Re: [ima-evm-utils PATCH v2 03/13] Update library function definitions to include a "public_keys" parameter

Stefan Berger
2024-01-02T13:11:20Z

On 12/6/23 14:27, Mimi Zohar wrote:
> Instead of relying on a global static "public_keys" variable, which is
> not concurrency-safe, update static library function definitions to
> include it as a parameter, define new library functions with it as
> a parameter, and deprecate existing functions.
>
> Define imaevm_init_public_keys(), imaevm_verify_hash(), and
> ima_verify_signature2() functions. Update static function definitions
> to include "public_keys".
>
> To avoid library incompatibility, make the existing functions -
> init_public_keys(), verify_hash(), ima_verify_signature() - wrappers
> for the new function versions.
>
> Deprecate init_public_keys(), verify_hash(), ima_verify_signature()
> functions.
>
> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
> src/imaevm.h | 4 +++
> src/libimaevm.c | 85 ++++++++++++++++++++++++++++++++++++-------------
> 2 files changed, 67 insertions(+), 22 deletions(-)
>
> diff --git a/src/imaevm.h b/src/imaevm.h
> index 470e8376f2fb..b29a4745fc77 100644
> --- a/src/imaevm.h
> +++ b/src/imaevm.h
> @@ -249,8 +249,12 @@ uint32_t imaevm_read_keyid(const char *certfile);
> int sign_hash(const char *algo, const unsigned char *hash, int size, const char *keyfile, const char *keypass, unsigned char *sig);
> 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);

Forward-declare struct public_key_entry here:
struct public_key_entry;

> +int ima_verify_signature2(void *public_keys, const char *file,

And use it instead of void * here. For the user it's going to be an
opaque type but better then a void*.

> + unsigned char *sig, int siglen,
> + unsigned char *digest, int digestlen);
> void imaevm_free_public_keys(void *public_keys);
> void init_public_keys(const char *keyfiles);
> +int imaevm_init_public_keys(const char *keyfiles, void **public_keys);
> int imaevm_hash_algo_from_sig(unsigned char *sig);
> const char *imaevm_hash_algo_by_id(int algo);
> int calc_hash_sigv3(enum evm_ima_xattr_type type, const char *algo, const unsigned char *in_hash, unsigned char *out_hash);
> diff --git a/src/libimaevm.c b/src/libimaevm.c
> index 534468fe99ca..6fecb2ffd139 100644
> --- a/src/libimaevm.c
> +++ b/src/libimaevm.c
> @@ -372,12 +372,13 @@ struct public_key_entry {
> };
> static struct public_key_entry *g_public_keys = NULL;
>
> -static EVP_PKEY *find_keyid(uint32_t keyid)
> +static EVP_PKEY *find_keyid(struct public_key_entry *public_keys,
> + uint32_t keyid)
> {
> - struct public_key_entry *entry, *tail = g_public_keys;
> + struct public_key_entry *entry, *tail = public_keys;
> int i = 1;
>
> - for (entry = g_public_keys; entry; entry = entry->next) {
> + for (entry = public_keys; entry; entry = entry->next) {
> if (entry->keyid == keyid)
> return entry->key;
> i++;
> @@ -394,7 +395,7 @@ static EVP_PKEY *find_keyid(uint32_t keyid)
> if (tail)
> tail->next = entry;
> else
> - g_public_keys = entry;
> + public_keys = (void *)entry;
> log_err("key %d: %x (unknown keyid)\n", i, __be32_to_cpup(&keyid));
> return 0;
> }
> @@ -412,7 +413,7 @@ void imaevm_free_public_keys(void *public_keys)
> }
> }
>
> -void init_public_keys(const char *keyfiles)
> +int imaevm_init_public_keys(const char *keyfiles, void **public_keys)
> {
> struct public_key_entry *entry;
> char *tmp_keyfiles, *keyfiles_free;
> @@ -420,6 +421,11 @@ void init_public_keys(const char *keyfiles)
> int err = 0;
> int i = 1;
>
> + if (!public_keys)
> + return -EINVAL;
> +
> + *public_keys = NULL;
> +
> tmp_keyfiles = strdup(keyfiles);
> keyfiles_free = tmp_keyfiles;
>
> @@ -444,12 +450,19 @@ void init_public_keys(const char *keyfiles)
> calc_keyid_v2(&entry->keyid, entry->name, entry->key);
> sprintf(entry->name, "%x", __be32_to_cpup(&entry->keyid));
> log_info("key %d: %s %s\n", i++, entry->name, keyfile);
> - entry->next = g_public_keys;
> - g_public_keys = entry;
> + entry->next = (struct public_key_entry *)*public_keys;
> + *public_keys = (void *)entry;
> }
> +
> free(keyfiles_free);
> if (err < 0)
> - imaevm_free_public_keys(g_public_keys);
> + imaevm_free_public_keys(public_keys);
> + return err;
> +}
> +
> +__attribute__((deprecated)) void init_public_keys(const char *keyfiles)

The attribute should go into the header file.

> +{
> + imaevm_init_public_keys(keyfiles, (void **)&g_public_keys);
> }
>
> /*
> @@ -466,7 +479,8 @@ void init_public_keys(const char *keyfiles)
> *
> * (Note: signature_v2_hdr struct does not contain the 'type'.)
> */
> -static int verify_hash_common(const char *file, const unsigned char *hash,
> +static int verify_hash_common(struct public_key_entry *public_keys,
> + const char *file, const unsigned char *hash,
> int size, unsigned char *sig, int siglen)
> {
> int ret = -1;
> @@ -481,7 +495,7 @@ static int verify_hash_common(const char *file, const unsigned char *hash,
> log_dump(hash, size);
> }
>
> - pkey = find_keyid(hdr->keyid);
> + pkey = find_keyid(public_keys, hdr->keyid);
> if (!pkey) {
> uint32_t keyid = hdr->keyid;
>
> @@ -543,11 +557,13 @@ err:
> *
> * Return: 0 verification good, 1 verification bad, -1 error.
> */
> -static int verify_hash_v2(const char *file, const unsigned char *hash,
> +static int verify_hash_v2(struct public_key_entry *public_keys,
> + const char *file, const unsigned char *hash,
> int size, unsigned char *sig, int siglen)
> {
> /* note: signature_v2_hdr does not contain 'type', use sig + 1 */
> - return verify_hash_common(file, hash, size, sig + 1, siglen - 1);
> + return verify_hash_common(public_keys, file, hash, size,
> + sig + 1, siglen - 1);
> }
>
> /*
> @@ -556,7 +572,8 @@ static int verify_hash_v2(const char *file, const unsigned char *hash,
> *
> * Return: 0 verification good, 1 verification bad, -1 error.
> */
> -static int verify_hash_v3(const char *file, const unsigned char *hash,
> +static int verify_hash_v3(struct public_key_entry *public_keys,
> + const char *file, const unsigned char *hash,
> int size, unsigned char *sig, int siglen)
> {
> unsigned char sigv3_hash[MAX_DIGEST_SIZE];
> @@ -567,7 +584,8 @@ static int verify_hash_v3(const char *file, const unsigned char *hash,
> return ret;
>
> /* note: signature_v2_hdr does not contain 'type', use sig + 1 */
> - return verify_hash_common(file, sigv3_hash, size, sig + 1, siglen - 1);
> + return verify_hash_common(public_keys, file, sigv3_hash, size,
> + sig + 1, siglen - 1);
> }
>
> #define HASH_MAX_DIGESTSIZE 64 /* kernel HASH_MAX_DIGESTSIZE is 64 bytes */
> @@ -710,8 +728,9 @@ int imaevm_hash_algo_from_sig(unsigned char *sig)
> return -1;
> }
>
> -int verify_hash(const char *file, const unsigned char *hash, int size,
> - unsigned char *sig, int siglen)
> +int imaevm_verify_hash(void *public_keys, const char *file,
> + const unsigned char *hash, int size,
> + unsigned char *sig, int siglen)
> {
> /* Get signature type from sig header */
> if (sig[1] == DIGSIG_VERSION_1) {
> @@ -730,15 +749,25 @@ int verify_hash(const char *file, const unsigned char *hash, int size,
> return -1;
> #endif
> } else if (sig[1] == DIGSIG_VERSION_2) {
> - return verify_hash_v2(file, hash, size, sig, siglen);
> + return verify_hash_v2(public_keys, file, hash, size,
> + sig, siglen);
> } else if (sig[1] == DIGSIG_VERSION_3) {
> - return verify_hash_v3(file, hash, size, sig, siglen);
> + return verify_hash_v3(public_keys, file, hash, size,
> + sig, siglen);
> } else
> return -1;
> }
>
> -int ima_verify_signature(const char *file, unsigned char *sig, int siglen,
> - unsigned char *digest, int digestlen)
> +__attribute__((deprecated)) int verify_hash(const char *file,
> + const unsigned char *hash, int size,
> + unsigned char *sig, int siglen)
> +{
> + return imaevm_verify_hash(g_public_keys, file, hash, size, sig, siglen);
> +}
> +
> +int ima_verify_signature2(void *public_keys, const char *file,
> + unsigned char *sig, int siglen,
> + unsigned char *digest, int digestlen)
> {
> unsigned char hash[MAX_DIGEST_SIZE];
> int hashlen, sig_hash_algo;
> @@ -766,14 +795,26 @@ int ima_verify_signature(const char *file, unsigned char *sig, int siglen,
> * measurement list, not by calculating the local file digest.
> */
> if (digest && digestlen > 0)
> - return verify_hash(file, digest, digestlen, sig, siglen);
> + return imaevm_verify_hash(public_keys, file, digest, digestlen,
> + sig, siglen);
>
> hashlen = ima_calc_hash(file, hash);
> if (hashlen <= 1)
> return hashlen;
> assert(hashlen <= sizeof(hash));
>
> - return verify_hash(file, hash, hashlen, sig, siglen);
> + return imaevm_verify_hash(public_keys, file, hash, hashlen,
> + sig, siglen);
> +}
> +
> +__attribute__((deprecated)) int ima_verify_signature(const char *file,
> + unsigned char *sig,
> + int siglen,
> + unsigned char *digest,
> + int digestlen)
> +{
> + return ima_verify_signature2(g_public_keys, file, sig, siglen,
> + digest, digestlen);
> }
>
> #if CONFIG_SIGV1