Subject: Re: [PATCH] treewide: fix various bugs w/ OpenSSL 3+ EVP API

From: Junio C Hamano <[email-masked]>
Date: Thu, 31 Aug 2023 22:32:06 -0700

Eric Wong <[email-masked]> writes:

> The OpenSSL 3+ EVP API for SHA-* cannot support our prior use cases
> supported by other SHA-* implementations.  It has the following
> differences:
>
> 1. ->init_fn is required before all use
> 2. struct assignments don't work and requires ->clone_fn
> 3. can't support ->update_fn after ->final_*fn
>
> While fixing cases 1 and 2 is merely the matter of calling ->init_fn and
> ->clone_fn as appropriate, fixing case 3 requires calling ->final_*fn on
> a temporary context that's cloned from the primary context.
>
> Reported-by: Bagas Sanjaya <[email-masked]>
> Link: https://lore.kernel.org/[email-masked]/
> Helped-by: brian m. carlson <[email-masked]>
> Fixes: 3e440ea0aba0 ("sha256: avoid functions deprecated in OpenSSL 3+")
> Fixes: bda9c12073e7 ("avoid SHA-1 functions deprecated in OpenSSL 3+")
> Signed-off-by: Eric Wong <[email-masked]>
> ---
>  Ugh, I wonder if I setup my config.mak incorrectly when testing
>  3e440ea0aba0 and bda9c12073e7 :x

The third kind looks like a fun one to diagnoise and fix.

Thanks.  Will queue.

>  There may be other misuses not exposed by the test suite.  Making
>  git_hash_ctx opaque could flush out some of them (but I dislike
>  APIs which force heap allocations in the first place).  In any case,
>  I really wish git relied less on globals so object lifetimes could be
>  more obvious and really wish all C projects could rely on
>  gcc/tinycc/clang-supported __attribute__((__cleanup__)) to make
>  lifetimes easier-to-manage...
>
>  builtin/fast-import.c    | 1 +
>  builtin/index-pack.c     | 5 ++++-
>  builtin/unpack-objects.c | 5 ++++-
>  bulk-checkin.c           | 1 +
>  csum-file.c              | 2 +-
>  5 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/builtin/fast-import.c b/builtin/fast-import.c
> index 4dbb10aff3..444f41cf8c 100644
> --- a/builtin/fast-import.c
> +++ b/builtin/fast-import.c
> @@ -1102,6 +1102,7 @@ static void stream_blob(uintmax_t len, struct object_id *oidout, uintmax_t mark)
>  		|| (pack_size + PACK_SIZE_THRESHOLD + len) < pack_size)
>  		cycle_packfile();
>  
> +	the_hash_algo->init_fn(&checkpoint.ctx);
>  	hashfile_checkpoint(pack_file, &checkpoint);
>  	offset = checkpoint.offset;
>  
> diff --git a/builtin/index-pack.c b/builtin/index-pack.c
> index 006ffdc9c5..dda94a9f46 100644
> --- a/builtin/index-pack.c
> +++ b/builtin/index-pack.c
> @@ -1166,6 +1166,7 @@ static void parse_pack_objects(unsigned char *hash)
>  	struct ofs_delta_entry *ofs_delta = ofs_deltas;
>  	struct object_id ref_delta_oid;
>  	struct stat st;
> +	git_hash_ctx tmp_ctx;
>  
>  	if (verbose)
>  		progress = start_progress(
> @@ -1202,7 +1203,9 @@ static void parse_pack_objects(unsigned char *hash)
>  
>  	/* Check pack integrity */
>  	flush();
> -	the_hash_algo->final_fn(hash, &input_ctx);
> +	the_hash_algo->init_fn(&tmp_ctx);
> +	the_hash_algo->clone_fn(&tmp_ctx, &input_ctx);
> +	the_hash_algo->final_fn(hash, &tmp_ctx);
>  	if (!hasheq(fill(the_hash_algo->rawsz), hash))
>  		die(_("pack is corrupted (SHA1 mismatch)"));
>  	use(the_hash_algo->rawsz);
> diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
> index 32505255a0..fef7423448 100644
> --- a/builtin/unpack-objects.c
> +++ b/builtin/unpack-objects.c
> @@ -609,6 +609,7 @@ int cmd_unpack_objects(int argc, const char **argv, const char *prefix UNUSED)
>  {
>  	int i;
>  	struct object_id oid;
> +	git_hash_ctx tmp_ctx;
>  
>  	disable_replace_refs();
>  
> @@ -669,7 +670,9 @@ int cmd_unpack_objects(int argc, const char **argv, const char *prefix UNUSED)
>  	the_hash_algo->init_fn(&ctx);
>  	unpack_all();
>  	the_hash_algo->update_fn(&ctx, buffer, offset);
> -	the_hash_algo->final_oid_fn(&oid, &ctx);
> +	the_hash_algo->init_fn(&tmp_ctx);
> +	the_hash_algo->clone_fn(&tmp_ctx, &ctx);
> +	the_hash_algo->final_oid_fn(&oid, &tmp_ctx);
>  	if (strict) {
>  		write_rest();
>  		if (fsck_finish(&fsck_options))
> diff --git a/bulk-checkin.c b/bulk-checkin.c
> index 73bff3a23d..92b9c8598b 100644
> --- a/bulk-checkin.c
> +++ b/bulk-checkin.c
> @@ -268,6 +268,7 @@ static int deflate_to_pack(struct bulk_checkin_packfile *state,
>  					  type, size);
>  	the_hash_algo->init_fn(&ctx);
>  	the_hash_algo->update_fn(&ctx, obuf, header_len);
> +	the_hash_algo->init_fn(&checkpoint.ctx);
>  
>  	/* Note: idx is non-NULL when we are writing */
>  	if ((flags & HASH_WRITE_OBJECT) != 0)
> diff --git a/csum-file.c b/csum-file.c
> index cd01713244..870748e016 100644
> --- a/csum-file.c
> +++ b/csum-file.c
> @@ -207,7 +207,7 @@ int hashfile_truncate(struct hashfile *f, struct hashfile_checkpoint *checkpoint
>  	    lseek(f->fd, offset, SEEK_SET) != offset)
>  		return -1;
>  	f->total = offset;
> -	f->ctx = checkpoint->ctx;
> +	the_hash_algo->clone_fn(&f->ctx, &checkpoint->ctx);
>  	f->offset = 0; /* hashflush() was called in checkpoint */
>  	return 0;
>  }