Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Which DCID determines Initial keys #3862

Merged
merged 1 commit into from
Jul 14, 2020
Merged

Which DCID determines Initial keys #3862

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 5 additions & 2 deletions draft-ietf-quic-transport.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1539,8 +1539,11 @@ Initial or Retry packet from the server, the client populates the Destination
Connection ID field with an unpredictable value. This Destination Connection ID
MUST be at least 8 bytes in length. Until a packet is received from the server,
the client MUST use the same Destination Connection ID value on all packets in
this connection. This Destination Connection ID is used to determine packet
protection keys for Initial packets.
this connection.

The Destination Connection ID field from the first Initial packet sent by a
client is used to determine packet protection keys for Initial packets. These
keys change after receiving a Retry packet; see Section 5.2 of {{QUIC-TLS}}.
Comment on lines +1544 to +1546
Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Suggested change
The Destination Connection ID field from the first Initial packet sent by a
client is used to determine packet protection keys for Initial packets. These
keys change after receiving a Retry packet; see Section 5.2 of {{QUIC-TLS}}.
Initial packets derive their packet protection key from their Destination Connection ID field. This means that these keys will change after receiving a Retry packet; see Section 5.2 of {{QUIC-TLS}}.

I don't think it helps to single out the first Initial which actually isn't special.

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

However, this suggestion is incorrect. You can change the value of the Destination Connection ID field. After receiving an Initial, the client sets the Destination Connection ID field to the value the server chooses in the Source Connection ID field. This updates the value used in Initial packets (such as an ACK), but does not change the keys.

Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Ugh. In that case this text needs to be really sharpened, and perhaps we need a diagram :)

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is plenty sharp in my view.

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

How about an additional sentence that spells this out? "The Destination Connection ID field from the first Initial packet sent by a client is used to determine packet protection keys for Initial packets. While the Destination Connection ID can change on subsequent Initial packets ({{negotiating-connection-ids}}), the packet protection keys used for Initial packets do not change. The keys change however after receiving a Retry packet; see ... "

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

We could, but that is the point of adding the reference.

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I'm fine with the reference, but if there's any question, then being explicit doesn't hurt. I'm fine either way. Separately, I noticed that Sec 5.2 in TLS says "the Initial packet". That should be "the first Initial packet from the client".


The client populates the Source Connection ID field with a value of its choosing
and sets the Source Connection ID Length field to indicate the length.
Expand Down