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From: Eric Biggers <ebiggers@kernel.org>
To: Jes Sorensen <jes.sorensen@gmail.com>
Cc: linux-fscrypt@vger.kernel.org, kernel-team@fb.com,
	Jes Sorensen <jsorensen@fb.com>
Subject: Re: [PATCH 4/9] Move hash algorithm code to shared library
Date: Sat, 21 Mar 2020 22:38:02 -0700
Message-ID: <20200322053802.GH111151@sol.localdomain> (raw)
In-Reply-To: <20200312214758.343212-5-Jes.Sorensen@gmail.com>

On Thu, Mar 12, 2020 at 05:47:53PM -0400, Jes Sorensen wrote:
> diff --git a/libfsverity.h b/libfsverity.h
> index 396a6ee..318dcd7 100644
> --- a/libfsverity.h
> +++ b/libfsverity.h
> @@ -18,6 +18,9 @@
>  #define FS_VERITY_HASH_ALG_SHA256       1
>  #define FS_VERITY_HASH_ALG_SHA512       2
>  
> +/* The hash algorithm that fsverity-utils assumes when none is specified */
> +#define FS_VERITY_HASH_ALG_DEFAULT	FS_VERITY_HASH_ALG_SHA256
> +
>  struct libfsverity_merkle_tree_params {
>  	uint16_t version;
>  	uint16_t hash_algorithm;	/* Matches the digest_algorithm type */
> @@ -27,6 +30,12 @@ struct libfsverity_merkle_tree_params {
>  	uint64_t reserved[11];
>  };
>  
> +/*
> + * Largest digest size among all hash algorithms supported by fs-verity.
> + * This can be increased if needed.
> + */
> +#define FS_VERITY_MAX_DIGEST_SIZE	64
> +
>  struct libfsverity_digest {
>  	char magic[8];			/* must be "FSVerity" */
>  	uint16_t digest_algorithm;
> @@ -57,9 +66,22 @@ struct fsverity_descriptor {
>  	uint8_t signature[];	/* optional PKCS#7 signature */
>  };
>  
> +struct fsverity_hash_alg {
> +	const char *name;
> +	unsigned int digest_size;
> +	unsigned int block_size;
> +	uint16_t hash_num;
> +	struct hash_ctx *(*create_ctx)(const struct fsverity_hash_alg *alg);
> +};
> +

It's still a bit weird to have struct fsverity_hash_alg as part of the library
API, since the .create_ctx() member is for internal library use only.  We at
least need to clearly comment this:

	struct fsverity_hash_alg {
		const char *name;
		unsigned int digest_size;
		unsigned int block_size;
		uint16_t hash_num;

		/* for library-internal use only */
		struct hash_ctx *(*create_ctx)(const struct fsverity_hash_alg *alg);
	};

But ideally there would be nothing library-internal in the API at all.

- Eric

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-12 21:47 [PATCH v3 0/9] Split fsverity-utils into a " Jes Sorensen
2020-03-12 21:47 ` [PATCH 1/9] Build basic shared library framework Jes Sorensen
2020-03-22  5:23   ` Eric Biggers
2020-03-22  5:33   ` Eric Biggers
2020-03-12 21:47 ` [PATCH 2/9] Change compute_file_measurement() to take a file descriptor as argument Jes Sorensen
2020-03-12 21:47 ` [PATCH 3/9] Move fsverity_descriptor definition to libfsverity.h Jes Sorensen
2020-03-22  4:57   ` Eric Biggers
2020-03-12 21:47 ` [PATCH 4/9] Move hash algorithm code to shared library Jes Sorensen
2020-03-22  5:38   ` Eric Biggers [this message]
2020-03-12 21:47 ` [PATCH 5/9] Create libfsverity_compute_digest() and adapt cmd_sign to use it Jes Sorensen
2020-03-22  5:40   ` Eric Biggers
2020-03-12 21:47 ` [PATCH 6/9] Introduce libfsverity_sign_digest() Jes Sorensen
2020-03-12 21:47 ` [PATCH 7/9] Validate input arguments to libfsverity_compute_digest() Jes Sorensen
2020-03-12 21:47 ` [PATCH 8/9] Validate input parameters for libfsverity_sign_digest() Jes Sorensen
2020-03-22  5:27   ` Eric Biggers
2020-03-12 21:47 ` [PATCH 9/9] Document API of libfsverity Jes Sorensen
2020-03-22  5:54   ` Eric Biggers
2020-03-22  5:05 ` [PATCH v3 0/9] Split fsverity-utils into a shared library Eric Biggers

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