Issue-3364: Reproduction + fix(Proposal)

Sign-off: Rajan Y.(rajanyadav0307@gmail.com)

Author: rajanyadav0307

src/aws-cpp-sdk-core/source/http/curl/CurlHttpClient.cpp

@@ -19,6 +19,7 @@
 #include <algorithm>
 #include <cassert>
 #include <thread>
+#include <ostream>
 
 using namespace Aws::Client;
 using namespace Aws::Http;
@@ -181,6 +182,27 @@ static int64_t GetContentLengthFromHeader(CURL* connectionHandle,
   return hasContentLength ? static_cast<int64_t>(contentLength) : -1;
 }
 
+// Best-effort output position probe for diagnostics only.
+// Returns false if the stream does not support positioning.
+static bool TryGetOutputPos(std::ostream& os,
+                            std::ostream::pos_type& outPos) noexcept
+{
+    std::streambuf* sb = os.rdbuf();
+    if (!sb)
+    {
+        return false;
+    }
+
+    const auto pos = sb->pubseekoff(0, std::ios_base::cur, std::ios_base::out);
+    if (pos == std::ostream::pos_type(std::ostream::off_type(-1)))
+    {
+        return false;
+    }
+
+    outPos = pos;
+    return true;
+}
+
 static size_t WriteData(char* ptr, size_t size, size_t nmemb, void* userdata)
 {
     if (ptr)
@@ -217,38 +239,51 @@ static size_t WriteData(char* ptr, size_t size, size_t nmemb, void* userdata)
           }
         }
 
-        if (response->GetResponseBody().fail()) {
-            const auto& ref = response->GetResponseBody();
-            AWS_LOGSTREAM_ERROR(CURL_HTTP_CLIENT_TAG, "Response output stream in bad state (eof: "
-                    << ref.eof() << ", bad: " << ref.bad() << ")");
-            return 0;
-        }
+        auto& body = response->GetResponseBody();
 
-        auto cur = response->GetResponseBody().tellp();
-        if (response->GetResponseBody().fail()) {
-            const auto& ref = response->GetResponseBody();
-            AWS_LOGSTREAM_ERROR(CURL_HTTP_CLIENT_TAG, "Unable to query response output position (eof: "
-                    << ref.eof() << ", bad: " << ref.bad() << ")");
+        if (body.fail()) {
+            const auto& ref = body;
+            AWS_LOGSTREAM_ERROR(CURL_HTTP_CLIENT_TAG,
+                "Response output stream in bad state (eof: "
+                << ref.eof() << ", bad: " << ref.bad() << ")");
             return 0;
         }
 
-        response->GetResponseBody().write(ptr, static_cast<std::streamsize>(sizeToWrite));
-        if (response->GetResponseBody().fail()) {
-            const auto& ref = response->GetResponseBody();
-            AWS_LOGSTREAM_ERROR(CURL_HTTP_CLIENT_TAG, "Failed to write " << size << " / " << sizeToWrite << " B response"
-                << " at " << cur << " (eof: " << ref.eof() << ", bad: " << ref.bad() << ")");
+        body.write(ptr, static_cast<std::streamsize>(sizeToWrite));
+        if (body.fail()) {
+            const auto& ref = body;
+
+            std::ostream::pos_type pos{};
+            const bool hasPos = TryGetOutputPos(body, pos);
+
+            Aws::StringStream ss;
+            ss << "Failed to write " << size << " / " << sizeToWrite << " B response";
+            if (hasPos) {
+                ss << " at " << pos;
+            } else {
+                ss << " (output stream not seekable)";
+            }
+            ss << " (received so far: "
+                << context->m_numBytesResponseReceived
+                << " B, eof: " << ref.eof()
+                << ", bad: " << ref.bad() << ")";
+
+            AWS_LOGSTREAM_ERROR(CURL_HTTP_CLIENT_TAG, ss.str());
             return 0;
         }
+
         if ((context->m_request->IsEventStreamRequest() || context->m_request->HasEventStreamResponse() )
             && !response->HasHeader(Aws::Http::X_AMZN_ERROR_TYPE))
         {
-            response->GetResponseBody().flush();
-            if (response->GetResponseBody().fail()) {
-                const auto& ref = response->GetResponseBody();
-                AWS_LOGSTREAM_ERROR(CURL_HTTP_CLIENT_TAG, "Failed to flush event response (eof: "
+            body.flush();
+            if (body.fail()) {
+                const auto& ref = body;
+                AWS_LOGSTREAM_ERROR(CURL_HTTP_CLIENT_TAG,
+                    "Failed to flush event response (eof: "
                     << ref.eof() << ", bad: " << ref.bad() << ")");
                 return 0;
             }
+
         }
         auto& receivedHandler = context->m_request->GetDataReceivedEventHandler();
         if (receivedHandler)

tests/aws-cpp-sdk-core-tests/http/HttpClientTest.cpp

@@ -67,6 +67,11 @@ class HttpClientTest : public Aws::Testing::AwsCppSdkGTestSuite
 {
 };
 
+class CURLHttpClientTest : public Aws::Testing::AwsCppSdkGTestSuite
+{
+};
+
+
 TEST_F(HttpClientTest, TestRandomURLWithNoProxy)
 {
     auto httpClient = CreateHttpClient(Aws::Client::ClientConfiguration());
@@ -382,7 +387,97 @@ TEST_F(CURLHttpClientTest, TestHttpRequestWorksFine)
     EXPECT_EQ(Aws::Http::HttpResponseCode::OK, response->GetResponseCode());
     EXPECT_EQ("", response->GetClientErrorMessage());
 }
+
+#include <aws/core/utils/memory/stl/AWSVector.h>
+#include <streambuf>
+
+// A streambuf that supports writing but does NOT support seeking.
+// This reproduces the behavior of many filtering / transforming streams.
+class NonSeekableWriteBuf final : public std::streambuf
+{
+public:
+    explicit NonSeekableWriteBuf(Aws::Vector<char>& out) : m_out(out) {}
+
+protected:
+    std::streamsize xsputn(const char* s, std::streamsize n) override
+    {
+        if (n > 0)
+        {
+            m_out.insert(m_out.end(), s, s + static_cast<size_t>(n));
+        }
+        return n;
+    }
+
+    int overflow(int ch) override
+    {
+        if (ch == traits_type::eof())
+        {
+            return traits_type::not_eof(ch);
+        }
+        m_out.push_back(static_cast<char>(ch));
+        return ch;
+    }
+
+    // Disallow positioning (seek/tell)
+    pos_type seekoff(off_type, std::ios_base::seekdir, std::ios_base::openmode) override
+    {
+        return pos_type(off_type(-1));
+    }
+
+    pos_type seekpos(pos_type, std::ios_base::openmode) override
+    {
+        return pos_type(off_type(-1));
+    }
+
+private:
+    Aws::Vector<char>& m_out;
+};
+
+class NonSeekableIOStream final : public Aws::IOStream
+{
+public:
+    NonSeekableIOStream(const Aws::String& /*allocationTag*/, Aws::Vector<char>& out)
+        : Aws::IOStream(nullptr), m_buf(out)
+    {
+        rdbuf(&m_buf);
+    }
+
+private:
+    NonSeekableWriteBuf m_buf;
+};
+
+// Regression test:
+// Ensure CurlHttpClient can write response bodies into a non-seekable output stream.
+// Older implementations that call tellp() as part of the write callback may fail here.
+TEST_F(CURLHttpClientTest, TestNonSeekableResponseStreamDoesNotAbortTransfer)
+{
+    Aws::Vector<char> captured;
+
+    auto request = CreateHttpRequest(
+        Aws::String("http://127.0.0.1:8778"),
+        HttpMethod::HTTP_GET,
+        Aws::Utils::Stream::DefaultResponseStreamFactoryMethod);
+        
+    request->SetHeaderValue("WaitSeconds", "1");
+
+    request->SetResponseStreamFactory([&captured]() -> Aws::IOStream*
+    {
+        return Aws::New<NonSeekableIOStream>(ALLOCATION_TAG, ALLOCATION_TAG, captured);
+    });
+
+    Aws::Client::ClientConfiguration config;
+    config.requestTimeoutMs = 10000;
+
+    auto httpClient = CreateHttpClient(config);
+    auto response = httpClient->MakeRequest(request);
+
+    ASSERT_NE(nullptr, response);
+
+    ASSERT_FALSE(response->HasClientError()) << response->GetClientErrorMessage();
+    EXPECT_EQ(Aws::Http::HttpResponseCode::OK, response->GetResponseCode());
+   
+}
 #endif // ENABLE_CURL_CLIENT
 #endif // ENABLE_HTTP_CLIENT_TESTING
 #endif // NO_HTTP_CLIENT
-#endif  // DISABLE_DNS_REQUIRED_TESTS
+#endif  // DISABLE_DNS_REQUIRED_TESTS