From 253ed9ecfffa3e50b95e08bb513fdf9efcc5a85f Mon Sep 17 00:00:00 2001 From: Taylor Blau Date: Thu, 26 Sep 2024 11:22:47 -0400 Subject: hash.h: scaffolding for _unsafe hashing variants Git's default SHA-1 implementation is collision-detecting, which hardens us against known SHA-1 attacks against Git objects. This makes Git object writes safer at the expense of some speed when hashing through the collision-detecting implementation, which is slower than non-collision detecting alternatives. Prepare for loading a separate "unsafe" SHA-1 implementation that can be used for non-cryptographic purposes, like computing the checksum of files that use the hashwrite() API. This commit does not actually introduce any new compile-time knobs to control which implementation is used as the unsafe SHA-1 variant, but does add scaffolding so that the "git_hash_algo" structure has five new function pointers which are "unsafe" variants of the five existing hashing-related function pointers: - git_hash_init_fn unsafe_init_fn - git_hash_clone_fn unsafe_clone_fn - git_hash_update_fn unsafe_update_fn - git_hash_final_fn unsafe_final_fn - git_hash_final_oid_fn unsafe_final_oid_fn The following commit will introduce compile-time knobs to specify which SHA-1 implementation is used for non-cryptographic uses. Signed-off-by: Taylor Blau Signed-off-by: Junio C Hamano --- hash.h | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) (limited to 'hash.h') diff --git a/hash.h b/hash.h index 72ffbc862e..96458b129f 100644 --- a/hash.h +++ b/hash.h @@ -44,14 +44,32 @@ #define platform_SHA1_Final SHA1_Final #endif +#ifndef platform_SHA_CTX_unsafe +# define platform_SHA_CTX_unsafe platform_SHA_CTX +# define platform_SHA1_Init_unsafe platform_SHA1_Init +# define platform_SHA1_Update_unsafe platform_SHA1_Update +# define platform_SHA1_Final_unsafe platform_SHA1_Final +# ifdef platform_SHA1_Clone +# define platform_SHA1_Clone_unsafe platform_SHA1_Clone +# endif +#endif + #define git_SHA_CTX platform_SHA_CTX #define git_SHA1_Init platform_SHA1_Init #define git_SHA1_Update platform_SHA1_Update #define git_SHA1_Final platform_SHA1_Final +#define git_SHA_CTX_unsafe platform_SHA_CTX_unsafe +#define git_SHA1_Init_unsafe platform_SHA1_Init_unsafe +#define git_SHA1_Update_unsafe platform_SHA1_Update_unsafe +#define git_SHA1_Final_unsafe platform_SHA1_Final_unsafe + #ifdef platform_SHA1_Clone #define git_SHA1_Clone platform_SHA1_Clone #endif +#ifdef platform_SHA1_Clone_unsafe +# define git_SHA1_Clone_unsafe platform_SHA1_Clone_unsafe +#endif #ifndef platform_SHA256_CTX #define platform_SHA256_CTX SHA256_CTX @@ -81,6 +99,13 @@ static inline void git_SHA1_Clone(git_SHA_CTX *dst, const git_SHA_CTX *src) memcpy(dst, src, sizeof(*dst)); } #endif +#ifndef SHA1_NEEDS_CLONE_HELPER_UNSAFE +static inline void git_SHA1_Clone_unsafe(git_SHA_CTX_unsafe *dst, + const git_SHA_CTX_unsafe *src) +{ + memcpy(dst, src, sizeof(*dst)); +} +#endif #ifndef SHA256_NEEDS_CLONE_HELPER static inline void git_SHA256_Clone(git_SHA256_CTX *dst, const git_SHA256_CTX *src) @@ -178,6 +203,8 @@ enum get_oid_result { /* A suitably aligned type for stack allocations of hash contexts. */ union git_hash_ctx { git_SHA_CTX sha1; + git_SHA_CTX_unsafe sha1_unsafe; + git_SHA256_CTX sha256; }; typedef union git_hash_ctx git_hash_ctx; @@ -222,6 +249,21 @@ struct git_hash_algo { /* The hash finalization function for object IDs. */ git_hash_final_oid_fn final_oid_fn; + /* The non-cryptographic hash initialization function. */ + git_hash_init_fn unsafe_init_fn; + + /* The non-cryptographic hash context cloning function. */ + git_hash_clone_fn unsafe_clone_fn; + + /* The non-cryptographic hash update function. */ + git_hash_update_fn unsafe_update_fn; + + /* The non-cryptographic hash finalization function. */ + git_hash_final_fn unsafe_final_fn; + + /* The non-cryptographic hash finalization function. */ + git_hash_final_oid_fn unsafe_final_oid_fn; + /* The OID of the empty tree. */ const struct object_id *empty_tree; -- cgit v1.2.3