Add support for outputting zip files with no data descriptors #337
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This commit adds a new `--zip-mode` parameter to `avbroot ota patch` to control whether the patched OTA zip is written with data descriptors or not. By default, the `streaming` mode is used, which matches the current behavior where the zip is hashed for signing as it is being written. The new `seekable` mode fully writes the zip before rereading it to hash the contents. The new mode is useful for devices with broken zip parsers that fail to properly handle data descriptors. All of the end-to-end tests have been duplicated to test both modes. Adding the seekable mode necessitated a couple other changes: * BufWriter is no longer used. Type erasure is very painful in Rust, so we need to keep the writer types the same for both the streaming and seekable modes. BufWriter is unusable in the seekable mode because we need to be able to read back what was written, which isn't supported. * HolePunchingWriter has been removed. It was a simple way to produce sparse files by seeking whenever a write buffer consists fully of zeros. When combined with BufWriter, there was previously never a situation where this was undesirable. However, with the new seekable mode and the zip library's pattern of writing one field at a time, the final 2 zero bytes (representing an empty archive comment) is never written and the file size is not increased either. Removing this is not a big deal since we no longer use stripped OTAs for the end-to-end tests. Those were really the only OTAs that benefitted from sparse files. A real OTA has very few zero bytes due to compression. Issue: #328 Signed-off-by: Andrew Gunnerson <[email protected]>
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Aug 21, 2024
Signed-off-by: Andrew Gunnerson <[email protected]>
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This commit adds a new
--zip-modeparameter toavbroot ota patchto control whether the patched OTA zip is written with data descriptors or not. By default, thestreamingmode is used, which matches the current behavior where the zip is hashed for signing as it is being written. The newseekablemode fully writes the zip before rereading it to hash the contents.The new mode is useful for devices with broken zip parsers that fail to properly handle data descriptors.
All of the end-to-end tests have been duplicated to test both modes.
Adding the seekable mode necessitated a couple other changes:
BufWriter is no longer used. Type erasure is very painful in Rust, so we need to keep the writer types the same for both the streaming and seekable modes. BufWriter is unusable in the seekable mode because we need to be able to read back what was written, which isn't supported.
HolePunchingWriter has been removed. It was a simple way to produce sparse files by seeking whenever a write buffer consists fully of zeros. When combined with BufWriter, there was previously never a situation where this was undesirable. However, with the new seekable mode and the zip library's pattern of writing one field at a time, the final 2 zero bytes (representing an empty archive comment) is never written and the file size is not increased either.
Removing this is not a big deal since we no longer use stripped OTAs for the end-to-end tests. Those were really the only OTAs that benefitted from sparse files. A real OTA has very few zero bytes due to compression.
Issue: #328