Minor optimization

data/txt/sha256sums.txt

@@ -162,7 +162,7 @@ df768bcb9838dc6c46dab9b4a877056cb4742bd6cfaaf438c4a3712c5cc0d264  extra/shutils/
 1966ca704961fb987ab757f0a4afddbf841d1a880631b701487c75cef63d60c3  extra/vulnserver/__init__.py
 617cec1b731e0baacafa6f58c2f56a85b6128d1416627cc1b2f61519c8539a2e  extra/vulnserver/vulnserver.py
 a2bf70d7f87c3a4e0675c0bad54119a4e04efa6ea2730a8338d5aebcd995630e  lib/controller/action.py
-f4fb3839e5accd1b58b34226e4b26f5079d9696e24d335d37d870cd5e62d1e80  lib/controller/checks.py
+d6d9159d00f47995cb7414a9e0be1dd088b584ef7ce1eeeb2c9008dec3363e5f  lib/controller/checks.py
 666935b658074dc9c42153622b75d4ec7bfe56fbe0742de827a5d30a1a0f9d96  lib/controller/controller.py
 d69e84f1648cdb907f5d2dd454f03874a4613752b07867510145d51d84b3c56f  lib/controller/handler.py
 1966ca704961fb987ab757f0a4afddbf841d1a880631b701487c75cef63d60c3  lib/controller/__init__.py
@@ -189,7 +189,7 @@ f8de57606325456928e46ae2896f5f8bbec9ad18b1c644b492a566fa992216f6  lib/core/decor
 9bf174058f15d14e24e94f9aaf42df045119d3617c6c54bd2f3af79b462f331d  lib/core/replication.py
 0b8c38a01bb01f843d94a6c5f2075ee47520d0c4aa799cecea9c3e2c5a4a23a6  lib/core/revision.py
 888daba83fd4a34e9503fe21f01fef4cc730e5cde871b1d40e15d4cbc847d56c  lib/core/session.py
-a2fb281b59c4526613f22fc0e994b68db91c1263db415aa86002ec4e20773639  lib/core/settings.py
+c6e83cef57c4b6d492cf3de91ea3b3b176971c36c773759737b6c95269cfadf9  lib/core/settings.py
 c7804223319e18eb0b8e2cbf0a8b6896d1cefb7b0b1a2e9f1cf826a8a3b56750  lib/core/shell.py
 a2e98a94b231432736d6b304fc75525c8b5fdb4768c418387c5b4c1a610dad64  lib/core/subprocessng.py
 19f1e3c5e3ba703d28d510cd7a9ab8284d5fbe9df5ce7e77c86e5931571364b7  lib/core/target.py

lib/controller/checks.py

@@ -93,6 +93,7 @@ from lib.core.settings import MAX_DIFFLIB_SEQUENCE_LENGTH
 from lib.core.settings import MAX_STABILITY_DELAY
 from lib.core.settings import NON_SQLI_CHECK_PREFIX_SUFFIX_LENGTH
 from lib.core.settings import NOSQL_ERROR_REGEX
+from lib.core.settings import NULL_CONNECTION_SKIP_READ_MIN_LENGTH
 from lib.core.settings import PRECONNECT_INCOMPATIBLE_SERVERS
 from lib.core.settings import SINGLE_QUOTE_MARKER
 from lib.core.settings import SLEEP_TIME_MARKER
@@ -1552,10 +1553,24 @@ def checkNullConnection():
                     _, headers, _ = Request.getPage(skipRead=True)
 
                     if HTTP_HEADER.CONTENT_LENGTH in (headers or {}):
-                        kb.nullConnection = NULLCONNECTION.SKIP_READ
+                        try:
+                            length = int(headers[HTTP_HEADER.CONTENT_LENGTH].split(',')[0])
+                        except ValueError:
+                            length = len(kb.originalPage or "")
 
-                        infoMsg = "NULL connection is supported with 'skip-read' method"
-                        logger.info(infoMsg)
+                        # Unlike HEAD/Range, 'skip-read' leaves the body unread and must close the
+                        # connection (an unread body cannot be reused), paying a fresh TCP/TLS handshake
+                        # per request. That only outweighs the avoided body transfer for large responses;
+                        # for small ones it is a net slowdown, so it is gated by the response size here
+                        if length >= NULL_CONNECTION_SKIP_READ_MIN_LENGTH:
+                            kb.nullConnection = NULLCONNECTION.SKIP_READ
+
+                            infoMsg = "NULL connection is supported with 'skip-read' method"
+                            logger.info(infoMsg)
+                        else:
+                            debugMsg = "'skip-read' NULL connection method is available but skipped because the "
+                            debugMsg += "response (%d B) is too small for it to outweigh the per-request reconnect cost" % length
+                            logger.debug(debugMsg)
 
         except SqlmapConnectionException:
             pass

lib/core/settings.py

@@ -20,7 +20,7 @@ from lib.core.enums import OS
 from thirdparty import six
 
 # sqlmap version (<major>.<minor>.<month>.<monthly commit>)
-VERSION = "1.10.6.199"
+VERSION = "1.10.6.200"
 TYPE = "dev" if VERSION.count('.') > 2 and VERSION.split('.')[-1] != '0' else "stable"
 TYPE_COLORS = {"dev": 33, "stable": 90, "pip": 34}
 VERSION_STRING = "sqlmap/%s#%s" % ('.'.join(VERSION.split('.')[:-1]) if VERSION.count('.') > 2 and VERSION.split('.')[-1] == '0' else VERSION, TYPE)
@@ -187,6 +187,13 @@ STRUCTURAL_TAG_REGEX = r"(?si)<\s*([a-z][a-z0-9]*)((?:\s+[^<>]*)?)/?>"
 STRUCTURAL_CLASS_REGEX = r"""(?si)\bclass\s*=\s*(?:"([^"]*)"|'([^']*)'|([^\s"'<>]+))"""
 STRUCTURAL_ID_REGEX = r"""(?si)\bid\s*=\s*(?:"([^"]*)"|'([^']*)'|([^\s"'<>]+))"""
 
+# Minimum response size (in bytes) for the 'skip-read' NULL connection method to be used. Unlike
+# HEAD/Range, 'skip-read' leaves the body unread and must therefore close the connection (an unread
+# body cannot be reused), paying a fresh TCP/TLS handshake per request. That only pays off when
+# avoiding the body transfer outweighs the reconnect - i.e. for large responses; for small ones it
+# is a net slowdown, so it is gated by this size
+NULL_CONNECTION_SKIP_READ_MIN_LENGTH = 256 * 1024
+
 # Regular expression used for recognition of IP addresses
 IP_ADDRESS_REGEX = r"\b(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\b"