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Message-ID: <2620780.1589289425@warthog.procyon.org.uk>
Date: Tue, 12 May 2020 14:17:05 +0100
From: David Howells <dhowells@...hat.com>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: dhowells@...hat.com, keyrings@...r.kernel.org,
linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
Greg KH <gregkh@...uxfoundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
kernel-hardening@...ts.openwall.com,
Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH v3] security/keys: rewrite big_key crypto to use library interface
Jason A. Donenfeld <Jason@...c4.com> wrote:
> - /* no ->update(); don't add it without changing big_key_crypt() nonce */
> + /* no ->update(); don't add it without changing chacha20poly1305's nonce
Note that ->update() doesn't have to modify the contents of the key, but can
just rather replace them entirely. See attached. The actual work is done in
big_key_preparse(); all big_key_update() has to do is apply it and dispose of
the old payload.
David
---
commit 724e76c185d517f35ead4f72f9958850c9218f4d
Author: David Howells <dhowells@...hat.com>
Date: Tue May 12 14:03:53 2020 +0100
keys: Implement update for the big_key type
Implement the ->update op for the big_key type.
Signed-off-by: David Howells <dhowells@...hat.com>
diff --git a/include/keys/big_key-type.h b/include/keys/big_key-type.h
index 3fee04f81439..988d90d77f53 100644
--- a/include/keys/big_key-type.h
+++ b/include/keys/big_key-type.h
@@ -18,5 +18,6 @@ extern void big_key_revoke(struct key *key);
extern void big_key_destroy(struct key *key);
extern void big_key_describe(const struct key *big_key, struct seq_file *m);
extern long big_key_read(const struct key *key, char *buffer, size_t buflen);
+extern int big_key_update(struct key *key, struct key_preparsed_payload *prep);
#endif /* _KEYS_BIG_KEY_TYPE_H */
diff --git a/security/keys/big_key.c b/security/keys/big_key.c
index d43f3daab2b8..dd708e8f13c0 100644
--- a/security/keys/big_key.c
+++ b/security/keys/big_key.c
@@ -47,7 +47,7 @@ struct key_type key_type_big_key = {
.destroy = big_key_destroy,
.describe = big_key_describe,
.read = big_key_read,
- /* no ->update(); don't add it without changing chacha20poly1305's nonce */
+ .update = big_key_update,
};
/*
@@ -191,6 +191,23 @@ void big_key_destroy(struct key *key)
key->payload.data[big_key_data] = NULL;
}
+/*
+ * Update a big key
+ */
+int big_key_update(struct key *key, struct key_preparsed_payload *prep)
+{
+ int ret;
+
+ ret = key_payload_reserve(key, prep->datalen);
+ if (ret < 0)
+ return ret;
+
+ if (key_is_positive(key))
+ big_key_destroy(key);
+
+ return generic_key_instantiate(key, prep);
+}
+
/*
* describe the big_key key
*/
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