diff options
| author | Kali Kaneko <kali@futeisha.org> | 2015-06-08 16:46:11 -0400 |
|---|---|---|
| committer | Kali Kaneko <kali@futeisha.org> | 2015-06-08 16:46:11 -0400 |
| commit | a5d46a4e38985be540b9127ddcd3d8e21bbecb9a (patch) | |
| tree | c6e0d6b8d38c29b742d73b4975dd556208a74696 /docs/Complete-Guide-to-Publishing-OpenPGP-in-DNS.md | |
| parent | 4bd0fa843176a112c054929fbe6dd99f45d718a2 (diff) | |
Imported Upstream version 2.0.2
Diffstat (limited to 'docs/Complete-Guide-to-Publishing-OpenPGP-in-DNS.md')
| -rw-r--r-- | docs/Complete-Guide-to-Publishing-OpenPGP-in-DNS.md | 832 |
1 files changed, 0 insertions, 832 deletions
diff --git a/docs/Complete-Guide-to-Publishing-OpenPGP-in-DNS.md b/docs/Complete-Guide-to-Publishing-OpenPGP-in-DNS.md deleted file mode 100644 index 5112c97..0000000 --- a/docs/Complete-Guide-to-Publishing-OpenPGP-in-DNS.md +++ /dev/null @@ -1,832 +0,0 @@ -<!-- - -Livejournal Introduction: - -I recently wrestled with something, learned quite a lot, and came up with a document that I'm really rather proud of, that -shares knowledge that's not all out there in one place anywhere else. Along the way I've written some software that I'm -releasing, that makes all of what I've learned a lot easier, and may help make the world a little more secure. I'd like to -share it here. - -This is going to be a technical post. For that I apologize. The target of this post is anyone who has a GPG key that they'd -like to expand to a greater audience, and who controls DNS for any of the email domains they publish. Anyone that I host DNS -or mail for is also welcome to do this, if you use PGP, as part of the goal of writing this is to encourage adoption and use -of these methods - -<lj-cut text="This will be long and technical"> ---> - -# The complete guide to publishing PGP keys in DNS - -## Introduction - -Publishing PGP keys is a pain. There are many disjoint keyservers, three or -four _networks_ of which, which do (or don't) share information with each -other. Some are corporate, some are private. And it's a crapshoot as to -whose key is going to be on which, or worse, which will have the latest copy -of a person's key. - -For a long time, GPG has had a way to publish keys in DNS, but it hasn't been -well documented. This document hopes to change that. - -After reading this, you should: - -* Know the three ways to publish a key - -* Have at least a couple tools to do so - -* Have learned a bit more about DNS - -The target audience for this guide is a technical one. It's expected you -understand what DNS is, and what an RFC and a resource record is. - -There are three ways to publish a PGP key in DNS. Most modern versions of GPG -can retrieve from all three, although it's not enabled by default. There are -no compile-time options you need to enable it, and it's simple to turn on. Of -the three key-publishing methods, there are two that you probably shouldn't -use at the same time, and there are advantages and disadvantages to each, -which I hope to outline below, both in general and for each method. - -### Advantages to DNS publishing of your keys - -* It's universal. Your DNS is your own, and you don't have to worry about - which network of vastly-disconnectedkeyservers is caching your key. - -* Using DNS does not stop you from publishing via other means. - -* If you run an organization, you can easily publish all your employee-keys - via this method, and in the same step,define a signing-policy, such that a - person need only assign trust to your organization's "keysigning key" (or - theCEO's key, or the CTO's), without the trouble of running a keyserver. - -* DNSSEC can be (somewhat) used as an additional trust-path vector. More on - this in the notes at the bottom. - -* You do not have to be searching DNS for keys in order to publish. On the - same note, you do not have to be publishing in this manner to search - forothers there. - -### Disadvantages to DNS publishing - -* If you don't control your own DNS (or have a good relationship with your DNS - admin), this isn't going to beas easy or even possible. Ideally, you want - to be running BIND. - -* With two of the three methods listed here, you're going to need to be able - to put a CERT record into your DNS. Mostweb-enabled DNS tools probably will - not give you this ability. The third uses TXT records, which SPF has caused - to befairly universal in web-interfaces. However, it's also the least - standards-defined of the three. - -* Using at least some of these methods, it's not always a "set it and forget - it" procedure. You may need toperiodically re-export your key and - re-publish it, especially if you gain new signatures. - -* Using some of these methods, you're going to be putting some pretty large, - pretty unwiedly lines in your DNS zones. Not everyone will easily be able - to retrieve them, but again, you can still publish other ways. - -* Using some of these methods, DNS is just a means to an end: you still need - to publish your key elsewhere, like a webpage,and the DNS records just point - at it. - -* Initial verifications of most of these seem to imply that only DSA keys are - supported, although I welcome feedback. Itseems the community is trying to - get RSA keys to make a comeback. They're the only type supported by the - gpg2.0 card, andthey are the default keytype. There was a while where they - weren't, though. Since writing this document, I've discoveredthat "new" RSA - keys work, but ancient RSA keys with no subkeys tend to misbehave. - -### Turning on key-fetching via DNS - -Inside your GPG "options" file, find the "auto-key-locate" line, and add -"cert" and/or "pka" to the options. - - auto-key-locate cert pka (as well as other methods, like keyserver URLs) - - -Don't be surprised if a lot of people don't use this method. - -Note that you can also turn on two options during signature verification. -They are specified in a "verify-options" clause in your config file, or on the -command line, and they are (right from the GPG manpage): - - pka-lookups - - Enable PKA lookups to verify sender addresses. Note that - PKA is based on DNS, and so enabling this option may dis- - close information on when and what signatures are veri- - fied or to whom data is encrypted. This is similar to the - "web bug" described for the auto-key-retrieve feature. - -And: - - pka-trust-increase - - Raise the trust in a signature to full if the signature - passes PKA validation. This option is only meaningful if - pka-lookups is set. - - -You can also use the same options on the command line (as you'll see in this -document). - -## Types of PGP Key Records - -### DNS PKA Records - -Relevant RFCs: None that I can find. - -Other Docs: The GPG source and mailing lists. - -#### Advantages - -* It's a TXT record. Easy to put in a zonefile with most management software. -* No special tools required to generate, just three simple pieces of data. -* Since it uses a special subzone, you can manage the _pka namespace in a - separate zonefile. -* GPG has an option, when verifying a signature, to look up these records - (--verify-options pka-lookups), so it's doubly useful, both from a - distribution and a verification point. - -#### Disadvantages - -* As with IPGP certs, you're at the mercy of the URL. This doesn't put your - key in DNS, just the location of it, and the fingerprint. Some clients may - not be able to support https or http 1.1. -* Not RFC standard. - -#### Howto - -1. Figure out which key you want to export: - - %gpg --list-keys danm@prime.gushi.org - Warning: using insecure memory! - pub 1024D/624BB249 2000-10-02 <-- I'm going to use this one. - uid Daniel P. Mahoney <danm@prime.gushi.org> - uid Daniel Mahoney (Secondary Email) <gushi@gushi.org> - sub 2048g/DE20C529 2000-10-02 - pub 1024R/309C17C5 1997-05-08 - uid Daniel P. Mahoney <danm@prime.gushi.org> - -2. Export the key to a file (I use keyid.pub.asc, but it can be anything) - - %gpg --export --armor 624BB249 > 624BB249.pub.asc - Warning: using insecure memory! - % - -3. Get the fingerprint for your key: - - %gpg --list-keys --fingerprint 624BB249 - gpg: WARNING: using insecure memory! - gpg: please see http://www.gnupg.org/faq.html for more information - pub 1024D/624BB249 2000-10-02 - Key fingerprint = C206 3054 5492 95F3 3490 37FF FBBE 5A30 624B B249 <-- That bit is your fingerprint. - uid Daniel P. Mahoney <danm@prime.gushi.org> - uid Daniel Mahoney (Secondary Email) <gushi@gushi.org> - sub 2048g/DE20C529 2000-10-02 - -4. Copy the file somewhere, like your webspace. It need not live on the same - server. It needs to be accessable by the url you create in the next step. - - %cp 624BB249.pub.asc public_html/danm.pubkey.txt - -5. Make up your text record. The format is: - - danm._pka.prime.gushi.org. TXT "v=pka1;fpr=C2063054549295F3349037FFFBBE5A30624BB249;uri=http://prime.gushi.org/danm.pubkey.txt" - - -We'll take this in several parts. The record label is simply the email -address with "._pka." replacing the "@". danm@prime.gushi.org becomes -danm._pka.prime.gushi.org. Don't forget the trailing dot, if you're using the -fully qualified name. I recommend sticking with fully-qualified, for -simplicity. - -The body of the record is also simple. The v portion is just a version. -There's only one version as far as I can tell, 'pka1'. The fpr is the -fingerprint, with all whitespace stripped, and in uppercase. The uri is the -location a key can be retrieved from. All the "names" are lowercase, -separated by semicolons. - -6. Publish the above record in your DNS. Bump your serial number and reload - your nameserver. If you're using DNSSEC, re-sign your zone. - -#### Testing - -Most of the tests we're going to do for these are essentially the same -activity. See if our DNS server is handing out an answer, and then see if GPG -can retrieve it. - -1. A simple dig: - - %dig +short danm._pka.prime.gushi.org. TXT - "v=pka1\;fpr=C2063054549295F3349037FFFBBE5A30624BB249\;uri=http://prime.gushi.org/danm.pubkey.txt" - -(The backslashes before the semicolons are normal). Other than that, it seems -to make sense and match what I put in.) - -2. Test it with GPG. Rather than messing around with, and adding-from and - deleting from live keyrings, you can do: - - %echo "foo" | gpg --no-default-keyring --keyring /tmp/gpg-$$ --encrypt --armor --auto-key-locate pka -r you@you.com - - -(where you@you.com is the address of your primary key.) The /tmp/gpg-$$ -creates a random file named after your PID. What you should see, and what I -see, is something like this: - - gpg: WARNING: using insecure memory! - gpg: please see http://www.gnupg.org/faq.html for more information - gpg: keyring `/tmp/gpg-39996' created - gpg: requesting key 624BB249 from http server prime.gushi.org - gpg: key 624BB249: public key "Daniel P. Mahoney <danm@prime.gushi.org>" imported - gpg: public key of ultimately trusted key CF45887D not found - gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model - gpg: depth: 0 valid: 1 signed: 0 trust: 0-, 0q, 0n, 0m, 0f, 1u - gpg: Total number processed: 1 - gpg: imported: 1 - gpg: automatically retrieved `danm@prime.gushi.org' via PKA - gpg: DE20C529: There is no assurance this key belongs to the named user - pub 2048g/DE20C529 2000-10-02 Daniel P. Mahoney <danm@prime.gushi.org> - Primary key fingerprint: C206 3054 5492 95F3 3490 37FF FBBE 5A30 624B B249 - Subkey fingerprint: CE40 B786 81E2 5CB9 F7D3 1318 9488 EB58 DE20 C529 - It is NOT certain that the key belongs to the person named - in the user ID. If you *really* know what you are doing, - you may answer the next question with yes. - Use this key anyway? (y/N) y - -----BEGIN PGP MESSAGE----- - Version: GnuPG v1.4.10 (FreeBSD) - hQIOA5SI61jeIMUpEAf/UotgWP8VQC9VTY36HaZeXO1CTFk90x0qlPrAhJk9YaoA - 2eHNKZSoHKqaLjzTbaWnWHnNZu0IllIS+qrAwNeIAhswfzDoc8Q9+/4sGSR3LmxA - 8SEwrJIvLmGVbqJEtnH8TTHIEao/lpL/d+ul4nLfbXRn0NW+MsaCAi8UsjbLlJeV - n4p0GQlpDoZCE55DTwMzfWMT84YVwuXTesuN+i7sSyJn2hT1rXuK1BCVcsgTcKdy - QhIo3EfKBlfFp74yiU7QCmlAujD6U6a93mmxezPIHVx/WGXgPExVRGgEzfT/tUcI - IQ2xMDUv4BF05hgm04GPGCbBY431j4UkdWWI6bvMLwgA2i01NmflH/6Z8+ss6J1M - e3RWnR7TPl5lDkXFBtLGAzO+HrsC5A32SbkTw+WsljCQLifJ2EalfoJ1QGY4Sp3v - H2YunwZLVPTc+D2JnrXfqNmi5zYZio8by3c8L0CgWdMwZ7PPxZpTOLN77/MIjBkJ - EBb8Z6SZCgzTIhN5z56ZgWFvmSKf1vKkeUcrgxMs+DnA+XqBMJ9w520JwoTLjJza - syrlYVhd+ktY21DYB9OJ5MZx2HMAtkUDRAzW1zoLcehk1kdZNzhpjU5hqSjT8/GN - trKFeqkmKemrq2GvMNyJyrEOB8e7KgbmXa95YKH0Wh2D4SWpXukegyCspmY4tDE+ - uckaFSao+48g8D6vs1irGSxBRjyhD/jPDblrgpo= - =NbgW - -----END PGP MESSAGE----- - -The "insecure memory" warning is a silly warning that the only way to turn off is to run GPG setuid root. -You can see in the output that the key comes from PKA. - -The "it is NOT certain" warning has nothing to do with the fact that it came -from DNS. You will get that warning every time you use that key (or any gpg -key) until you have edited it and assigned ownertrust to it, or until the key -is signed with a trusted signature, either from your personal web of trust, or -from a signing service like the pgp.com directory. - -3. Ask other people to run it for you and send you the resulting blob. You should be able to decrypt it with your private key. - -### PGP CERT Records - -Also known as: The "big" CERT record. - -Relevant RFCs: [RFC 2538](http://www.faqs.org/rfcs/rfc2538.html), -[RFC 4398](http://www.faqs.org/rfcs/rfc4398.html), specifically sections 2.1 -and 3.3 - -#### Advantages - -* DNS is all you need. You don't have to host the key elsewhere. As a DNS - nerd, this strikes me as very cool. - -* Suprisingly easy to verify with dig, if you have a base64 converter handy - (openssl includes one) - -#### Disadvantages - -* These records can get big. Really big. Especially if you have photo-ids on your keys. You can play with export-options to shrink it somewhat. Big dns packets may require EDNS, or dns-over-tcp, which not everyone supports, but support is becoming more widespread as a result of DNSSEC awareness. - -* Requires the make-dns-cert tool, which isn't built by default. - -* Requires you to have some control over your actual zonefile. Most control panels won't cut it. - -* Make-dns-cert currently generates a very ugly record for this. - - #### How to - -1. As before, the first step is to figure out which key we want. - - %gpg --list-keys danm@prime.gushi.org - Warning: using insecure memory! - pub 1024D/624BB249 2000-10-02 <-- I'm going to use this one. - uid Daniel P. Mahoney <danm@prime.gushi.org> - uid Daniel Mahoney (Secondary Email) <gushi@gushi.org> - sub 2048g/DE20C529 2000-10-02 - pub 1024R/309C17C5 1997-05-08 - uid Daniel P. Mahoney <danm@prime.gushi.org> - -2. We export the key, but this time, it needs to be binary. - - %gpg --export 624BB249 > 624BB249.pub.bin - Warning: using insecure memory! - -3. We run make-dns-cert on it. make-dns-cert comes with no manual or docs, - but running with -h gives you all the clue you need. - - make-dns-cert - -f fingerprint - -u URL - -k key file - -n DNS name - -So then, - - make-dns-cert -n danm.prime.gushi.org. -k 624BB249.pub.bin - <pre>`%make-dns-cert -n danm.prime.gushi.org. -k 624BB249.pub.bin - danm.prime.gushi.org. TYPE37 \# 1298 0003 0000 00 9901A20439D8DAF1110400F770EC6AA006076334BEC6DB6FBB237DC194BC0AB8 - 302C8953F04C28FC2085235D4F10EFA027234FBD63D142CCADD5213AD2B79A22C89ED9B4138370D8220D0F987F993A5364A4A7AC3D42F3765C384 - 71DDD0FF3372E4AE6F7BEE1E18EF464A0BEB5BBE860A08238891455EBE7CB53D567E981F78ADBD263206B0493ADCB74DD00A0FF0E9A1CD245415E - CEF59435162AFCE4CDD14BC70400EA38FF501256E773DEA299404854D99F4EDB2757AA911A9C77C68AB8D6622E517A556C43D21F0523C568F016C - D0DB89EF435F0D53B4E07434213F899E6578955DC2C147931E7B6901C9FD8A02705417D69A879B3CC196D2AC2EAEF311192EE89ABAF5A60942167 - B4625735FCBDFB5DE0E3AC1236A53FA4D7CDD7D75F5DE85AF50400867D9546B28B79AF10541053CF4AB06A6171BFD21458BFD12AF1AE2B2401CAD - 8851661F8AF6602F80EDAC99C79616BE1F910F4156242003779C68D7A079A8B18F89DD293E1B247E7420471300A4A0730AA61DE281CCC211FC405 - A0A8A79877999FF9042AD892AB927DA371E8883BBB370AB7A97841408C3486BB18598CF2559BB42844616E69656C20502E204D61686F6E6579203 - C64616E6D407072696D652E67757368692E6F72673E884E04101102000E050239D8DAF1040B030102021901000A0910FBBE5A30624BB249FA2E00 - 9B057503ED498695AE5ED73CA1B98EBAEE13F717E500A0921E0D92724459100266FEBBC29E911C8B0F530BB43244616E69656C204D61686F6E657 - 920285365636F6E6461727920456D61696C29203C67757368694067757368692E6F72673E8860041311020020050245D49FD7021B23060B090807 - 030204150208030416020301021E01021780000A0910FBBE5A30624BB249158400A082C8AF43DA8B85F740D6B1A6E9FF0B4490520B8C00A08F77D - 21FBF86C842963E8090DC0646D1DD7F95C9B9020D0439D8DAF4100800F64257B7087F081772A2BAD6A942F305E8F95311394FB6F16EB94B3820DA - 01A756A314E98F4055F3D007C6CB43A994ADF74C648649F80C83BD65E917D4A1D350F8F5595FDC76524F3D3D8DDBCE99E1579259CDFDB8AE744FC - 5FC76BC83C5473061CE7CC966FF15F9BBFD915EC701AAD35B9E8DA0A5723AD41AF0BF4600582BE5F488FD584E49DBCD20B49DE49107366B336C38 - 0D451D0F7C88B31C7C5B2D8EF6F3C923C043F0A55B188D8EBB558CB85D38D334FD7C175743A31D186CDE33212CB52AFF3CE1B1294018118D7C84A - 70A72D686C40319C807297ACA950CD9969FABD00A509B0246D3083D66A45D419F9C7CBD894B221926BAABA25EC355E9320B3B00020207FF5E1A3C - C5DA00E1E94EC8EF6C7FE9B49D944C71D8BBC817DD8E64A7344B9E48392E0B833B3B1DB7E6D5A38BE2826DEF0060F78C6417871EAF1CFBCBC47D2 - 7E93718D975E0A3A36D868C021D6B771740CE2918307D69D614BBF0632DC31932EA31397A7F3B04618C9A76C2F38265C7037E303EDD8AEF03D069 - 208E3FE9C4EA77D83E6311ED36C013D58C54E914B263A459E22D463A0288510C4752B99C163EEA0A55686979691AB0D9F9AA0C06C834446D7A723 - EC534D819301382621ACF8930C74E9FD28C8797718AEC2C30CF601E24194B799234104A3D6239657B1D4AD545BDAA637F61541435CB51B4D138FB - F55E1A9FD2EED860E4459D6795B6FCCA23155A8846041811020006050239D8DAF4000A0910FBBE5A30624BB249415A009E37BCFDC64E76CBF6A86 - 82B85EA161BD1DFB793DF00A0C471BC7B9723535CD855D8FF1EB93F01E251B698 - % - -The program prints that all on **one line**. - -Immediately, we notice a few things. - -* The record type isn't "CERT", it's "TYPE37". This confused me for a while until I discovered [RFC3597](http://www.faqs.org/rfcs/rfc3597.html) Basically, it's a way that a DNS server can handle a resource record it doesn't know about, by giving it some special fields like the "#", as well as a length (which is the 1298 you see there). - -* The rest of the record is on one line. I wrapped it for the purposes of brevity. If I were using this in a zonefile, I would need to be careful that I wrapped it on a byte-boundary (every two characters is a byte). If I miss the boundary, named will refuse to load it, dnssec-signzone won't touch it, etc. - -4. So the thing is ugly and you don't want to touch it. The easiest way to work with it is to drop all that into a file: - - %make-dns-cert -n danm.prime.gushi.org. -k 624BB249.pub.bin > 624BB249.big.cert - - -5. And then either read it into your editor, or tack it on like this: - - %cat 624BB249.big.cert >> your.zonefile - -Be sure to make a backup first. Either way, you never have to copy/paste the raw hex and worry about newlines being inserted where you don't want them. - -6. Before you reload your zone, you might want to use named-checkzone on it first: - - prime# named-checkzone gushi.org gushi.org.hosts - zone gushi.org/IN: loaded serial 2009102909 - OK - prime# - -7. Voice of experience: You may want to dial the TTL (which controls how long servers will cache your data) way down on the record above. It's not hard, just put a number before the TYPE37, with a space, i.e: - - danm.prime.gushi.org. 30 TYPE37 - -This way if it all goes terribly wrong, or you need to make changes, it won't be cached for very long. - -8. If it looks okay, bump your serial number and reload. - -#### Testing - -1. As above, you can dig, but you won't be able to easily read the results: - - prime# dig +short danm.prime.gushi.org CERT - ;; Truncated, retrying in TCP mode. - - -PGP 0 0 -mQGiBDnY2vERBAD3cOxqoAYHYzS+xttvuyN9wZS8CrgwLIlT8Ewo/CCF -I11PEO+gJyNPvWPRQsyt1SE60reaIsie2bQTg3DYIg0PmH+ZOlNkpKes -PULzdlw4Rx3dD/M3Lkrm977h4Y70ZKC+tbvoYKCCOIkUVevny1PVZ+mB -94rb0mMgawSTrct03QCg/w6aHNJFQV7O9ZQ1Fir85M3RS8cEAOo4/1AS -Vudz3qKZQEhU2Z9O2ydXqpEanHfGirjWYi5RelVsQ9IfBSPFaPAWzQ24 -nvQ18NU7TgdDQhP4meZXiVXcLBR5Mee2kByf2KAnBUF9aah5s8wZbSrC -6u8xEZLuiauvWmCUIWe0Ylc1/L37XeDjrBI2pT+k183X119d6Fr1BACG -fZVGsot5rxBUEFPPSrBqYXG/0hRYv9Eq8a4rJAHK2IUWYfivZgL4DtrJ -nHlha+H5EPQVYkIAN3nGjXoHmosY+J3Sk+GyR+dCBHEwCkoHMKph3igc -zCEfxAWgqKeYd5mf+QQq2JKrkn2jceiIO7s3CrepeEFAjDSGuxhZjPJV -m7QoRGFuaWVsIFAuIE1haG9uZXkgPGRhbm1AcHJpbWUuZ3VzaGkub3Jn -PohOBBARAgAOBQI52NrxBAsDAQICGQEACgkQ+75aMGJLskn6LgCbBXUD -7UmGla5e1zyhuY667hP3F+UAoJIeDZJyRFkQAmb+u8KekRyLD1MLtDJE -YW5pZWwgTWFob25leSAoU2Vjb25kYXJ5IEVtYWlsKSA8Z3VzaGlAZ3Vz -aGkub3JnPohgBBMRAgAgBQJF1J/XAhsjBgsJCAcDAgQVAggDBBYCAwEC -HgECF4AACgkQ+75aMGJLskkVhACggsivQ9qLhfdA1rGm6f8LRJBSC4wA -oI930h+/hshClj6AkNwGRtHdf5XJuQINBDnY2vQQCAD2Qle3CH8IF3Ki -utapQvMF6PlTETlPtvFuuUs4INoBp1ajFOmPQFXz0AfGy0OplK33TGSG -SfgMg71l6RfUodNQ+PVZX9x2Uk89PY3bzpnhV5JZzf24rnRPxfx2vIPF -RzBhznzJZv8V+bv9kV7HAarTW56NoKVyOtQa8L9GAFgr5fSI/VhOSdvN -ILSd5JEHNmszbDgNRR0PfIizHHxbLY7288kjwEPwpVsYjY67VYy4XTjT -NP18F1dDox0YbN4zISy1Kv884bEpQBgRjXyEpwpy1obEAxnIByl6ypUM -2Zafq9AKUJsCRtMIPWakXUGfnHy9iUsiGSa6q6Jew1XpMgs7AAICB/9e -GjzF2gDh6U7I72x/6bSdlExx2LvIF92OZKc0S55IOS4Lgzs7Hbfm1aOL -4oJt7wBg94xkF4cerxz7y8R9J+k3GNl14KOjbYaMAh1rdxdAzikYMH1p -1hS78GMtwxky6jE5en87BGGMmnbC84JlxwN+MD7diu8D0Gkgjj/pxOp3 -2D5jEe02wBPVjFTpFLJjpFniLUY6AohRDEdSuZwWPuoKVWhpeWkasNn5 -qgwGyDREbXpyPsU02BkwE4JiGs+JMMdOn9KMh5dxiuwsMM9gHiQZS3mS -NBBKPWI5ZXsdStVFvapjf2FUFDXLUbTROPv1Xhqf0u7YYORFnWeVtvzK -IxVaiEYEGBECAAYFAjnY2vQACgkQ+75aMGJLsklBWgCeN7z9xk52y/ao -aCuF6hYb0d+3k98AoMRxvHuXI1Nc2FXY/x65PwHiUbaY - - -It's still ugly, but it's not AS ugly because it's base64, which includes -spaces, at least, and is easier to search for a pattern. Base64 can also be -easily wrapped on any boundary, which is nice. - -You can run your existing exported key through a base64 converter, like the -one built into the openssl binary, if you want to compare: - - %cat 624BB249.pub.bin | openssl enc -base64 - mQGiBDnY2vERBAD3cOxqoAYHYzS+xttvuyN9wZS8CrgwLIlT8Ewo/CCFI11PEO+g - JyNPvWPRQsyt1SE60reaIsie2bQTg3DYIg0PmH+ZOlNkpKesPULzdlw4Rx3dD/M3 - Lkrm977h4Y70ZKC+tbvoYKCCOIkUVevny1PVZ+mB94rb0mMgawSTrct03QCg/w6a - (...etc...) - OPv1Xhqf0u7YYORFnWeVtvzKIxVaiEYEGBECAAYFAjnY2vQACgkQ+75aMGJLsklB - WgCeN7z9xk52y/aoaCuF6hYb0d+3k98AoMRxvHuXI1Nc2FXY/x65PwHiUbaY - - -Now, while you could compare things byte-by-byte here, what I've done as a -"casual check" is just pick random strings in the text and see if they match -up. For example, you can see that "reaIsie2" is present in both. They both -start with and end with similar strings on every line. The real test, of -course, is to see if GPG recognizes it as a valid key. - -By the way, since I use DNSSEC, dnssec-signzone rewrites this record into the -proper "presentation format" for me, which is base64. If you want a similar -function, you can use named-compilezone to get some of the same effects, or -you can use the shell script I provide later in this document, with which you -don't even need make-dns-cert. - -2. Testing with gpg - -As above, the command to test this is remarkably simple: - - %rm /tmp/gpg-* - %echo "foo" | gpg --no-default-keyring --keyring /tmp/gpg-$$ --encrypt --armor --auto-key-locate cert -r danm@prime.gushi.org - gpg: keyring `/tmp/gpg-39996' created - gpg: key 624BB249: public key "Daniel P. Mahoney <danm@prime.gushi.org>" imported - gpg: Total number processed: 1 - gpg: imported: 1 - gpg: automatically retrieved `danm@prime.gushi.org' via DNS CERT - gpg: DE20C529: There is no assurance this key belongs to the named user - pub 2048g/DE20C529 2000-10-02 Daniel P. Mahoney <danm@prime.gushi.org> - Primary key fingerprint: C206 3054 5492 95F3 3490 37FF FBBE 5A30 624B B249 - Subkey fingerprint: CE40 B786 81E2 5CB9 F7D3 1318 9488 EB58 DE20 C529 - It is NOT certain that the key belongs to the person named - in the user ID. If you *really* know what you are doing, - you may answer the next question with yes. - Use this key anyway? (y/N) y - -----BEGIN PGP MESSAGE----- - Version: GnuPG v1.4.10 (FreeBSD) - hQIOA5SI61jeIMUpEAf/Sx7MKWm+e9EpUTSrDaBp4nJfDcBeqbYJulPRbDZz7eVW - 2+ol6sG0jWjuirbG1YppZccEr9mgqaQujdSXb/bleD8POS0TEWuf3aPswFQvHf90 - NLEzHt6BnfLoeobXXxyCflNaGX8zW+XgJtwZqAc2+jietuz8MOUhrf5m17CsW/wZ - IuEqwaek+K1irJp+w3rhaE08Jzb/S4CCifeW9J3mK57chQoPOu7Nz3rY666YKp/3 - 9T9StOgmFiNpvtFPNy4N7hHMHvbQwRsKlnkl+a7n0Aq2+OF4d1+/k2EE4uSGgcz0 - oHvee8DnuOx3P92mO4Jz5/0O0lwBD7I51iOjzUurTAgAiIM5sHV8/QFCVzH9Ule+ - gd8Wo5momcphkU/AXpce5Xgi/Vm4oGQ0x0queii8afUrzkpeN5SuwgQfAdOPiXW5 - 2bo527jBllxOxjeBasfky82XheTnLzbAQNvQNTEM9zE7zCl1LQJUZEJ1hVzcOevI - s+cm/AaGII9VkrAtSt3aLSRZuRJHFmhGvYd2Hz5WzcV1YFjXXP1eLwfetDBlaeB9 - /K5v4hZBkIZPbHX0DcLVrP96mCIT4wCBYSJw+I6n0E6Fz3IfybQG2HMfqWp966/c - 00ijx/aRDh42Dr/fTropuzzFzQr7weYDa1JnN3Zoftv6Zb/n+NcrmMiDCH8jJV6E - uMkaeeB5Mv7ssDQ9kPhO989CHFcznrE1lgOxjX8= - =NTLY - -----END PGP MESSAGE----- - -Okay, as above, try to decrypt that with your private key. - -### IPGP CERT Records - -Also known as: The "little" or "short" CERT record. (These terms are purely my -own). - -Relevant RFCs: [RFC 2538](http://www.faqs.org/rfcs/rfc2538.html), -[RFC 4398](http://www.faqs.org/rfcs/rfc4398.html), specifically sections 2.1 -and 3.3 - -IPGP certs are interesting. It's basically the same pieces of infomation that -are in the PKA record, as above, except that it's supported by an RFC. -Despite the RFC compliance, I am not sure if any non-gpg client knows to look -for them. However, because it's a DNS cert, make-dns-cert encodes the -information in binary, and your DNS server will see it in base64. So -verifying it visually is harder than verifying either of the above. - -#### Advantages - -* Small, easy-to-transmit records. -* Can use the same uri as the PKA record. - -#### Disadvantages - -* Relies on the URI scheme. I haven't yet been able to get a definitive list - of what uri schemes are supported, although I've seen http and finger. I've - also seen reports that unless gpg is compiled against curl, http 1.1 is not - supported (what this actually means is that any host that supports SSL will - probably work, because of some of the nuances of SSL). -* With PGP certs and IPGP certs, GPG will only parse the first key it gets, so - if you publish both, and one doesn't work, there's no failover. I've argued - that this should be fixed. -* Requires make-dns-cert, which is not built in GPG by default. (But see "A - Better Way" below) -* Requires publication in your main DNS zone. -* Despite being RFC compliant, GPG has additional trust vectors for PKA but - not this, despite the fact that they share basically the same information. -* Harder to verify with dig. - -#### Howto - -1. Note that some of these steps are redundant. If you're already doing a PKA - key, skip to step 5. - -2. Dig: - - %gpg --list-keys danm@prime.gushi.org - Warning: using insecure memory! - pub 1024D/624BB249 2000-10-02 <-- I'm going to use this one. - uid Daniel P. Mahoney <danm@prime.gushi.org> - uid Daniel Mahoney (Secondary Email) <gushi@gushi.org> - sub 2048g/DE20C529 2000-10-02 - pub 1024R/309C17C5 1997-05-08 - uid Daniel P. Mahoney <danm@prime.gushi.org> - -3. Export the key to a file (I use keyid.pub.asc, but it can be anything) - - %gpg --export --armor 624BB249 > 624BB249.pub.asc - Warning: using insecure memory! - % - -4. Get the fingerprint for your key: - - %gpg --list-keys --fingerprint 624BB249 - gpg: WARNING: using insecure memory! - gpg: please see http://www.gnupg.org/faq.html for more information - pub 1024D/624BB249 2000-10-02 - Key fingerprint = C206 3054 5492 95F3 3490 37FF FBBE 5A30 624B B249 <-- That bit is your fingerprint. - uid Daniel P. Mahoney <danm@prime.gushi.org> - uid Daniel Mahoney (Secondary Email) <gushi@gushi.org> - sub 2048g/DE20C529 2000-10-02 - -5. As above, run make-dns-cert. This time we use the -n, -f, and -u options: - - %make-dns-cert -n danm.prime.gushi.org. -f C2063054549295F3349037FFFBBE5A30624BB249 -u http://prime.gushi.org/danm.pubkey.txt - danm.prime.gushi.org. TYPE37 \# 64 0006 0000 00 14 C2063054549295F3349037FFFBBE5A30624BB249 687474703A2F2F7072696D652E67757368692E6F72672F64616E6D2E7075626B65792E747874 - % - - -6. Put the above in DNS. All on one line. Optionally add a TTL. - -7. IMPORTANT: make sure you don't have any other CERT records with the same - label (i.e. a "big" cert, as above). While it won't break things, you have - no control over which (of multiple) people will get. - -8. Reload your zone, and test. Testing will probably look VERY MUCH like the - above, but here are the steps anyway: - -#### Testing - -1. Dig: - - %dig +short danm.prime.gushi.org CERT - 6 0 0 FMIGMFRUkpXzNJA3//u+WjBiS7JJaHR0cDovL3ByaW1lLmd1c2hpLm9y Zy9kYW5tLnB1YmtleS50eHQ= - -Sadly, I haven't come across an easy way to decipher it yet, but there's -always gpg. - -2. GPG: - -Since we're fetching the same kind of record, the command is exactly the same -as before: - - %echo "foo" | gpg --no-default-keyring --keyring /tmp/gpg-$$ --encrypt --armor --auto-key-locate cert -r danm@prime.gushi.org - gpg: WARNING: using insecure memory! - gpg: please see http://www.gnupg.org/faq.html for more information - gpg: keyring `/tmp/gpg-39996' created - gpg: requesting key 624BB249 from http server prime.gushi.org - gpg: key 624BB249: public key "Daniel P. Mahoney <danm@prime.gushi.org>" imported - gpg: public key of ultimately trusted key CF45887D not found - gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model - gpg: depth: 0 valid: 1 signed: 0 trust: 0-, 0q, 0n, 0m, 0f, 1u - gpg: Total number processed: 1 - gpg: imported: 1 - gpg: automatically retrieved `danm@prime.gushi.org' via DNS CERT - gpg: DE20C529: There is no assurance this key belongs to the named user - pub 2048g/DE20C529 2000-10-02 Daniel P. Mahoney <danm@prime.gushi.org> - Primary key fingerprint: C206 3054 5492 95F3 3490 37FF FBBE 5A30 624B B249 - Subkey fingerprint: CE40 B786 81E2 5CB9 F7D3 1318 9488 EB58 DE20 C529 - It is NOT certain that the key belongs to the person named - in the user ID. If you *really* know what you are doing, - you may answer the next question with yes. - Use this key anyway? (y/N) y - -----BEGIN PGP MESSAGE----- - Version: GnuPG v1.4.10 (FreeBSD) - hQIOA5SI61jeIMUpEAgApZurJi3hZmDaUFjB2j93eX/lTl96xq6T//sz6nT6jcTx - IPnq1RN8IrIQPjDBByHdqOZBT5hhblr9xi7NKIIv3W4q4L0z0fJx7NERPZNvn/H0 - DkTwfDgAvCRxcKjenpLSwKZFwLjyfS7wjlDr3HFX7Tila0hbzplHslvgTE0QMcd7 - 7oNmEyOL3z+yZr/afQGp2wpzDv4YB9zOiNHcHcenqX0yrtiqKozZ9VAldi53rb/q - f38lwInbveyAcEQkE2iFwhRsbMR4VLcsBoxY6D9brsBprt23ey8Rnv+bQ9IAR0VN - /WYzU4zUUqb8HmpNFXQLEgH8A2BENw+bxkVYHjSfWQf/cBSGAzfBQQVJ7qp4tN0Z - FRVe51dokbU4NM9tGBdCzFHWARVkQX/Ulekd4F3sxBR/sum1UOT2xl2THVBz7/Pq - UCrTRPA0uH4dIbL5JpfGZhqsJ079+wmUWUtJIiO2wXi7ePEA/DrBC6p7jlmjyYN/ - AeSKcPoTeLX+zryV5bECx4RO6S56EEcy0Ns0pASGMsgUnKL6Adrv3Y6ea3ZAOQMn - H9Uo28BKTKNUvUaBpN8cV8jIbKYPPW9i04kvEQRqs5rdamERCY1vVTqYTrcLsNqz - fF3KopX+V82X1oE2QuGdFfd8mK57ZXJL3VRUrfohQjhfYNKzougiP46rQQv79MYT - j8kazWyJUuufm6NVco1/35Zdp1UhHu8qTgXxrjo= - =zY9G - -----END PGP MESSAGE----- - % - -Strangely, the output doesn't say what PKA does (a PKA retrieval has a line -about fetching via HTTP), however, by checking my webserver logs, I can see it -retrieved it from there: - - %tail -200 /usr/local/apache/logs/prime.gushi.org.log | grep pubkey | tail -1 - prime.gushi.org 72.9.101.130 - - [28/Oct/2009:23:50:43 -0400] "GET /danm.pubkey.txt HTTP/1.1" 200 4337 "-" "-" - % - -As usual, test decryption, etc. You're done. - -## Further Steps - -* Figure out which of these are useful to you, and use them.* When someone - asks for your public key, tell them to run the above command instead of - mailing them your key or sending them a keyserver URL. - -* Consider using the pka-related verify-options. - -* Look into embracing DNSSEC. With a signed root, there's a good trust-path - vector here. Who knows, maybe some day GPG will be dnssec-aware so it will - give more credit to a secure DNS transaction. Without a signed root, there - are still ways to have those who care about security use it, through - services such as [ISC's DLV registry](http://dlv.isc.org). - -* On DNSSEC: At present, GPG cannot see the difference between an insecure - response (one from an unsigned zone) and a correctly validated one from a - signed zone. (In a signed zone, an unsigned or malformed will simply get a - SERVFAIL dns response). Look into sponsoring development of GPG to make it - as an application more aware of this. - -## A better way to generate records - -In reading over a lot of these commands, I've come across a few problems with -the tools involved. They either require you to assemble large records by -hand, or manipulate huge files. - -DNS has also come a long way since these tools were written, and RFCs have -solidified that have determined the "presentation format" (i.e. the "master -file format") of what CERT records should look like. - -On top of everything, the make-dns-cert tool is not built by default, and is -not present in most binary distributions (RPM's, deb packages, FreeBSD's -ports). - -Thus, I took it upon myself to rewrite make-dns-cert as a shell script. - -### Advantages - -* Extracts your key for you (takes a keyid as the argument). -* Formats all three record types for you, you can pipe it right into your zone - file. -* Takes email address as an argument, generates record label. -* No compiling needed. -* Should work with most systems. Requires openssl and sed, a few other - standard utilities. -* Generates base64-ified CERT records, split into easy, manageable pieces. -* Generates DNS-friendly comments, so repeating tasks are easy to reference. -* (Eventually) available as a tarball, or as a paste-and-go script. -* Arguments are in logical DNS record order `emailaddress keyid [url]`. -* Will generate an IPGP CERT record without a URI (this is legal per RFC4398). - -You can see sample output -[here](http://www.gushi.org/make-dns-cert/sample-output.txt), and you can view -the script itself -[here](http://www.gushi.org/make-dns-cert/make-dns-cert.sh.txt). Depending on -your MIME settings, you can probably get a download link if you go -[here](http://www.gushi.org/make-dns-cert/make-dns-cert.sh). If you see the -script rather than getting a download prompt, you can just save-as. - -README, Changelog, TODO coming soon. - -## Other notes - -I'm not 100 percent sure (mainly because I haven't tried), but with IPGP cert, -and PKA, I believe I could in theory point at a keyserver directly, for -example, specify a uri of -[http://pgp.mit.edu:11371/pks/lookup?op=get&search=0xB0307039309C17C5](http://pgp.mit.edu:11371/pks/lookup?op=get&search=0xB0307039309C17C5). -I'm a bit dubious about the question marks and equals-signs, or if I might -have to uri-encode things. It's something to be tried. - -I'm trying to convince the GPG people that this would be much better adopted -if the make-dns-cert tool was built/included by default, or if its function -were included in gpg rather than a third-party tool. This is analagous as to -how dnssec-keygen is used to generate SSHFP DNS records. - -It doesn't do any actual cryptography, just some binary conversion, so in -theory it could be rewritten in pure-perl, so there's nothing to compile. - -I've made the argument to the GPG developers that if multiple CERT records are -available, all should be tried if one fails. So far, if multiple exist, only -the first received is parsed, and of course, DNS round-robins the answers by -default. - -It took me quite a lot of trial and error to realize that there's a difference -between "modern" RSA keys, like this: - - %gpg --list-keys --fingerprint gushi@prime.gushi.org - pub 2048R/CF45887D 2009-10-29 - Key fingerprint = FCB0 485E 050D DDFA 83C6 76E3 E722 3C05 CF45 887D - uid Gushi Test <gushi@prime.gushi.org> - sub 2048R/C9761244 2009-10-29 - -and ancient RSA keys like this pgp2.6.2 monster: - - %gpg --list-keys --fingerprint danm@prime.gushi.org - pub 1024R/309C17C5 1997-05-08 - Key fingerprint = 04 4B 1A 2E C4 62 95 73 73 A4 EA D0 08 A4 45 76 - uid Daniel P. Mahoney <danm@prime.gushi.org> - -Note the lack of a subkey there. Note the weird fingerprint. I have not been -able to get this key to properly export with gpg. If someone knows the Deep -Magic, let me know. - -## References - -### Blog posts and list threads - -While researching this I came across little more than a few blog posts, and a -few short discussions on the gpg-devel mailing list. - -* [A blog entry](http://www.df7cb.de/blog/2007/openpgp-dns.html) that seems to - have things mostly right. - -* [GPG Mailing List Discussion](http://lists.gnupg.org/pipermail/gnupg-users/2006-April/028314.html) - which seems to date towhen these features were first added. - -* [My own thread](http://www.mail-archive.com/gnupg-users@gnupg.org/msg12336.html) - on the gnupg-users mailing list that led upto this doc. - -* [A slideshow of a talk given on PKA](ftp://ftp.g10code.com/people/werner/talks/pka-intro.ps.gz) - (really the only doc I couldfind with regard to PKA). Note that this is a - postscript doc, for reasons I cannot fathom. - -### RFCs - -* [RFC 3597](http://www.faqs.org/rfcs/rfc3597.html) defines the odd format of - the records that make-dns-cert generates, if itconfuses you. - -* [RFC 2538](http://www.faqs.org/rfcs/rfc2538.html), which was superseded by - [RFC4398](http://www.faqs.org/rfcs/rfc4398.html), defines the format for a - CERT record. - -## Todo - -* At least one GPG enthusiast has suggested to me that any tools I write to - handle keys should simply be able to insert themusing nsupdate. I don't - disagree, but there's a complicated metric there as some of these require - manipulation of a site'smain zone, or at the very least, many subzones. In - doing this I'd also like to find out a bit about how to do nsupdate - withsig(0) and KEY records, which with the right policies would mean I could - do this without touching named.conf. That may be the subject of a whole - other howto. - -* (Done) I need to get the shell script cleaned up a bit more, and generate - proper docs, and start tracking it with version control. - -* I should probably get the gumption up to formally license all this stuff. - For right now, I declare it under the - [ISCLicense](http://en.wikipedia.org/wiki/ISC_license). - -* I'd like to track down the full list of supported URI types for PKA/IPGP - CERT records. There doesn't seem to be a defined standard for it. - -## Epilogue - -### About the author - -Dan Mahoney is a Systems Admin in the Bay Area, California. In his spare time -he enjoys thinking for those brief fleeting moments what he would do if he had -more free time. Keyid 624BB249, or email address danm@prime.gushi.org. - -### About this Document - -This document was written in [gnu nano](http://nano-editor.org), and HTML was -generated using [Markdown](http://daringfireball.net/projects/markdown). - -Markdown rocks. - -Originally published on my livejournal at -[http://gushi.livejournal.com/524199.html](http://gushi.livejournal.com/524199.html), -its main home is at -[http://www.gushi.org/make-dns-cert/HOWTO.html](http://www.gushi.org/make-dns-cert/HOWTO.html), -which is where later versions will be published. - -Free to use, comments to the above email address are welcome. |