2 files changed, 50 insertions, 10 deletions

diff --git a/src/mongo/util/bufreader.h b/src/mongo/util/bufreader.h
index 8c30070bada..b8d931add9a 100644
--- a/src/mongo/util/bufreader.h
+++ b/src/mongo/util/bufreader.h
@@ -106,6 +106,11 @@ public:
         invariant(_pos >= _start);
     }
 
+    /** back up to beginging of buffer */
+    void rewindToStart() {
+        _pos = _start;
+    }
+
     /** return current position pointer, and advance by len */
     const void* skip(unsigned len) {
         ConstDataRangeCursor cdrc(_pos, _end);
@@ -124,6 +129,14 @@ public:
         s = readCStr().toString();
     }
 
+    /**
+     * Return a view of the next len bytes and advance by len.
+     */
+    StringData readBytes(size_t len) {
+        // Note: the call to skip() includes a check that at least 'len' bytes remain in the buffer.
+        return StringData(reinterpret_cast<const char*>(skip(len)), len);
+    }
+
     const void* pos() {
         return _pos;
     }
diff --git a/src/mongo/util/net/http_client_curl.cpp b/src/mongo/util/net/http_client_curl.cpp
index 3e6183d2ebf..82433b4caf0 100644
--- a/src/mongo/util/net/http_client_curl.cpp
+++ b/src/mongo/util/net/http_client_curl.cpp
@@ -53,6 +53,7 @@
 #include "mongo/util/alarm.h"
 #include "mongo/util/alarm_runner_background_thread.h"
 #include "mongo/util/assert_util.h"
+#include "mongo/util/bufreader.h"
 #include "mongo/util/concurrency/thread_pool.h"
 #include "mongo/util/functional.h"
 #include "mongo/util/net/hostandport.h"
@@ -159,20 +160,40 @@ size_t WriteMemoryCallback(void* ptr, size_t size, size_t nmemb, void* data) {
  */
 size_t ReadMemoryCallback(char* buffer, size_t size, size_t nitems, void* instream) {
 
-    auto* cdrc = reinterpret_cast<ConstDataRangeCursor*>(instream);
+    auto* bufReader = reinterpret_cast<BufReader*>(instream);
 
     size_t ret = 0;
 
-    if (cdrc->length() > 0) {
-        size_t readSize = std::min(size * nitems, cdrc->length());
-        memcpy(buffer, cdrc->data(), readSize);
-        invariant(cdrc->advanceNoThrow(readSize).isOK());
+    if (bufReader->remaining() > 0) {
+        size_t readSize =
+            std::min(size * nitems, static_cast<unsigned long>(bufReader->remaining()));
+        auto buf = bufReader->readBytes(readSize);
+        memcpy(buffer, buf.rawData(), readSize);
         ret = readSize;
     }
 
     return ret;
 }
 
+/**
+ * Seek into for data to the remote side
+ */
+size_t SeekMemoryCallback(void* clientp, curl_off_t offset, int origin) {
+
+    // Curl will call this in readrewind but only to reset the stream to the beginning
+    // In other protocols (like FTP, SSH) or HTTP resumption they may ask for partial buffers which
+    // we do not support.
+    if (offset != 0 || origin != SEEK_SET) {
+        return CURL_SEEKFUNC_CANTSEEK;
+    }
+
+    auto* bufReader = reinterpret_cast<BufReader*>(clientp);
+
+    bufReader->rewindToStart();
+
+    return CURL_SEEKFUNC_OK;
+}
+
 struct CurlEasyCleanup {
     void operator()(CURL* handle) {
         if (handle) {
@@ -630,7 +651,7 @@ private:
 
         curl_easy_setopt(handle, CURLOPT_CONNECTTIMEOUT, longSeconds(_connectTimeout));
 
-        ConstDataRangeCursor cdrc(cdr);
+        BufReader bufReader(cdr.data(), cdr.length());
         switch (method) {
             case HttpMethod::kGET:
                 uassert(ErrorCodes::BadValue,
@@ -645,16 +666,22 @@ private:
                 curl_easy_setopt(handle, CURLOPT_POST, 1);
 
                 curl_easy_setopt(handle, CURLOPT_READFUNCTION, ReadMemoryCallback);
-                curl_easy_setopt(handle, CURLOPT_READDATA, &cdrc);
-                curl_easy_setopt(handle, CURLOPT_POSTFIELDSIZE, (long)cdrc.length());
+                curl_easy_setopt(handle, CURLOPT_READDATA, &bufReader);
+                curl_easy_setopt(handle, CURLOPT_POSTFIELDSIZE, (long)bufReader.remaining());
+
+                curl_easy_setopt(handle, CURLOPT_SEEKFUNCTION, SeekMemoryCallback);
+                curl_easy_setopt(handle, CURLOPT_SEEKDATA, &bufReader);
                 break;
             case HttpMethod::kPUT:
                 curl_easy_setopt(handle, CURLOPT_POST, 0);
                 curl_easy_setopt(handle, CURLOPT_PUT, 1);
 
                 curl_easy_setopt(handle, CURLOPT_READFUNCTION, ReadMemoryCallback);
-                curl_easy_setopt(handle, CURLOPT_READDATA, &cdrc);
-                curl_easy_setopt(handle, CURLOPT_INFILESIZE_LARGE, (long)cdrc.length());
+                curl_easy_setopt(handle, CURLOPT_READDATA, &bufReader);
+                curl_easy_setopt(handle, CURLOPT_INFILESIZE_LARGE, (long)bufReader.remaining());
+
+                curl_easy_setopt(handle, CURLOPT_SEEKFUNCTION, SeekMemoryCallback);
+                curl_easy_setopt(handle, CURLOPT_SEEKDATA, &bufReader);
                 break;
             default:
                 MONGO_UNREACHABLE;