[Openvpn-devel,v3] Implement ED448 and ED25519 support in xkey_provider

  OpenSSL's implementation of ED448 and ED25519 has a few idiosyncrasies.
Instead of belonging to the elliptic curve type or to a common Edwards
curve type, ED448 and ED25519 have each their own type.

Also, OpenSSL expects signatures using these curves to be done with the
EVP_DigestSign API instead of the EVP_Sign API but using md=NULL.

This has been tested using a "fake" external key that used a normal
software key instead of a hardware implementation but that makes no
difference from the perspective of xkey_provider/management interface.

Patch v2: remove name functions from ed448/ed25519, ensure md is NULL
          for ed448/ed25519 and handle NULL/none better in general.

Patch v3: do not pass NULL as string for the OSSL params.
---
 src/openvpn/xkey_common.h                |  2 +-
 src/openvpn/xkey_helper.c                |  7 +-
 src/openvpn/xkey_provider.c              | 97 ++++++++++++++++++++++--
 tests/unit_tests/openvpn/test_provider.c | 36 +++++++--
 4 files changed, 126 insertions(+), 16 deletions(-)
  

Hi,

Thanks for the new version. Looks good (only compile tested).

Acked-by: Selva Nair <selva.nair@gmail.com>




Selva

On Mon, May 16, 2022 at 6:49 AM Arne Schwabe <arne@rfc2549.org> wrote:
>
> OpenSSL's implementation of ED448 and ED25519 has a few idiosyncrasies.
> Instead of belonging to the elliptic curve type or to a common Edwards
> curve type, ED448 and ED25519 have each their own type.
>
> Also, OpenSSL expects signatures using these curves to be done with the
> EVP_DigestSign API instead of the EVP_Sign API but using md=NULL.
>
> This has been tested using a "fake" external key that used a normal
> software key instead of a hardware implementation but that makes no
> difference from the perspective of xkey_provider/management interface.
>
> Patch v2: remove name functions from ed448/ed25519, ensure md is NULL
>           for ed448/ed25519 and handle NULL/none better in general.
>
> Patch v3: do not pass NULL as string for the OSSL params.
> ---
>  src/openvpn/xkey_common.h                |  2 +-
>  src/openvpn/xkey_helper.c                |  7 +-
>  src/openvpn/xkey_provider.c              | 97 ++++++++++++++++++++++--
>  tests/unit_tests/openvpn/test_provider.c | 36 +++++++--
>  4 files changed, 126 insertions(+), 16 deletions(-)
>
> diff --git a/src/openvpn/xkey_common.h b/src/openvpn/xkey_common.h
> index 35cbcf576..e0e5ed5b2 100644
> --- a/src/openvpn/xkey_common.h
> +++ b/src/openvpn/xkey_common.h
> @@ -43,7 +43,7 @@ OSSL_provider_init_fn xkey_provider_init;
>  #define XKEY_PROV_PROPS "provider=ovpn.xkey"
>
>  /**
> - * Stuct to encapsulate signature algorithm parameters to pass
> + * Struct to encapsulate signature algorithm parameters to pass
>   * to sign operation.
>   */
>  typedef struct {
> diff --git a/src/openvpn/xkey_helper.c b/src/openvpn/xkey_helper.c
> index ecc7b1204..c1b1dfdbf 100644
> --- a/src/openvpn/xkey_helper.c
> +++ b/src/openvpn/xkey_helper.c
> @@ -179,7 +179,8 @@ xkey_management_sign(void *unused, unsigned char *sig, size_t *siglen,
>      bool is_message = !strcmp(alg.op, "DigestSign"); /* tbs is message, not digest */
>
>      /* if management client cannot do digest -- we do it here */
> -    if (!strcmp(alg.op, "DigestSign") && !(flags & MF_EXTERNAL_KEY_DIGEST))
> +    if (!strcmp(alg.op, "DigestSign") && !(flags & MF_EXTERNAL_KEY_DIGEST)
> +        && strcmp(alg.mdname, "none"))
>      {
>          dmsg(D_XKEY, "xkey_management_sign: computing digest");
>          if (xkey_digest(tbs, tbslen, buf, &buflen, alg.mdname))
> @@ -206,6 +207,10 @@ xkey_management_sign(void *unused, unsigned char *sig, size_t *siglen,
>              openvpn_snprintf(alg_str, sizeof(alg_str), "ECDSA,hashalg=%s", alg.mdname);
>          }
>      }
> +    else if (!strcmp(alg.keytype, "ED448") || !strcmp(alg.keytype, "ED25519"))
> +    {
> +        strncpynt(alg_str, alg.keytype, sizeof(alg_str));
> +    }
>      /* else assume RSA key */
>      else if (!strcmp(alg.padmode, "pkcs1") && (flags & MF_EXTERNAL_KEY_PKCS1PAD))
>      {
> diff --git a/src/openvpn/xkey_provider.c b/src/openvpn/xkey_provider.c
> index 46e57e0fe..67000004e 100644
> --- a/src/openvpn/xkey_provider.c
> +++ b/src/openvpn/xkey_provider.c
> @@ -99,12 +99,28 @@ typedef struct
>      int refcount;                /**< reference count */
>  } XKEY_KEYDATA;
>
> -static int
> -KEYTYPE(const XKEY_KEYDATA *key)
> +static inline const char *
> +get_keytype(const XKEY_KEYDATA *key)
>  {
> -    return key->pubkey ? EVP_PKEY_get_id(key->pubkey) : 0;
> +    int keytype = key->pubkey ? EVP_PKEY_get_id(key->pubkey) : 0;
> +
> +    switch (keytype)
> +    {
> +        case EVP_PKEY_RSA:
> +            return "RSA";
> +
> +        case EVP_PKEY_ED448:
> +            return "ED448";
> +
> +        case EVP_PKEY_ED25519:
> +            return "ED25519";
> +
> +        default:
> +            return "EC";
> +    }
>  }
>
> +
>  static int
>  KEYSIZE(const XKEY_KEYDATA *key)
>  {
> @@ -310,6 +326,22 @@ ec_keymgmt_import(void *keydata, int selection, const OSSL_PARAM params[])
>      return keymgmt_import(keydata, selection, params, "EC");
>  }
>
> +static int
> +ed448_keymgmt_import(void *keydata, int selection, const OSSL_PARAM params[])
> +{
> +    xkey_dmsg(D_XKEY, "entry");
> +
> +    return keymgmt_import(keydata, selection, params, "ED448");
> +}
> +
> +static int
> +ed25519_keymgmt_import(void *keydata, int selection, const OSSL_PARAM params[])
> +{
> +    xkey_dmsg(D_XKEY, "entry");
> +
> +    return keymgmt_import(keydata, selection, params, "ED25519");
> +}
> +
>  /* This function has to exist for key import to work
>   * though we do not support import of individual params
>   * like n or e. We simply return an empty list here for
> @@ -449,7 +481,7 @@ keymgmt_import_helper(XKEY_KEYDATA *key, const OSSL_PARAM *params)
>          ASSERT(pkey);
>
>          int id = EVP_PKEY_get_id(pkey);
> -        if (id != EVP_PKEY_RSA && id != EVP_PKEY_EC)
> +        if (id != EVP_PKEY_RSA && id != EVP_PKEY_EC && id != EVP_PKEY_ED25519 && id != EVP_PKEY_ED448)
>          {
>              msg(M_WARN, "Error: xkey keymgmt_import: unknown key type (%d)", id);
>              return 0;
> @@ -588,10 +620,43 @@ static const OSSL_DISPATCH ec_keymgmt_functions[] = {
>      {0, NULL }
>  };
>
> +static const OSSL_DISPATCH ed448_keymgmt_functions[] = {
> +    {OSSL_FUNC_KEYMGMT_NEW, (void (*)(void))keymgmt_new},
> +    {OSSL_FUNC_KEYMGMT_FREE, (void (*)(void))keymgmt_free},
> +    {OSSL_FUNC_KEYMGMT_LOAD, (void (*)(void))keymgmt_load},
> +    {OSSL_FUNC_KEYMGMT_HAS, (void (*)(void))keymgmt_has},
> +    {OSSL_FUNC_KEYMGMT_MATCH, (void (*)(void))keymgmt_match},
> +    {OSSL_FUNC_KEYMGMT_IMPORT, (void (*)(void))ed448_keymgmt_import},
> +    {OSSL_FUNC_KEYMGMT_IMPORT_TYPES, (void (*)(void))keymgmt_import_types},
> +    {OSSL_FUNC_KEYMGMT_GETTABLE_PARAMS, (void (*)(void))keymgmt_gettable_params},
> +    {OSSL_FUNC_KEYMGMT_GET_PARAMS, (void (*)(void))keymgmt_get_params},
> +    {OSSL_FUNC_KEYMGMT_SET_PARAMS, (void (*)(void))keymgmt_set_params},
> +    {OSSL_FUNC_KEYMGMT_SETTABLE_PARAMS, (void (*)(void))keymgmt_gettable_params},       /* same as gettable */
> +    {0, NULL }
> +};
> +
> +static const OSSL_DISPATCH ed25519_keymgmt_functions[] = {
> +    {OSSL_FUNC_KEYMGMT_NEW, (void (*)(void))keymgmt_new},
> +    {OSSL_FUNC_KEYMGMT_FREE, (void (*)(void))keymgmt_free},
> +    {OSSL_FUNC_KEYMGMT_LOAD, (void (*)(void))keymgmt_load},
> +    {OSSL_FUNC_KEYMGMT_HAS, (void (*)(void))keymgmt_has},
> +    {OSSL_FUNC_KEYMGMT_MATCH, (void (*)(void))keymgmt_match},
> +    {OSSL_FUNC_KEYMGMT_IMPORT, (void (*)(void))ed25519_keymgmt_import},
> +    {OSSL_FUNC_KEYMGMT_IMPORT_TYPES, (void (*)(void))keymgmt_import_types},
> +    {OSSL_FUNC_KEYMGMT_GETTABLE_PARAMS, (void (*)(void))keymgmt_gettable_params},
> +    {OSSL_FUNC_KEYMGMT_GET_PARAMS, (void (*)(void))keymgmt_get_params},
> +    {OSSL_FUNC_KEYMGMT_SET_PARAMS, (void (*)(void))keymgmt_set_params},
> +    {OSSL_FUNC_KEYMGMT_SETTABLE_PARAMS, (void (*)(void))keymgmt_gettable_params},       /* same as gettable */
> +    {0, NULL }
> +};
> +
> +
>  const OSSL_ALGORITHM keymgmts[] = {
>      {"RSA:rsaEncryption", XKEY_PROV_PROPS, rsa_keymgmt_functions, "OpenVPN xkey RSA Key Manager"},
>      {"RSA-PSS:RSASSA-PSS", XKEY_PROV_PROPS, rsa_keymgmt_functions, "OpenVPN xkey RSA-PSS Key Manager"},
>      {"EC:id-ecPublicKey", XKEY_PROV_PROPS, ec_keymgmt_functions, "OpenVPN xkey EC Key Manager"},
> +    {"ED448", XKEY_PROV_PROPS, ed448_keymgmt_functions, "OpenVPN xkey ED448 Key Manager"},
> +    {"ED25519", XKEY_PROV_PROPS, ed25519_keymgmt_functions, "OpenVPN xkey ED25519 Key Manager"},
>      {NULL, NULL, NULL, NULL}
>  };
>
> @@ -649,6 +714,11 @@ static const char *saltlen_names[] = {"digest", "max", "auto", NULL};
>  static const char *
>  xkey_mdname(const char *name)
>  {
> +    if (name == NULL)
> +    {
> +        return "none";
> +    }
> +
>      int i = 0;
>
>      int nid = EVP_MD_get_type(EVP_get_digestbyname(name));
> @@ -835,7 +905,7 @@ signature_sign_init(void *ctx, void *provkey, const OSSL_PARAM params[])
>      }
>      sctx->keydata = provkey;
>      sctx->keydata->refcount++; /* we are keeping a copy */
> -    sctx->sigalg.keytype = KEYTYPE(sctx->keydata) == EVP_PKEY_RSA ? "RSA" : "EC";
> +    sctx->sigalg.keytype = get_keytype(sctx->keydata);
>
>      signature_set_ctx_params(sctx, params);
>
> @@ -929,10 +999,21 @@ signature_digest_sign_init(void *ctx, const char *mdname,
>      }
>      sctx->keydata = provkey; /* used by digest_sign */
>      sctx->keydata->refcount++;
> -    sctx->sigalg.keytype = KEYTYPE(sctx->keydata) == EVP_PKEY_RSA ? "RSA" : "EC";
> +    sctx->sigalg.keytype = get_keytype(sctx->keydata);
>
>      signature_set_ctx_params(ctx, params);
> -    if (mdname)
> +    if (!strcmp(sctx->sigalg.keytype, "ED448") || !strcmp(sctx->sigalg.keytype, "ED25519"))
> +    {
> +        /* EdDSA requires NULL as digest for the DigestSign API instead
> +         * of using the normal Sign API. Ensure it is actually NULL too */
> +        if (mdname != NULL)
> +        {
> +            msg(M_WARN, "xkey digest_sign_init: mdname must be NULL for ED448/ED25519.");
> +            return 0;
> +        }
> +        sctx->sigalg.mdname = "none";
> +    }
> +    else if (mdname)
>      {
>          sctx->sigalg.mdname = xkey_mdname(mdname); /* get a string literal pointer */
>      }
> @@ -1073,6 +1154,8 @@ static const OSSL_DISPATCH signature_functions[] = {
>  const OSSL_ALGORITHM signatures[] = {
>      {"RSA:rsaEncryption", XKEY_PROV_PROPS, signature_functions, "OpenVPN xkey RSA Signature"},
>      {"ECDSA", XKEY_PROV_PROPS, signature_functions, "OpenVPN xkey ECDSA Signature"},
> +    {"ED448", XKEY_PROV_PROPS, signature_functions, "OpenVPN xkey Ed448 Signature"},
> +    {"ED25519", XKEY_PROV_PROPS, signature_functions, "OpenVPN xkey Ed25519 Signature"},
>      {NULL, NULL, NULL, NULL}
>  };
>
> diff --git a/tests/unit_tests/openvpn/test_provider.c b/tests/unit_tests/openvpn/test_provider.c
> index 0b0952ee2..0045b61a6 100644
> --- a/tests/unit_tests/openvpn/test_provider.c
> +++ b/tests/unit_tests/openvpn/test_provider.c
> @@ -66,7 +66,11 @@ static const char *const pubkey2 = "-----BEGIN PUBLIC KEY-----\n"
>                                     "u95ff1JiUaJIkYNIkZA+hwIPFVH5aJcSCv3SPIeDS2VUAESNKHZJBQ==\n"
>                                     "-----END PUBLIC KEY-----\n";
>
> -static const char *pubkeys[] = {pubkey1, pubkey2};
> +static const char *const pubkey3 = "-----BEGIN PUBLIC KEY-----\n"
> +                                   "MCowBQYDK2VwAyEA+q5xjF5hGyyqYZidJdz/0saEQabL3N4wIZJBxNGbgJE=\n"
> +                                   "-----END PUBLIC KEY-----";
> +
> +static const char *pubkeys[] = {pubkey1, pubkey2, pubkey3};
>
>  static const char *prov_name = "ovpn.xkey";
>
> @@ -158,12 +162,17 @@ management_query_pk_sig(struct management *man, const char *b64_data,
>      if (strstr(algorithm, "data=message"))
>      {
>          expected_tbs = test_msg_b64;
> -        assert_non_null(strstr(algorithm, "hashalg=SHA256"));
> +        /* ED25519 does not have a hash algorithm even though it goes via
> +         * the DigestSign path (data=message) */
> +        if (!strstr(algorithm, "ED25519"))
> +        {
> +            assert_non_null(strstr(algorithm, "hashalg=SHA256"));
> +        }
>      }
>      assert_string_equal(b64_data, expected_tbs);
>
> -    /* We test using ECDSA or PSS with saltlen = digest */
> -    if (!strstr(algorithm, "ECDSA"))
> +    /* We test using ED25519, ECDSA or PSS with saltlen = digest */
> +    if (!strstr(algorithm, "ECDSA") && !strstr(algorithm, "ED25519"))
>      {
>          assert_non_null(strstr(algorithm, "RSA_PKCS1_PSS_PADDING,hashalg=SHA256,saltlen=digest"));
>      }
> @@ -228,6 +237,12 @@ digest_sign(EVP_PKEY *pkey)
>          params[3] = OSSL_PARAM_construct_utf8_string(OSSL_SIGNATURE_PARAM_MGF1_DIGEST, (char *)saltlen, 0);
>          params[4] = OSSL_PARAM_construct_end();
>      }
> +    else if (EVP_PKEY_get_id(pkey) == EVP_PKEY_ED25519)
> +    {
> +        mdname = NULL;
> +        params[0] = OSSL_PARAM_construct_end();
> +    }
> +
>
>      EVP_PKEY_CTX *pctx = NULL;
>      EVP_MD_CTX *mctx = EVP_MD_CTX_new();
> @@ -328,13 +343,20 @@ xkey_sign(void *handle, unsigned char *sig, size_t *siglen,
>          assert_memory_equal(tbs, test_digest, sizeof(test_digest));
>      }
>
> -    /* For the test use sha256 and PSS padding for RSA */
> -    assert_int_equal(OBJ_sn2nid(s.mdname), NID_sha256);
> +    /* For the test use sha256 and PSS padding for RSA and none for EDDSA */
> +    if (!strcmp(s.keytype,"ED25519"))
> +    {
> +        assert_string_equal(s.mdname, "none");
> +    }
> +    else
> +    {
> +        assert_int_equal(OBJ_sn2nid(s.mdname), NID_sha256);
> +    }
>      if (!strcmp(s.keytype, "RSA"))
>      {
>          assert_string_equal(s.padmode, "pss"); /* we use PSS for the test */
>      }
> -    else if (strcmp(s.keytype, "EC"))
> +    else if (strcmp(s.keytype, "EC") && strcmp(s.keytype,"ED25519"))
>      {
>          fail_msg("Unknown keytype: %s", s.keytype);
>      }
> --
> 2.32.0 (Apple Git-132)
>
>
>
> _______________________________________________
> Openvpn-devel mailing list
> Openvpn-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/openvpn-devel
  

I have only stared a bit at the code, and then run "make check" on 
a FreeBSD / OpenSSL 3.0.3 - which passes, including test_provider
(the t_client check succeeds, but does not excercise this code at all -
so I'm not really testing it).

Uncrustify / pre-applypatch complained about the new ",<blank>" rules
in test_provider.c, so I fixed them :-) - thanks, Frank!

Your patch has been applied to the master branch.

commit c0323aa63d638ee72eb73fcf2a6983b568f952f9
Author: Arne Schwabe
Date:   Mon May 16 12:48:07 2022 +0200

     Implement ED448 and ED25519 support in xkey_provider

     Acked-by: Selva Nair <selva.nair@gmail.com>
     Message-Id: <20220516104807.2568937-1-arne@rfc2549.org>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg24363.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering