisectability
Patch 2: crypto: Add BPF hash algorithm type registration module - Adds bpf_crypto_shash module in crypto/ subsystem - Registers hash type with BPF crypto infrastructure - Enables hash algorithm access through unified bpf_crypto_type interface - Implements callbacks: alloc_tfm, free_tfm, hash, digestsize, get_flags - Manages shash_desc lifecycle internally
Patch 3: bpf: Add SHA hash kfunc for cryptographic hashing - Adds bpf_crypto_hash() kfunc for SHA-256/384/512 - Updates bpf_crypto_ctx_create() to support keyless operations - Protected by CONFIG_CRYPTO_HASH2 guards - Uses kernel's crypto library implementations - Fixed u64 types for dynptr sizes to prevent truncation
Patch 4: selftests/bpf: Add tests for bpf_crypto_hash kfunc - Tests basic functionality with NIST "abc" test vectors - Validates error handling for invalid parameters (zero-length input) - Ensures correct hash output for SHA-256, SHA-384, and SHA-512 - Adds CONFIG_CRYPTO_HASH2 and CONFIG_CRYPTO_SHA512 to selftest config - Refactored test setup code to reduce duplication
Patch 5: bpf: Add ECDSA signature verification kfuncs - Context-based API: bpf_ecdsa_ctx_create/acquire/release pattern - Supports NIST curves (P-256, P-384, P-521) - Adds bpf_ecdsa_verify() for signature verification - Includes size query functions: keysize, digestsize, maxsize - Enables use in non-sleepable contexts via pre-allocated contexts - Uses crypto_sig API with p1363 format (r || s signatures)
Patch 6: selftests/bpf: Add tests for ECDSA signature verification - Tests valid signature acceptance with RFC 6979 test vectors for P-256 - Tests invalid signature rejection - Tests size query functions (keysize, digestsize, maxsize) - Uses well-known NIST test vectors with "sample" message - Adds CONFIG_CRYPTO_ECDSA to selftest config
v2: - Fixed redundant __bpf_dynptr_is_rdonly() checks (Vadim) - Added BPF hash algorithm type registration module in crypto/ subsystem - Added CONFIG_CRYPTO_HASH2 guards around bpf_crypto_hash() kfunc and its BTF registration, matching the pattern used for CONFIG_CRYPTO_ECDSA - Added mandatory digestsize validation for hash operations
v3: - Fixed patch ordering - header changes now in separate first commit before crypto module to ensure bisectability (bot+bpf-ci) - Fixed type mismatch - changed u32 to u64 for dynptr sizes in bpf_crypto_hash() to match __bpf_dynptr_size() return type (Mykyta) - Added CONFIG_CRYPTO_ECDSA to selftest config (Song) - Refactored test code duplication with setup_skel() helper (Song) - Added copyright notices to all new files
Daniel Hodges (6): bpf: Extend bpf_crypto_type with hash operations crypto: Add BPF hash algorithm type registration module bpf: Add SHA hash kfunc for cryptographic hashing selftests/bpf: Add tests for bpf_crypto_hash kfunc bpf: Add ECDSA signature verification kfuncs selftests/bpf: Add tests for ECDSA signature verification kfuncs
crypto/Makefile | 3 + crypto/bpf_crypto_shash.c | 95 ++++++ include/linux/bpf_crypto.h | 2 + kernel/bpf/crypto.c | 306 +++++++++++++++++- tools/testing/selftests/bpf/config | 3 + .../selftests/bpf/prog_tests/crypto_hash.c | 147 +++++++++ .../selftests/bpf/prog_tests/ecdsa_verify.c | 75 +++++ .../testing/selftests/bpf/progs/crypto_hash.c | 142 ++++++++ .../selftests/bpf/progs/ecdsa_verify.c | 160 +++++++++ 9 files changed, 925 insertions(+), 8 deletions(-) create mode 100644 crypto/bpf_crypto_shash.c create mode 100644 tools/testing/selftests/bpf/prog_tests/crypto_hash.c create mode 100644 tools/testing/selftests/bpf/prog_tests/ecdsa_verify.c create mode 100644 tools/testing/selftests/bpf/progs/crypto_hash.c create mode 100644 tools/testing/selftests/bpf/progs/ecdsa_verify.c