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wireaddr: relax is_dnsaddr to allow for underscore in hostname #5789

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merged 2 commits into from
Dec 6, 2022
Merged

wireaddr: relax is_dnsaddr to allow for underscore in hostname #5789

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bb3efcd
wireaddr: is_dnsaddr allow underscore in hostname
m-schmoock Dec 5, 2022
8bff0e8
wireaddr: adds test for punycode
m-schmoock Dec 6, 2022
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4 changes: 4 additions & 0 deletions common/test/run-ip_port_parsing.c
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Original file line number Diff line number Diff line change
Expand Up @@ -126,11 +126,15 @@ int main(int argc, char *argv[])
assert(is_dnsaddr("123example.com"));
assert(is_dnsaddr("example123.com"));
assert(is_dnsaddr("is-valid.3hostname123.com"));
assert(is_dnsaddr("just-a-hostname-with-dashes"));
assert(is_dnsaddr("lightningd_dest.underscore.allowed.in.hostname.part.com"));
assert(is_dnsaddr("punycode.xn--bcher-kva.valid.com"));
assert(!is_dnsaddr("UPPERCASE.invalid.com"));
assert(!is_dnsaddr("-.invalid.com"));
assert(!is_dnsaddr("invalid.-example.com"));
assert(!is_dnsaddr("invalid.example-.com"));
assert(!is_dnsaddr("invalid..example.com"));
assert(!is_dnsaddr("underscore.not.allowed.in.domain_name.com"));

/* Grossly invalid. */
assert(!separate_address_and_port(tmpctx, "[", &ip, &port));
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17 changes: 14 additions & 3 deletions common/wireaddr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -375,18 +375,24 @@ bool is_wildcardaddr(const char *arg)
return streq(arg, "");
}

/* Rules:
/* The rules to check for DNS FQDNs, see `man 7 hostname`
*
* - not longer than 255
* - segments are separated with . dot
* - segments do not start or end with - hyphen
* - segments must be longer thant zero
* - lowercase a-z and digits 0-9 and - hyphen
* - segments must be longer than zero
* - allow lowercase a-z and digits 0-9 and - hyphen
* - additionall we allow for an '_' underscore in the hostname part.
*
* See issue #5657
* https://github.com/ElementsProject/lightning/issues/5657
* https://en.wikipedia.org/wiki/Hostname
*/
bool is_dnsaddr(const char *arg)
{
size_t i, arglen;
int lastdot;
int numdot;

if (is_ipaddr(arg) || is_toraddr(arg) || is_wildcardaddr(arg))
return false;
Expand All @@ -396,8 +402,10 @@ bool is_dnsaddr(const char *arg)
if (arglen > 255)
return false;
lastdot = -1;
numdot = 0;
for (i = 0; i < arglen; i++) {
if (arg[i] == '.') {
numdot++;
/* segment must be longer than zero */
if (i - lastdot == 1)
return false;
Expand All @@ -416,6 +424,9 @@ bool is_dnsaddr(const char *arg)
continue;
if (arg[i] == '-')
continue;
/* allow for _ underscores in the first hostname part */
if (arg[i] == '_' && numdot == 0)
continue;
return false;
}
return true;
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