98 lines
3.9 KiB
Markdown
98 lines
3.9 KiB
Markdown
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template: post
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title: nds-constrain't
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author: flewkey
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timestamp: 1594525504
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license: CC-BY
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Once upon a time, shutterbug2000 discovered nds-constrain't: a bug in Nintendo's
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NTR SSL library that allowed it's connections to be easily intercepted. This
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made it possible to connect to alternative online services without ROM patching.
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The bug itself is simple: the NDS SSL library does not care whether or not a
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certificate is authorized to act as a certificate authority. This means that
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— with any valid certificate — we can sign whatever we want, even a
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certificate under a false hostname.
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A guide to using this bug for fun and profit is now available on the
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[official page](https://github.com/KaeruTeam/nds-constraint), which is much
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better written than mine. However, you are free to keep reading this one.
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---
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### Getting the Wii client certificate
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As explained in the [official page](https://github.com/KaeruTeam/nds-constraint)
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for nds-constrain't, the Wii client certificate is signed by Nintendo and
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considered valid. Therefore, we can use it's key to sign whatever we want. You
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_could_ grab it from a Wii, but it is much easier to download it from
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[Larsenv's page](https://larsenv.github.io/NintendoCerts/index.html). You will
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want to use the link labelled "Wii NWC Prod 1", by the way.
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### Converting it to a useable format
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The file is a PKCS12, and we can't do anything useful with it until we extract
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the certificate and the private key. Thankfully, this is pretty simple.
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openssl pkcs12 -in WII_NWC_1_CERT.p12 -passin pass:alpine -passout pass:alpine -out keys.txt
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That command will export the X.509 certificate and private key from the archive,
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and store the output in keys.txt. They can then be copied into their appropriate
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files, which I will name NWC.crt and NWC.key.
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### Signing your certificate
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Instructions for this are listed on the official GitHub page, but I have copied
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them for reference. If I remember correctly, the DS can only handle the SHA-1
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and MD5 hash formats, so pay attention to the `-sha1` flag.
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openssl genrsa -out server.key 1024
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openssl req -new -key server.key -out server.csr
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openssl x509 -req -in server.csr -CA NWC.crt -CAkey NWC.key -CAcreateserial -out server.crt -days 3650 -sha1
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Your webserver probably wants the certificate chain as well, so let's generate
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that as well.
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cat server.crt NWC.crt > server-chain.crt
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We are ready to rock and roll!
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### Using your phony certificate
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Once the SSL certificate is installed, you may run into issues connecting with
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your DS. This because your NDS only knows how to use SSLv3, with the SHA-1 or
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MD5 cipher sets. Enabling SSLv3 and SHA-1 isn't always possible with webservers,
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so I recommend using NGINX as a reverse-proxy. To enable DS compatibility for
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NGINX, add the following lines to your NGINX configuration.
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ssl_protocols SSLv3;
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ssl_ciphers ECDHE-RSA-AES128-SHA;
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Most services on Nintendo consoles make liberal use of headers. Because of this,
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some extra options need to be enabled.
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underscores_in_headers on;
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proxy_pass_request_headers on;
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Because we have enabled insecure SSL settings on NGINX, you probably don't want
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to use it for any mission-critical web applications. If you continue having
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issues with NDS connectivity, please contact me.
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### Having fun
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The possibilities are infinite. Want to run services through a debugging proxy?
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Implement WFC protocols? Make a Flipnote Studio server? All of this is possible
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without ROM patches!
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---
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### Update
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After receiving some e-mails, I have learned that the NDS-supported ciphers have
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been disabled in OpenSSL versions past 1.0.2g, unless configured with
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"enable-weak-ssl-ciphers". This means that you may have to re-build NGINX (or
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mod_ssl for Apache) to get it working.
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If you have the means, I suggest taking Wireshark captures to find the cause of
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any SSL issues. Enabling debug logging in NGINX can also help you pinpoint
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handshake errors. If all else fails, you can find my e-mail on the about page.
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