32c6bd5303
Joshua Rogers
2026-09-15
Subject
hash: vary bucket placement across process runs
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Architecture & Compiler Flags
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Build Log
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Commit Diff GitHub →
lib/easy.c+5 -0
| @@ -177,6 +177,11 @@ static CURLcode global_init(long flags, bool memoryfuncs) | |
| goto fail; | |
| } | |
| + | if(Curl_hash_global_init()) { |
| + | DEBUGF(curl_mfprintf(stderr, "Error: Curl_hash_global_init failed\n")); |
| + | goto fail; |
| + | } |
| + | |
| if(!Curl_vquic_init()) { | |
| DEBUGF(curl_mfprintf(stderr, "Error: Curl_vquic_init failed\n")); | |
| goto fail; | |
lib/hash.c+44 -3
| @@ -26,6 +26,7 @@ | |
| #include <stddef.h> /* for offsetof() */ | |
| #include "hash.h" | |
| + | #include "rand.h" |
| /* random patterns for API verification */ | |
| #ifdef DEBUGBUILD | |
| @@ -52,14 +53,46 @@ struct hash_functions { | |
| comp_function compare; | |
| }; | |
| + | /* set at global init, read-only afterwards */ |
| + | static size_t hash_seed; |
| + | |
| + | CURLcode Curl_hash_global_init(void) |
| + | { |
| + | static bool seeded; |
| + | unsigned char buf[sizeof(size_t)]; |
| + | size_t seed = 0; |
| + | size_t i; |
| + | CURLcode result; |
| + | |
| + | if(seeded) |
| + | return CURLE_OK; |
| + | |
| + | result = Curl_rand_bytes(NULL, |
| + | #ifdef DEBUGBUILD |
| + | FALSE, |
| + | #endif |
| + | buf, sizeof(buf)); |
| + | if(result) |
| + | return result; |
| + | |
| + | for(i = 0; i < sizeof(buf); i++) |
| + | seed = (seed << 8) | buf[i]; |
| + | |
| + | hash_seed = seed ? seed : 1; |
| + | seeded = TRUE; |
| + | return CURLE_OK; |
| + | } |
| + | |
| /* @unittest 1603 | |
| */ | |
| - | UNITTEST size_t hash_str(const void *key, size_t key_length, size_t slots_num); |
| - | UNITTEST size_t hash_str(const void *key, size_t key_length, size_t slots_num) |
| + | UNITTEST size_t hash_str_seeded(const void *key, size_t key_length, |
| + | size_t slots_num, size_t seed); |
| + | UNITTEST size_t hash_str_seeded(const void *key, size_t key_length, |
| + | size_t slots_num, size_t seed) |
| { | |
| const char *key_str = (const char *)key; | |
| const char *end = key_str + key_length; | |
| - | size_t h = 5381; |
| + | size_t h = 5381 ^ seed; |
| while(key_str < end) { | |
| size_t j = (size_t)*key_str++; | |
| @@ -70,6 +103,14 @@ UNITTEST size_t hash_str(const void *key, size_t key_length, size_t slots_num) | |
| return (h % slots_num); | |
| } | |
| + | /* @unittest 1603 |
| + | */ |
| + | UNITTEST size_t hash_str(const void *key, size_t key_length, size_t slots_num); |
| + | UNITTEST size_t hash_str(const void *key, size_t key_length, size_t slots_num) |
| + | { |
| + | return hash_str_seeded(key, key_length, slots_num, hash_seed); |
| + | } |
| + | |
| /* Avoid treating the variable-length key[1] as a one-byte object. */ | |
| static char *hash_elem_key(struct Curl_hash_element *he) | |
| { | |
lib/hash.h+2 -0
| @@ -65,6 +65,8 @@ struct Curl_hash_iterator { | |
| #endif | |
| }; | |
| + | CURLcode Curl_hash_global_init(void); |
| + | |
| void Curl_hash_init(struct Curl_hash *h, | |
| size_t slots, | |
| Curl_hash_type type, | |
lib/rand.h+2 -0
| @@ -23,6 +23,8 @@ | |
| * SPDX-License-Identifier: curl | |
| * | |
| ***************************************************************************/ | |
| + | struct Curl_easy; |
| + | |
| CURLcode Curl_rand_bytes(struct Curl_easy *data, | |
| #ifdef DEBUGBUILD | |
| bool env_override, | |
tests/unit/unit1603.c+3 -0
| @@ -122,6 +122,9 @@ static CURLcode test_unit1603(const char *arg) | |
| const char *nodep; | |
| int rc; | |
| + | fail_unless(hash_str_seeded("a", 1, 97, 0x1234) == 95, |
| + | "seeded hash is not computed as expected"); |
| + | |
| /* Ensure the key hashes are as expected in order to test both hash | |
| collisions and a full table. Unfortunately, the hashes can vary | |
| between architectures. */ | |