74 lines
2.1 KiB
C
74 lines
2.1 KiB
C
/*
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* Copyright (C) 2022 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <linux/types.h>
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#include <linux/bpf.h>
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#include <netinet/in.h>
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#include <stdint.h>
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// The resulting .o needs to load on the Android T beta 3 bpfloader
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#define BPFLOADER_MIN_VER BPFLOADER_T_BETA3_VERSION
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#include "bpf_helpers.h"
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#define ALLOW 1
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#define DISALLOW 0
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DEFINE_BPF_MAP_GRW(blocked_ports_map, ARRAY, int, uint64_t,
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1024 /* 64K ports -> 1024 u64s */, AID_SYSTEM)
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static inline __always_inline int block_port(struct bpf_sock_addr *ctx) {
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if (!ctx->user_port) return ALLOW;
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switch (ctx->protocol) {
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case IPPROTO_TCP:
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case IPPROTO_MPTCP:
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case IPPROTO_UDP:
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case IPPROTO_UDPLITE:
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case IPPROTO_DCCP:
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case IPPROTO_SCTP:
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break;
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default:
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return ALLOW; // unknown protocols are allowed
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}
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int key = ctx->user_port >> 6;
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int shift = ctx->user_port & 63;
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uint64_t *val = bpf_blocked_ports_map_lookup_elem(&key);
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// Lookup should never fail in reality, but if it does return here to keep the
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// BPF verifier happy.
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if (!val) return ALLOW;
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if ((*val >> shift) & 1) return DISALLOW;
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return ALLOW;
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}
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DEFINE_BPF_PROG_KVER("bind4/block_port", AID_ROOT, AID_SYSTEM,
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bind4_block_port, KVER(5, 4, 0))
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(struct bpf_sock_addr *ctx) {
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return block_port(ctx);
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}
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DEFINE_BPF_PROG_KVER("bind6/block_port", AID_ROOT, AID_SYSTEM,
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bind6_block_port, KVER(5, 4, 0))
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(struct bpf_sock_addr *ctx) {
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return block_port(ctx);
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}
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LICENSE("Apache 2.0");
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CRITICAL("ConnectivityNative");
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