CupsProxyService now accepts PS too

PluginVm will be sending PS to be printed, now the pipeline can handle
both PS and PDF.

Bug: chromium:945409
Test: manually confirmed printer PS doc
Change-Id: Id3d3303f4673f65c4098495c83ea19a14f35736d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1795993
Commit-Queue: Luum Habtemariam <luum@chromium.org>
Reviewed-by: Sean Kau <skau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695724}

chrome/services/cups_proxy/ipp_validator.cc

@@ -80,6 +80,14 @@ size_t GetAttributeValuesSize(const ipp_parser::mojom::IppAttributePtr& attr) {
   return 0;
 }
 
+// Returns true if |data| starts with the full |prefix|, false otherwise.
+bool StartsWith(base::span<uint8_t const> data,
+                base::span<uint8_t const> prefix) {
+  if (data.size() < prefix.size())
+    return false;
+  return std::equal(data.begin(), data.begin() + prefix.size(), prefix.begin());
+}
+
 }  // namespace
 
 // Verifies that |method|, |endpoint|, and |http_version| form a valid HTTP
@@ -257,24 +265,16 @@ ipp_t* IppValidator::ValidateIppMessage(
   return ipp.release();
 }
 
-// Requires IPP data portion is either empty or looks like a pdf.
+// Requires |ipp_data| to be empty or look like a PDF or PostScript document.
 bool IppValidator::ValidateIppData(const std::vector<uint8_t>& ipp_data) {
-  const int pdf_magic_bytes_size = 4;
-  constexpr std::array<uint8_t, pdf_magic_bytes_size> pdf_magic_bytes = {
-      0x25, 0x50, 0x44, 0x46};  // { %PDF }
-
   // Empty IPP data portion.
   if (ipp_data.empty()) {
     return true;
   }
 
-  if (ipp_data.size() < pdf_magic_bytes_size) {
-    return false;
-  }
-
-  // Check that |ipp_data| starts with pdf_magic_bytes.
-  return std::equal(ipp_data.begin(), ipp_data.begin() + pdf_magic_bytes_size,
-                    pdf_magic_bytes.begin());
+  // Check if |ipp_data| looks like a PDF or PostScript document.
+  return StartsWith(ipp_data, pdf_magic_bytes) ||
+         StartsWith(ipp_data, ps_magic_bytes);
 }
 
 IppValidator::IppValidator(CupsProxyServiceDelegate* const delegate)

chrome/services/cups_proxy/ipp_validator_unittest.cc

@@ -11,6 +11,7 @@
 #include <utility>
 
 #include "chrome/services/cups_proxy/fake_cups_proxy_service_delegate.h"
+#include "chrome/services/cups_proxy/public/cpp/cups_util.h"
 #include "chrome/services/cups_proxy/public/cpp/ipp_messages.h"
 #include "printing/backend/cups_ipp_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -196,6 +197,22 @@ TEST_F(IppValidatorTest, UnknownAttribute) {
   EXPECT_FALSE(ippFindAttribute(ipp, fake_attr_name.c_str(), IPP_TAG_TEXT));
 }
 
+TEST_F(IppValidatorTest, IppDataVerification) {
+  auto request = GetBasicIppRequest();
+
+  // Should fail since the data too short to be a valid document.
+  request->data = {0x0};
+  EXPECT_FALSE(RunValidateIppRequest(request));
+
+  // Valid PDF.
+  request->data = {pdf_magic_bytes.begin(), pdf_magic_bytes.end()};
+  EXPECT_TRUE(RunValidateIppRequest(request));
+
+  // Valid PS.
+  request->data = {ps_magic_bytes.begin(), ps_magic_bytes.end()};
+  EXPECT_TRUE(RunValidateIppRequest(request));
+}
+
 // TODO(crbug.com/945409): Test IPP validation.
 
 }  // namespace

chrome/services/cups_proxy/public/cpp/cups_util.h

@@ -27,6 +27,12 @@ namespace cups_proxy {
 // Note: This is assumed to be stable.
 static const size_t kHttpMaxBufferSize = 2048;
 
+// PDF and PostScript document format identifiers.
+constexpr std::array<uint8_t, 5> pdf_magic_bytes = {0x25, 0x50, 0x44, 0x46,
+                                                    0x2d};  // { %PDF- }
+constexpr std::array<uint8_t, 4> ps_magic_bytes = {0x25, 0x21, 0x50,
+                                                   0x53};  // { %!PS }
+
 // Expects |request| to be an IPP_OP_GET_PRINTERS IPP request. This function
 // creates an appropriate IPP response referencing |printers|.
 // TODO(crbug.com/945409): Expand testing suite.