libsodium: add harnesses for KEM, ipcrypt, HKDF, SHA-3/XOF, pwhash, stream, secretstream, etc.#73
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libsodium: add harnesses for KEM, ipcrypt, HKDF, SHA-3/XOF, pwhash, stream, secretstream, etc.#73tc-agent wants to merge 2 commits into
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Fuzzing Coverage ReportTested: project OSS-Fuzz: Fuzz Introspector · build status
Per-harness
Δ = (after − before) / before, to accommodate that denominators may change. "new" when before is 0; "deleted" when after is 0. |
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Summary
Expands the libsodium fuzzing surface with 13 new harnesses and broadens the
existing crypto_box, crypto_secretbox, and crypto_sign harnesses to exercise
their non-_easy APIs. The existing surface only covered ~8 primitives
(AEAD, box, secretbox, generichash, kdf, kx, sign, secret_key_auth);
substantial primitive families had no harness at all.
Fuzz Introspector baseline
https://introspector.oss-fuzz.com/project-profile?project=libsodium
(report dated 2026-05-19): runtime line coverage 51.89% (5524/10646),
static reachability 24.64%, function coverage 46.00%, fuzzer count 8.
https://storage.googleapis.com/oss-fuzz-coverage/libsodium/reports/20260519/linux/src/libsodium/src/libsodium/report.html
shows several whole subdirectories at very low coverage that no existing
harness reached, e.g. crypto_pwhash/ 1.45% (Argon2 / scrypt entirely
untouched), crypto_box/ 0.00%, crypto_stream/ 31.34%,
crypto_kdf/ 35.29%, sodium/ 27.46%.
New harnesses (13)
drive the encoded-string parser. Uses MIN ops/mem.
XChaCha20 XOR round-trip with offset variant.
flipped-tag verify rejection.
mult, point validation, _from_uniform, scalar reduce/negate/invert, ed25519
add/sub - all on attacker-controlled bytes.
push/pull with TAG_MESSAGE / TAG_PUSH / TAG_REKEY / TAG_FINAL mix.
through seal_open.
sodium_bin2base64/_base642bin (all 4 variants), sodium_compare/_increment/
_add/_sub/_is_zero, sodium_ip2bin.
the streaming _extract_init/_update/_final form.
_enc/_enc_deterministic, _dec, plus attacker-controlled ciphertext through
_dec to exercise the implicit-rejection branch.
xchacha20poly1305 secretbox round-trip + sealed-box variant.
one-shot vs streaming equivalence.
multiple key-length classes plus flipped-tag verify rejection.
All new harnesses gate on a selector byte from the fuzzer input so the same
input shape exercises several primitives, and they round-trip / cross-check
where applicable so libfuzzer sees a useful signal beyond "does not crash".
Modifications to existing harnesses
the precomputed _beforenm/_easy_afternm path. The _easy variants delegate
around box_curve25519xsalsa20poly1305.c, so the previous harness left it
uncovered.
crypto_secretbox/_open API to reach crypto_secretbox.c and
secretbox_xsalsa20poly1305.c.
crypto_sign/crypto_sign_open API, and the pk_to_curve25519/sk_to_curve25519/
sk_to_seed/sk_to_pk conversions.
Local coverage
After 5 minutes of fuzz_for_pr per harness:
Largest per-subdirectory deltas vs baseline (accumulated corpus):
The remaining gap is largely CPU-dispatch siblings linked into the static
library that never execute on this CPU (e.g.
argon2-fill-block-{ref,ssse3,avx512f}.c - only the AVX2 variant runs;
chacha20_ref.c, softaes.c, crypto_ipcrypt/ipcrypt_soft.c, poly1305_donna64.h,
pwhash_scryptsalsa208sha256_nosse.c, blake2b-compress-{ref,ssse3}.c).