[PATCH 1/1] tools: use adequate entropy source for initialization vector

[Mark Kettenis]

> From: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> Date: Thu, 11 Apr 2024 01:31:16 +0200
> 
> The random() function is unsafe to initialize cryptographic data.
> Use getrandom() which reads from /dev/urandom instead.
> 
> getrandom() is available on Linux sine release 3.17 and on BSD.

NACK

getrandom() isn't evailable on OpenBSD.  Either use getentropy() or
arc4random_buf() instead.

> Addresses-Coverity-ID: 312953 Calling risky function
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> ---
>  tools/image-host.c | 36 +++---------------------------------
>  1 file changed, 3 insertions(+), 33 deletions(-)
> 
> diff --git a/tools/image-host.c b/tools/image-host.c
> index b2a0f2e6d16..d30a235baf6 100644
> --- a/tools/image-host.c
> +++ b/tools/image-host.c
> @@ -13,11 +13,11 @@
>  #include <fdt_region.h>
>  #include <image.h>
>  #include <version.h>
> -
>  #if CONFIG_IS_ENABLED(FIT_SIGNATURE)
>  #include <openssl/pem.h>
>  #include <openssl/evp.h>
>  #endif
> +#include <sys/random.h>
>  
>  /**
>   * fit_set_hash_value - set hash value in requested has node
> @@ -364,36 +364,6 @@ static int fit_image_read_key_iv_data(const char *keydir, const char *key_iv_nam
>  	return ret;
>  }
>  
> -static int get_random_data(void *data, int size)
> -{
> -	unsigned char *tmp = data;
> -	struct timespec date;
> -	int i, ret;
> -
> -	if (!tmp) {
> -		fprintf(stderr, "%s: pointer data is NULL\n", __func__);
> -		ret = -1;
> -		goto out;
> -	}
> -
> -	ret = clock_gettime(CLOCK_MONOTONIC, &date);
> -	if (ret) {
> -		fprintf(stderr, "%s: clock_gettime has failed (%s)\n", __func__,
> -			strerror(errno));
> -		goto out;
> -	}
> -
> -	srandom(date.tv_nsec);
> -
> -	for (i = 0; i < size; i++) {
> -		*tmp = random() & 0xff;
> -		tmp++;
> -	}
> -
> - out:
> -	return ret;
> -}
> -
>  static int fit_image_setup_cipher(struct image_cipher_info *info,
>  				  const char *keydir, void *fit,
>  				  const char *image_name, int image_noffset,
> @@ -465,8 +435,8 @@ static int fit_image_setup_cipher(struct image_cipher_info *info,
>  		if (ret < 0)
>  			goto out;
>  	} else {
> -		/* Generate an ramdom IV */
> -		ret = get_random_data((void *)info->iv, info->cipher->iv_len);
> +		/* Generate a ramdom initialization vector */
> +		ret = getrandom((void *)info->iv, info->cipher->iv_len, 0);
>  	}
>  
>   out:
> -- 
> 2.43.0
> 
>