implement uacomment config parameter which can add comments to user agent as per BIP-0014 #6462

prusnak · 2015-07-22T11:35:51Z

User can add the following into theirs bitcoin.conf:

uacomment=Prague
uacomment=BeagleBone

which will result in the following user agent:

/Satoshi:0.11.99(Prague; BeagleBone)/

jgarzik · 2015-07-23T19:01:21Z

Concept ACK. Needs some sort of size limiting.

laanwj · 2015-07-24T11:30:47Z

src/clientversion.cpp

@@ -99,11 +100,20 @@ std::string FormatSubVersion(const std::string& name, int nClientVersion, const
    std::ostringstream ss;
    ss << "/";
    ss << name << ":" << FormatVersion(nClientVersion);
-    if (!comments.empty())
+
+    const std::string key = "-uacomment";


Right now, FormatSubVersion is a pure utility function that doesn't use any global state. I think it should stay that way. E.g. by adding an const std::vector<std::string> &commentList argument. Then pass in this data at the caller side.

Also makes it easier to test this in util_tests.

laanwj · 2015-07-24T11:33:17Z

Concept ACK.

sipa · 2015-07-24T18:00:02Z

Concept ACK, agree with @laanwj.

prusnak · 2015-07-27T23:59:59Z

Updated commit to reflect @laanwj request (to not have FormatSubVersion function dependent on global object).

(Actually, this was my original code, but I changed it, because I did not want to duplicate the logic in two files).

prusnak · 2015-07-29T17:11:42Z

@jgarzik What is the maximum desired length of user agent string? Or should we just limit the number of comments and their length (e.g. max 5 comments of max 40 characters)?

sipa · 2015-07-29T17:46:11Z

Bitcoin Core will reject strings longer than 256 characters for the subser string in "version" messages.

laanwj · 2015-07-31T14:05:59Z

Tested ACK. Named a few nodes.

  "subversion": "/Satoshi:0.11.99(Inanna)/",
...
  "subversion": "/Satoshi:0.11.99(Ishtar)/",
...
  "subversion": "/Satoshi:0.11.99(Ereshkigal)/",

Names are returned both by getnetworkinfo and the version P2P message, which I verified with bitcoin-submittx:

recv msg_version(nVersion=70002 nServices=1 nTime=Fri Jul 31 15:41:00 2015 addrTo=CAddress(nTime=0 nServices=1 ip=0.0.0.0 port=0) addrFrom=CAddress(nTime=0 nServices=1 ip=0.0.0.0 port=18444) nNonce=0x95FDC41E438E8122 strSubVer=/Satoshi:0.11.99(Ishtar)/ nStartingHeight=0)

It will happily send a subversion longer than 256 bytes, though:

recv msg_version(nVersion=70002 nServices=1 nTime=Fri Jul 31 15:53:46 2015 addrTo=CAddress(nTime=0 nServices=1 ip=0.0.0.0 port=0) addrFrom=CAddress(nTime=0 nServices=1 ip=0.0.0.0 port=18333) nNonce=0x8782C2C672C750F3 strSubVer=/Satoshi:0.11.99(Ishtar; 0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef; 0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef; 0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef; 0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef)/ nStartingHeight=5178)

... which, as expected, gets me only connections to old versions. The result is quite interesting. Some nodes send me a REJECT message, which, as it arrives before full version negotiation is seen as misbehavior:

2015-07-31 13:52:46 Misbehaving: 52.1.41.179:18333 (0 -> 1)
2015-07-31 13:52:46 ProcessMessages(reject, 31 bytes) FAILED peer=1

Although not an easy to trigger issue, we should avoid sending a string longer than we accept ourselves.

I share your concern about duplicating code: but you could still define a function that calls FormatSubVersion(CLIENT_NAME, CLIENT_VERSION, mapMultiArgs.count("-uacomment") ? mapMultiArgs["-uacomment"] : std::vector<string>())));

which can add comments to user agent as per BIP-0014

prusnak · 2015-07-31T14:20:14Z

Easiest logic would be to discard all of the comments if strlen > 256.

laanwj · 2015-07-31T15:29:35Z

It's a workable solution but failing silently is unexpected behavior. I'd prefer to check this in AppInit2 and fail if the subversion string is too long.

prusnak · 2015-07-31T16:07:07Z

Added check to AppInit2 function. (No more than 4 comments and no longer than 40 characters allowed).

jonasschnelli · 2015-08-01T07:46:26Z

utACK.

Nit: now you can provide 4string x 40bytes. What if one likes to provide 1x50 bytes?
Would it not make more sense to limit the combined string to 240 (or 255) bytes?

prusnak · 2015-08-01T13:34:37Z

Reworked check to check total length of all comments altogether. If it is more than 200 characters the error is issued.

jgarzik · 2015-08-01T16:59:22Z

ut ACK

sipa · 2015-08-01T18:47:58Z

utACK

Reworked-By: Wladimir J. van der Laan <laanwj@gmail.com>

laanwj · 2015-08-05T07:46:33Z

@prusnak I slightly reworked the last commit:

Add a constant MAX_SUBVERSION_LENGTH in net.h and use where appropriate
Compute strSubVersion only once, during initialization, and check the size immediately
Use stored strSubVersion in PushVersion and GetNetworkInfo
Remove translation for the error.

This reduces the amount of code, and cuts down on magic values.
https://github.com/laanwj/bitcoin/tree/2015_08_prusnak_uacomment
Can you please take it over?

prusnak · 2015-08-05T10:40:22Z

@laanwj Updated PR to your code.

7b79cbd limit total length of user agent comments (Pavol Rusnak) 557f8ea implement uacomment config parameter which can add comments to user agent as per BIP-0014 (Pavol Rusnak)

prusnak · 2015-08-05T13:51:03Z

Thanks!

ABISprotocol · 2015-08-06T01:51:34Z

I can't help but wonder if this conflicts somehow with #253 and the effort there which seemed to be to not identify or associate users... what might be the long-term effects of this effort which is to associate a bitcoin address with a node? No need to answer me here.

Diapolo · 2015-08-06T06:49:08Z

src/init.cpp

+    // format user agent, check total size
+    strSubVersion = FormatSubVersion(CLIENT_NAME, CLIENT_VERSION, mapMultiArgs.count("-uacomment") ? mapMultiArgs["-uacomment"] : std::vector<string>());
+    if (strSubVersion.size() > MAX_SUBVERSION_LENGTH) {
+        return InitError(strprintf("Total length of network version string %i exceeds maximum of %i characters. Reduce the number and/or size of uacomments.",


Shouldn't that one be translatable?

No, I'd say. Apart from being a specific technical error (which we don't translate for Googlability, see translation_strings_policy.md) it's an extremely rare condition caused by almost-abuse of the configuration system. No need to waste translator time on that.

laanwj · 2015-08-06T16:31:30Z

@ABISprotocol How is having this option a problem? It's not always a good idea to use it, but many people run essentially public nodes without wallet, and for those there is no need to 'hide in the crowd'.

ABISprotocol · 2015-08-10T19:13:27Z

@laanwj Since you asked, my thinking was that there might be ancillary effects on other users, a butterfly effect if you will in the privacy context. Though different functionally (and thus not comparable in the way one might consider it to be), the address reuse problem comes to mind (again, this is perhaps not relevant here because it is addressed in other ways, such as implementing stealth or confidential transactions); but at the core of this, the concern is that when you have an option which encourages or motivates users to associate a node with an address, then that will have privacy implications not only for the user who makes that choice, but for other users in the network as well.

sipa · 2015-08-10T19:20:46Z

The ability to change what software your node advertizes as is not the same as encouraging to put an address there (which is indeed a bad idea IMHO).

maflcko · 2015-09-01T22:00:29Z

I might be missing something but how does this implement BIP-0014? Current master happily accepts comments containing any of the "reserved symbols" mentioned in BIP-0014 and silently drops other characters when pushing to the network.
E.g. -:

My local node:

getnetworkinfo
[...]
"subversion": "/Satoshi:0.11.99(node-bob_12);:/:)()/",
[...]

Some remote node:

getpeerinfo
[...]
"subver": "/Satoshi:0.11.99(nodebob_12);:/:)()/",
[...]

Misc upstream PRs Cherry-picked from the following upstream PRs: - bitcoin/bitcoin#6077 - Second commit only (first was already applied to 0.11.X and then reverted) - bitcoin/bitcoin#6284 - bitcoin/bitcoin#6489 - bitcoin/bitcoin#6462 - bitcoin/bitcoin#6647 - bitcoin/bitcoin#6235 - bitcoin/bitcoin#6905 - bitcoin/bitcoin#6780 - Excluding second commit (QT) and third commit (requires bitcoin/bitcoin#6993) - bitcoin/bitcoin#6961 - Excluding QT parts, and a small `src/policy/policy.cpp` change which depends on a bunch of other PRs, which we'll have to remember to come back to. - bitcoin/bitcoin#7044 - bitcoin/bitcoin#8856 - bitcoin/bitcoin#9002 Part of #2074 and #2132.

prusnak mentioned this pull request Jul 22, 2015

Add possibility to change an User Agent via an option in the Config File #5909

Closed

laanwj reviewed Jul 24, 2015
View reviewed changes

jonasschnelli mentioned this pull request Jul 24, 2015

Refactor user-agent handling to be more extensible #6385

Closed

laanwj added the P2P label Jul 31, 2015

implement uacomment config parameter

557f8ea

which can add comments to user agent as per BIP-0014

limit total length of user agent comments

7b79cbd

Reworked-By: Wladimir J. van der Laan <laanwj@gmail.com>

laanwj merged commit 7b79cbd into bitcoin:master Aug 5, 2015

laanwj added a commit that referenced this pull request Aug 5, 2015

Merge pull request #6462

c384800

7b79cbd limit total length of user agent comments (Pavol Rusnak) 557f8ea implement uacomment config parameter which can add comments to user agent as per BIP-0014 (Pavol Rusnak)

prusnak mentioned this pull request Aug 5, 2015

Add possibility to associate a Bitcoin address with a node #5783

Closed

Diapolo reviewed Aug 6, 2015
View reviewed changes

maflcko mentioned this pull request Sep 4, 2015

Handle reserved symbols in uacomment (BIP-0014) #6634

Closed

jonasschnelli mentioned this pull request Sep 12, 2015

implement uacomment config parameter bitcoinxt/bitcoinxt#69

Closed

This was referenced May 18, 2017

mapArgs is modified by setgenerate RPC without locking zcash/zcash#2132

Open

Misc upstream PRs zcash/zcash#2390

Merged

str4d mentioned this pull request Jul 14, 2017

Bitcoin 0.12 P2P/Net PRs 1 zcash/zcash#2534

Draft

str4d mentioned this pull request Dec 19, 2017

Implement uacomment config parameter zcash/zcash#2813

Merged

bitcoin locked as resolved and limited conversation to collaborators Sep 8, 2021

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implement uacomment config parameter which can add comments to user agent as per BIP-0014 #6462

implement uacomment config parameter which can add comments to user agent as per BIP-0014 #6462

prusnak commented Jul 22, 2015

jgarzik commented Jul 23, 2015

laanwj Jul 24, 2015

laanwj commented Jul 24, 2015

sipa commented Jul 24, 2015

prusnak commented Jul 27, 2015

prusnak commented Jul 29, 2015

sipa commented Jul 29, 2015

laanwj commented Jul 31, 2015

prusnak commented Jul 31, 2015

laanwj commented Jul 31, 2015

prusnak commented Jul 31, 2015

jonasschnelli commented Aug 1, 2015

prusnak commented Aug 1, 2015

jgarzik commented Aug 1, 2015

sipa commented Aug 1, 2015

laanwj commented Aug 5, 2015

prusnak commented Aug 5, 2015

prusnak commented Aug 5, 2015

ABISprotocol commented Aug 6, 2015

Diapolo Aug 6, 2015

laanwj Aug 6, 2015

laanwj commented Aug 6, 2015

ABISprotocol commented Aug 10, 2015

sipa commented Aug 10, 2015 via email

maflcko commented Sep 1, 2015

implement uacomment config parameter which can add comments to user agent as per BIP-0014 #6462

implement uacomment config parameter which can add comments to user agent as per BIP-0014 #6462

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