From: Chuck Lever chuck.lever@oracle.com
The Camellia enctypes use the KDF_FEEDBACK_CMAC Key Derivation Function defined in RFC 6803 Section 3.
Tested-by: Scott Mayhew smayhew@redhat.com Signed-off-by: Chuck Lever chuck.lever@oracle.com --- net/sunrpc/auth_gss/gss_krb5_internal.h | 6 + net/sunrpc/auth_gss/gss_krb5_keys.c | 143 +++++++++++++++++++++++++++++++ net/sunrpc/auth_gss/gss_krb5_mech.c | 2 3 files changed, 151 insertions(+)
diff --git a/net/sunrpc/auth_gss/gss_krb5_internal.h b/net/sunrpc/auth_gss/gss_krb5_internal.h index fd2ae11c5067..c955e7b76c4d 100644 --- a/net/sunrpc/auth_gss/gss_krb5_internal.h +++ b/net/sunrpc/auth_gss/gss_krb5_internal.h @@ -58,6 +58,12 @@ int krb5_kdf_hmac_sha2(const struct gss_krb5_enctype *gk5e, const struct xdr_netobj *in_constant, gfp_t gfp_mask);
+int krb5_kdf_feedback_cmac(const struct gss_krb5_enctype *gk5e, + const struct xdr_netobj *inkey, + struct xdr_netobj *outkey, + const struct xdr_netobj *in_constant, + gfp_t gfp_mask); + /** * krb5_derive_key - Derive a subkey from a protocol key * @kctx: Kerberos 5 context diff --git a/net/sunrpc/auth_gss/gss_krb5_keys.c b/net/sunrpc/auth_gss/gss_krb5_keys.c index 724be20f5417..99251f15723a 100644 --- a/net/sunrpc/auth_gss/gss_krb5_keys.c +++ b/net/sunrpc/auth_gss/gss_krb5_keys.c @@ -363,6 +363,149 @@ int krb5_derive_key_v2(const struct gss_krb5_enctype *gk5e, return ret; }
+/* + * K(i) = CMAC(key, K(i-1) | i | constant | 0x00 | k) + * + * i: A block counter is used with a length of 4 bytes, represented + * in big-endian order. + * + * constant: The label input to the KDF is the usage constant supplied + * to the key derivation function + * + * k: The length of the output key in bits, represented as a 4-byte + * string in big-endian order. + * + * Caller fills in K(i-1) in @step, and receives the result K(i) + * in the same buffer. + */ +static int +krb5_cmac_Ki(struct crypto_shash *tfm, const struct xdr_netobj *constant, + u32 outlen, u32 count, struct xdr_netobj *step) +{ + __be32 k = cpu_to_be32(outlen * 8); + SHASH_DESC_ON_STACK(desc, tfm); + __be32 i = cpu_to_be32(count); + u8 zero = 0; + int ret; + + desc->tfm = tfm; + ret = crypto_shash_init(desc); + if (ret) + goto out_err; + + ret = crypto_shash_update(desc, step->data, step->len); + if (ret) + goto out_err; + ret = crypto_shash_update(desc, (u8 *)&i, sizeof(i)); + if (ret) + goto out_err; + ret = crypto_shash_update(desc, constant->data, constant->len); + if (ret) + goto out_err; + ret = crypto_shash_update(desc, &zero, sizeof(zero)); + if (ret) + goto out_err; + ret = crypto_shash_update(desc, (u8 *)&k, sizeof(k)); + if (ret) + goto out_err; + ret = crypto_shash_final(desc, step->data); + if (ret) + goto out_err; + +out_err: + shash_desc_zero(desc); + return ret; +} + +/** + * krb5_kdf_feedback_cmac - Derive a subkey for a Camellia/CMAC-based enctype + * @gk5e: Kerberos 5 enctype parameters + * @inkey: base protocol key + * @outkey: OUT: derived key + * @constant: subkey usage label + * @gfp_mask: memory allocation control flags + * + * RFC 6803 Section 3: + * + * "We use a key derivation function from the family specified in + * [SP800-108], Section 5.2, 'KDF in Feedback Mode'." + * + * n = ceiling(k / 128) + * K(0) = zeros + * K(i) = CMAC(key, K(i-1) | i | constant | 0x00 | k) + * DR(key, constant) = k-truncate(K(1) | K(2) | ... | K(n)) + * KDF-FEEDBACK-CMAC(key, constant) = random-to-key(DR(key, constant)) + * + * Caller sets @outkey->len to the desired length of the derived key (k). + * + * On success, returns 0 and fills in @outkey. A negative errno value + * is returned on failure. + */ +int +krb5_kdf_feedback_cmac(const struct gss_krb5_enctype *gk5e, + const struct xdr_netobj *inkey, + struct xdr_netobj *outkey, + const struct xdr_netobj *constant, + gfp_t gfp_mask) +{ + struct xdr_netobj step = { .data = NULL }; + struct xdr_netobj DR = { .data = NULL }; + unsigned int blocksize, offset; + struct crypto_shash *tfm; + int n, count, ret; + + /* + * This implementation assumes the CMAC used for an enctype's + * key derivation is the same as the CMAC used for its + * checksumming. This happens to be true for enctypes that + * are currently supported by this implementation. + */ + tfm = crypto_alloc_shash(gk5e->cksum_name, 0, 0); + if (IS_ERR(tfm)) { + ret = PTR_ERR(tfm); + goto out; + } + ret = crypto_shash_setkey(tfm, inkey->data, inkey->len); + if (ret) + goto out_free_tfm; + + blocksize = crypto_shash_digestsize(tfm); + n = (outkey->len + blocksize - 1) / blocksize; + + /* K(0) is all zeroes */ + ret = -ENOMEM; + step.len = blocksize; + step.data = kzalloc(step.len, gfp_mask); + if (!step.data) + goto out_free_tfm; + + DR.len = blocksize * n; + DR.data = kmalloc(DR.len, gfp_mask); + if (!DR.data) + goto out_free_tfm; + + /* XXX: Does not handle partial-block key sizes */ + for (offset = 0, count = 1; count <= n; count++) { + ret = krb5_cmac_Ki(tfm, constant, outkey->len, count, &step); + if (ret) + goto out_free_tfm; + + memcpy(DR.data + offset, step.data, blocksize); + offset += blocksize; + } + + /* k-truncate and random-to-key */ + memcpy(outkey->data, DR.data, outkey->len); + ret = 0; + +out_free_tfm: + crypto_free_shash(tfm); +out: + kfree_sensitive(step.data); + kfree_sensitive(DR.data); + return ret; +} + /* * K1 = HMAC-SHA(key, 0x00000001 | label | 0x00 | k) * diff --git a/net/sunrpc/auth_gss/gss_krb5_mech.c b/net/sunrpc/auth_gss/gss_krb5_mech.c index 4e7cb49a06de..e616ec536265 100644 --- a/net/sunrpc/auth_gss/gss_krb5_mech.c +++ b/net/sunrpc/auth_gss/gss_krb5_mech.c @@ -166,6 +166,7 @@ static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = { .Ki_length = BITS2OCTETS(128),
.import_ctx = gss_krb5_import_ctx_v2, + .derive_key = krb5_kdf_feedback_cmac, .encrypt = gss_krb5_aes_encrypt, .decrypt = gss_krb5_aes_decrypt,
@@ -192,6 +193,7 @@ static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = { .Ki_length = BITS2OCTETS(256),
.import_ctx = gss_krb5_import_ctx_v2, + .derive_key = krb5_kdf_feedback_cmac, .encrypt = gss_krb5_aes_encrypt, .decrypt = gss_krb5_aes_decrypt,