From: David Howells Date: Fri, 11 Apr 2025 09:52:54 +0000 (+0100) Subject: rxrpc: rxgk: Implement connection rekeying X-Git-Tag: v6.16-rc1~132^2~308^2~5 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7a7513a3081c6a2729d8570c77bbed1978277dc9;p=thirdparty%2Fkernel%2Flinux.git 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 cc: Marc Dionne cc: Herbert Xu cc: Chuck Lever cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20250411095303.2316168-10-dhowells@redhat.com Signed-off-by: Jakub Kicinski --- diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h index aab81e8196aee..920439df1f6fe 100644 --- a/include/trace/events/rxrpc.h +++ b/include/trace/events/rxrpc.h @@ -2725,6 +2725,30 @@ TRACE_EVENT(rxrpc_rack_timer, ktime_to_us(__entry->delay)) ); +TRACE_EVENT(rxrpc_rxgk_rekey, + TP_PROTO(struct rxrpc_connection *conn, + unsigned int current_key, unsigned int requested_key), + + TP_ARGS(conn, current_key, requested_key), + + TP_STRUCT__entry( + __field(unsigned int, conn) + __field(unsigned int, current_key) + __field(unsigned int, requested_key) + ), + + TP_fast_assign( + __entry->conn = conn->debug_id; + __entry->current_key = current_key; + __entry->requested_key = requested_key; + ), + + TP_printk("C=%08x cur=%x req=%x", + __entry->conn, + __entry->current_key, + __entry->requested_key) + ); + #undef EM #undef E_ diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 57ea6d61b7a2a..fd235bfa226d7 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -565,13 +565,16 @@ 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 enctype; /* Kerberos 5 encoding type */ + u32 key_number; /* Current key number */ } rxgk; }; + rwlock_t security_use_lock; /* Security use/modification lock */ struct sk_buff *tx_response; /* Response packet to be transmitted */ + 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 d14a802d2001f..37340becb224d 100644 --- a/net/rxrpc/conn_object.c +++ b/net/rxrpc/conn_object.c @@ -73,6 +73,7 @@ struct rxrpc_connection *rxrpc_alloc_connection(struct rxrpc_net *rxnet, skb_queue_head_init(&conn->rx_queue); conn->rxnet = rxnet; conn->security = &rxrpc_no_security; + rwlock_init(&conn->security_use_lock); spin_lock_init(&conn->state_lock); conn->debug_id = atomic_inc_return(&rxrpc_debug_id); conn->idle_timestamp = jiffies; diff --git a/net/rxrpc/rxgk.c b/net/rxrpc/rxgk.c index 02752eeb23954..8b1ccdf8bc58e 100644 --- a/net/rxrpc/rxgk.c +++ b/net/rxrpc/rxgk.c @@ -76,11 +76,155 @@ 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 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->security_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->security_lock); + rxgk_put(dead); + return gk; + +crank_window: + trace_rxrpc_rxgk_rekey(conn, current_key, + specific_key_number ? *specific_key_number : -1); + 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->security_lock); + return gk; + } + + write_lock(&conn->security_use_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_use_lock); + goto grab; + +bad_key: + mutex_unlock(&conn->security_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_use_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_use_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_use_lock); + return rxgk_rekey(conn, specific_key_number); +bad_key: + read_unlock(&conn->security_use_lock); + return ERR_PTR(-ESTALE); } /* @@ -92,7 +236,8 @@ 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->key)); + _enter("{%d,%u},{%x}", + conn->debug_id, conn->rxgk.key_number, key_serial(conn->key)); conn->security_ix = token->security_index; conn->security_level = token->rxgk->level; @@ -102,11 +247,12 @@ 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.enctype = gk->krb5->etype; - conn->rxgk.keys[0] = gk; + conn->rxgk.keys[gk->key_number & 3] = gk; switch (conn->security_level) { case RXRPC_SECURITY_PLAIN: