TLS connection to marmalade-repo.org:443 is insecure after updating to Emacs 25

Question

When I run M-x list-packages I get the following error with Marmalade after updating to Emacs 25.

Certificate information
Issued by:          COMODO RSA Domain Validation Secure Server CA
Issued to:          Domain Control Validated
Hostname:           marmalade-repo.org
Public key:         RSA, signature: RSA-SHA256
Protocol:           TLS1.2, key: ECDHE-RSA, cipher: AES-256-GCM, mac: AEAD
Security level:     Medium
Valid:              From 2015-07-12 to 2018-07-11


The TLS connection to marmalade-repo.org:443 is insecure for the
following reasons:

the certificate was signed by an unknown and therefore untrusted authority
certificate could not be verified

Relevant .emacs code: (full .emacs here)

(require 'package)
(add-to-list 'package-archives
         '("melpa" . "http://melpa.org/packages/") t)
(add-to-list 'package-archives
         '("gnu" . "http://elpa.gnu.org/packages/") t)
(add-to-list 'package-archives
         '("marmalade" . "http://marmalade-repo.org/packages/") t)
(package-initialize)

;; bootstrap use-package
;; https://github.com/jwiegley/use-package/
(unless (package-installed-p 'use-package)
  (package-refresh-contents)
  (package-install 'use-package))
(eval-when-compile (require 'use-package))

I've also tried to solve it with gnutils-cli suggestion: $ gnutls-cli --tofu marmalade-repo.org but couldn't make it work yet. Any ideas?

$ gnutls-cli --tofu marmalade-repo.org
gnutls-cli --tofu marmalade-repo.org                                                                              
Processed 173 CA certificate(s).                                                                                                      
Resolving 'marmalade-repo.org:443'...                                                                                                 
Connecting to '80.69.77.43:443'...                                                                                                    
- Certificate type: X.509                                                                                                             
- Got a certificate list of 1 certificates.                                                                                           
- Certificate[0] info:                                                                                                                
 - subject `CN=marmalade-repo.org,OU=PositiveSSL,OU=Domain Control Validated', issuer `CN=COMODO RSA Domain Validation Secure Server C
A,O=COMODO CA Limited,L=Salford,ST=Greater Manchester,C=GB', serial 0x5f7ce5cf6602297b4cbd14639b670e7d, RSA key 2048 bits, signed usin
g RSA-SHA256, activated `2015-07-12 00:00:00 UTC', expires `2018-07-11 23:59:59 UTC', SHA-1 fingerprint `6e080a477d14631d2edf839de582a
c04d4363d09'                                                                                                                          
        Public Key ID:                                                                                                                
                aba6d76ab3d363fa190d654160236eefd32a46dc                                                                              
        Public key's random art:                                                                                                      
                +--[ RSA 2048]----+
                |      . +oo      |
                |     . o . .     |
                |      o   o      |
                |     . . o       |
                |     . .S        |
                |      o.E=       |
                |     . o= o      |
                |      O.==       |
                |    .*=X+.       |
                +-----------------+

- Status: The certificate is NOT trusted. The certificate issuer is unknown.
*** PKI verification of server certificate failed...
- Description: (TLS1.2)-(ECDHE-RSA-SECP256R1)-(AES-256-GCM)
- Session ID: 53:BF:2F:D2:86:74:BD:BC:85:A8:67:12:0B:39:7A:12:EA:2F:91:1F:8E:06:5E:94:7F:20:11:4F:FC:51:60:8F
- Ephemeral EC Diffie-Hellman parameters
 - Using curve: SECP256R1
 - Curve size: 256 bits
- Key Exchange: ECDHE-RSA
- Server Signature: RSA-SHA256
- Cipher: AES-256-GCM
- MAC: AEAD
- Compression: NULL
- Options: safe renegotiation,
- Handshake was completed

- Simple Client Mode:



*** Fatal error: The TLS connection was non-properly terminated.
*** Server has terminated the connection abnormally.

Related unsolved issue: Server TLS configuration is broken and vulnerable #144

Answer 1

The server configuration on marmalade.org is broken: It does not serve the intermediate certificate it is using. This has been pointed out in half a dozen of issues now at https://github.com/nicferrier/elmarmalade -- I can discern no action.

So one can say that marmalade is defunct.

Unfortunately, I also don't know yet how to make the Emacs package manager work again in the presence of this error.

Answer 2

Now in 2021, the error message still is the same but the certificate in question is even expired. Moreover, fetching the package list from marmelade is unacceptably slow, and eventually results in an error.

There are also other indicators of obsolescence. Thus, the currently best answer I can give is:

Do not use the marmalade-repo.org package repository.

It is very unfortunate, even unfraternal by the maintainer, not to declare it officially dead.

Answer 3

I got this to work by downloading the PEM file for [Intermediate CA #2] COMODO RSA Organization Validation Secure Server CA (SHA-2) into ~/etc/tls/certificates/comodo.rsa.ca.intermediate.crt and adding the following to .emacs:

  (require 'gnutls)
  (add-to-list 'gnutls-trustfiles
               (expand-file-name
                "~/etc/tls/certificates/comodo.rsa.ca.intermediate.crt"))