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ima-evm-utils: Allow EVM verify to determine hash algo

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Previously for EVM verify you should specify `--hashalgo' option while
for IMA ima_verify you didn't.

Allow EVM verify to determine hash algo from signature.

Also, this makes two previously static functions to become exportable
and renamed:

  get_hash_algo_from_sig -> imaevm_hash_algo_from_sig
  get_hash_algo_by_id    -> imaevm_hash_algo_by_id

This is needed because EVM hash is calculated (in calc_evm_hash) outside
of library.

imaevm_hash_algo_by_id() will now return NULL if algo is not found.

Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Vitaly Chikunov 2019-07-29 09:18:07 +03:00 committed by Mimi Zohar
parent 90176e835a
commit cf1b8fda8d
3 changed files with 20 additions and 10 deletions
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18
src/evmctl.c
View File

@ -810,14 +810,10 @@ static int verify_evm(const char *file)
{
unsigned char hash[MAX_DIGEST_SIZE];
unsigned char sig[MAX_SIGNATURE_SIZE];
int sig_hash_algo;
int mdlen;
int len;
mdlen = calc_evm_hash(file, hash);
if (mdlen <= 1)
return mdlen;
assert(mdlen <= sizeof(hash));
len = lgetxattr(file, xattr_evm, sig, sizeof(sig));
if (len < 0) {
log_err("getxattr failed: %s\n", file);
@ -829,6 +825,18 @@ static int verify_evm(const char *file)
return -1;
}
sig_hash_algo = imaevm_hash_algo_from_sig(sig + 1);
if (sig_hash_algo < 0) {
log_err("unknown hash algo: %s\n", file);
return -1;
}
imaevm_params.hash_algo = imaevm_hash_algo_by_id(sig_hash_algo);
mdlen = calc_evm_hash(file, hash);
if (mdlen <= 1)
return mdlen;
assert(mdlen <= sizeof(hash));
return verify_hash(file, hash, mdlen, sig + 1, len - 1);
}

2
src/imaevm.h
View File

@ -223,5 +223,7 @@ int sign_hash(const char *algo, const unsigned char *hash, int size, const char
int verify_hash(const char *file, const unsigned char *hash, int size, unsigned char *sig, int siglen);
int ima_verify_signature(const char *file, unsigned char *sig, int siglen, unsigned char *digest, int digestlen);
void init_public_keys(const char *keyfiles);
int imaevm_hash_algo_from_sig(unsigned char *sig);
const char *imaevm_hash_algo_by_id(int algo);
#endif

10
src/libimaevm.c
View File

@ -105,7 +105,7 @@ void imaevm_hexdump(const void *ptr, int len)
imaevm_do_hexdump(stdout, ptr, len, true);
}
static const char *get_hash_algo_by_id(int algo)
const char *imaevm_hash_algo_by_id(int algo)
{
if (algo < PKEY_HASH__LAST)
return pkey_hash_algo[algo];
@ -113,7 +113,7 @@ static const char *get_hash_algo_by_id(int algo)
return hash_algo_name[algo];
log_err("digest %d not found\n", algo);
return "unknown";
return NULL;
}
/* Output all remaining openssl error messages. */
@ -575,7 +575,7 @@ int imaevm_get_hash_algo(const char *algo)
return -1;
}
static int get_hash_algo_from_sig(unsigned char *sig)
int imaevm_hash_algo_from_sig(unsigned char *sig)
{
uint8_t hashalgo;
@ -632,13 +632,13 @@ int ima_verify_signature(const char *file, unsigned char *sig, int siglen,
return -1;
}
sig_hash_algo = get_hash_algo_from_sig(sig + 1);
sig_hash_algo = imaevm_hash_algo_from_sig(sig + 1);
if (sig_hash_algo < 0) {
log_err("Invalid signature\n");
return -1;
}
/* Use hash algorithm as retrieved from signature */
imaevm_params.hash_algo = get_hash_algo_by_id(sig_hash_algo);
imaevm_params.hash_algo = imaevm_hash_algo_by_id(sig_hash_algo);
/*
* Validate the signature based on the digest included in the