TON DNS documentation

05.03.2020
in: Instructions

The aim of this document is to provide a very brief introduction to TON DNS, a service for translating human-readable domain names (such as test.ton or mysite.temp.ton) into TON smart contract addresses, ADNL addresses employed by services running in the TON Network (such as TON Sites), and so on.

1. Domain names

TON DNS employs familiarly-looking domain names, consisting of a UTF-8 encoded string up to 126 bytes, with different sections of the domain name separated by dots (.). Null characters (i.e. zero bytes) and, more generally, bytes in range 0..32 are not allowed in domain names. For instance, test.ton and mysite.temp.ton are valid TON DNS domains. A major difference from usual domain names is that TON DNS domains are case-sensitive; one could convert all domains to lowercase before performing a TON DNS lookup in order to obtain case-insensitivity if desired.

Currently, only domains ending in .ton are recognized as valid TON DNS domains. This could change in the future. Notice, however, that it is a bad idea to define first-level domains coinciding with first-level domains already existing in the Internet, such as .com or .to, because one could then register a TON domain google.com, deploy a TON site there, create a hidden link to a page at this TON site from his other innocently-looking TON site, and steal google.com cookies from unsuspecting visitors.

Internally, TON DNS transforms domain names as follows. First, a domain name is split into its components delimited by dot characters .. Then null characters are appended to each component, and all components are concatenated in reverse order. For example, google.com becomes com\0google\0.

2. Resolving TON DNS domains

A TON DNS domain is resolved as follows. First, the root DNS smart contract is located by inspecting the value of configuration parameter #4 in a recent masterchain state. This parameter contains the 256-bit address of the root DNS smart contract inside the masterchain.

Then a special get-method dnsresolve (method id 123660) is invoked for the root DNS smart contract, with two parameters. The first parameter is a CellSlice with 8n data bits containing the internal representation of the domain being resolved, where n is the length of the internal representation in bytes (at most 127). The second parameter is a signed 16-bit Integer containing the required category. If the category is zero, then all categories are requested.

If this get-method fails, then the TON DNS lookup is unsuccessful. Otherwise the get-method returns two values. The first is 8m, the length (in bits) of the prefix of the internal representation of the domain that has been resolved, 0 < m <= n. The second is a Cell with the TON DNS record for the required domain in the required category, or the root a Dictionary with 16-bit signed integer keys (categories) and values equal to the serializations of corresponding TON DNS records. If the domain cannot be resolved by the root DNS smart contract, i.e. if no non-empty prefix is a valid domain known to the smart contract, then (0, null) is returned. In other words, m = 0 means that the TON DNS lookup has found no data for the required domain. In that case, the TON DNS lookup is also unsuccessful.

If m = n, then the second component of the result is either a Cell with a valid TON DNS record for the required domain and category, or a Null if there is no TON DNS record for this domain with this category. In either case, the resolution process stops, and the TON DNS record thus obtained is deserialized and the required information (such as the type of the record and its parameters, such as a smart contract address or a ADNL address).

Finally, if m < n, then the lookup is successful so far, but only a partial result is available for the m-byte prefix of the original internal representation of the domain. The longest of all such prefixes known to the DNS smart contract is returned. For instance, an attempt to look up mysite.test.ton (i.e. ton\0test\0mysite\0 in the internal representation) in the root DNS smart contract might return 8m=72, corresponding to prefix ton\0test\0, i.e. to subdomain “test.ton” in the usual domain representation. In that case, dnsresolve() returns the value for category -1 for this prefix regardless of the category originally requested by the client. By convention, category -1 usually contains a TON DNS Record of type dns_next_resolver, containing the address of next resolver smart contract (which can reside in any other workchain, such as the basechain). If that is indeed the case, the resolution process continues by running get-method dnsresolve for the next resolver, with the internal representation of the domain name containing only its part unresolved so far (if we were looking up ton\0test\0mysite\0, and prefix ton\0test\0 was found by the root DNS smart contract, then the next dnsresolve will be invoked with mysite\0 as its first argument). Then either the next resolver smart contract reports an error or the absence of any records for the required domain or any of its prefixes, or the final result is obtained, or another prefix and next resolver smart contract is returned. In the latter case, the process continues in the same fashion until all of the original domain is resolved.

3. Using LiteClient and TonLib to resolve TON DNS domains

The above process can be invoked automatically using the TON LiteClient or TONLib. For instance, one can invoke the command dnsresolve test.ton 1 in the LiteClient to resolve “test.ton” with category 1 and obtain the following result:

> dnsresolve test.ton
...
Result for domain 'test.ton' category 1
raw data: x{AD011B3CBBE404F47FFEF92D0D7894C5C6F215F677732A49E544F16D1E75643D46AB00}

category #1 : (dns_adnl_address adnl_addr:x1B3CBBE404F47FFEF92D0D7894C5C6F215F677732A49E544F16D1E75643D46AB flags:0)
	adnl address 1B3CBBE404F47FFEF92D0D7894C5C6F215F677732A49E544F16D1E75643D46AB = UNTZO7EAT2H77XZFUGXRFGFY3ZBL5TXOMVETZKE6FWR45LEHVDKXAUY

In this case, the TON DNS record for “test.ton” is a dns_adnl_address record containing ADNL address UNTZO7EAT2H77XZFUGXRFGFY3ZBL5TXOMVETZKE6FWR45LEHVDKXAUY

Alternatively, one can invoke tonlib-cli and enter the following command:

> dns resolve root test.ton 1
Redirect resolver
...
Done
  test.ton 1 ADNL:untzo7eat2h77xzfugxrfgfy3zbl5txomvetzke6fwr45lehvdkxauy

This is a more compact representation of the same result.

Finally, if one uses RLDP-HTTP Proxy in the client mode to access TON Sites from a browser as explained in TON Sites How-to, the TONLib resolver is automatically invoked to resolve all domains entered by the end user, so that a HTTP query to http://test.ton/testnet/last is automatically forwarded to ADNL address untzo7eat2h77xzfugxrfgfy3zbl5txomvetzke6fwr45lehvdkxauy via RLDP.

4. Registering new domains

Suppose that you have a new TON Site with a newly-generated ADNL address, such as vcqmha5j3ceve35ammfrhqty46rkhi455otydstv66pk2tmf7rl25f3. Of course, the end user might type http://vcqmha5j3ceve35ammfrhqty46rkhi455otydstv66pk2tmf7rl25f3.adnl/ to visit your TON Site from a browser using a RLDP-HTTP Proxy in client mode, but this is not very convenient. Instead, you could register a new domain, say, mysite.temp.ton with a dns_adnl_address record in category 1 containing the ADNL address vcq…25f3 of your TON Site. Then the user would access your TON Site by simply typing mysite.temp.ton in a browser.

In general, you would need to contact the owner of the higher-level domain and ask him to add a record for your subdomain in his DNS resolver smart contract. However, the TestNet of the TON Blockchain has a special resolver smart contract for temp.ton that allows anyone to automatically register any subdomains of temp.ton not registered yet, provided a small fee (in test Grams) is paid to that smart contract. In our case, we first need to find out the address of this smart contract, for example by using the Lite Client:

> dnsresolve temp.ton -1
...
category #-1 : (dns_next_resolver
  resolver:(addr_std
    anycast:nothing workchain_id:0 address:x190BD756F6C0E7948DC26CB47968323177FB20344F8F9A50918CAF87ECB34B79))
	next resolver 0:190BD756F6C0E7948DC26CB47968323177FB20344F8F9A50918CAF87ECB34B79 = EQAZC9dW9sDnlI3CbLR5aDIxd_sgNE-PmlCRjK-H7LNLeUXN

We see that the address of this automatic DNS smart contract is EQAZC9dW9sDnlI3CbLR5aDIxd_sgNE-PmlCRjK-H7LNLeUXN. We can run several get methods to compute the required price for registering a subdomain, and to learn the period for which the subdomain will be registered:

> runmethod EQAZC9dW9sDnlI3CbLR5aDIxd_sgNE-PmlCRjK-H7LNLeUXN getstdperiod
...
arguments:  [ 67418 ] 
result:  [ 700000 ] 
remote result (not to be trusted):  [ 700000 ] 
> runmethod EQAZC9dW9sDnlI3CbLR5aDIxd_sgNE-PmlCRjK-H7LNLeUXN getppr
...
arguments:  [ 109522 ] 
result:  [ 100000000 ] 
remote result (not to be trusted):  [ 100000000 ] 

We see that subdomains are registered for 700000 seconds (about eight days), and that the registration price is 100000000ng = 0.1 test Grams per domain, plus a price for each bit and cell of stored data, which can be learned by running get-methods getppb and getppc.

Now we want this smart contract to register our subdomain. In order to do this, we have to create a special message from our wallet to the automatic DNS smart contract. Let us assume that we have a wallet my_new_wallet with address kQABzslAMKOVwkSkkWfelS1pYSDOSyTcgn0yY_loQvyo_ZgI. Then we run the following Fift script (from the subdirectory crypto/smartcont of the source tree):

fift -s auto-dns.fif <auto-dns-smc-addr> add <my-subdomain> <expire-time> owner <my-wallet-addr> cat 1 adnl <my-site-adnl-address>

For example:

$ fift -s auto-dns.fif EQAZC9dW9sDnlI3CbLR5aDIxd_sgNE-PmlCRjK-H7LNLeUXN add 'mysite' 700000 owner kQABzslAMKOVwkSkkWfelS1pYSDOSyTcgn0yY_loQvyo_ZgI cat 1 adnl vcqmha5j3ceve35ammfrhqty46rkhi455otydstv66pk2tmf7rl25f3
Automatic DNS smart contract address = 0:190bd756f6c0e7948dc26cb47968323177fb20344f8f9a50918caf87ecb34b79 
kQAZC9dW9sDnlI3CbLR5aDIxd_sgNE-PmlCRjK-H7LNLef5H
Action: add mysite 1583865040 
Operation code: 0x72656764 
Value: x{2_}
 x{BC000C_}
  x{AD0145061C1D4EC44A937D0318589E13C73D151D1CEF5D3C0E53AFBCF56A6C2FE2BD00}
 x{BFFFF4_}
  x{9FD3800039D928061472B84894922CFBD2A5AD2C2419C9649B904FA64C7F2D085F951FA01_}

Internal message body is: x{726567645E5D2E700481CE3F0EDAF2E6D2E8CA00BCCFB9A1_}
 x{2_}
  x{BC000C_}
   x{AD0145061C1D4EC44A937D0318589E13C73D151D1CEF5D3C0E53AFBCF56A6C2FE2BD00}
  x{BFFFF4_}
   x{9FD3800039D928061472B84894922CFBD2A5AD2C2419C9649B904FA64C7F2D085F951FA01_}

B5EE9C7241010601007800012F726567645E5D2E700481CE3F0EDAF2E6D2E8CA00BCCFB9A10102012002030105BC000C040105BFFFF4050046AD0145061C1D4EC44A937D0318589E13C73D151D1CEF5D3C0E53AFBCF56A6C2FE2BD0000499FD3800039D928061472B84894922CFBD2A5AD2C2419C9649B904FA64C7F2D085F951FA01070E6337D
Query_id is 6799642071046147647 = 0x5E5D2E700481CE3F 
(Saved to file dns-msg-body.boc)

We see that the internal message body for this query has been created and saved into file dns-msg-body.boc. Now you have to send a payment from your wallet kQAB..ZgI to the automatic DNS smart contract EQA..UXN, along with message body from file dns-msg-body.boc, so that the automatic DNS smart contract knows what you want it to do. If your wallet has been created by means of new-wallet.fif, you can simply use -B command-line argument to wallet.fif while performing this transfer:

$ fift -s wallet.fif my_new_wallet EQAZC9dW9sDnlI3CbLR5aDIxd_sgNE-PmlCRjK-H7LNLeUXN 1 1.7 -B dns-msg-body.boc
Source wallet address = 0:01cec94030a395c244a49167de952d696120ce4b24dc827d3263f96842fca8fd 
kQABzslAMKOVwkSkkWfelS1pYSDOSyTcgn0yY_loQvyo_ZgI
Loading private key from file my_new_wallet.pk
Transferring GR$1.7 to account kQAZC9dW9sDnlI3CbLR5aDIxd_sgNE-PmlCRjK-H7LNLef5H = 0:190bd756f6c0e7948dc26cb47968323177fb20344f8f9a50918caf87ecb34b79 seqno=0x1 bounce=-1 
Body of transfer message is x{726567645E5D2E700481CE3F0EDAF2E6D2E8CA00BCCFB9A1_}
 x{2_}
  x{BC000C_}
   x{AD0145061C1D4EC44A937D0318589E13C73D151D1CEF5D3C0E53AFBCF56A6C2FE2BD00}
  x{BFFFF4_}
   x{9FD3800039D928061472B84894922CFBD2A5AD2C2419C9649B904FA64C7F2D085F951FA01_}

signing message: x{0000000103}
 x{62000C85EBAB7B6073CA46E1365A3CB41918BBFD901A27C7CD2848C657C3F659A5BCA32A9F880000000000000000000000000000726567645E5D2E700481CE3F0EDAF2E6D2E8CA00BCCFB9A1_}
  x{2_}
   x{BC000C_}
    x{AD0145061C1D4EC44A937D0318589E13C73D151D1CEF5D3C0E53AFBCF56A6C2FE2BD00}
   x{BFFFF4_}
    x{9FD3800039D928061472B84894922CFBD2A5AD2C2419C9649B904FA64C7F2D085F951FA01_}

resulting external message: x{8800039D928061472B84894922CFBD2A5AD2C2419C9649B904FA64C7F2D085F951FA050E3817FC01F564AECE810B8077D72E3EE15C81392E8B4AE9CDD0D6575821481C996AE8FFBABA0513F131E10E27C006C6544E99D71E0A6AACF7D02C677342B040000000081C_}
 x{62000C85EBAB7B6073CA46E1365A3CB41918BBFD901A27C7CD2848C657C3F659A5BCA32A9F880000000000000000000000000000726567645E5D2E700481CE3F0EDAF2E6D2E8CA00BCCFB9A1_}
  x{2_}
   x{BC000C_}
    x{AD0145061C1D4EC44A937D0318589E13C73D151D1CEF5D3C0E53AFBCF56A6C2FE2BD00}
   x{BFFFF4_}
    x{9FD3800039D928061472B84894922CFBD2A5AD2C2419C9649B904FA64C7F2D085F951FA01_}

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
(Saved to file wallet-query.boc)

(You have to replace 1 with the correct sequence number for your wallet.) Once you obtain a signed external message in wallet-query.boc, addressed to your wallet and instructing it to transfer 1.7 test Grams to the automatic DNS smart contract along with the description of your new domain to be registered, you can upload this message using the LiteClient by typing

> sendfile wallet-query.boc 
[ 1][t 1][!testnode]	sending query from file wallet-query.boc
[ 3][t 1][!query]	external message status is 1

If all works correctly, you’ll obtain some change from the automatic DNS smart contract in a confirmation message (it will charge only the storage fees for your subdomain and processing fees for running the smart contract and sending messages, and return the rest), and your new domain will be registered:

> last
...
> dnsresolve mysite.temp.ton 1
...
Result for domain 'mysite.temp.ton' category 1
category #1 : (dns_adnl_address adnl_addr:x45061C1D4EC44A937D0318589E13C73D151D1CEF5D3C0E53AFBCF56A6C2FE2BD flags:0)
	adnl address 45061C1D4EC44A937D0318589E13C73D151D1CEF5D3C0E53AFBCF56A6C2FE2BD = vcqmha5j3ceve35ammfrhqty46rkhi455otydstv66pk2tmf7rl25f3

You can modify or prolong this domain in essentially the same manner, by first creating a request in file dns-msg-body.boc by means of auto-dns.fif, using such actions as update or prolong, and then embedding this request into a message from your wallet to the automatic DNS smart contract using wallet.fif or a similar script with command-line argument -B dns-msg-body.boc.

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