# README

Let's Debug

Let's Debug is a diagnostic website, API, CLI and Go package for quickly and accurately finding and reporting issues for any domain that may prevent issuance of a Let's Encrypt SSL certificate for any ACME validation method.

It is motivated by this community thread.

Status

Currently deployed to letsdebug.net and regularly in use.

Problems Detected

Name	Description	Examples
InvalidMethod, ValidationMethodDisabled, ValidationMethodNotSuitable	Checks the ACME validation method is valid and usable for the provided domain name.	Example
InvalidDomain	Checks the domain is a valid domain name on a public TLD.	Example
StatusNotOperational	Checks that the Let's Encrypt service is not experiencing an outage, according to status.io	-
DNSLookupFailed, TXTRecordError	Checks that the Unbound resolver (via libunbound) is able to resolve a variety records relevant to Let's Encrypt. Discovers problems such as DNSSEC issues, 0x20 mixed case randomization, timeouts etc, in the spirit of jsha's unboundtest.com	Example
CAAIssuanceNotAllowed	Checks that no CAA records are preventing the issuance of Let's Encrypt certificates.	Example
CAACriticalUnknown	Checks that no CAA critical flags unknown to Let's Encrypt are used	-
RateLimit	Checks that the domain name is not currently affected by any of the domain-based rate limits imposed by Let's Encrypt, using the public certwatch Postgres interface from Comodo's crt.sh.	Example
NoRecords, ReservedAddress	Checks that sufficient valid A/AAAA records are present to perform HTTP-01 validation	Example
BadRedirect	Checks that no bad HTTP redirects are present. Discovers redirects that aren't accessible, unacceptable ports, unacceptable schemes, accidental missing trailing slash on redirect.	Example
WebserverMisconfiguration	Checks whether the server is serving the wrong protocol on the wrong port as the result of an HTTP-01 validation request.	-
ANotWorking, AAAANotWorking	Checks whether listed IP addresses are not functioning properly for HTTP-01 validation, including timeouts and other classes of network and HTTP errors.	Example
MultipleIPAddressDiscrepancy	For domains with multiple A/AAAA records, checks whether there are major discrepancies between the server responses to reveal when the addresses may be pointing to different servers accidentally.	Example
CloudflareCDN	Checks whether the domain is being served via Cloudflare's proxy service (and therefore SSL termination is occurring at Cloudflare)	-
CloudflareSSLNotProvisioned	Checks whether the domain has its SSL terminated by Cloudflare and Cloudflare has not provisioned a certificate yet (leading to a TLS handshake error).	Example
IssueFromLetsEncrypt	Attempts to detect issues with a high degree of accuracy via the Let's Encrypt v2 staging service by attempting to perform an authorization for the domain. Discovers issues such as CA-based domain blacklists & other policies, specific networking issues.	Example
TXTDoubleLabel	Checks for the presence of records that are doubled up (e.g. `_acme-challenge.example.org.example.org`). Usually indicates that the user has been incorrectly creating records in their DNS user interface.	Example
PortForwarding	Checks whether the domain is serving a modem-router administrative interface instead of an intended webserver, which is indicative of a port-forwarding misconfiguration.	Example
SanctionedDomain	Checks whether the Registered Domain is present on the USG OFAC SDN List. Updated daily.	Example
BlockedByNginxTestCookie	Checks whether the HTTP-01 validation requests are being intercepted by testcookie-nginx-module.	Example
HttpOnHttpsPort	Checks whether the server reported receiving an HTTP request on an HTTPS-only port	Example
BlockedByFirewall	Checks whether HTTP-01 validation requests are being blocked by Palo Alto firewall devices	Example
UnexpectedHttpResponse	Checks whether HTTP-01 validation requests are being answered with unusual HTTP response codes	Example

Web API Usage

There is a JSON-based API available as part of the web frontend.

Submitting a test

$ curl --data '{"method":"http-01","domain":"example.com"}' -H 'content-type: application/json' https://letsdebug.net

{"Domain":"example.com","ID":674477}

Submitting a test with custom options

curl --data '{"method":"http-01","domain":"example.com","options":{"http_request_path":"custom-path","http_expect_response":"abc123"}}' -H 'content-type: application/json' https://letsdebug.net

Available options are as follows:

Option	Description
`http_request_path`	What path within `/.well-known/acme-challenge/` to use instead of `letsdebug-test` (default) for the HTTP check. Max length 255.
`http_expect_response`	What exact response to expect from each server during the HTTP check. By default, no particular response is expected. If present and the response does not match, the test will fail with an Error severity. It is highly recommended to always use a completely random value. Max length 255.

Viewing tests

$ curl -H 'accept: application/json' https://letsdebug.net/example.com/674477

{"id":674477,"domain":"example.com","method":"http-01","status":"Complete","created_at":"2021-09-08T04:02:26.416259Z","started_at":"2021-09-08T04:02:26.419336Z","completed_at":"2021-09-08T04:02:30.529766Z","result":{}}

or to view all recent tests

$ curl -H 'accept: application/json' https://letsdebug.net/example.com

Performing a query against the Certwatch database

$ curl "https://letsdebug.net/certwatch-query?q=<urlencoded SQL query>"

{
  "query": "select c.id as crtsh_id, x509_subjectName(c.CERTIFICATE), x509_notAfter(c.CERTIFICATE) from certificate c where x509_notAfter(c.CERTIFICATE) = '2018-06-01 16:25:44' AND x509_issuerName(c.CERTIFICATE) LIKE 'C=US, O=Let''s Encrypt%';",
  "results": [
    {
      "crtsh_id": 346300797,
      "x509_notafter": "2018-06-01T16:25:44Z",
      "x509_subjectname": "CN=hivdatingzimbabwe.com"
    },
    /* ... */
  ]
}

CLI Usage

You can download binaries for tagged releases for Linux for both the CLi and the server from the releases page.

letsdebug-cli -domain example.org -method http-01 -debug

Library Usage


import "github.com/letsdebug/letsdebug"

problems, _ := letsdebug.Check("example.org", letsdebug.HTTP01)

Installation

Dependencies

This package relies on a fairly recent version of libunbound.

On Debian-based distributions:

apt install libunbound8 libunbound-dev
On EL-based distributions, you may need to build from source because the packages are ancient on e.g. CentOS, but you can try:

yum install unbound-libs unbound-devel
On OSX, Homebrew contains the latest version of unbound:

brew install unbound

You will also need Go's dep dependency manager.

Releases

You can save time by downloading tagged releases for 64-bit Linux. Keep in mind you will still need to have libunbound present on your system.

Building

go get -u github.com/letsdebug/letsdebug/...
cd $GOPATH/src/github.com/letsdebug/letsdebug
make clean letsdebug-cli letsdebug-server

Contributing

Any contributions containing JavaScript will be discarded, but other feedback, bug reports, suggestions and enhancements are welcome - please open an issue first.