On Mon, 2019-02-11 at 20:52 +0300, Vitaly Chikunov wrote:
> Mimi,
>
> On Mon, Feb 11, 2019 at 12:38:58PM -0500, Mimi Zohar wrote:
> > On Mon, 2018-12-03 at 06:35 +0300, Vitaly Chikunov wrote:
> > > For compatibility with older OpenSSL try to load digest by its alias if
> > > load by its proper name is failed.
> > >
> > > This is configured in pkey_hash_algo by mentioning loadable alias first in the
> > > comma separated list of algo names.
> >
> > After this patch, I can not verify the signature. It's failing to
> > find the hash algorithm.
>
> Yes, it's fixed in "ima-evm-utils: convert sign v2 from RSA to EVP_PKEY
> API". I didn't consider it a problem since streebog256 should not work
> for sign/verify anyway (since RSA should not support it). That EVP_PKEY
> patch which adds ability to sign/verify for Streebog also fixes above
> problem.
I've been having second thoughts about this patch in general, as it
made the hash algorithm comparison unnecessarily more complex for the
simple case. As there hasn't been a new ima-evm-utils release with
patch, perhaps we should simple remove/revert it?
Mimi
>
> > evmctl ima_sign -k <private key> -p -a streebog256 ./foo.txt --xattr-user
> > evmctl ima_verify -k <public key> ./foo.txt --xattr-user
> >
> > Mimi
> >
> > >
> > > Signed-off-by: Vitaly Chikunov <vt@xxxxxxxxxxxx>
> > > ---
> > > Changes since v1:
> > > - New patch.
> > > Changes since v2:
> > > - No changes.
> > >
> > > src/imaevm.h | 1 +
> > > src/libimaevm.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++----
> > > 2 files changed, 52 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/src/imaevm.h b/src/imaevm.h
> > > index c81bf21..795966a 100644
> > > --- a/src/imaevm.h
> > > +++ b/src/imaevm.h
> > > @@ -75,6 +75,7 @@
> > > #define DATA_SIZE 4096
> > > #define SHA1_HASH_LEN 20
> > >
> > > +#define MAX_DIGEST_NAME 32
> > > #define MAX_DIGEST_SIZE 64
> > > #define MAX_SIGNATURE_SIZE 1024
> > >
> > > diff --git a/src/libimaevm.c b/src/libimaevm.c
> > > index cb4721b..7501303 100644
> > > --- a/src/libimaevm.c
> > > +++ b/src/libimaevm.c
> > > @@ -41,6 +41,7 @@
> > > /* should we use logger instead for library? */
> > > #define USE_FPRINTF
> > >
> > > +#define _GNU_SOURCE
> > > #include <sys/types.h>
> > > #include <sys/param.h>
> > > #include <sys/stat.h>
> > > @@ -56,6 +57,7 @@
> > > #include <openssl/pem.h>
> > > #include <openssl/evp.h>
> > > #include <openssl/x509.h>
> > > +#include <openssl/engine.h>
> > > #include <openssl/err.h>
> > >
> > > #include "imaevm.h"
> > > @@ -70,8 +72,8 @@ const char *const pkey_hash_algo[PKEY_HASH__LAST] = {
> > > [PKEY_HASH_SHA384] = "sha384",
> > > [PKEY_HASH_SHA512] = "sha512",
> > > [PKEY_HASH_SHA224] = "sha224",
> > > - [PKEY_HASH_STREEBOG_256] = "streebog256",
> > > - [PKEY_HASH_STREEBOG_512] = "streebog512",
> > > + [PKEY_HASH_STREEBOG_256] = "md_gost12_256,streebog256",
> > > + [PKEY_HASH_STREEBOG_512] = "md_gost12_512,streebog512",
> > > };
> > >
> > > /*
> > > @@ -284,6 +286,35 @@ static int add_dev_hash(struct stat *st, EVP_MD_CTX *ctx)
> > > return !EVP_DigestUpdate(ctx, &dev, sizeof(dev));
> > > }
> > >
> > > +/* Call EVP_get_digestbyname with provided name and with alias,
> > > + * which is first name in the comma separated list of names
> > > + * in pkey_hash_algo.
> > > + */
> > > +static const EVP_MD *get_digestbyname(const char *name)
> > > +{
> > > + const EVP_MD *md;
> > > +
> > > + md = EVP_get_digestbyname(params.hash_algo);
> > > + if (!md) {
> > > + char alias[MAX_DIGEST_NAME];
> > > + int len;
> > > + int algo_id;
> > > + const char *algo_alias;
> > > +
> > > + /* try to get algo by its alias */
> > > + algo_id = get_hash_algo(params.hash_algo);
> > > + algo_alias = get_hash_algo_by_id(algo_id);
> > > + len = strchrnul(algo_alias, ',') - algo_alias;
> > > + if (len < sizeof(alias)) {
> > > + memcpy(alias, algo_alias, len);
> > > + alias[len] = '\0';
> > > + if (strcmp(params.hash_algo, alias))
> > > + md = EVP_get_digestbyname(alias);
> > > + }
> > > + }
> > > + return md;
> > > +}
> > > +
> > > int ima_calc_hash(const char *file, uint8_t *hash)
> > > {
> > > const EVP_MD *md;
> > > @@ -305,7 +336,7 @@ int ima_calc_hash(const char *file, uint8_t *hash)
> > > return err;
> > > }
> > >
> > > - md = EVP_get_digestbyname(params.hash_algo);
> > > + md = get_digestbyname(params.hash_algo);
> > > if (!md) {
> > > log_err("EVP_get_digestbyname(%s) failed\n", params.hash_algo);
> > > return 1;
> > > @@ -561,6 +592,22 @@ static int algocmp(const char *a, const char *b)
> > > return *a || *b;
> > > }
> > >
> > > +static int strmatch(const char *needle, const char *haystack)
> > > +{
> > > + int len = strlen(needle);
> > > + const char *p = haystack;
> > > + const char *t;
> > > +
> > > + for (t = strchrnul(p, ','); *p; p = t, t = strchrnul(p, ',')) {
> > > + if (t - p == len &&
> > > + !strncmp(needle, p, len))
> > > + return 0;
> > > + if (!*t++)
> > > + break;
> > > + }
> > > + return 1;
> > > +}
> > > +
> > > int get_hash_algo(const char *algo)
> > > {
> > > int i;
> > > @@ -568,7 +615,7 @@ int get_hash_algo(const char *algo)
> > > /* first iterate over builtin algorithms */
> > > for (i = 0; i < PKEY_HASH__LAST; i++)
> > > if (pkey_hash_algo[i] &&
> > > - !strcmp(algo, pkey_hash_algo[i]))
> > > + !strmatch(algo, pkey_hash_algo[i]))
> > > return i;
> > >
> > > /* iterate over algorithms provided by kernel-headers */
>
