Re: [ima-evm-utils PATCH 11/12] Use a file specific hash algorithm variable for signing files

Stefan Berger
2023-11-22T14:09:44Z

On 11/19/23 11:50, Mimi Zohar wrote:
> Instead of relying on the library "imaevm_params.algo" global variable,
> which is not concurrency-safe, define and use an evmctl file specific
> hash algorithm variable.
>
> Propogate using the file specific hash algorithm variable in sign_evm(),

-> Propagate

> sign_ima(), hash_ima(), and sign_hash() function.
>
> Replace using the library function ima_calc_hash() with ima_calc_hash2().
>
> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
> src/evmctl.c | 21 +++++++++++----------
> 1 file changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/src/evmctl.c b/src/evmctl.c
> index 7ae897d8b8b3..b802eeb1bf15 100644
> --- a/src/evmctl.c
> +++ b/src/evmctl.c
> @@ -140,6 +140,7 @@ static bool evm_immutable;
> static bool evm_portable;
> static bool veritysig;
> static bool hwtpm;
> +static char *hash_algo;

g_hash_algo to avoid shadowing this variable in some cases where there
is a function parameter of the same name?

>
> #define HMAC_FLAG_NO_UUID 0x0001
> #define HMAC_FLAG_CAPS_SET 0x0002
> @@ -570,12 +571,12 @@ static int sign_evm(const char *file, const char *key)

Add hash_algo to the parameters here and call it sign_evm(file, key,
g_hash_algo)? It makes sense to pass the hash_algo into this function
that needs to know this for the signature and pushed the usage of global
variables further out.

> unsigned char sig[MAX_SIGNATURE_SIZE];
> int len, err;
>
> - len = calc_evm_hash(file, imaevm_params.hash_algo, hash);
> + len = calc_evm_hash(file, hash_algo, hash);
> if (len <= 1)
> return len;
> assert(len <= sizeof(hash));
>
> - len = sign_hash(imaevm_params.hash_algo, hash, len, key, NULL, sig + 1);
> + len = sign_hash(hash_algo, hash, len, key, NULL, sig + 1);
> if (len <= 1)
> return len;
> assert(len < sizeof(sig));
> @@ -609,10 +610,10 @@ static int hash_ima(const char *file)
> {
> unsigned char hash[MAX_DIGEST_SIZE + 2]; /* +2 byte xattr header */
> int len, err, offset;
> - int algo = imaevm_get_hash_algo(imaevm_params.hash_algo);
> + int algo = imaevm_get_hash_algo(hash_algo);
>
> if (algo < 0) {
> - log_err("Unknown hash algo: %s\n", imaevm_params.hash_algo);
> + log_err("Unknown hash algo: %s\n", hash_algo);
> return -1;
> }
> if (algo > PKEY_HASH_SHA1) {
> @@ -624,7 +625,7 @@ static int hash_ima(const char *file)
> offset = 1;
> }
>
> - len = ima_calc_hash(file, hash + offset);
> + len = ima_calc_hash2(file, hash_algo, hash + offset);
> if (len <= 1)
> return len;
> assert(len + offset <= sizeof(hash));
> @@ -632,7 +633,7 @@ static int hash_ima(const char *file)
> len += offset;
>
> if (imaevm_params.verbose >= LOG_INFO)
> - log_info("hash(%s): ", imaevm_params.hash_algo);
> + log_info("hash(%s): ", hash_algo);
>
> if (sigdump || imaevm_params.verbose >= LOG_INFO)
> imaevm_hexdump(hash, len);
> @@ -656,12 +657,12 @@ static int sign_ima(const char *file, const char *key)
> unsigned char sig[MAX_SIGNATURE_SIZE];
> int len, err;
>
> - len = ima_calc_hash(file, hash);
> + len = ima_calc_hash2(file, hash_algo, hash);
> if (len <= 1)
> return len;
> assert(len <= sizeof(hash));
>
> - len = sign_hash(imaevm_params.hash_algo, hash, len, key, NULL, sig + 1);
> + len = sign_hash(hash_algo, hash, len, key, NULL, sig + 1);
> if (len <= 1)
> return len;
> assert(len < sizeof(sig));
> @@ -854,7 +855,7 @@ static int cmd_sign_hash(struct command *cmd)
> assert(hashlen / 2 <= sizeof(hash));
> hex2bin(hash, line, hashlen / 2);
>
> - siglen = sign_hash(imaevm_params.hash_algo, hash,
> + siglen = sign_hash(hash_algo, hash,
> hashlen / 2, key, NULL, sig + 1);
> sig[0] = EVM_IMA_XATTR_DIGSIG;
> }
> @@ -3077,7 +3078,7 @@ int main(int argc, char *argv[])
> sigdump = 1;
> break;
> case 'a':
> - imaevm_params.hash_algo = optarg;
> + hash_algo = optarg;
> break;
> case 'p':
> if (optarg)