From eae92b214a34d4811127f5fd24566a63f9f83d61 Mon Sep 17 00:00:00 2001
From: levlam <levlam@telegram.org>
Date: Sun, 26 Jan 2020 01:22:07 +0300
Subject: [PATCH] Really fix too long TLS-proxy domain.

GitOrigin-RevId: a07726e8bb75b467d26043d6c9b4ad834a961567
---
 td/mtproto/ProxySecret.cpp | 14 +++++++++-----
 td/mtproto/ProxySecret.h   |  8 ++++++--
 td/mtproto/TlsInit.cpp     |  6 ++++--
 td/telegram/net/Proxy.h    |  2 +-
 4 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/td/mtproto/ProxySecret.cpp b/td/mtproto/ProxySecret.cpp
index 1d53b30fe..571cd8f77 100644
--- a/td/mtproto/ProxySecret.cpp
+++ b/td/mtproto/ProxySecret.cpp
@@ -12,7 +12,7 @@
 namespace td {
 namespace mtproto {
 
-Result<ProxySecret> ProxySecret::from_link(Slice encoded_secret) {
+Result<ProxySecret> ProxySecret::from_link(Slice encoded_secret, bool truncate_if_needed) {
   auto r_decoded = hex_decode(encoded_secret);
   if (r_decoded.is_error()) {
     r_decoded = base64url_decode(encoded_secret);
@@ -20,12 +20,16 @@ Result<ProxySecret> ProxySecret::from_link(Slice encoded_secret) {
   if (r_decoded.is_error()) {
     return Status::Error(400, "Wrong proxy secret");
   }
-  return from_binary(r_decoded.ok());
+  return from_binary(r_decoded.ok(), truncate_if_needed);
 }
 
-Result<ProxySecret> ProxySecret::from_binary(Slice raw_unchecked_secret) {
-  if (raw_unchecked_secret.size() > 17 + 255) {
-    return Status::Error(400, "Too long secret");
+Result<ProxySecret> ProxySecret::from_binary(Slice raw_unchecked_secret, bool truncate_if_needed) {
+  if (raw_unchecked_secret.size() > 17 + MAX_DOMAIN_LENGTH) {
+    if (truncate_if_needed) {
+      raw_unchecked_secret.truncate(17 + MAX_DOMAIN_LENGTH);
+    } else {
+      return Status::Error(400, "Too long secret");
+    }
   }
   if (raw_unchecked_secret.size() == 16 ||
       (raw_unchecked_secret.size() == 17 && static_cast<unsigned char>(raw_unchecked_secret[0]) == 0xdd) ||
diff --git a/td/mtproto/ProxySecret.h b/td/mtproto/ProxySecret.h
index c4aade6cf..199d02a6e 100644
--- a/td/mtproto/ProxySecret.h
+++ b/td/mtproto/ProxySecret.h
@@ -15,8 +15,12 @@ namespace mtproto {
 
 class ProxySecret {
  public:
-  static Result<ProxySecret> from_link(Slice encoded_secret);
-  static Result<ProxySecret> from_binary(Slice raw_unchecked_secret);
+  static constexpr size_t MAX_DOMAIN_LENGTH = 182;  // must be small enough to not overflow TLS-hello length
+
+  static Result<ProxySecret> from_link(Slice encoded_secret, bool truncate_if_needed = false);
+
+  static Result<ProxySecret> from_binary(Slice raw_unchecked_secret, bool truncate_if_needed = false);
+
   static ProxySecret from_raw(Slice raw_secret) {
     ProxySecret result;
     result.secret_ = raw_secret.str();
diff --git a/td/mtproto/TlsInit.cpp b/td/mtproto/TlsInit.cpp
index d36b94f39..4e956a6a9 100644
--- a/td/mtproto/TlsInit.cpp
+++ b/td/mtproto/TlsInit.cpp
@@ -6,6 +6,8 @@
 //
 #include "td/mtproto/TlsInit.h"
 
+#include "td/mtproto/ProxySecret.h"
+
 #include "td/utils/as.h"
 #include "td/utils/BigNum.h"
 #include "td/utils/common.h"
@@ -157,7 +159,7 @@ class TlsHelloContext {
     return grease_.size();
   }
   Slice get_domain() const {
-    return Slice(domain_).substr(0, 255);
+    return Slice(domain_).substr(0, ProxySecret::MAX_DOMAIN_LENGTH);
   }
 
  private:
@@ -225,7 +227,7 @@ class TlsHelloCalcLength {
   }
 
   Result<size_t> finish() {
-    if (size_ > 515) {
+    if (size_ > 514) {
       on_error(Status::Error("Too long for zero padding"));
     }
     if (size_ < 11 + 32) {
diff --git a/td/telegram/net/Proxy.h b/td/telegram/net/Proxy.h
index a9dca8a4d..947930c39 100644
--- a/td/telegram/net/Proxy.h
+++ b/td/telegram/net/Proxy.h
@@ -134,7 +134,7 @@ class Proxy {
     } else if (type_ == Proxy::Type::Mtproto) {
       parse(server_, parser);
       parse(port_, parser);
-      secret_ = mtproto::ProxySecret::from_link(parser.template fetch_string<Slice>()).move_as_ok();
+      secret_ = mtproto::ProxySecret::from_link(parser.template fetch_string<Slice>(), true).move_as_ok();
     } else {
       CHECK(type_ == Proxy::Type::None);
     }