crypto/krb5: Add an API to perform requests

Add an API by which users of the krb5 crypto library can perform crypto
requests, such as encrypt, decrypt, get_mic and verify_mic. These
functions take the previously prepared crypto objects to work on.

Signed-off-by: David Howells <[e-mail]>
cc: Herbert Xu <[e-mail]>
cc: "David S. Miller" <[e-mail]>
cc: Chuck Lever <[e-mail]>
cc: Marc Dionne <[e-mail]>
cc: Eric Dumazet <[e-mail]>
cc: Jakub Kicinski <[e-mail]>
cc: Paolo Abeni <[e-mail]>
cc: Simon Horman <[e-mail]>
cc: [e-mail]
cc: [e-mail]
cc: [e-mail]
cc: [e-mail]

crypto/krb5/krb5_api.c

···
 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(crypto_krb5_prepare_checksum);
+
+/**
+ * crypto_krb5_encrypt - Apply Kerberos encryption and integrity.
+ * @krb5: The encoding to use.
+ * @aead: The keyed crypto object to use.
+ * @sg: Scatterlist defining the crypto buffer.
+ * @nr_sg: The number of elements in @sg.
+ * @sg_len: The size of the buffer.
+ * @data_offset: The offset of the data in the @sg buffer.
+ * @data_len: The length of the data.
+ * @preconfounded: True if the confounder is already inserted.
+ *
+ * Using the specified Kerberos encoding, insert a confounder and padding as
+ * needed, encrypt this and the data in place and insert an integrity checksum
+ * into the buffer.
+ *
+ * The buffer must include space for the confounder, the checksum and any
+ * padding required.  The caller can preinsert the confounder into the buffer
+ * (for testing, for example).
+ *
+ * The resulting secured blob may be less than the size of the buffer.
+ *
+ * Returns the size of the secure blob if successful, -ENOMEM on an allocation
+ * failure, -EFAULT if there is insufficient space, -EMSGSIZE if the confounder
+ * is too short or the data is misaligned.  Other errors may also be returned
+ * from the crypto layer.
+ */
+ssize_t crypto_krb5_encrypt(const struct krb5_enctype *krb5,
+			    struct crypto_aead *aead,
+			    struct scatterlist *sg, unsigned int nr_sg,
+			    size_t sg_len,
+			    size_t data_offset, size_t data_len,
+			    bool preconfounded)
+{
+	if (WARN_ON(data_offset > sg_len ||
+		    data_len > sg_len ||
+		    data_offset > sg_len - data_len))
+		return -EMSGSIZE;
+	return krb5->profile->encrypt(krb5, aead, sg, nr_sg, sg_len,
+				      data_offset, data_len, preconfounded);
+}
+EXPORT_SYMBOL(crypto_krb5_encrypt);
+
+/**
+ * crypto_krb5_decrypt - Validate and remove Kerberos encryption and integrity.
+ * @krb5: The encoding to use.
+ * @aead: The keyed crypto object to use.
+ * @sg: Scatterlist defining the crypto buffer.
+ * @nr_sg: The number of elements in @sg.
+ * @_offset: Offset of the secure blob in the buffer; updated to data offset.
+ * @_len: The length of the secure blob; updated to data length.
+ *
+ * Using the specified Kerberos encoding, check and remove the integrity
+ * checksum and decrypt the secure region, stripping off the confounder.
+ *
+ * If successful, @_offset and @_len are updated to outline the region in which
+ * the data plus the trailing padding are stored.  The caller is responsible
+ * for working out how much padding there is and removing it.
+ *
+ * Returns the 0 if successful, -ENOMEM on an allocation failure; sets
+ * *_error_code and returns -EPROTO if the data cannot be parsed, or -EBADMSG
+ * if the integrity checksum doesn't match).  Other errors may also be returned
+ * from the crypto layer.
+ */
+int crypto_krb5_decrypt(const struct krb5_enctype *krb5,
+			struct crypto_aead *aead,
+			struct scatterlist *sg, unsigned int nr_sg,
+			size_t *_offset, size_t *_len)
+{
+	return krb5->profile->decrypt(krb5, aead, sg, nr_sg, _offset, _len);
+}
+EXPORT_SYMBOL(crypto_krb5_decrypt);
+
+/**
+ * crypto_krb5_get_mic - Apply Kerberos integrity checksum.
+ * @krb5: The encoding to use.
+ * @shash: The keyed hash to use.
+ * @metadata: Metadata to add into the hash before adding the data.
+ * @sg: Scatterlist defining the crypto buffer.
+ * @nr_sg: The number of elements in @sg.
+ * @sg_len: The size of the buffer.
+ * @data_offset: The offset of the data in the @sg buffer.
+ * @data_len: The length of the data.
+ *
+ * Using the specified Kerberos encoding, calculate and insert an integrity
+ * checksum into the buffer.
+ *
+ * The buffer must include space for the checksum at the front.
+ *
+ * Returns the size of the secure blob if successful, -ENOMEM on an allocation
+ * failure, -EFAULT if there is insufficient space, -EMSGSIZE if the gap for
+ * the checksum is too short.  Other errors may also be returned from the
+ * crypto layer.
+ */
+ssize_t crypto_krb5_get_mic(const struct krb5_enctype *krb5,
+			    struct crypto_shash *shash,
+			    const struct krb5_buffer *metadata,
+			    struct scatterlist *sg, unsigned int nr_sg,
+			    size_t sg_len,
+			    size_t data_offset, size_t data_len)
+{
+	if (WARN_ON(data_offset > sg_len ||
+		    data_len > sg_len ||
+		    data_offset > sg_len - data_len))
+		return -EMSGSIZE;
+	return krb5->profile->get_mic(krb5, shash, metadata, sg, nr_sg, sg_len,
+				      data_offset, data_len);
+}
+EXPORT_SYMBOL(crypto_krb5_get_mic);
+
+/**
+ * crypto_krb5_verify_mic - Validate and remove Kerberos integrity checksum.
+ * @krb5: The encoding to use.
+ * @shash: The keyed hash to use.
+ * @metadata: Metadata to add into the hash before adding the data.
+ * @sg: Scatterlist defining the crypto buffer.
+ * @nr_sg: The number of elements in @sg.
+ * @_offset: Offset of the secure blob in the buffer; updated to data offset.
+ * @_len: The length of the secure blob; updated to data length.
+ *
+ * Using the specified Kerberos encoding, check and remove the integrity
+ * checksum.
+ *
+ * If successful, @_offset and @_len are updated to outline the region in which
+ * the data is stored.
+ *
+ * Returns the 0 if successful, -ENOMEM on an allocation failure; sets
+ * *_error_code and returns -EPROTO if the data cannot be parsed, or -EBADMSG
+ * if the checksum doesn't match).  Other errors may also be returned from the
+ * crypto layer.
+ */
+int crypto_krb5_verify_mic(const struct krb5_enctype *krb5,
+			   struct crypto_shash *shash,
+			   const struct krb5_buffer *metadata,
+			   struct scatterlist *sg, unsigned int nr_sg,
+			   size_t *_offset, size_t *_len)
+{
+	return krb5->profile->verify_mic(krb5, shash, metadata, sg, nr_sg,
+					 _offset, _len);
+}
+EXPORT_SYMBOL(crypto_krb5_verify_mic);

include/crypto/krb5.h

···
 struct crypto_shash *crypto_krb5_prepare_checksum(const struct krb5_enctype *krb5,
 						  const struct krb5_buffer *TK,
 						  u32 usage, gfp_t gfp);
+ssize_t crypto_krb5_encrypt(const struct krb5_enctype *krb5,
+			    struct crypto_aead *aead,
+			    struct scatterlist *sg, unsigned int nr_sg,
+			    size_t sg_len,
+			    size_t data_offset, size_t data_len,
+			    bool preconfounded);
+int crypto_krb5_decrypt(const struct krb5_enctype *krb5,
+			struct crypto_aead *aead,
+			struct scatterlist *sg, unsigned int nr_sg,
+			size_t *_offset, size_t *_len);
+ssize_t crypto_krb5_get_mic(const struct krb5_enctype *krb5,
+			    struct crypto_shash *shash,
+			    const struct krb5_buffer *metadata,
+			    struct scatterlist *sg, unsigned int nr_sg,
+			    size_t sg_len,
+			    size_t data_offset, size_t data_len);
+int crypto_krb5_verify_mic(const struct krb5_enctype *krb5,
+			   struct crypto_shash *shash,
+			   const struct krb5_buffer *metadata,
+			   struct scatterlist *sg, unsigned int nr_sg,
+			   size_t *_offset, size_t *_len);
 
 #endif /* _CRYPTO_KRB5_H */