Unstable signature verification from c library

[carnun]

I am by no means a crypto expert, but on a recent project we were having issues tracing down problems verifying signatures. In the end we reduced it to the difference between the way the secp256k1 c library verified signatures vs the way elliptic.js verified signatures. I can't tell you what is going wrong on the maths side but hopefully the following test case can help:

msg = Buffer("7f83b1657ff1fc53b92dc18148a1d65dfc2d4b1fa3d677284addd200126d9069", 'hex');
sig = Buffer("3046022100c74b47f51776096053d01dea04bc67f77f1145df46a5b4c5c817aa2acdfad7ff022100efbbe32d7d7b2109365290427cf19bdbdc14304608441aaf19781216da53d6da", 'hex')
publicKey = Buffer("040db450c7aca2a501d6e8f04338f7e93f4fef29fa5881fcc180ec8324f3b40a1fa22bccd174898e2bcb5247f2d648ea899a95dae8bf84ba8a13e7dcc9cb7f08bd", 'hex')

var secp256k1 = require('secp256k1');

//this one fails
sigImport = secp256k1.signatureImport(sig);
if(secp256k1.verifySync(msg, sigImport, publicKey)) {
  console.log("sig ok");
} else {
  console.log("is not ok")
}

var EC = require("elliptic").ec;
//this one succeeds
var ec = new EC("secp256k1");
if (ec.verify(msg, sig, publicKey)) {
  console.log("sig ok");
} else {
  console.log("is not ok");
}

[fanatid]

@carnun it's happened because secp256k1 return false for non lower-s signatures,
so, working example:

var msg = Buffer('7f83b1657ff1fc53b92dc18148a1d65dfc2d4b1fa3d677284addd200126d9069', 'hex')
var sig = Buffer('3046022100c74b47f51776096053d01dea04bc67f77f1145df46a5b4c5c817aa2acdfad7ff022100efbbe32d7d7b2109365290427cf19bdbdc14304608441aaf19781216da53d6da', 'hex')
var publicKey = Buffer('040db450c7aca2a501d6e8f04338f7e93f4fef29fa5881fcc180ec8324f3b40a1fa22bccd174898e2bcb5247f2d648ea899a95dae8bf84ba8a13e7dcc9cb7f08bd', 'hex')

var secp256k1 = require('secp256k1')

// this one fails
var sigImport = secp256k1.signatureImport(sig)
var normalizedSig = secp256k1.signatureNormalize(sigImport)
if (secp256k1.verify(msg, normalizedSig, publicKey)) {
  console.log('sig ok')
} else {
  console.log('is not ok')
}