From 3ee79c1674fd6f99e8efca52cd7510e08b766770 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Wed, 2 Aug 2023 23:34:48 +0200
Subject: [PATCH] http: return error when receiving too large header set

To avoid abuse. The limit is set to 300 KB for the accumulated size of
all received HTTP headers for a single response. Incomplete research
suggests that Chrome uses a 256-300 KB limit, while Firefox allows up to
1MB.

Closes #11582
---
 lib/c-hyper.c     | 12 +++++++-----
 lib/cf-h1-proxy.c |  4 +++-
 lib/http.c        | 34 ++++++++++++++++++++++++++++++----
 lib/http.h        |  9 +++++++++
 lib/pingpong.c    |  4 +++-
 lib/urldata.h     | 17 ++++++++---------
 6 files changed, 60 insertions(+), 20 deletions(-)

diff --git a/lib/c-hyper.c b/lib/c-hyper.c
index c29983c0b24a6..0b9d9ab478e67 100644
--- a/lib/c-hyper.c
+++ b/lib/c-hyper.c
@@ -182,8 +182,11 @@ static int hyper_each_header(void *userdata,
     }
   }
 
-  data->info.header_size += (curl_off_t)len;
-  data->req.headerbytecount += (curl_off_t)len;
+  result = Curl_bump_headersize(data, len, FALSE);
+  if(result) {
+    data->state.hresult = result;
+    return HYPER_ITER_BREAK;
+  }
   return HYPER_ITER_CONTINUE;
 }
 
@@ -313,9 +316,8 @@ static CURLcode status_line(struct Curl_easy *data,
     if(result)
       return result;
   }
-  data->info.header_size += (curl_off_t)len;
-  data->req.headerbytecount += (curl_off_t)len;
-  return CURLE_OK;
+  result = Curl_bump_headersize(data, len, FALSE);
+  return result;
 }
 
 /*
diff --git a/lib/cf-h1-proxy.c b/lib/cf-h1-proxy.c
index c9b157c9bccc7..b1d8cb618b7d1 100644
--- a/lib/cf-h1-proxy.c
+++ b/lib/cf-h1-proxy.c
@@ -587,7 +587,9 @@ static CURLcode recv_CONNECT_resp(struct Curl_cfilter *cf,
         return result;
     }
 
-    data->info.header_size += (long)perline;
+    result = Curl_bump_headersize(data, perline, TRUE);
+    if(result)
+      return result;
 
     /* Newlines are CRLF, so the CR is ignored as the line isn't
        really terminated until the LF comes. Treat a following CR
diff --git a/lib/http.c b/lib/http.c
index f7c71afd7d847..bc78ff97435c4 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -3920,6 +3920,29 @@ static CURLcode verify_header(struct Curl_easy *data)
   return CURLE_OK;
 }
 
+CURLcode Curl_bump_headersize(struct Curl_easy *data,
+                              size_t delta,
+                              bool connect_only)
+{
+  size_t bad = 0;
+  if(delta < MAX_HTTP_RESP_HEADER_SIZE) {
+    if(!connect_only)
+      data->req.headerbytecount += (unsigned int)delta;
+    data->info.header_size += (unsigned int)delta;
+    if(data->info.header_size > MAX_HTTP_RESP_HEADER_SIZE)
+      bad = data->info.header_size;
+  }
+  else
+    bad = data->info.header_size + delta;
+  if(bad) {
+    failf(data, "Too large response headers: %zu > %zu",
+          bad, MAX_HTTP_RESP_HEADER_SIZE);
+    return CURLE_RECV_ERROR;
+  }
+  return CURLE_OK;
+}
+
+
 /*
  * Read any HTTP header lines from the server and pass them to the client app.
  */
@@ -4173,8 +4196,9 @@ CURLcode Curl_http_readwrite_headers(struct Curl_easy *data,
       if(result)
         return result;
 
-      data->info.header_size += (long)headerlen;
-      data->req.headerbytecount += (long)headerlen;
+      result = Curl_bump_headersize(data, headerlen, FALSE);
+      if(result)
+        return result;
 
       /*
        * When all the headers have been parsed, see if we should give
@@ -4496,8 +4520,10 @@ CURLcode Curl_http_readwrite_headers(struct Curl_easy *data,
     if(result)
       return result;
 
-    data->info.header_size += Curl_dyn_len(&data->state.headerb);
-    data->req.headerbytecount += Curl_dyn_len(&data->state.headerb);
+    result = Curl_bump_headersize(data, Curl_dyn_len(&data->state.headerb),
+                                  FALSE);
+    if(result)
+      return result;
 
     Curl_dyn_reset(&data->state.headerb);
   }
diff --git a/lib/http.h b/lib/http.h
index df3b4e38b8a88..4aeabc345938c 100644
--- a/lib/http.h
+++ b/lib/http.h
@@ -64,6 +64,10 @@ extern const struct Curl_handler Curl_handler_wss;
 
 struct dynhds;
 
+CURLcode Curl_bump_headersize(struct Curl_easy *data,
+                              size_t delta,
+                              bool connect_only);
+
 /* Header specific functions */
 bool Curl_compareheader(const char *headerline,  /* line to check */
                         const char *header,   /* header keyword _with_ colon */
@@ -183,6 +187,11 @@ CURLcode Curl_http_auth_act(struct Curl_easy *data);
 #define EXPECT_100_THRESHOLD (1024*1024)
 #endif
 
+/* MAX_HTTP_RESP_HEADER_SIZE is the maximum size of all response headers
+   combined that libcurl allows for a single HTTP response, any HTTP
+   version. This count includes CONNECT response headers. */
+#define MAX_HTTP_RESP_HEADER_SIZE (300*1024)
+
 #endif /* CURL_DISABLE_HTTP */
 
 /****************************************************************************
diff --git a/lib/pingpong.c b/lib/pingpong.c
index f3f7cb93cb9b7..523bbec189fe6 100644
--- a/lib/pingpong.c
+++ b/lib/pingpong.c
@@ -341,7 +341,9 @@ CURLcode Curl_pp_readresp(struct Curl_easy *data,
       ssize_t clipamount = 0;
       bool restart = FALSE;
 
-      data->req.headerbytecount += (long)gotbytes;
+      result = Curl_bump_headersize(data, gotbytes, FALSE);
+      if(result)
+        return result;
 
       pp->nread_resp += gotbytes;
       for(i = 0; i < gotbytes; ptr++, i++) {
diff --git a/lib/urldata.h b/lib/urldata.h
index e5446b6840f63..d21aa415dc94b 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -629,17 +629,16 @@ struct SingleRequest {
   curl_off_t bytecount;         /* total number of bytes read */
   curl_off_t writebytecount;    /* number of bytes written */
 
-  curl_off_t headerbytecount;   /* only count received headers */
-  curl_off_t deductheadercount; /* this amount of bytes doesn't count when we
-                                   check if anything has been transferred at
-                                   the end of a connection. We use this
-                                   counter to make only a 100 reply (without a
-                                   following second response code) result in a
-                                   CURLE_GOT_NOTHING error code */
-
   curl_off_t pendingheader;      /* this many bytes left to send is actually
                                     header and not body */
   struct curltime start;         /* transfer started at this time */
+  unsigned int headerbytecount;  /* only count received headers */
+  unsigned int deductheadercount; /* this amount of bytes doesn't count when
+                                     we check if anything has been transferred
+                                     at the end of a connection. We use this
+                                     counter to make only a 100 reply (without
+                                     a following second response code) result
+                                     in a CURLE_GOT_NOTHING error code */
   enum {
     HEADER_NORMAL,              /* no bad header at all */
     HEADER_PARTHEADER,          /* part of the chunk is a bad header, the rest
@@ -1089,7 +1088,6 @@ struct PureInfo {
   int httpversion; /* the http version number X.Y = X*10+Y */
   time_t filetime; /* If requested, this is might get set. Set to -1 if the
                       time was unretrievable. */
-  curl_off_t header_size;  /* size of read header(s) in bytes */
   curl_off_t request_size; /* the amount of bytes sent in the request(s) */
   unsigned long proxyauthavail; /* what proxy auth types were announced */
   unsigned long httpauthavail;  /* what host auth types were announced */
@@ -1097,6 +1095,7 @@ struct PureInfo {
   char *contenttype; /* the content type of the object */
   char *wouldredirect; /* URL this would've been redirected to if asked to */
   curl_off_t retry_after; /* info from Retry-After: header */
+  unsigned int header_size;  /* size of read header(s) in bytes */
 
   /* PureInfo members 'conn_primary_ip', 'conn_primary_port', 'conn_local_ip'
      and, 'conn_local_port' are copied over from the connectdata struct in

