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Support DNS-MITM redirection exceptions

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This commit is contained in:
znxDomain 2021-03-19 14:06:40 -04:00
parent 3afd9a737c
commit 7c50a6a3d1
2 changed files with 42 additions and 1 deletions
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1
docs/features/dns_mitm.md
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@ -10,6 +10,7 @@ DNS.mitm can be configured through the usage of a slightly-extended `hosts` file
In particular, hosts files parsed by DNS.mitm have the following extensions to the usual format:
+ `*` is treated as a wildcard character, matching any collection of 0 or more characters wherever it occurs in a hostname.
+ `%` is treated as a stand-in for the value of `nsd!environment_identifier`. This is always `lp1`, on production devices.
+ `-` is used to begin a line and indicates that this line contains a single hostname that is to be excepted from being redirected. It can be used to override a wildcard or other entry.
If multiple entries in a host file match a domain, the last-defined match is used.

42
stratosphere/ams_mitm/source/dns_mitm/dnsmitm_host_redirection.cpp
View file

@ -70,6 +70,7 @@ namespace ams::mitm::socket::resolver {
constinit os::SdkMutex g_redirection_lock;
std::vector<std::pair<std::string, ams::socket::InAddrT>> g_redirection_list;
std::vector<std::string> g_exception_list;
void RemoveRedirection(const char *hostname) {
for (auto it = g_redirection_list.begin(); it != g_redirection_list.end(); ++it) {
@ -84,6 +85,12 @@ namespace ams::mitm::socket::resolver {
RemoveRedirection(hostname);
g_redirection_list.emplace(g_redirection_list.begin(), std::string(hostname), addr);
}
void AddException(const char *hostname) {
if (!(std::find(g_exception_list.begin(), g_exception_list.end(), hostname) != g_exception_list.end())){
g_exception_list.emplace(g_exception_list.begin(), std::string(hostname));
}
}
constinit char g_specific_emummc_hosts_path[0x40] = {};
@ -105,6 +112,7 @@ namespace ams::mitm::socket::resolver {
Ip4,
WhiteSpace,
HostName,
ExceptList,
};
ams::socket::InAddrT current_address;
@ -127,6 +135,9 @@ namespace ams::mitm::socket::resolver {
state = State::Ip1;
} else if (c == '\n') {
state = State::BeginLine;
} else if (c == '-') {
work = 0;
state = State::ExceptList;
} else {
state = State::IgnoredLine;
}
@ -217,6 +228,26 @@ namespace ams::mitm::socket::resolver {
state = State::HostName;
}
break;
case State::ExceptList:
if (c == '\r' || c == '\n') {
AMS_ABORT_UNLESS(work < sizeof(current_hostname));
current_hostname[work] = '\x00';
AddException(current_hostname);
work = 0;
if (c == '\n') {
state = State::BeginLine;
}
} else if (c == '%') {
AMS_ABORT_UNLESS(work < sizeof(current_hostname) - env_len);
std::memcpy(current_hostname + work, env.value, env_len);
work += env_len;
} else {
AMS_ABORT_UNLESS(work < sizeof(current_hostname) - 1);
current_hostname[work++] = c;
}
break;
case State::HostName:
if (c == ' ' || c == '\r' || c == '\n' || c == '\t') {
AMS_ABORT_UNLESS(work < sizeof(current_hostname));
@ -311,6 +342,9 @@ namespace ams::mitm::socket::resolver {
/* Clear the redirections map. */
g_redirection_list.clear();
/* Clear the exceptions. */
g_exception_list.clear();
/* Open log file. */
::FsFile log_file;
mitm::fs::DeleteAtmosphereSdFile("/logs/dns_mitm_startup.log");
@ -381,13 +415,19 @@ namespace ams::mitm::socket::resolver {
for (const auto &[host, address] : g_redirection_list) {
Log(log_file, " `%s` -> %u.%u.%u.%u\n", host.c_str(), (address >> 0) & 0xFF, (address >> 8) & 0xFF, (address >> 16) & 0xFF, (address >> 24) & 0xFF);
}
/* Print the exceptions. */
Log(log_file, "Exceptions:\n");
for (const auto &host : g_exception_list) {
Log(log_file, " `%s`\n", host.c_str());
}
}
bool GetRedirectedHostByName(ams::socket::InAddrT *out, const char *hostname) {
std::scoped_lock lk(g_redirection_lock);
for (const auto &[host, address] : g_redirection_list) {
if (wildcardcmp(host.c_str(), hostname)) {
if (wildcardcmp(host.c_str(), hostname) &&
!(std::find(g_exception_list.begin(), g_exception_list.end(), hostname) != g_exception_list.end())) {
*out = address;
return true;
}