fix: fallback use addr hostname as SNI for TLS socks proxied connection by circleous · Pull Request #6218 · projectdiscovery/nuclei

circleous · 2025-05-14T02:53:08Z

Proposed changes

Should fixes #6211. Nuclei scan with -proxy set to a socks5 proxy server produce tls: unrecognized name / tls: handshake failure. Not all hosts encounter this issue, but I found that most websites behind cloudflare have this tls issue.

The fixes is simply fallback to use hostname from addr string as ServerName (sni) for TLS Config.

Before

$ ./bin/nuclei -p socks5://127.0.0.1:1080 -u https://myipv4.addr.tools -t ~/nuclei-templates/http/technologies/tech-detect.yaml -duc  -debug
                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v3.4.3

                projectdiscovery.io

[INF] Current nuclei version: v3.4.3 (unknown) - remove '-duc' flag to enable update checks
[INF] Current nuclei-templates version: v10.2.1 (unknown) - remove '-duc' flag to enable update checks
[WRN] Scan results upload to cloud is disabled.
[INF] New templates added in latest release: 42
[INF] Templates loaded for current scan: 1
[INF] Executing 1 signed templates from projectdiscovery/nuclei-templates
[INF] Targets loaded for current scan: 1
[INF] [tech-detect] Dumped HTTP request for https://myipv4.addr.tools

GET / HTTP/1.1
Host: myipv4.addr.tools
User-Agent: Mozilla/5.0 (Debian; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36
Connection: close
Accept: */*
Accept-Language: en
Accept-Encoding: gzip

[WRN] [tech-detect] Could not execute request for https://myipv4.addr.tools: cause="tls: unrecognized name" chain="got err while executing https://myipv4.addr.tools"
[INF] Scan completed in 2.405888417s. No results found.

After

$ ./bin/nuclei -p socks5://127.0.0.1:1080 -u https://myipv4.addr.tools -t ~/nuclei-templates/http/technologies/tech-detect.yaml -duc  -debug

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v3.4.3

                projectdiscovery.io

[INF] Current nuclei version: v3.4.3 (unknown) - remove '-duc' flag to enable update checks
[INF] Current nuclei-templates version: v10.2.1 (unknown) - remove '-duc' flag to enable update checks
[WRN] Scan results upload to cloud is disabled.
[INF] New templates added in latest release: 42
[INF] Templates loaded for current scan: 1
[INF] Executing 1 signed templates from projectdiscovery/nuclei-templates
[INF] Targets loaded for current scan: 1
[INF] [tech-detect] Dumped HTTP request for https://myipv4.addr.tools

GET / HTTP/1.1
Host: myipv4.addr.tools
User-Agent: Mozilla/5.0 (Mac OS X 13_2) AppleWebKit/537.36 (KHTML, like Gecko) Edge/117.0 Safari/537.36
Connection: close
Accept: */*
Accept-Language: en
Accept-Encoding: gzip

[DBG] [tech-detect] Dumped HTTP response https://myipv4.addr.tools

HTTP/1.1 200 OK
Connection: close
Content-Length: 12
Access-Control-Allow-Origin: *
Alt-Svc: h3=":443"; ma=2592000
Cache-Control: no-store
Content-Type: text/plain
Date: Wed, 14 May 2025 02:17:38 GMT
Server: nginx

XX.XX.XX.XX
[tech-detect:nginx] [http] [info] https://myipv4.addr.tools
[INF] Scan completed in 1.003708s. 1 matches found.

Checklist

Pull request is created against the dev branch
All checks passed (lint, unit/integration/regression tests etc.) with my changes
I have added tests that prove my fix is effective or that my feature works
I have added necessary documentation (if appropriate)

Summary by CodeRabbit

Bug Fixes
- Improved TLS connection handling when using a SOCKS proxy by ensuring the server name is correctly set, enhancing connection reliability and security.

coderabbitai · 2025-05-14T02:53:16Z

Walkthrough

The change modifies the DialTLSContext function in the HTTP client pool to ensure that when using a SOCKS proxy and the TLS configuration lacks a server name, the server name is extracted from the address and set in the TLS configuration before establishing a connection.

Changes

File(s)	Change Summary
pkg/protocols/http/httpclientpool/clientpool.go	Added logic in `DialTLSContext` to set `tlsConfig.ServerName` from the address if it is empty when using a SOCKS proxy.

Sequence Diagram(s)

sequenceDiagram
    participant Caller
    participant ClientPool
    participant TLSConfig

    Caller->>ClientPool: DialTLSContext(addr, tlsConfig)
    alt Using SOCKS proxy and tlsConfig.ServerName is empty
        ClientPool->>ClientPool: Extract host from addr
        alt Extraction fails
            ClientPool-->>Caller: Return error
        else Extraction succeeds
            ClientPool->>TLSConfig: Set ServerName to host
        end
    end
    ClientPool->>Caller: Establish TLS connection with updated tlsConfig

Assessment against linked issues

Objective	Addressed	Explanation
Fix TLS handshake failure when using a SOCKS5 proxy by ensuring ServerName is set (#6211)	✅

Poem

In the warren of code, a bug did hide,
SOCKS5 and TLS, not side by side.
With host now set, the handshake’s complete,
No more errors, just connections neat!
A hop, a fix, a joyous cheer—
The rabbit’s code runs smooth this year! 🐇✨

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📥 Commits

Reviewing files that changed from the base of the PR and between 6d25a5c and 7968f4d.

📒 Files selected for processing (1)

pkg/protocols/http/httpclientpool/clientpool.go (1 hunks)

🔇 Additional comments (1)

pkg/protocols/http/httpclientpool/clientpool.go (1)

310-317: Excellent fix for TLS handshake issues when using SOCKS proxies

This is a solid fix for the TLS handshake failures occurring with SOCKS proxies. When the server name isn't explicitly set, extracting it from the address ensures proper SNI (Server Name Indication) during the TLS handshake, which is particularly important for sites behind Cloudflare.

The implementation correctly:

Checks if ServerName is empty

Extracts the host from the address

Sets it as the ServerName for the TLS config

The error handling is also appropriate, returning any errors from SplitHostPort.

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circleous · 2025-05-14T06:17:55Z

Hi @dogancanbakir, will it be possible to get this as hotfix or will need to wait for next month release? 🙇

dogancanbakir · 2025-05-14T06:27:23Z

Let's wait for review to be done, releasing is the easy part - no worries!

tarunKoyalwar

lgtm !

the core issue seems to be originiating from fastdialer which is not using proxyDialer when dialing tls connections projectdiscovery/fastdialer#457

once we resolve that we can remove this DialTLSContext override block completely

ehsandeep · 2025-05-15T11:17:57Z

thank you @circleous for identifying and fixing this issue.

dogancanbakir · 2025-05-15T12:52:58Z

@circleous Preparing for the release at #6224 once reviewed I will make the release, fyi.

fix: fallback set SNI to host if not specified when using socks proxy

7968f4d

auto-assign bot requested a review from dogancanbakir May 14, 2025 02:53

circleous changed the title ~~fix: fallback use default go net.DialTLS for socks proxied connection~~ fix: fallback use addr hostname as SNI for TLS socks proxied connection May 14, 2025

dogancanbakir approved these changes May 14, 2025

View reviewed changes

dogancanbakir requested a review from Mzack9999 May 14, 2025 03:11

tarunKoyalwar approved these changes May 15, 2025

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ehsandeep merged commit b03c304 into projectdiscovery:dev May 15, 2025
19 of 20 checks passed

ehsandeep removed the request for review from Mzack9999 May 15, 2025 11:16

BrewTestBot mentioned this pull request May 16, 2025

nuclei 3.4.4 Homebrew/homebrew-core#223740

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fix: fallback use addr hostname as SNI for TLS socks proxied connection#6218

fix: fallback use addr hostname as SNI for TLS socks proxied connection#6218
ehsandeep merged 1 commit intoprojectdiscovery:devfrom
circleous:tls-over-socks-proxy

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