Add support for regular expression matching and sanitizing of headers in ASGI.

Next part of #1184

Details:

Add test cases for regular expression matching.
Add test cases for "all" keyword.
Add test cases for header sanitizing.
Add documentation for regular expression matching and header sanitation.
Various documentation cleanups and standardization.
Fix keys() in class ASGIGetter so it returns the HTTP header keys instead of a list of available request data. This makes it consistent with the WSGIGetter keys() method.
Make ASGIGetter.get() compare all keys in a case insensitive manner.

Author: Daniel Rogers

CHANGELOG.md

@@ -16,6 +16,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1242](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1242))
 - `opentelemetry-util-http` Add support for sanitizing HTTP header values.
   ([#1253](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1253))
+- `opentelemetry-instrumentation-asgi` Add support for regular expression matching of HTTP headers.
+  ([#1333](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1333))
 
 ### Fixed
 
@@ -29,6 +31,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - ([#1246](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1246))
 - Add _is_openetlemetry_instrumented check in _InstrumentedFastAPI class
   ([#1313](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1313))
+- `opentelemetry-instrumentation-asgi` Fix keys() in class ASGIGetter so it returns the HTTP header keys instead of a list of available request data.
+  ([#1333](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1333))
+- `opentelemetry-instrumentation-asgi` Make ASGIGetter.get() compare all keys in a case insensitive manner.
+  ([#1333](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1333))
 
 ## [1.12.0-0.33b0](https://github.com/open-telemetry/opentelemetry-python/releases/tag/v1.12.0-0.33b0) - 2022-08-08
 

instrumentation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py

@@ -15,8 +15,7 @@
 
 """
 The opentelemetry-instrumentation-asgi package provides an ASGI middleware that can be used
-on any ASGI framework (such as Django-channels / Quart) to track requests
-timing through OpenTelemetry.
+on any ASGI framework (such as Django-channels / Quart) to track request timing through OpenTelemetry.
 
 Usage (Quart)
 -------------
@@ -71,9 +70,14 @@ async def hello():
 Request/Response hooks
 **********************
 
-Utilize request/response hooks to execute custom logic to be performed before/after performing a request. The server request hook takes in a server span and ASGI
-scope object for every incoming request. The client request hook is called with the internal span and an ASGI scope which is sent as a dictionary for when the method receive is called.
-The client response hook is called with the internal span and an ASGI event which is sent as a dictionary for when the method send is called.
+This instrumentation supports request and response hooks. These are functions that get called
+right after a span is created for a request and right before the span is finished for the response.
+
+- The server request hook is passed a server span and ASGI scope object for every incoming request.
+- The client request hook is called with the internal span and an ASGI scope when the method ``receive`` is called.
+- The client response hook is called with the internal span and an ASGI event when the method ``send`` is called.
+
+For example,
 
 .. code-block:: python
 
@@ -93,59 +97,99 @@ def client_response_hook(span: Span, message: dict):
 
 Capture HTTP request and response headers
 *****************************************
-You can configure the agent to capture predefined HTTP headers as span attributes, according to the `semantic convention <https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#http-request-and-response-headers>`_.
+You can configure the agent to capture specified HTTP headers as span attributes, according to the
+`semantic convention <https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#http-request-and-response-headers>`_.
 
 Request headers
 ***************
-To capture predefined HTTP request headers as span attributes, set the environment variable ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST``
-to a comma-separated list of HTTP header names.
+To capture HTTP request headers as span attributes, set the environment variable
+``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST`` to a comma delimited list of HTTP header names.
 
 For example,
-
 ::
 
     export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="content-type,custom_request_header"
 
-will extract ``content-type`` and ``custom_request_header`` from request headers and add them as span attributes.
+will extract ``content-type`` and ``custom_request_header`` from the request headers and add them as span attributes.
+
+Request header names in ASGI are case-insensitive. So, giving the header name as ``CUStom-Header`` in the environment
+variable will capture the header named ``custom-header``.
+
+Regular expressions may also be used to match multiple headers that correspond to the given pattern.  For example:
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="Accept.*,X-.*"
+
+Would match all request headers that start with ``Accept`` and ``X-``.
+
+Additionally, the special keyword ``all`` can be used to capture all request headers.
+::
 
-It is recommended that you should give the correct names of the headers to be captured in the environment variable.
-Request header names in ASGI are case insensitive. So, giving header name as ``CUStom-Header`` in environment variable will be able capture header with name ``custom-header``.
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="all"
 
-The name of the added span attribute will follow the format ``http.request.header.<header_name>`` where ``<header_name>`` being the normalized HTTP header name (lowercase, with - characters replaced by _ ).
-The value of the attribute will be single item list containing all the header values.
+The name of the added span attribute will follow the format ``http.request.header.<header_name>`` where ``<header_name>``
+is the normalized HTTP header name (lowercase, with ``-`` replaced by ``_``). The value of the attribute will be a
+single item list containing all the header values.
 
-Example of the added span attribute,
+For example:
 ``http.request.header.custom_request_header = ["<value1>,<value2>"]``
 
 Response headers
 ****************
-To capture predefined HTTP response headers as span attributes, set the environment variable ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE``
-to a comma-separated list of HTTP header names.
+To capture HTTP response headers as span attributes, set the environment variable
+``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE`` to a comma delimited list of HTTP header names.
 
 For example,
-
 ::
 
     export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="content-type,custom_response_header"
 
-will extract ``content-type`` and ``custom_response_header`` from response headers and add them as span attributes.
+will extract ``content-type`` and ``custom_response_header`` from the response headers and add them as span attributes.
+
+Response header names in ASGI are case-insensitive. So, giving the header name as ``CUStom-Header`` in the environment
+variable will capture the header named ``custom-header``.
+
+Regular expressions may also be used to match multiple headers that correspond to the given pattern.  For example:
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="Content.*,X-.*"
 
-It is recommended that you should give the correct names of the headers to be captured in the environment variable.
-Response header names captured in ASGI are case insensitive. So, giving header name as ``CUStomHeader`` in environment variable will be able capture header with name ``customheader``.
+Would match all response headers that start with ``Content`` and ``X-``.
 
-The name of the added span attribute will follow the format ``http.response.header.<header_name>`` where ``<header_name>`` being the normalized HTTP header name (lowercase, with - characters replaced by _ ).
-The value of the attribute will be single item list containing all the header values.
+Additionally, the special keyword ``all`` can be used to capture all response headers.
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="all"
+
+The name of the added span attribute will follow the format ``http.response.header.<header_name>`` where ``<header_name>``
+is the normalized HTTP header name (lowercase, with ``-`` replaced by ``_``). The value of the attribute will be a
+single item list containing all the header values.
 
-Example of the added span attribute,
+For example:
 ``http.response.header.custom_response_header = ["<value1>,<value2>"]``
 
+Sanitizing headers
+******************
+In order to prevent storing sensitive data such as personally identifiable information (PII), session keys, passwords,
+etc, set the environment variable ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS``
+to a comma delimited list of HTTP header names to be sanitized.  Regexes may be used, and all header names will be
+matched in a case-insensitive manner.
+
+For example,
+::
+
+    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS=".*session.*,set-cookie"
+
+will replace the value of headers such as ``session-id`` and ``set-cookie`` with ``[REDACTED]`` in the span.
+
 Note:
-    Environment variable names to capture http headers are still experimental, and thus are subject to change.
+    The environment variable names used to capture HTTP headers are still experimental, and thus are subject to change.
 
 API
 ---
 """
 
+import re
 import typing
 import urllib
 from functools import wraps
@@ -169,8 +213,10 @@ def client_response_hook(span: Span, message: dict):
 from opentelemetry.trace import Span, set_span_in_context
 from opentelemetry.trace.status import Status, StatusCode
 from opentelemetry.util.http import (
+    OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS,
     OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST,
     OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE,
+    SanitizeValue,
     _parse_active_request_count_attrs,
     _parse_duration_attrs,
     get_custom_headers,
@@ -202,19 +248,21 @@ def get(
         if not headers:
             return None
 
-        # asgi header keys are in lower case
+        # ASGI header keys are in lower case
         key = key.lower()
         decoded = [
             _value.decode("utf8")
             for (_key, _value) in headers
-            if _key.decode("utf8") == key
+            if _key.decode("utf8").lower() == key
         ]
         if not decoded:
             return None
         return decoded
 
     def keys(self, carrier: dict) -> typing.List[str]:
-        return list(carrier.keys())
+        return [
+            _key.decode("utf8") for (_key, _value) in carrier.get("headers")
+        ]
 
 
 asgi_getter = ASGIGetter()
@@ -290,15 +338,37 @@ def collect_custom_request_headers_attributes(scope):
     Refer specification https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#http-request-and-response-headers"""
 
     attributes = {}
-    custom_request_headers = get_custom_headers(
+
+    sanitized_fields = get_custom_headers(
+        OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS
+    )
+
+    sanitize = SanitizeValue(sanitized_fields)
+
+    custom_request_headers_name = get_custom_headers(
         OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST
     )
 
-    for header in custom_request_headers:
-        values = asgi_getter.get(scope, header)
-        if values:
-            key = normalise_request_header_name(header)
-            attributes.setdefault(key, []).extend(values)
+    if custom_request_headers_name:
+        custom_request_headers_regex_compiled = re.compile(
+            "|".join("^" + i + "$" for i in custom_request_headers_name),
+            re.IGNORECASE,
+        )
+
+        for header_name in list(
+            filter(
+                custom_request_headers_regex_compiled.match,
+                asgi_getter.keys(scope),
+            )
+        ):
+            header_values = asgi_getter.get(scope, header_name.lower())
+            if header_values:
+                key = normalise_request_header_name(header_name.lower())
+                attributes[key] = [
+                    sanitize.sanitize_header_value(
+                        header=header_name, value=header_values[0]
+                    )
+                ]
 
     return attributes
 
@@ -307,15 +377,37 @@ def collect_custom_response_headers_attributes(message):
     """returns custom HTTP response headers to be added into SERVER span as span attributes
     Refer specification https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#http-request-and-response-headers"""
     attributes = {}
-    custom_response_headers = get_custom_headers(
+
+    sanitized_fields = get_custom_headers(
+        OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS
+    )
+
+    sanitize = SanitizeValue(sanitized_fields)
+
+    custom_response_headers_name = get_custom_headers(
         OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE
     )
 
-    for header in custom_response_headers:
-        values = asgi_getter.get(message, header)
-        if values:
-            key = normalise_response_header_name(header)
-            attributes.setdefault(key, []).extend(values)
+    if custom_response_headers_name:
+        custom_response_headers_regex_compiled = re.compile(
+            "|".join("^" + i + "$" for i in custom_response_headers_name),
+            re.IGNORECASE,
+        )
+
+        for header_name in list(
+            filter(
+                custom_response_headers_regex_compiled.match,
+                asgi_getter.keys(message),
+            )
+        ):
+            header_values = asgi_getter.get(message, header_name.lower())
+            if header_values:
+                key = normalise_response_header_name(header_name.lower())
+                attributes[key] = [
+                    sanitize.sanitize_header_value(
+                        header=header_name, value=header_values[0]
+                    )
+                ]
 
     return attributes
 
@@ -353,7 +445,7 @@ def set_status_code(span, status_code):
 def get_default_span_details(scope: dict) -> Tuple[str, dict]:
     """Default implementation for get_default_span_details
     Args:
-        scope: the asgi scope dictionary
+        scope: the ASGI scope dictionary
     Returns:
         a tuple of the span name, and any attributes to attach to the span.
     """
@@ -427,7 +519,7 @@ async def __call__(self, scope, receive, send):
         """The ASGI application
 
         Args:
-            scope: A ASGI environment.
+            scope: An ASGI environment.
             receive: An awaitable callable yielding dictionaries
             send: An awaitable callable taking a single dictionary as argument.
         """