From 68f678f566b533396a9c629784289ae3653f40ed Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Wed, 4 Jan 2023 15:34:25 -0500
Subject: LibGfx+icc: Print if profile id is valid

---
 Userland/Libraries/LibGfx/ICCProfile.cpp | 24 ++++++++++++++++++++++++
 Userland/Libraries/LibGfx/ICCProfile.h   |  2 ++
 Userland/Utilities/icc.cpp               | 11 ++++++++---
 3 files changed, 34 insertions(+), 3 deletions(-)

(limited to 'Userland')

diff --git a/Userland/Libraries/LibGfx/ICCProfile.cpp b/Userland/Libraries/LibGfx/ICCProfile.cpp
index e8a4098563..bcdb839c60 100644
--- a/Userland/Libraries/LibGfx/ICCProfile.cpp
+++ b/Userland/Libraries/LibGfx/ICCProfile.cpp
@@ -248,6 +248,9 @@ Optional<Crypto::Hash::MD5::DigestType> parse_profile_id(ICCHeader const& header
     Crypto::Hash::MD5::DigestType md5;
     static_assert(sizeof(md5.data) == sizeof(header.profile_md5));
     memcpy(md5.data, header.profile_md5, sizeof(md5.data));
+
+    // FIXME: Consider comparing read id with compute_id() result and failing if they aren't equal.
+
     return md5;
 }
 }
@@ -386,4 +389,25 @@ ErrorOr<NonnullRefPtr<Profile>> Profile::try_load_from_externally_owned_memory(R
     return profile;
 }
 
+Crypto::Hash::MD5::DigestType Profile::compute_id(ReadonlyBytes bytes)
+{
+    // ICC v4, 7.2.18 Profile ID field
+    // The Profile ID shall be calculated using the MD5 fingerprinting method as defined in Internet RFC 1321.
+    // The entire profile, whose length is given by the size field in the header,
+    // with the profile flags field (bytes 44 to 47, see 7.2.11),
+    // rendering intent field (bytes 64 to 67, see 7.2.15),
+    // and profile ID field (bytes 84 to 99) in the profile header
+    // temporarily set to zeros (00h), shall be used to calculate the ID.
+    const u8 zero[16] = {};
+    Crypto::Hash::MD5 md5;
+    md5.update(bytes.slice(0, 44));
+    md5.update(ReadonlyBytes { zero, 4 }); // profile flags field
+    md5.update(bytes.slice(48, 64 - 48));
+    md5.update(ReadonlyBytes { zero, 4 }); // rendering intent field
+    md5.update(bytes.slice(68, 84 - 68));
+    md5.update(ReadonlyBytes { zero, 16 }); // profile ID field
+    md5.update(bytes.slice(100));
+    return md5.digest();
+}
+
 }
diff --git a/Userland/Libraries/LibGfx/ICCProfile.h b/Userland/Libraries/LibGfx/ICCProfile.h
index 2d85bd4dcd..e4e0140699 100644
--- a/Userland/Libraries/LibGfx/ICCProfile.h
+++ b/Userland/Libraries/LibGfx/ICCProfile.h
@@ -139,6 +139,8 @@ public:
     XYZ const& pcs_illuminant() const { return m_pcs_illuminant; }
     Optional<Crypto::Hash::MD5::DigestType> const& id() const { return m_id; }
 
+    static Crypto::Hash::MD5::DigestType compute_id(ReadonlyBytes);
+
 private:
     Version m_version;
     DeviceClass m_device_class;
diff --git a/Userland/Utilities/icc.cpp b/Userland/Utilities/icc.cpp
index 6c67b7fec1..67d0ced9d9 100644
--- a/Userland/Utilities/icc.cpp
+++ b/Userland/Utilities/icc.cpp
@@ -40,9 +40,14 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     outln("pcs illuminant: {}", profile->pcs_illuminant());
 
     out("id: ");
-    if (auto id = profile->id(); id.has_value())
-        outln("{}", *id);
-    else
+    if (auto id = profile->id(); id.has_value()) {
+        out("{}", *id);
+        auto computed = Gfx::ICC::Profile::compute_id(icc_file->bytes());
+        if (*id == computed)
+            outln(" (valid)");
+        else
+            outln(" (invalid! valid would be {})", computed);
+    } else
         outln("(not set)");
 
     return 0;
-- 
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