signable single file apps on mac

[VSadov]

Resolves:#3671

After adding bundle data to the singlefile host, we need to patch up the file structure so it would satisfy expectations of codesign.

The approach is basically a copy of @swaroop-sridhar changes in https://github.com/dotnet/core-setup/compare/master...swaroop-sridhar:macsign?expand=1
We are extending the size of string table in __LINKEDIT segment to include bundle data.
This makes the bundle data to appear as a large string in a string table in otherwise compliant Mach-O file.

The approach is similar to what codesign_alocate itself does for the -p option ("page align the code signature data by padding string table and changing its size").

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Issue Details

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After adding bundle data to the singlefile host, we need to patch up the file structure so it would satisfy expectations of codesign.

Current approach is basically a copy of @swaroop-sridhar changes in https://github.com/dotnet/core-setup/compare/master...swaroop-sridhar:macsign?expand=1
We are extending the size of string table in __LINKEDIT segment to include bundle data.
This makes the bundle data to appear as a large string in a string table in otherwise compliant Mach-O file.

Alternatively we could try inserting bundle data as a segment/section before __LINKEDIT. Such insertion would require patching existing offsets that point into __LINKEDIT segment. I am not yet sure if this is a viable approach.

Author:	VSadov
Assignees:	-
Labels:	area-HostModel
Milestone:	-

[janvorli]

LGTM, thank you!

[VSadov]

Thanks!!