Fix multipart user-data MIME framing#20
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The multipart/mixed user-data was missing the RFC 2046 close delimiter (--==BOUNDARY==--), so strict MIME parsers treated the final part as unterminated and dropped it; with a single cloud-config part the entire payload was lost. Also add the blank line separating the container headers from the body and each part's headers from its body, so a body whose first line contains a colon is not mis-parsed as a header. The close delimiter is only emitted when at least one part was written, avoiding an orphan delimiter for empty input. Tests now round-trip the output through MimeKit to confirm parts survive a spec-conformant parser.
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Pull request overview
Fixes MIME framing in UserDataSerializer’s multipart user-data output so it is RFC 2046–conformant and survives strict MIME parsing (preventing the final part from being treated as unterminated/dropped).
Changes:
- Add required blank line separation between multipart container headers and body, and between each part’s headers and body.
- Append the multipart close delimiter (
--==BOUNDARY==--) when at least one part is written. - Add MimeKit-based round-trip tests to validate parsing behavior and update existing string assertions.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/CloudInit.ConfigDrive.Core/UserDataSerializer.cs | Writes proper header/body separation and emits the multipart closing boundary delimiter. |
| test/CloudInit.ConfigDrive.Core.Test/UserDataSerializerTests.cs | Updates expected MIME output and adds parser round-trip tests for strict MIME handling. |
| test/CloudInit.ConfigDrive.Core.Test/CloudInit.ConfigDrive.Core.Test.csproj | Adds MimeKit dependency for MIME parsing tests. |
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The multipart/mixed user-data produced by
UserDataSerializerwas missing the RFC 2046 close delimiter (--==BOUNDARY==--). Strict MIME parsers treated the final part as unterminated and dropped it — with a single cloud-config part the entire payload was silently lost.Changes: