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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 17/18] rxrpc: rxgk: Implement connection rekeying From: David Howells To: herbert@gondor.apana.org.au, bfields@fieldses.org Cc: dhowells@redhat.com, trond.myklebust@hammerspace.com, linux-crypto@vger.kernel.org, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 12 Nov 2020 13:00:05 +0000 Message-ID: <160518600537.2277919.5458566746685787619.stgit@warthog.procyon.org.uk> In-Reply-To: <160518586534.2277919.14475638653680231924.stgit@warthog.procyon.org.uk> References: <160518586534.2277919.14475638653680231924.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org Implement rekeying of connections with the RxGK security class. This involves regenerating the keys with a different key number as part of the input data after a certain amount of time or a certain amount of bytes encrypted. Rekeying may be triggered by either end. The LSW of the key number is inserted into the security-specific field in the RX header, and we try and expand it to 32-bits to make it last longer. Signed-off-by: David Howells --- net/rxrpc/ar-internal.h | 6 ++ net/rxrpc/conn_object.c | 2 + net/rxrpc/rxgk.c | 156 +++++++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 157 insertions(+), 7 deletions(-) diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index efdb3334ad88..3f2469714422 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -462,11 +462,15 @@ struct rxrpc_connection { u32 nonce; /* response re-use preventer */ } rxkad; struct { - struct rxgk_context *keys[1]; + struct rxgk_context *keys[4]; /* (Re-)keying buffer */ u64 start_time; /* The start time for TK derivation */ u8 nonce[20]; /* Response re-use preventer */ + u32 key_number; /* Current key number */ } rxgk; }; + rwlock_t security_lock; /* Lock allowing modification of security */ + struct mutex rekeying_lock; /* Lock allowing rekeying */ + unsigned long flags; unsigned long events; unsigned long idle_timestamp; /* Time at which last became idle */ diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c index 8dd1ef25b98f..ff60526d0e0f 100644 --- a/net/rxrpc/conn_object.c +++ b/net/rxrpc/conn_object.c @@ -47,6 +47,8 @@ struct rxrpc_connection *rxrpc_alloc_connection(gfp_t gfp) INIT_LIST_HEAD(&conn->link); skb_queue_head_init(&conn->rx_queue); conn->security = &rxrpc_no_security; + rwlock_init(&conn->security_lock); + mutex_init(&conn->rekeying_lock); spin_lock_init(&conn->state_lock); conn->debug_id = atomic_inc_return(&rxrpc_debug_id); conn->size_align = 4; diff --git a/net/rxrpc/rxgk.c b/net/rxrpc/rxgk.c index 703e46e8b508..0aa6da93b8d4 100644 --- a/net/rxrpc/rxgk.c +++ b/net/rxrpc/rxgk.c @@ -90,11 +90,153 @@ static void rxgk_describe_server_key(const struct key *key, struct seq_file *m) seq_printf(m, ": %s", krb5->name); } +/* + * Handle rekeying the connection when the we see our limits overrun or when + * the far side decided to rekey. + * + * Returns a ref on the context if successful or -ESTALE if the key is out of + * date. + */ +static struct rxgk_context *rxgk_rekey(struct rxrpc_connection *conn, + const u16 *specific_key_number) +{ + struct rxgk_context *gk, *dead = NULL; + unsigned int key_number, current_key, mask = ARRAY_SIZE(conn->rxgk.keys) - 1; + bool crank = false; + + _enter("%d", specific_key_number ? *specific_key_number : -1); + + mutex_lock(&conn->rekeying_lock); + + current_key = conn->rxgk.key_number; + if (!specific_key_number) { + key_number = current_key; + } else { + if (*specific_key_number == (u16)current_key) + key_number = current_key; + else if (*specific_key_number == (u16)(current_key - 1)) + key_number = current_key - 1; + else if (*specific_key_number == (u16)(current_key + 1)) + goto crank_window; + else + goto bad_key; + } + + gk = conn->rxgk.keys[key_number & mask]; + if (!gk) + goto generate_key; + if (!specific_key_number && + test_bit(RXGK_TK_NEEDS_REKEY, &gk->flags)) + goto crank_window; + +grab: + refcount_inc(&gk->usage); + mutex_unlock(&conn->rekeying_lock); + rxgk_put(dead); + return gk; + +crank_window: + if (current_key == UINT_MAX) + goto bad_key; + if (current_key + 1 == UINT_MAX) + set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags); + + key_number = current_key + 1; + if (WARN_ON(conn->rxgk.keys[key_number & mask])) + goto bad_key; + crank = true; + +generate_key: + gk = conn->rxgk.keys[current_key & mask]; + gk = rxgk_generate_transport_key(conn, gk->key, key_number, GFP_NOFS); + if (IS_ERR(gk)) { + mutex_unlock(&conn->rekeying_lock); + return gk; + } + + write_lock(&conn->security_lock); + if (crank) { + current_key++; + conn->rxgk.key_number = current_key; + dead = conn->rxgk.keys[(current_key - 2) & mask]; + conn->rxgk.keys[(current_key - 2) & mask] = NULL; + } + conn->rxgk.keys[current_key & mask] = gk; + write_unlock(&conn->security_lock); + goto grab; + +bad_key: + mutex_unlock(&conn->rekeying_lock); + return ERR_PTR(-ESTALE); +} + +/* + * Get the specified keying context. + * + * Returns a ref on the context if successful or -ESTALE if the key is out of + * date. + */ static struct rxgk_context *rxgk_get_key(struct rxrpc_connection *conn, - u16 *specific_key_number) + const u16 *specific_key_number) { - refcount_inc(&conn->rxgk.keys[0]->usage); - return conn->rxgk.keys[0]; + struct rxgk_context *gk; + unsigned int key_number, current_key, mask = ARRAY_SIZE(conn->rxgk.keys) - 1; + + _enter("{%u},%d", + conn->rxgk.key_number, specific_key_number ? *specific_key_number : -1); + + read_lock(&conn->security_lock); + + current_key = conn->rxgk.key_number; + if (!specific_key_number) { + key_number = current_key; + } else { + /* Only the bottom 16 bits of the key number are exposed in the + * header, so we try and keep the upper 16 bits in step. The + * whole 32 bits are used to generate the TK. + */ + if (*specific_key_number == (u16)current_key) + key_number = current_key; + else if (*specific_key_number == (u16)(current_key - 1)) + key_number = current_key - 1; + else if (*specific_key_number == (u16)(current_key + 1)) + goto rekey; + else + goto bad_key; + } + + gk = conn->rxgk.keys[key_number & mask]; + if (!gk) + goto slow_path; + if (!specific_key_number && + key_number < UINT_MAX) { + if (time_after(jiffies, gk->expiry) || + gk->bytes_remaining < 0) { + set_bit(RXGK_TK_NEEDS_REKEY, &gk->flags); + goto slow_path; + } + + if (test_bit(RXGK_TK_NEEDS_REKEY, &gk->flags)) + goto slow_path; + } + + refcount_inc(&gk->usage); + read_unlock(&conn->security_lock); + return gk; + +rekey: + _debug("rekey"); + if (current_key == UINT_MAX) + goto bad_key; + gk = conn->rxgk.keys[current_key & mask]; + if (gk) + set_bit(RXGK_TK_NEEDS_REKEY, &gk->flags); +slow_path: + read_unlock(&conn->security_lock); + return rxgk_rekey(conn, specific_key_number); +bad_key: + read_unlock(&conn->security_lock); + return ERR_PTR(-ESTALE); } /* @@ -106,7 +248,8 @@ static int rxgk_init_connection_security(struct rxrpc_connection *conn, struct rxgk_context *gk; int ret; - _enter("{%d},{%x}", conn->debug_id, key_serial(conn->params.key)); + _enter("{%d,%u},{%x}", + conn->debug_id, conn->rxgk.key_number, key_serial(conn->params.key)); conn->security_ix = token->security_index; conn->params.security_level = token->rxgk->level; @@ -116,10 +259,11 @@ static int rxgk_init_connection_security(struct rxrpc_connection *conn, do_div(conn->rxgk.start_time, 100); } - gk = rxgk_generate_transport_key(conn, token->rxgk, 0, GFP_NOFS); + gk = rxgk_generate_transport_key(conn, token->rxgk, conn->rxgk.key_number, + GFP_NOFS); if (IS_ERR(gk)) return PTR_ERR(gk); - conn->rxgk.keys[0] = gk; + conn->rxgk.keys[gk->key_number & 3] = gk; switch (conn->params.security_level) { case RXRPC_SECURITY_PLAIN: