[PATCH net 07/24] crypto/krb5: Add an API to alloc and prepare a crypto object

David Howells
2025-02-03T14:24:46Z

Add an API by which users of the krb5 crypto library can get an allocated
and keyed crypto object.

For encryption-mode operation, an AEAD object is returned; for
checksum-mode operation, a synchronous hash object is returned.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: "David S. Miller" <davem@davemloft.net>
cc: Chuck Lever <chuck.lever@oracle.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-crypto@vger.kernel.org
cc: netdev@vger.kernel.org
---
crypto/krb5/internal.h | 10 +++
crypto/krb5/krb5_api.c | 144 +++++++++++++++++++++++++++++++++++++++++
include/crypto/krb5.h | 7 ++
3 files changed, 161 insertions(+)

diff --git a/crypto/krb5/internal.h b/crypto/krb5/internal.h
index 3ede858be4f7..b542d24e5fa5 100644
--- a/crypto/krb5/internal.h
+++ b/crypto/krb5/internal.h
@@ -110,3 +110,13 @@ struct krb5_crypto_profile {
#define krb5_digest_size(TFM) \
crypto_roundup(crypto_shash_digestsize(TFM))
#define round16(x) (((x) + 15) & ~15)
+
+/*
+ * krb5_api.c
+ */
+struct crypto_aead *krb5_prepare_encryption(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *keys,
+ gfp_t gfp);
+struct crypto_shash *krb5_prepare_checksum(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *Kc,
+ gfp_t gfp);
diff --git a/crypto/krb5/krb5_api.c b/crypto/krb5/krb5_api.c
index f6d1bc813daa..f7f2528b3895 100644
--- a/crypto/krb5/krb5_api.c
+++ b/crypto/krb5/krb5_api.c
@@ -148,3 +148,147 @@ void crypto_krb5_where_is_the_data(const struct krb5_enctype *krb5,
}
}
EXPORT_SYMBOL(crypto_krb5_where_is_the_data);
+
+/*
+ * Prepare the encryption with derived key data.
+ */
+struct crypto_aead *krb5_prepare_encryption(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *keys,
+ gfp_t gfp)
+{
+ struct crypto_aead *ci = NULL;
+ int ret = -ENOMEM;
+
+ ci = crypto_alloc_aead(krb5->encrypt_name, 0, 0);
+ if (IS_ERR(ci)) {
+ ret = PTR_ERR(ci);
+ if (ret == -ENOENT)
+ ret = -ENOPKG;
+ goto err;
+ }
+
+ ret = crypto_aead_setkey(ci, keys->data, keys->len);
+ if (ret < 0) {
+ pr_err("Couldn't set AEAD key %s: %d\n", krb5->encrypt_name, ret);
+ goto err_ci;
+ }
+
+ ret = crypto_aead_setauthsize(ci, krb5->cksum_len);
+ if (ret < 0) {
+ pr_err("Couldn't set AEAD authsize %s: %d\n", krb5->encrypt_name, ret);
+ goto err_ci;
+ }
+
+ return ci;
+err_ci:
+ crypto_free_aead(ci);
+err:
+ return ERR_PTR(ret);
+}
+
+/**
+ * crypto_krb5_prepare_encryption - Prepare AEAD crypto object for encryption-mode
+ * @krb5: The encoding to use.
+ * @TK: The transport key to use.
+ * @usage: The usage constant for key derivation.
+ * @gfp: Allocation flags.
+ *
+ * Allocate a crypto object that does all the necessary crypto, key it and set
+ * its parameters and return the crypto handle to it. This can then be used to
+ * dispatch encrypt and decrypt operations.
+ */
+struct crypto_aead *crypto_krb5_prepare_encryption(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage, gfp_t gfp)
+{
+ struct crypto_aead *ci = NULL;
+ struct krb5_buffer keys = {};
+ int ret;
+
+ ret = krb5->profile->derive_encrypt_keys(krb5, TK, usage, &keys, gfp);
+ if (ret < 0)
+ goto err;
+
+ ci = krb5_prepare_encryption(krb5, &keys, gfp);
+ if (IS_ERR(ci)) {
+ ret = PTR_ERR(ci);
+ goto err;
+ }
+
+ kfree(keys.data);
+ return ci;
+err:
+ kfree(keys.data);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(crypto_krb5_prepare_encryption);
+
+/*
+ * Prepare the checksum with derived key data.
+ */
+struct crypto_shash *krb5_prepare_checksum(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *Kc,
+ gfp_t gfp)
+{
+ struct crypto_shash *ci = NULL;
+ int ret = -ENOMEM;
+
+ ci = crypto_alloc_shash(krb5->cksum_name, 0, 0);
+ if (IS_ERR(ci)) {
+ ret = PTR_ERR(ci);
+ if (ret == -ENOENT)
+ ret = -ENOPKG;
+ goto err;
+ }
+
+ ret = crypto_shash_setkey(ci, Kc->data, Kc->len);
+ if (ret < 0) {
+ pr_err("Couldn't set shash key %s: %d\n", krb5->cksum_name, ret);
+ goto err_ci;
+ }
+
+ return ci;
+err_ci:
+ crypto_free_shash(ci);
+err:
+ return ERR_PTR(ret);
+}
+
+/**
+ * crypto_krb5_prepare_checksum - Prepare AEAD crypto object for checksum-mode
+ * @krb5: The encoding to use.
+ * @TK: The transport key to use.
+ * @usage: The usage constant for key derivation.
+ * @gfp: Allocation flags.
+ *
+ * Allocate a crypto object that does all the necessary crypto, key it and set
+ * its parameters and return the crypto handle to it. This can then be used to
+ * dispatch get_mic and verify_mic operations.
+ */
+struct crypto_shash *crypto_krb5_prepare_checksum(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage, gfp_t gfp)
+{
+ struct crypto_shash *ci = NULL;
+ struct krb5_buffer keys = {};
+ int ret;
+
+ ret = krb5->profile->derive_checksum_key(krb5, TK, usage, &keys, gfp);
+ if (ret < 0) {
+ pr_err("get_Kc failed %d\n", ret);
+ goto err;
+ }
+
+ ci = krb5_prepare_checksum(krb5, &keys, gfp);
+ if (IS_ERR(ci)) {
+ ret = PTR_ERR(ci);
+ goto err;
+ }
+
+ kfree(keys.data);
+ return ci;
+err:
+ kfree(keys.data);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(crypto_krb5_prepare_checksum);
diff --git a/include/crypto/krb5.h b/include/crypto/krb5.h
index b414141b8b42..94af2c558fa1 100644
--- a/include/crypto/krb5.h
+++ b/include/crypto/krb5.h
@@ -10,6 +10,7 @@

#include <linux/crypto.h>
#include <crypto/aead.h>
+#include <crypto/hash.h>

struct crypto_shash;
struct scatterlist;
@@ -110,5 +111,11 @@ size_t crypto_krb5_how_much_data(const struct krb5_enctype *krb5,
void crypto_krb5_where_is_the_data(const struct krb5_enctype *krb5,
enum krb5_crypto_mode mode,
size_t *_offset, size_t *_len);
+struct crypto_aead *crypto_krb5_prepare_encryption(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage, gfp_t gfp);
+struct crypto_shash *crypto_krb5_prepare_checksum(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage, gfp_t gfp);

#endif /* _CRYPTO_KRB5_H */