build: fix C string encoding for PRODUCT_DIR_ABS

Since the `PRODUCT_DIR_ABS` gyp variable is meant to be used
in a C string in the OpenSSL config, provide a version of it
that actually provides it in a way that is always usable as a
C string. Otherwise, unescaped characters in the path can mess
with the string definitions; for example, building in paths
on Windows whose directories start with valid or invalid escape
sequences (e.g.: `C:\...\x61foobar\...` or `C:\...\456789\...`)
can result in failing builds or incorrect paths provided to
OpenSSL.

Author: addaleax

deps/openssl/openssl.gyp

@@ -5,19 +5,13 @@
     'nasm_version%': '0.0',
     'openssl-cli': '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)openssl-cli<(EXECUTABLE_SUFFIX)',
     'conditions': [
-      ['OS == "win"', {
-        'obj_dir_abs': '<(PRODUCT_DIR_ABS)/obj',
-      }],
       ['GENERATOR == "ninja"', {
-        'obj_dir_abs': '<(PRODUCT_DIR_ABS)/obj',
-        'modules_dir': '<(PRODUCT_DIR_ABS)/obj/lib/openssl-modules',
+        'modules_dir': '<(PRODUCT_DIR_ABS_CSTR)/obj/lib/openssl-modules',
       }, {
-        'obj_dir_abs%': '<(PRODUCT_DIR_ABS)/obj.target',
-        'modules_dir': '<(PRODUCT_DIR_ABS)/obj.target/deps/openssl/lib/openssl-modules',
+        'modules_dir': '<(PRODUCT_DIR_ABS_CSTR)/obj.target/deps/openssl/lib/openssl-modules',
       }],
       ['OS=="mac"', {
-        'obj_dir_abs%': '<(PRODUCT_DIR_ABS)/obj.target',
-        'modules_dir': '<(PRODUCT_DIR_ABS)/obj.target/deps/openssl/lib/openssl-modules',
+        'modules_dir': '<(PRODUCT_DIR_ABS_CSTR)/obj.target/deps/openssl/lib/openssl-modules',
       }],
     ],
   },

tools/gyp/pylib/gyp/__init__.py

@@ -24,6 +24,17 @@
 DEBUG_VARIABLES = "variables"
 DEBUG_INCLUDES = "includes"
 
+def EscapeForCString(string):
+    if isinstance(string, str):
+        string = string.encode(encoding='utf8')
+
+    result = ''
+    for char in string:
+        if not (32 <= char < 127) or char in (ord('\\'), ord('"')):
+            result += '\\%03o' % char
+        else:
+            result += chr(char)
+    return result
 
 def DebugOutput(mode, message, *args):
     if "all" in gyp.debug or mode in gyp.debug:
@@ -106,18 +117,19 @@ def Load(
 
     output_dir = params["options"].generator_output or params["options"].toplevel_dir
     if default_variables["GENERATOR"] == "ninja":
-        default_variables.setdefault(
-            "PRODUCT_DIR_ABS",
-            os.path.join(
-                output_dir, "out", default_variables.get("build_type", "default")
-            ),
+        product_dir_abs = os.path.join(
+            output_dir, "out", default_variables.get("build_type", "default")
         )
     else:
-        default_variables.setdefault(
-            "PRODUCT_DIR_ABS",
-            os.path.join(output_dir, default_variables["CONFIGURATION_NAME"]),
+        product_dir_abs = os.path.join(
+            output_dir, default_variables["CONFIGURATION_NAME"]
         )
 
+    default_variables.setdefault("PRODUCT_DIR_ABS", product_dir_abs)
+    default_variables.setdefault(
+        "PRODUCT_DIR_ABS_CSTR", EscapeForCString(product_dir_abs)
+    )
+
     # Give the generator the opportunity to set additional variables based on
     # the params it will receive in the output phase.
     if getattr(generator, "CalculateVariables", None):