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 --- object-file.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) (limited to 'object-file.c') diff --git a/object-file.c b/object-file.c index 440c5c6850..206ff625d9 100644 --- a/object-file.c +++ b/object-file.c @@ -115,6 +115,33 @@ static void git_hash_sha1_final_oid(struct object_id *oid, git_hash_ctx *ctx) oid->algo = GIT_HASH_SHA1; } +static void git_hash_sha1_init_unsafe(git_hash_ctx *ctx) +{ + git_SHA1_Init_unsafe(&ctx->sha1_unsafe); +} + +static void git_hash_sha1_clone_unsafe(git_hash_ctx *dst, const git_hash_ctx *src) +{ + git_SHA1_Clone_unsafe(&dst->sha1_unsafe, &src->sha1_unsafe); +} + +static void git_hash_sha1_update_unsafe(git_hash_ctx *ctx, const void *data, + size_t len) +{ + git_SHA1_Update_unsafe(&ctx->sha1_unsafe, data, len); +} + +static void git_hash_sha1_final_unsafe(unsigned char *hash, git_hash_ctx *ctx) +{ + git_SHA1_Final_unsafe(hash, &ctx->sha1_unsafe); +} + +static void git_hash_sha1_final_oid_unsafe(struct object_id *oid, git_hash_ctx *ctx) +{ + git_SHA1_Final_unsafe(oid->hash, &ctx->sha1_unsafe); + memset(oid->hash + GIT_SHA1_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA1_RAWSZ); + oid->algo = GIT_HASH_SHA1; +} static void git_hash_sha256_init(git_hash_ctx *ctx) { @@ -189,6 +216,11 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = { .update_fn = git_hash_unknown_update, .final_fn = git_hash_unknown_final, .final_oid_fn = git_hash_unknown_final_oid, + .unsafe_init_fn = git_hash_unknown_init, + .unsafe_clone_fn = git_hash_unknown_clone, + .unsafe_update_fn = git_hash_unknown_update, + .unsafe_final_fn = git_hash_unknown_final, + .unsafe_final_oid_fn = git_hash_unknown_final_oid, .empty_tree = NULL, .empty_blob = NULL, .null_oid = NULL, @@ -204,6 +236,11 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = { .update_fn = git_hash_sha1_update, .final_fn = git_hash_sha1_final, .final_oid_fn = git_hash_sha1_final_oid, + .unsafe_init_fn = git_hash_sha1_init_unsafe, + .unsafe_clone_fn = git_hash_sha1_clone_unsafe, + .unsafe_update_fn = git_hash_sha1_update_unsafe, + .unsafe_final_fn = git_hash_sha1_final_unsafe, + .unsafe_final_oid_fn = git_hash_sha1_final_oid_unsafe, .empty_tree = &empty_tree_oid, .empty_blob = &empty_blob_oid, .null_oid = &null_oid_sha1, @@ -219,6 +256,11 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = { .update_fn = git_hash_sha256_update, .final_fn = git_hash_sha256_final, .final_oid_fn = git_hash_sha256_final_oid, + .unsafe_init_fn = git_hash_sha256_init, + .unsafe_clone_fn = git_hash_sha256_clone, + .unsafe_update_fn = git_hash_sha256_update, + .unsafe_final_fn = git_hash_sha256_final, + .unsafe_final_oid_fn = git_hash_sha256_final_oid, .empty_tree = &empty_tree_oid_sha256, .empty_blob = &empty_blob_oid_sha256, .null_oid = &null_oid_sha256, -- cgit 1.2.3-korg