Abo
  • Services:
Anzeige
Private keys on the web server - that's not a good idea.
Private keys on the web server - that's not a good idea. (Bild: Hanno Böck)

HTTPS: Private Keys on Web Servers

Private keys on the web server - that's not a good idea.
Private keys on the web server - that's not a good idea. (Bild: Hanno Böck)

Each certificate for encrypted HTTPS connections has a private key. But what happens if the private key finds its way onto the web server - and is no longer private? We found various web pages that allow downloading their private key.

Dieser Text ist auch auf Deutsch verfügbar.

Customers of the free mail provider Firemail were surprised by an error message some days ago: The certificate for the web page firemail.de was invalid. Comodo had revoked it after we found out that the corresponding private key could be downloaded from the page.

Anzeige

Firemail wasn't the only one with this problem. We found a number of web pages where the private key was no longer private and was accidentally published on the web server. We were able to obtain private keys for 90 valid web page certificates. We obtained them by simply trying out common filenames for keys. In the case of Firemail the filename was "server.key".

File names from popular web instruction guides

Other filenames for private keys were privatekey.key, myserver.key and key.pem. But the most successful search was for filenames of the schema [domainname].key. All these filenames are used in instruction guides that can easily be found with a Google search.

Every web page certificate has a corresponding private key. As the name indicates this key needs to remain private and should never fall into the hands of unauthorized people. Otherwise the HTTPS protected connection is no longer secure. An attacker can use the private key to perform a man-in-the-middle attack and therefore read and manipulate data.

When a certificate authority learns about a compromised certificate then it should revoke it. The OCSP protocol allows checking whether a certificate has been revoked.

OCSP has some problems. In the past browsers have implemented OCSP in a soft fail mode. If a connection to an OCSP server failed then the browser still accepted the certificate as valid. As this hardly provides any security the developers of Chrome have decided to disable OCSP altogether. Better revocation checks could be implemented with a combination of OCSP stapling and the must-staple extension for certificates, but the support for OCSP stapling in common web servers is only rudimentary.

While OCSP only provides limited utility it is still the common mechanism with which certificate authorities can signal that a certificate is no longer valid.

24 hour deadline for compromised certificates

According to the Baseline Reqirements, a set of rules that certificate authorities and browser vendors have agreed upon, certificate authorities shall revoke certificates within 24 hours if a key is compromised.

We informed the corresponding certificate authorities about all the certificates and private keys we found. In most cases this simply works by e-mail. Symantec and its subsidiaries and the company Gandi use a web form for those contacts. In the case of Symantec it is necessary to solve a captcha in order to send the form.

Notable is the way Let's Encrypt handles revocations. The free certificate authoritiy automates certificate issuances with the ACME protocol. The revocation of certificates is also automated. Whoever owns the private key to a certificate can revoke it. The tool Certbot can be used for this.

Mozilla recently has investigated how reporting mechanisms for compromised certificates work. In their CA Communications that is sent regularly to certificate authorities they asked them how to best report such problems. A list of the answers is available online.

Many certificate authorities don't seem to take the 24 hour deadline very seriously. Almost all affected certificate authorities - Comodo, DigiCert, Gandi, Globalsign, Go Daddy and Symantec - took longer than 24 hours for some revocations. To be fair: One of our reports was sent on a Saturday. But the Baseline Requirements rule doesn't have an exception for weekends. Apart from Let's Encrypt only StartCom always reacted within 24 hours. But currently StartCom certificates aren't accepted by popular browsers.

Gandi and Globalsign took particularly long to revoke certificates. Globalsign needed four days to revoke a certificate reported to them. Gandi doesn't operate its certificate authority, it is operated by Comodo. After Comodo learned about this incident they immediately revoked the certificates.

New certificate with old key

A particularly odd case happened with a certificate issued by Comodo. They revoked the certificate shortly after it had been reported, but then issued shortly after that a new certificate with the same private key. After we reported this to Comodo we learned that the same problem occured with a second certificate. In both cases Comodo revoked these new certificates immediately.

This incident shows that data on web servers is an underestimated security risk. Recently we had reported that the German postal service ("Deutsche Post") and many other companies had made private customer data available as SQL dumps. Also Git repositories in web directories often are the reason for private data like passwords being made public.

Private keys for valid certificates were recently also found in other places. The software developer Koen Rouwhorst found a private key embedded in an application from Cisco. Similarly a private key was also included in a software from Spotify. Rouwhorst also found various private keys in Github repositories.


eye home zur Startseite

Anzeige

Stellenmarkt
  1. A.M.P.E.R.E. Deutschland GmbH, Dietzenbach
  2. Groz-Beckert KG, Albstadt
  3. Safran Electronics & Defense Germany GmbH, Stuttgart
  4. Telekom Deutschland GmbH, Bonn


Anzeige
Hardware-Angebote
  1. 99,99€ inkl. Abzug, Preis wird im Warenkorb angezeigt
  2. (Core i5-7600K + Asus GTX 1060 Dual OC)
  3. 193,02€

Folgen Sie uns
       

  1. Ronny Verhelst

    Tele-Columbus-Chef geht nach Hause

  2. Alphabet

    Googles Gewinn geht wegen EU-Strafe zurück

  3. Microsoft

    Nächste Hololens nutzt Deep-Learning-Kerne

  4. Schwerin

    Livestream-Mitschnitt des Stadtrats kostet 250.000 Euro

  5. Linux-Distributionen

    Mehr als 90 Prozent der Debian-Pakete reproduzierbar

  6. Porsche Design

    Huaweis Porsche-Smartwatch kostet 800 Euro

  7. Smartphone

    Neues Huawei Y6 für 150 Euro bei Aldi erhältlich

  8. Nahverkehr

    18 jähriger E-Ticket-Hacker in Ungarn festgenommen

  9. Bundesinnenministerium

    Neues Online-Bürgerportal kostet 500 Millionen Euro

  10. Linux-Kernel

    Android O filtert Apps großzügig mit Seccomp



Haben wir etwas übersehen?

E-Mail an news@golem.de


Anzeige
Creoqode 2048 im Test: Wir programmieren die größte portable Spielkonsole der Welt
Creoqode 2048 im Test
Wir programmieren die größte portable Spielkonsole der Welt
  1. Arduino 101 Intel stellt auch das letzte Bastler-Board ein
  2. 1Sheeld für Arduino angetestet Sensor-Platine hat keine Sensoren und liefert doch Daten
  3. Calliope Mini im Test Neuland lernt programmieren

Ikea Trådfri im Test: Drahtlos (und sicher) auf Schwedisch
Ikea Trådfri im Test
Drahtlos (und sicher) auf Schwedisch
  1. Die Woche im Video Kündigungen, Kernaussagen und KI-Fahrer
  2. Augmented Reality Ikea will mit iOS 11 Wohnungen virtuell einrichten
  3. Space10 Ikea-Forschungslab untersucht Umgang mit KI

Microsoft Surface Pro im Test: Dieses Tablet kann lange
Microsoft Surface Pro im Test
Dieses Tablet kann lange
  1. Microsoft Neues Surface Pro fährt sich ohne Grund selbst herunter
  2. iFixit-Teardown Surface Laptop ist fast nicht reparabel
  3. Surface Studio Microsofts Grafikerstation kommt nach Deutschland

  1. Re: nächste Hololens, wo ist die momentane Hololens?

    Emulex | 06:53

  2. Re: Eine Beleidigung für echte Fotografen

    Dennisb456 | 06:52

  3. Re: USB Anschluss

    Peter Brülls | 06:44

  4. Re: DSLRs?

    ArcherV | 06:38

  5. Re: Andersherum: Wieso nicht das Unternehmen...

    oleurgast | 05:16


  1. 23:54

  2. 22:48

  3. 16:37

  4. 16:20

  5. 15:50

  6. 15:35

  7. 14:30

  8. 14:00


  1. Themen
  2. A
  3. B
  4. C
  5. D
  6. E
  7. F
  8. G
  9. H
  10. I
  11. J
  12. K
  13. L
  14. M
  15. N
  16. O
  17. P
  18. Q
  19. R
  20. S
  21. T
  22. U
  23. V
  24. W
  25. X
  26. Y
  27. Z
  28. #
 
    •  / 
    Zum Artikel