From: Chuck Lever <chuck.lever@xxxxxxxxxx>
The Camellia enctypes use the KDF_FEEDBACK_CMAC Key Derivation
Function defined in RFC 6803 Section 3.
Tested-by: Scott Mayhew <smayhew@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
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,
