http2: implement maxSessionMemory

The maxSessionMemory is a cap for the amount of memory an
Http2Session is permitted to consume. If exceeded, new
`Http2Stream` sessions will be rejected with an
`ENHANCE_YOUR_CALM` error and existing `Http2Stream`
instances that are still receiving headers will be
terminated with an `ENHANCE_YOUR_CALM` error.

Backport-PR-URL: #18050
Backport-PR-URL: #20456
PR-URL: #17967
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Author: jasnell

doc/api/http2.md

@@ -1652,6 +1652,15 @@ changes:
 * `options` {Object}
   * `maxDeflateDynamicTableSize` {number} Sets the maximum dynamic table size
     for deflating header fields. **Default:** `4Kib`
+  * `maxSessionMemory`{number} Sets the maximum memory that the `Http2Session`
+    is permitted to use. The value is expressed in terms of number of megabytes,
+    e.g. `1` equal 1 megabyte. The minimum value allowed is `1`. **Default:**
+    `10`. This is a credit based limit, existing `Http2Stream`s may cause this
+    limit to be exceeded, but new `Http2Stream` instances will be rejected
+    while this limit is exceeded. The current number of `Http2Stream` sessions,
+    the current memory use of the header compression tables, current data
+    queued to be sent, and unacknowledged PING and SETTINGS frames are all
+    counted towards the current limit.
   * `maxHeaderListPairs` {number} Sets the maximum number of header entries.
     **Default:** `128`. The minimum value is `4`.
   * `maxOutstandingPings` {number} Sets the maximum number of outstanding,
@@ -1730,6 +1739,15 @@ changes:
     `false`. See the [`'unknownProtocol'`][] event. See [ALPN negotiation][].
   * `maxDeflateDynamicTableSize` {number} Sets the maximum dynamic table size
     for deflating header fields. **Default:** `4Kib`
+  * `maxSessionMemory`{number} Sets the maximum memory that the `Http2Session`
+    is permitted to use. The value is expressed in terms of number of megabytes,
+    e.g. `1` equal 1 megabyte. The minimum value allowed is `1`. **Default:**
+    `10`. This is a credit based limit, existing `Http2Stream`s may cause this
+    limit to be exceeded, but new `Http2Stream` instances will be rejected
+    while this limit is exceeded. The current number of `Http2Stream` sessions,
+    the current memory use of the header compression tables, current data
+    queued to be sent, and unacknowledged PING and SETTINGS frames are all
+    counted towards the current limit.
   * `maxHeaderListPairs` {number} Sets the maximum number of header entries.
     **Default:** `128`. The minimum value is `4`.
   * `maxOutstandingPings` {number} Sets the maximum number of outstanding,
@@ -1813,6 +1831,15 @@ changes:
 * `options` {Object}
   * `maxDeflateDynamicTableSize` {number} Sets the maximum dynamic table size
     for deflating header fields. **Default:** `4Kib`
+  * `maxSessionMemory`{number} Sets the maximum memory that the `Http2Session`
+    is permitted to use. The value is expressed in terms of number of megabytes,
+    e.g. `1` equal 1 megabyte. The minimum value allowed is `1`. **Default:**
+    `10`. This is a credit based limit, existing `Http2Stream`s may cause this
+    limit to be exceeded, but new `Http2Stream` instances will be rejected
+    while this limit is exceeded. The current number of `Http2Stream` sessions,
+    the current memory use of the header compression tables, current data
+    queued to be sent, and unacknowledged PING and SETTINGS frames are all
+    counted towards the current limit.
   * `maxHeaderListPairs` {number} Sets the maximum number of header entries.
     **Default:** `128`. The minimum value is `1`.
   * `maxOutstandingPings` {number} Sets the maximum number of outstanding,

lib/internal/http2/util.js

@@ -175,7 +175,8 @@ const IDX_OPTIONS_PADDING_STRATEGY = 4;
 const IDX_OPTIONS_MAX_HEADER_LIST_PAIRS = 5;
 const IDX_OPTIONS_MAX_OUTSTANDING_PINGS = 6;
 const IDX_OPTIONS_MAX_OUTSTANDING_SETTINGS = 7;
-const IDX_OPTIONS_FLAGS = 8;
+const IDX_OPTIONS_MAX_SESSION_MEMORY = 8;
+const IDX_OPTIONS_FLAGS = 9;
 
 function updateOptionsBuffer(options) {
   var flags = 0;
@@ -219,6 +220,11 @@ function updateOptionsBuffer(options) {
     optionsBuffer[IDX_OPTIONS_MAX_OUTSTANDING_SETTINGS] =
       Math.max(1, options.maxOutstandingSettings);
   }
+  if (typeof options.maxSessionMemory === 'number') {
+    flags |= (1 << IDX_OPTIONS_MAX_SESSION_MEMORY);
+    optionsBuffer[IDX_OPTIONS_MAX_SESSION_MEMORY] =
+      Math.max(1, options.maxSessionMemory);
+  }
   optionsBuffer[IDX_OPTIONS_FLAGS] = flags;
 }
 

src/node_http2.cc

@@ -174,6 +174,18 @@ Http2Options::Http2Options(Environment* env) {
   if (flags & (1 << IDX_OPTIONS_MAX_OUTSTANDING_SETTINGS)) {
     SetMaxOutstandingSettings(buffer[IDX_OPTIONS_MAX_OUTSTANDING_SETTINGS]);
   }
+
+  // The HTTP2 specification places no limits on the amount of memory
+  // that a session can consume. In order to prevent abuse, we place a
+  // cap on the amount of memory a session can consume at any given time.
+  // this is a credit based system. Existing streams may cause the limit
+  // to be temporarily exceeded but once over the limit, new streams cannot
+  // created.
+  // Important: The maxSessionMemory option in javascript is expressed in
+  //            terms of MB increments (i.e. the value 1 == 1 MB)
+  if (flags & (1 << IDX_OPTIONS_MAX_SESSION_MEMORY)) {
+    SetMaxSessionMemory(buffer[IDX_OPTIONS_MAX_SESSION_MEMORY] * 1e6);
+  }
 }
 
 void Http2Session::Http2Settings::Init() {
@@ -482,11 +494,13 @@ Http2Session::Http2Session(Environment* env,
   // Capture the configuration options for this session
   Http2Options opts(env);
 
-  int32_t maxHeaderPairs = opts.GetMaxHeaderPairs();
+  max_session_memory_ = opts.GetMaxSessionMemory();
+
+  uint32_t maxHeaderPairs = opts.GetMaxHeaderPairs();
   max_header_pairs_ =
       type == NGHTTP2_SESSION_SERVER
-          ? std::max(maxHeaderPairs, 4)     // minimum # of request headers
-          : std::max(maxHeaderPairs, 1);    // minimum # of response headers
+          ? std::max(maxHeaderPairs, 4U)     // minimum # of request headers
+          : std::max(maxHeaderPairs, 1U);    // minimum # of response headers
 
   max_outstanding_pings_ = opts.GetMaxOutstandingPings();
   max_outstanding_settings_ = opts.GetMaxOutstandingSettings();
@@ -673,18 +687,21 @@ inline bool Http2Session::CanAddStream() {
   size_t maxSize =
       std::min(streams_.max_size(), static_cast<size_t>(maxConcurrentStreams));
   // We can add a new stream so long as we are less than the current
-  // maximum on concurrent streams
-  return streams_.size() < maxSize;
+  // maximum on concurrent streams and there's enough available memory
+  return streams_.size() < maxSize &&
+         IsAvailableSessionMemory(sizeof(Http2Stream));
 }
 
 inline void Http2Session::AddStream(Http2Stream* stream) {
   CHECK_GE(++statistics_.stream_count, 0);
   streams_[stream->id()] = stream;
+  IncrementCurrentSessionMemory(stream->self_size());
 }
 
 
-inline void Http2Session::RemoveStream(int32_t id) {
-  streams_.erase(id);
+inline void Http2Session::RemoveStream(Http2Stream* stream) {
+  streams_.erase(stream->id());
+  DecrementCurrentSessionMemory(stream->self_size());
 }
 
 // Used as one of the Padding Strategy functions. Will attempt to ensure
@@ -1678,7 +1695,7 @@ Http2Stream::Http2Stream(
 
 Http2Stream::~Http2Stream() {
   if (session_ != nullptr) {
-    session_->RemoveStream(id_);
+    session_->RemoveStream(this);
     session_ = nullptr;
   }
 
@@ -2008,7 +2025,7 @@ inline int Http2Stream::DoWrite(WriteWrap* req_wrap,
       i == nbufs - 1 ? req_wrap : nullptr,
       bufs[i]
     });
-    available_outbound_length_ += bufs[i].len;
+    IncrementAvailableOutboundLength(bufs[i].len);
   }
   CHECK_NE(nghttp2_session_resume_data(**session_, id_), NGHTTP2_ERR_NOMEM);
   return 0;
@@ -2030,7 +2047,10 @@ inline bool Http2Stream::AddHeader(nghttp2_rcbuf* name,
   if (this->statistics_.first_header == 0)
     this->statistics_.first_header = uv_hrtime();
   size_t length = GetBufferLength(name) + GetBufferLength(value) + 32;
-  if (current_headers_.size() == max_header_pairs_ ||
+  // A header can only be added if we have not exceeded the maximum number
+  // of headers and the session has memory available for it.
+  if (!session_->IsAvailableSessionMemory(length) ||
+      current_headers_.size() == max_header_pairs_ ||
       current_headers_length_ + length > max_header_length_) {
     return false;
   }
@@ -2174,7 +2194,7 @@ ssize_t Http2Stream::Provider::Stream::OnRead(nghttp2_session* handle,
       // Just return the length, let Http2Session::OnSendData take care of
       // actually taking the buffers out of the queue.
       *flags |= NGHTTP2_DATA_FLAG_NO_COPY;
-      stream->available_outbound_length_ -= amount;
+      stream->DecrementAvailableOutboundLength(amount);
     }
   }
 
@@ -2197,6 +2217,15 @@ ssize_t Http2Stream::Provider::Stream::OnRead(nghttp2_session* handle,
   return amount;
 }
 
+inline void Http2Stream::IncrementAvailableOutboundLength(size_t amount) {
+  available_outbound_length_ += amount;
+  session_->IncrementCurrentSessionMemory(amount);
+}
+
+inline void Http2Stream::DecrementAvailableOutboundLength(size_t amount) {
+  available_outbound_length_ -= amount;
+  session_->DecrementCurrentSessionMemory(amount);
+}
 
 
 // Implementation of the JavaScript API
@@ -2690,6 +2719,7 @@ Http2Session::Http2Ping* Http2Session::PopPing() {
   if (!outstanding_pings_.empty()) {
     ping = outstanding_pings_.front();
     outstanding_pings_.pop();
+    DecrementCurrentSessionMemory(ping->self_size());
   }
   return ping;
 }
@@ -2698,6 +2728,7 @@ bool Http2Session::AddPing(Http2Session::Http2Ping* ping) {
   if (outstanding_pings_.size() == max_outstanding_pings_)
     return false;
   outstanding_pings_.push(ping);
+  IncrementCurrentSessionMemory(ping->self_size());
   return true;
 }
 
@@ -2706,6 +2737,7 @@ Http2Session::Http2Settings* Http2Session::PopSettings() {
   if (!outstanding_settings_.empty()) {
     settings = outstanding_settings_.front();
     outstanding_settings_.pop();
+    DecrementCurrentSessionMemory(settings->self_size());
   }
   return settings;
 }
@@ -2714,6 +2746,7 @@ bool Http2Session::AddSettings(Http2Session::Http2Settings* settings) {
   if (outstanding_settings_.size() == max_outstanding_settings_)
     return false;
   outstanding_settings_.push(settings);
+  IncrementCurrentSessionMemory(settings->self_size());
   return true;
 }
 

src/node_http2.h

@@ -82,6 +82,9 @@ void inline debug_vfprintf(const char* format, ...) {
 // Also strictly limit the number of outstanding SETTINGS frames a user sends
 #define DEFAULT_MAX_SETTINGS 10
 
+// Default maximum total memory cap for Http2Session.
+#define DEFAULT_MAX_SESSION_MEMORY 1e7;
+
 // These are the standard HTTP/2 defaults as specified by the RFC
 #define DEFAULT_SETTINGS_HEADER_TABLE_SIZE 4096
 #define DEFAULT_SETTINGS_ENABLE_PUSH 1
@@ -500,8 +503,17 @@ class Http2Options {
     return max_outstanding_settings_;
   }
 
+  void SetMaxSessionMemory(uint64_t max) {
+    max_session_memory_ = max;
+  }
+
+  uint64_t GetMaxSessionMemory() {
+    return max_session_memory_;
+  }
+
  private:
   nghttp2_option* options_;
+  uint64_t max_session_memory_ = DEFAULT_MAX_SESSION_MEMORY;
   uint32_t max_header_pairs_ = DEFAULT_MAX_HEADER_LIST_PAIRS;
   padding_strategy_type padding_strategy_ = PADDING_STRATEGY_NONE;
   size_t max_outstanding_pings_ = DEFAULT_MAX_PINGS;
@@ -628,6 +640,9 @@ class Http2Stream : public AsyncWrap,
   // Returns the stream identifier for this stream
   inline int32_t id() const { return id_; }
 
+  inline void IncrementAvailableOutboundLength(size_t amount);
+  inline void DecrementAvailableOutboundLength(size_t amount);
+
   inline bool AddHeader(nghttp2_rcbuf* name,
                         nghttp2_rcbuf* value,
                         uint8_t flags);
@@ -848,7 +863,7 @@ class Http2Session : public AsyncWrap {
   inline void AddStream(Http2Stream* stream);
 
   // Removes a stream instance from this session
-  inline void RemoveStream(int32_t id);
+  inline void RemoveStream(Http2Stream* stream);
 
   // Write data to the session
   inline ssize_t Write(const uv_buf_t* bufs, size_t nbufs);
@@ -906,6 +921,30 @@ class Http2Session : public AsyncWrap {
   Http2Settings* PopSettings();
   bool AddSettings(Http2Settings* settings);
 
+  void IncrementCurrentSessionMemory(uint64_t amount) {
+    current_session_memory_ += amount;
+  }
+
+  void DecrementCurrentSessionMemory(uint64_t amount) {
+    current_session_memory_ -= amount;
+  }
+
+  // Returns the current session memory including the current size of both
+  // the inflate and deflate hpack headers, the current outbound storage
+  // queue, and pending writes.
+  uint64_t GetCurrentSessionMemory() {
+    uint64_t total = current_session_memory_ + sizeof(Http2Session);
+    total += nghttp2_session_get_hd_deflate_dynamic_table_size(session_);
+    total += nghttp2_session_get_hd_inflate_dynamic_table_size(session_);
+    total += outgoing_storage_.size();
+    return total;
+  }
+
+  // Return true if current_session_memory + amount is less than the max
+  bool IsAvailableSessionMemory(uint64_t amount) {
+    return GetCurrentSessionMemory() + amount <= max_session_memory_;
+  }
+
   struct Statistics {
     uint64_t start_time;
     uint64_t end_time;
@@ -1035,6 +1074,10 @@ class Http2Session : public AsyncWrap {
   // The maximum number of header pairs permitted for streams on this session
   uint32_t max_header_pairs_ = DEFAULT_MAX_HEADER_LIST_PAIRS;
 
+  // The maximum amount of memory allocated for this session
+  uint64_t max_session_memory_ = DEFAULT_MAX_SESSION_MEMORY;
+  uint64_t current_session_memory_ = 0;
+
   // The collection of active Http2Streams associated with this session
   std::unordered_map<int32_t, Http2Stream*> streams_;
 

src/node_http2_state.h

@@ -50,6 +50,7 @@ namespace http2 {
     IDX_OPTIONS_MAX_HEADER_LIST_PAIRS,
     IDX_OPTIONS_MAX_OUTSTANDING_PINGS,
     IDX_OPTIONS_MAX_OUTSTANDING_SETTINGS,
+    IDX_OPTIONS_MAX_SESSION_MEMORY,
     IDX_OPTIONS_FLAGS
   };
 

test/parallel/test-http2-util-update-options-buffer.js

@@ -20,7 +20,8 @@ const IDX_OPTIONS_PADDING_STRATEGY = 4;
 const IDX_OPTIONS_MAX_HEADER_LIST_PAIRS = 5;
 const IDX_OPTIONS_MAX_OUTSTANDING_PINGS = 6;
 const IDX_OPTIONS_MAX_OUTSTANDING_SETTINGS = 7;
-const IDX_OPTIONS_FLAGS = 8;
+const IDX_OPTIONS_MAX_SESSION_MEMORY = 8;
+const IDX_OPTIONS_FLAGS = 9;
 
 {
   updateOptionsBuffer({
@@ -31,7 +32,8 @@ const IDX_OPTIONS_FLAGS = 8;
     paddingStrategy: 5,
     maxHeaderListPairs: 6,
     maxOutstandingPings: 7,
-    maxOutstandingSettings: 8
+    maxOutstandingSettings: 8,
+    maxSessionMemory: 9
   });
 
   strictEqual(optionsBuffer[IDX_OPTIONS_MAX_DEFLATE_DYNAMIC_TABLE_SIZE], 1);
@@ -42,6 +44,7 @@ const IDX_OPTIONS_FLAGS = 8;
   strictEqual(optionsBuffer[IDX_OPTIONS_MAX_HEADER_LIST_PAIRS], 6);
   strictEqual(optionsBuffer[IDX_OPTIONS_MAX_OUTSTANDING_PINGS], 7);
   strictEqual(optionsBuffer[IDX_OPTIONS_MAX_OUTSTANDING_SETTINGS], 8);
+  strictEqual(optionsBuffer[IDX_OPTIONS_MAX_SESSION_MEMORY], 9);
 
   const flags = optionsBuffer[IDX_OPTIONS_FLAGS];
 

test/sequential/test-http2-max-session-memory.js

@@ -0,0 +1,44 @@
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const http2 = require('http2');
+
+// Test that maxSessionMemory Caps work
+
+const largeBuffer = Buffer.alloc(1e6);
+
+const server = http2.createServer({ maxSessionMemory: 1 });
+
+server.on('stream', common.mustCall((stream) => {
+  stream.respond();
+  stream.end(largeBuffer);
+}));
+
+server.listen(0, common.mustCall(() => {
+  const client = http2.connect(`http://localhost:${server.address().port}`);
+
+  {
+    const req = client.request();
+
+    req.on('response', () => {
+      // This one should be rejected because the server is over budget
+      // on the current memory allocation
+      const req = client.request();
+      req.on('error', common.expectsError({
+        code: 'ERR_HTTP2_STREAM_ERROR',
+        type: Error,
+        message: 'Stream closed with error code 11'
+      }));
+      req.on('close', common.mustCall(() => {
+        server.close();
+        client.destroy();
+      }));
+    });
+
+    req.resume();
+    req.on('close', common.mustCall());
+  }
+}));