Re: [PATCH] crypto: lib/sha256 - add sha256_value function

[Eric Biggers]

On Sat, Aug 07, 2021 at 11:06:39AM +0800, Chen Li wrote:
> Add a function sha256_value() which accepts a string and store SHA256 hash
> of this string into dest.
> 
> Signed-off-by: Chen Li <chenli@xxxxxxxxxxxxx>
> ---
>  include/crypto/sha2.h |  1 +
>  lib/crypto/sha256.c   | 23 +++++++++++++++++++++++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/include/crypto/sha2.h b/include/crypto/sha2.h
> index 2838f529f31e..ce17954cab38 100644
> --- a/include/crypto/sha2.h
> +++ b/include/crypto/sha2.h
> @@ -115,6 +115,7 @@ static inline void sha256_init(struct sha256_state *sctx)
>  void sha256_update(struct sha256_state *sctx, const u8 *data, unsigned int len);
>  void sha256_final(struct sha256_state *sctx, u8 *out);
>  void sha256(const u8 *data, unsigned int len, u8 *out);
> +int  sha256_value(u8 **dest, const u8 *src);
>  
>  static inline void sha224_init(struct sha256_state *sctx)
>  {
> diff --git a/lib/crypto/sha256.c b/lib/crypto/sha256.c
> index 72a4b0b1df28..ce1de7a3e32e 100644
> --- a/lib/crypto/sha256.c
> +++ b/lib/crypto/sha256.c
> @@ -13,6 +13,8 @@
>  
>  #include <linux/bitops.h>
>  #include <linux/export.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
>  #include <linux/module.h>
>  #include <linux/string.h>
>  #include <crypto/sha2.h>
> @@ -206,4 +208,25 @@ void sha256(const u8 *data, unsigned int len, u8 *out)
>  }
>  EXPORT_SYMBOL(sha256);
>  
> +int sha256_value(u8 **dest, const u8 *src)
> +{
> +	u8 out[SHA256_DIGEST_SIZE];
> +	int i, k;
> +	unsigned char hex[2];
> +
> +	*dest = kvmalloc(sizeof(u8) * (SHA256_BLOCK_SIZE + 1), GFP_KERNEL);
> +	if (ZERO_OR_NULL_PTR(*dest))
> +		return -ENOMEM;
> +	sha256(src, strlen(src), out);
> +
> +	for (i = 0, k = 0; i < SHA256_DIGEST_SIZE; i++) {
> +		sprintf(hex, "%02x", out[i]);
> +		(*dest)[k++] = hex[0];
> +		(*dest)[k++] = hex[1];
> +	}
> +	(*dest)[k] = '\0';
> +	return 0;
> +}
> +EXPORT_SYMBOL(sha256_value);

You forgot to include something that actually calls this function.

Anyway, there should be no need for this.  If you're trying to convert a SHA-256
hash value to a string, just use the %*phN printk format specifier which
converts bytes to hex.

- Eric