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  3. I reported an insecure DKIM key to Deutsche Telekom / T-Systems.

I reported an insecure DKIM key to Deutsche Telekom / T-Systems.

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  • badkeys@infosec.exchangeB badkeys@infosec.exchange

    I reported an insecure DKIM key to Deutsche Telekom / T-Systems. They first asked me to further explain things (not sure why 'Here's your DKIM private key' needs more explanation, but whatever...). Then they told me it's out of scope for their bugbounty.

    I guess then there's really no reason not to tell you: They have a 384 bit RSA DKIM key configured at: dkim._domainkey.t-systems.nl

    384 bit RSA is... how shall I put it? I think 512 bit is the lowest RSA key size that was ever really used. 384 bit RSA is crackable in a few hours on a modern PC (using cado-nfs). The private key is:
    -----BEGIN RSA PRIVATE KEY-----
    MIHxAgEAAjEAtTliQYV2Xvx1OGkDyOL799BTFEuobY2dn2AgtiKCQgrh78NVK1JK
    j0yRXgNnPpGBAgMBAAECMF0t+TBZUCi8xATSMij7VLTxv5Xi5OIXesNiXOKtYIRP
    LkpYfR5PggaMScfbmqSssQIZAMwOhm9d7Y7Qi7I2j1AlYbiqdtqO54T7FQIZAONa
    9dJFkC6lM3EPXR+0SZ4dqwwpiM0nvQIYYgz8thi5JK264ohq9sTvnu9yKvUN9I09
    AhgfgMYZKcxtujRjkSZtMzUUNLYzzDmJe90CGDKwqcBI0v9ChaR8WHht+/chMdxj
    7ez94w==
    -----END RSA PRIVATE KEY-----

    buherator@infosec.placeB This user is from outside of this forum
    buherator@infosec.placeB This user is from outside of this forum
    buherator@infosec.place
    wrote sidst redigeret af
    #8
    @badkeys My educated guess is they couldn't fit larger keys into their DNS records...
    gerdesj@mastodonapp.ukG mcr314@todon.nlM 2 Replies Last reply
    0
    • badkeys@infosec.exchangeB badkeys@infosec.exchange

      I reported an insecure DKIM key to Deutsche Telekom / T-Systems. They first asked me to further explain things (not sure why 'Here's your DKIM private key' needs more explanation, but whatever...). Then they told me it's out of scope for their bugbounty.

      I guess then there's really no reason not to tell you: They have a 384 bit RSA DKIM key configured at: dkim._domainkey.t-systems.nl

      384 bit RSA is... how shall I put it? I think 512 bit is the lowest RSA key size that was ever really used. 384 bit RSA is crackable in a few hours on a modern PC (using cado-nfs). The private key is:
      -----BEGIN RSA PRIVATE KEY-----
      MIHxAgEAAjEAtTliQYV2Xvx1OGkDyOL799BTFEuobY2dn2AgtiKCQgrh78NVK1JK
      j0yRXgNnPpGBAgMBAAECMF0t+TBZUCi8xATSMij7VLTxv5Xi5OIXesNiXOKtYIRP
      LkpYfR5PggaMScfbmqSssQIZAMwOhm9d7Y7Qi7I2j1AlYbiqdtqO54T7FQIZAONa
      9dJFkC6lM3EPXR+0SZ4dqwwpiM0nvQIYYgz8thi5JK264ohq9sTvnu9yKvUN9I09
      AhgfgMYZKcxtujRjkSZtMzUUNLYzzDmJe90CGDKwqcBI0v9ChaR8WHht+/chMdxj
      7ez94w==
      -----END RSA PRIVATE KEY-----

      wall_e@ioc.exchangeW This user is from outside of this forum
      wall_e@ioc.exchangeW This user is from outside of this forum
      wall_e@ioc.exchange
      wrote sidst redigeret af
      #9

      @badkeys bruh

      1 Reply Last reply
      0
      • buherator@infosec.placeB buherator@infosec.place
        @badkeys My educated guess is they couldn't fit larger keys into their DNS records...
        gerdesj@mastodonapp.ukG This user is from outside of this forum
        gerdesj@mastodonapp.ukG This user is from outside of this forum
        gerdesj@mastodonapp.uk
        wrote sidst redigeret af
        #10

        @buherator @badkeys

        I installed a MariaDB cluster backed set of PowerDNS servers for that exact reason! There were a couple of other reasons but that was what finally made me roll up my sleeves.

        1 Reply Last reply
        0
        • dragonfrog@mastodon.sdf.orgD dragonfrog@mastodon.sdf.org

          @badkeys
          Looks like they've fixed it now (?)

          The TXT record is now
          "v=DKIM1; k=rsa; g=*; s=email; p=MEwwDQYJKoZIhvcNAQEBBQADOwAwOAIxALU5YkGFdl78dThpA8ji+/fQUxRLqG2NnZ9gILYigkIK4e/DVStSSo9MkV4DZz6RgQIDAQAB"

          I really hope they generated a new key, and didn't just switch from publishing the private key to the corresponding public one...

          millie@infosec.exchangeM This user is from outside of this forum
          millie@infosec.exchangeM This user is from outside of this forum
          millie@infosec.exchange
          wrote sidst redigeret af
          #11

          @dragonfrog @badkeys Most people might not be fluent in base64-encoded ASN.1, but a trained eye can see that it's the same key.

          Hint: A sufficiently strong RSA key cannot possibly be that short, and you know it's a DER-encoded pubkey because it starts with "ME" and ends with "AQAB" (0x10001, common RSA public exponent)

          dragonfrog@mastodon.sdf.orgD 1 Reply Last reply
          0
          • buherator@infosec.placeB buherator@infosec.place
            @badkeys My educated guess is they couldn't fit larger keys into their DNS records...
            mcr314@todon.nlM This user is from outside of this forum
            mcr314@todon.nlM This user is from outside of this forum
            mcr314@todon.nl
            wrote sidst redigeret af
            #12

            @buherator @badkeys No, they thought they were generating an ECDSA key, for which a 256 or 384 bit would be strong. But, they didn't provide the right arguments, and wound up with RSA. I think the OP posted the private key that they were able to crack trivially.

            buherator@infosec.placeB 1 Reply Last reply
            0
            • millie@infosec.exchangeM millie@infosec.exchange

              @dragonfrog @badkeys Most people might not be fluent in base64-encoded ASN.1, but a trained eye can see that it's the same key.

              Hint: A sufficiently strong RSA key cannot possibly be that short, and you know it's a DER-encoded pubkey because it starts with "ME" and ends with "AQAB" (0x10001, common RSA public exponent)

              dragonfrog@mastodon.sdf.orgD This user is from outside of this forum
              dragonfrog@mastodon.sdf.orgD This user is from outside of this forum
              dragonfrog@mastodon.sdf.org
              wrote sidst redigeret af
              #13

              @millie @badkeys
              Oh gosh, so they've removed the private key, but it's still the public key that goes with a private key that they already published.

              A sound as if a thousand faces rested in a thousand palms, and a thousand IT people sighed heavily...

              millie@infosec.exchangeM 1 Reply Last reply
              0
              • dragonfrog@mastodon.sdf.orgD dragonfrog@mastodon.sdf.org

                @millie @badkeys
                Oh gosh, so they've removed the private key, but it's still the public key that goes with a private key that they already published.

                A sound as if a thousand faces rested in a thousand palms, and a thousand IT people sighed heavily...

                millie@infosec.exchangeM This user is from outside of this forum
                millie@infosec.exchangeM This user is from outside of this forum
                millie@infosec.exchange
                wrote sidst redigeret af
                #14

                @dragonfrog @badkeys No, the private key was never published by t-systems, but it's so weak that it's very easy to crack. OP cracked and published the private key.

                dragonfrog@mastodon.sdf.orgD 1 Reply Last reply
                0
                • mcr314@todon.nlM mcr314@todon.nl

                  @buherator @badkeys No, they thought they were generating an ECDSA key, for which a 256 or 384 bit would be strong. But, they didn't provide the right arguments, and wound up with RSA. I think the OP posted the private key that they were able to crack trivially.

                  buherator@infosec.placeB This user is from outside of this forum
                  buherator@infosec.placeB This user is from outside of this forum
                  buherator@infosec.place
                  wrote sidst redigeret af
                  #15
                  @mcr314 @badkeys Source? I doubt someone who makes a mistake like this knows what ECDSA is.
                  1 Reply Last reply
                  0
                  • millie@infosec.exchangeM millie@infosec.exchange

                    @dragonfrog @badkeys No, the private key was never published by t-systems, but it's so weak that it's very easy to crack. OP cracked and published the private key.

                    dragonfrog@mastodon.sdf.orgD This user is from outside of this forum
                    dragonfrog@mastodon.sdf.orgD This user is from outside of this forum
                    dragonfrog@mastodon.sdf.org
                    wrote sidst redigeret af
                    #16

                    @millie @badkeys thank you, I get it now. Iguess I'm having a slow day!

                    1 Reply Last reply
                    0
                    • badkeys@infosec.exchangeB badkeys@infosec.exchange

                      I reported an insecure DKIM key to Deutsche Telekom / T-Systems. They first asked me to further explain things (not sure why 'Here's your DKIM private key' needs more explanation, but whatever...). Then they told me it's out of scope for their bugbounty.

                      I guess then there's really no reason not to tell you: They have a 384 bit RSA DKIM key configured at: dkim._domainkey.t-systems.nl

                      384 bit RSA is... how shall I put it? I think 512 bit is the lowest RSA key size that was ever really used. 384 bit RSA is crackable in a few hours on a modern PC (using cado-nfs). The private key is:
                      -----BEGIN RSA PRIVATE KEY-----
                      MIHxAgEAAjEAtTliQYV2Xvx1OGkDyOL799BTFEuobY2dn2AgtiKCQgrh78NVK1JK
                      j0yRXgNnPpGBAgMBAAECMF0t+TBZUCi8xATSMij7VLTxv5Xi5OIXesNiXOKtYIRP
                      LkpYfR5PggaMScfbmqSssQIZAMwOhm9d7Y7Qi7I2j1AlYbiqdtqO54T7FQIZAONa
                      9dJFkC6lM3EPXR+0SZ4dqwwpiM0nvQIYYgz8thi5JK264ohq9sTvnu9yKvUN9I09
                      AhgfgMYZKcxtujRjkSZtMzUUNLYzzDmJe90CGDKwqcBI0v9ChaR8WHht+/chMdxj
                      7ez94w==
                      -----END RSA PRIVATE KEY-----

                      irelephant@app.wafrn.netI This user is from outside of this forum
                      irelephant@app.wafrn.netI This user is from outside of this forum
                      irelephant@app.wafrn.net
                      wrote sidst redigeret af
                      #17

                      @badkeys@infosec.exchange

                      send an email coming from them.

                      1 Reply Last reply
                      0
                      • kkarhan@jorts.horseK kkarhan@jorts.horse

                        @momo @badkeys sadly this is being normalized today.

                        • #Microsoft literally demands people to self-d0x or they just silently drop all eMails, even replies to their customers.
                          • And OFC neither @BNetzA nor @EUCommission did anything about this.
                        bebef@mastodon.socialB This user is from outside of this forum
                        bebef@mastodon.socialB This user is from outside of this forum
                        bebef@mastodon.social
                        wrote sidst redigeret af
                        #18

                        @kkarhan @momo @badkeys @BNetzA @EUCommission Had the same issue just recently. I wonder how this can even be legal. 🤔

                        I wanted to ask a lawyer about this, but never came around doing so.

                        yacc143@mastodon.socialY 1 Reply Last reply
                        0
                        • q@glauca.spaceQ This user is from outside of this forum
                          q@glauca.spaceQ This user is from outside of this forum
                          q@glauca.space
                          wrote sidst redigeret af
                          #19

                          @16af93 @badkeys for once, its not the Germans

                          sys64738@www.librepunk.clubS 1 Reply Last reply
                          0
                          • badkeys@infosec.exchangeB badkeys@infosec.exchange

                            I reported an insecure DKIM key to Deutsche Telekom / T-Systems. They first asked me to further explain things (not sure why 'Here's your DKIM private key' needs more explanation, but whatever...). Then they told me it's out of scope for their bugbounty.

                            I guess then there's really no reason not to tell you: They have a 384 bit RSA DKIM key configured at: dkim._domainkey.t-systems.nl

                            384 bit RSA is... how shall I put it? I think 512 bit is the lowest RSA key size that was ever really used. 384 bit RSA is crackable in a few hours on a modern PC (using cado-nfs). The private key is:
                            -----BEGIN RSA PRIVATE KEY-----
                            MIHxAgEAAjEAtTliQYV2Xvx1OGkDyOL799BTFEuobY2dn2AgtiKCQgrh78NVK1JK
                            j0yRXgNnPpGBAgMBAAECMF0t+TBZUCi8xATSMij7VLTxv5Xi5OIXesNiXOKtYIRP
                            LkpYfR5PggaMScfbmqSssQIZAMwOhm9d7Y7Qi7I2j1AlYbiqdtqO54T7FQIZAONa
                            9dJFkC6lM3EPXR+0SZ4dqwwpiM0nvQIYYgz8thi5JK264ohq9sTvnu9yKvUN9I09
                            AhgfgMYZKcxtujRjkSZtMzUUNLYzzDmJe90CGDKwqcBI0v9ChaR8WHht+/chMdxj
                            7ez94w==
                            -----END RSA PRIVATE KEY-----

                            yacc143@mastodon.socialY This user is from outside of this forum
                            yacc143@mastodon.socialY This user is from outside of this forum
                            yacc143@mastodon.social
                            wrote sidst redigeret af
                            #20

                            @badkeys
                            That was crackable with private entity resources decades ago.

                            That's not even funny.

                            1 Reply Last reply
                            0
                            • q@glauca.spaceQ q@glauca.space

                              @16af93 @badkeys for once, its not the Germans

                              sys64738@www.librepunk.clubS This user is from outside of this forum
                              sys64738@www.librepunk.clubS This user is from outside of this forum
                              sys64738@www.librepunk.club
                              wrote sidst redigeret af
                              #21

                              @q @16af93 @badkeys iirc 256-bit rsa is satcomms 'standards'

                              1 Reply Last reply
                              0
                              • badkeys@infosec.exchangeB badkeys@infosec.exchange

                                I reported an insecure DKIM key to Deutsche Telekom / T-Systems. They first asked me to further explain things (not sure why 'Here's your DKIM private key' needs more explanation, but whatever...). Then they told me it's out of scope for their bugbounty.

                                I guess then there's really no reason not to tell you: They have a 384 bit RSA DKIM key configured at: dkim._domainkey.t-systems.nl

                                384 bit RSA is... how shall I put it? I think 512 bit is the lowest RSA key size that was ever really used. 384 bit RSA is crackable in a few hours on a modern PC (using cado-nfs). The private key is:
                                -----BEGIN RSA PRIVATE KEY-----
                                MIHxAgEAAjEAtTliQYV2Xvx1OGkDyOL799BTFEuobY2dn2AgtiKCQgrh78NVK1JK
                                j0yRXgNnPpGBAgMBAAECMF0t+TBZUCi8xATSMij7VLTxv5Xi5OIXesNiXOKtYIRP
                                LkpYfR5PggaMScfbmqSssQIZAMwOhm9d7Y7Qi7I2j1AlYbiqdtqO54T7FQIZAONa
                                9dJFkC6lM3EPXR+0SZ4dqwwpiM0nvQIYYgz8thi5JK264ohq9sTvnu9yKvUN9I09
                                AhgfgMYZKcxtujRjkSZtMzUUNLYzzDmJe90CGDKwqcBI0v9ChaR8WHht+/chMdxj
                                7ez94w==
                                -----END RSA PRIVATE KEY-----

                                keksdosenmann@mastodon.socialK This user is from outside of this forum
                                keksdosenmann@mastodon.socialK This user is from outside of this forum
                                keksdosenmann@mastodon.social
                                wrote sidst redigeret af
                                #22

                                @badkeys Telekom. Die machen das.

                                christianrickert@23.socialC 1 Reply Last reply
                                0
                                • bebef@mastodon.socialB bebef@mastodon.social

                                  @kkarhan @momo @badkeys @BNetzA @EUCommission Had the same issue just recently. I wonder how this can even be legal. 🤔

                                  I wanted to ask a lawyer about this, but never came around doing so.

                                  yacc143@mastodon.socialY This user is from outside of this forum
                                  yacc143@mastodon.socialY This user is from outside of this forum
                                  yacc143@mastodon.social
                                  wrote sidst redigeret af
                                  #23

                                  @Bebef
                                  It's probably not, some countries have really tough laws that they apply to email delivery and privacy that makes even spam filtering a legally dicey proposition

                                  But let me put it like this, who wants to sue a company that has a legal budget bigger than the whole government budget of some of the poorer EU MS?

                                  And in the end as long as the users won't start moving their fat posteriors away from the big tech monopolies, ...
                                  @kkarhan @momo @badkeys @BNetzA @EUCommission

                                  yacc143@mastodon.socialY 1 Reply Last reply
                                  0
                                  • badkeys@infosec.exchangeB badkeys@infosec.exchange

                                    I reported an insecure DKIM key to Deutsche Telekom / T-Systems. They first asked me to further explain things (not sure why 'Here's your DKIM private key' needs more explanation, but whatever...). Then they told me it's out of scope for their bugbounty.

                                    I guess then there's really no reason not to tell you: They have a 384 bit RSA DKIM key configured at: dkim._domainkey.t-systems.nl

                                    384 bit RSA is... how shall I put it? I think 512 bit is the lowest RSA key size that was ever really used. 384 bit RSA is crackable in a few hours on a modern PC (using cado-nfs). The private key is:
                                    -----BEGIN RSA PRIVATE KEY-----
                                    MIHxAgEAAjEAtTliQYV2Xvx1OGkDyOL799BTFEuobY2dn2AgtiKCQgrh78NVK1JK
                                    j0yRXgNnPpGBAgMBAAECMF0t+TBZUCi8xATSMij7VLTxv5Xi5OIXesNiXOKtYIRP
                                    LkpYfR5PggaMScfbmqSssQIZAMwOhm9d7Y7Qi7I2j1AlYbiqdtqO54T7FQIZAONa
                                    9dJFkC6lM3EPXR+0SZ4dqwwpiM0nvQIYYgz8thi5JK264ohq9sTvnu9yKvUN9I09
                                    AhgfgMYZKcxtujRjkSZtMzUUNLYzzDmJe90CGDKwqcBI0v9ChaR8WHht+/chMdxj
                                    7ez94w==
                                    -----END RSA PRIVATE KEY-----

                                    kate@mk.absturztau.beK This user is from outside of this forum
                                    kate@mk.absturztau.beK This user is from outside of this forum
                                    kate@mk.absturztau.be
                                    wrote sidst redigeret af
                                    #24

                                    @badkeys@infosec.exchange ..OMFG ..​​

                                    1 Reply Last reply
                                    0
                                    • yacc143@mastodon.socialY yacc143@mastodon.social

                                      @Bebef
                                      It's probably not, some countries have really tough laws that they apply to email delivery and privacy that makes even spam filtering a legally dicey proposition

                                      But let me put it like this, who wants to sue a company that has a legal budget bigger than the whole government budget of some of the poorer EU MS?

                                      And in the end as long as the users won't start moving their fat posteriors away from the big tech monopolies, ...
                                      @kkarhan @momo @badkeys @BNetzA @EUCommission

                                      yacc143@mastodon.socialY This user is from outside of this forum
                                      yacc143@mastodon.socialY This user is from outside of this forum
                                      yacc143@mastodon.social
                                      wrote sidst redigeret af
                                      #25

                                      @Bebef
                                      The really odd thing is it's not the oldies that nowadays are a problem, it's the youngsters, we literally had a complaint today about the PIM/office suite we use, our CEO nicely played that one. He's open to all proposals for alternatives from a company headquartered in the EEA for legal reasons.

                                      Interestingly the C level has no problem IMAP, and accessing the calendar over CalDAV. But the youngsters have never heard of these @kkarhan @momo @badkeys @BNetzA @EUCommission

                                      yacc143@mastodon.socialY 1 Reply Last reply
                                      0
                                      • yacc143@mastodon.socialY yacc143@mastodon.social

                                        @Bebef
                                        The really odd thing is it's not the oldies that nowadays are a problem, it's the youngsters, we literally had a complaint today about the PIM/office suite we use, our CEO nicely played that one. He's open to all proposals for alternatives from a company headquartered in the EEA for legal reasons.

                                        Interestingly the C level has no problem IMAP, and accessing the calendar over CalDAV. But the youngsters have never heard of these @kkarhan @momo @badkeys @BNetzA @EUCommission

                                        yacc143@mastodon.socialY This user is from outside of this forum
                                        yacc143@mastodon.socialY This user is from outside of this forum
                                        yacc143@mastodon.social
                                        wrote sidst redigeret af
                                        #26

                                        things. And are shocked that email can be provided by something else then Google, outlook or Apple. On which of these is our email hosted I was asked. I had to explain very slowly that we are on the small option "other".
                                        @kkarhan @momo @badkeys @BNetzA @EUCommission @Bebef

                                        1 Reply Last reply
                                        0
                                        • keksdosenmann@mastodon.socialK keksdosenmann@mastodon.social

                                          @badkeys Telekom. Die machen das.

                                          christianrickert@23.socialC This user is from outside of this forum
                                          christianrickert@23.socialC This user is from outside of this forum
                                          christianrickert@23.social
                                          wrote sidst redigeret af
                                          #27

                                          @keksdosenmann @badkeys

                                          Die schaffen uns. 😮‍💨

                                          1 Reply Last reply
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