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Date: Thu, 12 Nov 2020 13:00:05 +0000
From: David Howells <dhowells@...hat.com>
To: herbert@...dor.apana.org.au, bfields@...ldses.org
Cc: dhowells@...hat.com, trond.myklebust@...merspace.com,
linux-crypto@...r.kernel.org, linux-afs@...ts.infradead.org,
linux-cifs@...r.kernel.org, linux-nfs@...r.kernel.org,
linux-fsdevel@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 17/18] rxrpc: rxgk: Implement connection rekeying
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 <dhowells@...hat.com>
---
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:
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