[Photos - Desktop] Could checksums be created with every release?

[taivlam]

Currently SHA256 sums are generated with every Linux desktop release of Ente Auth, but currently there are no checksums generated with each release of Ente Photos desktop client.

I noticed this because I just submitted ente-desktop-bin on the MPR. Also, I am the maintainer of ente-auth-bin.

[mnvr]

The checksums are present in the various latest.yaml files that are generated:

---

^ screenshot from https://github.com/ente-io/photos-desktop/releases/tag/v1.7.3

That said, I agree the ergonomics can be improved. One particular thing that'll be nice is integrating artifact attestations.

[mnvr]

rKAfSjlhn4kbxDEn6bfJ/svmtbO0dXr0Dd5p6/vDQEkra3ljfeF7K81mBtGJACfyYmDdSARpGDNn8A+1sB/NFg== is the base 64 encoding of the binary data represented by the hex string aca01f4a39619f891bc43127e9b7c9fecbe6b5b3b4757af40dde69ebfbc340492b6b79637de17b2bcd6606d1890027f26260dd480469183367f00fb5b01fcd16.

i.e. the sha string you got from shasum represents the hex digits of the binary sha. the string in the yaml file is the base64 representation of this binary sha.

Here is a way to decode this using libsodium (note: this is just an example, you don't need to use libsodium here, any way of converting hex => binary and then binary => base 64 would work below):

$ node
> const _sodium = require("libsodium-wrappers"); await _sodium.ready; const sodium = _sodium;
undefined
> sodium.to_base64(sodium.from_hex("aca01f4a39619f891bc43127e9b7c9fecbe6b5b3b4757af40dde69ebfbc340492b6b79637de17b2bcd6606d1890027f26260dd480469183367f00fb5b01fcd16"), sodium.base64_variants.ORIGINAL)
'rKAfSjlhn4kbxDEn6bfJ/svmtbO0dXr0Dd5p6/vDQEkra3ljfeF7K81mBtGJACfyYmDdSARpGDNn8A+1sB/NFg=='

[taivlam]

Thank you for the explanation!

According to this answer on Unix Stack Exchange (and adding the -w0 flag, from a comment, to the base64 command), this 1-line command used on the Linux binary will convert the SHA512 checksum from hexadecimal form into base 64 form:

sha512sum <latest-fente-photos-desktop-binary>.deb | cut -f1 -d\  | xxd -r -p | base64 -w0

[taivlam]

@mnvr Could you explain why the process needs an in-between step of converting into binary (i.e., why we need to do hexadecimal -> binary -> base 64; instead of directly doing hexadecimal -> base 64)?

I noticed all solutions required this high-level step.

[mnvr]

These checksums are not calculated by us, they're calculated by the library we're using to allow auto updates - https://github.com/electron-userland/electron-builder. So I don't know why they chose to represent the sha as a hex string instead of the base64 encoding, except just note that it both sort of representations (hex, base64) of binary data are fine really.

For example, git commit shas are hex representations, not base64.

As to your question about why

hexadecimal -> binary -> base 64

Notice that is is more like

hexadecimal -> binary 
               binary -> base 64

That is,

• The checksums produced by electron-builder are hexadecimal string representations of the underlying binary SHA value.
• The checksums produced by shasum are base64 string representations of the underlying binary SHA value.
• We can compare them converting both to binary, and then comparing the binary value (electron-builder's hexadecimal -> binary, shasum's base64 -> binary, then compare the binary).
• However, an alternative way of comparison is to let the shasum's base64 be as it is, and instead do electron-builder's hexadecimal -> binary -> base64, and then compare the two base64 strings.

[aramaicus]

I believe that adopting a more transparent and simple checksum policy would help to promote the app. It would also help to build trust with users, who would know that they can always verify the integrity of the app they are using.

I would also like to add that it is important to make the checksums easily accessible to users. They should be published on the app's website and in the release notes.

I hope that the developers of Ente Photos will consider implementing checksums for all releases of the app. This would be a great way to improve the security and transparency of the app.