tl;dr: exiv2 source archive was updated in-place and the verification below gives us confidence that we can safely update the hash.
On current master, the following happens: $ guix build exiv2 Starting download of /gnu/store/jcapi6vk4a14hch5jgsh5zps958g91sb-exiv2-0.26-trunk.tar.gz >From http://www.exiv2.org/builds/exiv2-0.26-trunk.tar.gz... [...] sha256 hash mismatch for output path `/gnu/store/jcapi6vk4a14hch5jgsh5zps958g91sb-exiv2-0.26-trunk.tar.gz' expected: 1hsdzlzgkipprqh93yj81mrckl2l7c2mn2i84691pallnjz5qqhc actual: 1yza317qxd8yshvqnay164imm0ks7cvij8y8j86p1gqi1153qpn7 Looking at what happened at the source obtained through the Wayback Machine at the time it was last updated in Guix[1] compared to now[2], we see that: 1. The project maintainers updated the MD5 and filesize of the file "exiv2-0.26-trunk.tar.gz", which name and URL remained unchanged. Let's validate those weak MD5 hashes: $ md5sum exiv2-0.26-trunk.tar.gz # old one f936d2ca5cbe1e18c71ca2baa5e84fb4 exiv2-0.26-trunk.tar.gz $ md5sum exiv2-0.26-trunk\(1\).tar.gz # new one 5399e3b570d7f9205f0e76d47582da4c exiv2-0.26-trunk(1).tar.gz OK, at least the advertized signature validates. 2. When extracting those two archives and diffing them, we see the changes: $ diff -ur exiv2-trunk-old/ exiv2-trunk-new/ Only in exiv2-trunk-old/: ._AUTHORS Only in exiv2-trunk-old/: ._bootstrap.macports Only in exiv2-trunk-old/: ._bootstrap.mxe Only in exiv2-trunk-old/: ._CMakeLists.txt Only in exiv2-trunk-old/: ._CMake_msvc.txt Only in exiv2-trunk-old/config: ._aclocal.m4 Only in exiv2-trunk-old/config: ._CMakeChecks.txt [...] Only in exiv2-trunk-old/xmpsdk/src: ._XMPMeta-Serialize.cpp Only in exiv2-trunk-old/xmpsdk/src: ._XMPUtils.cpp Only in exiv2-trunk-old/xmpsdk/src: ._XMPUtils-FileInfo.cpp Only in exiv2-trunk-old/xmpsdk/src: ._XMPUtils.hpp Only in exiv2-trunk-old/xmpsdk: ._src Only in exiv2-trunk-old/: ._xmpsdk A pretty harmless cleanup. Still, the practice of updating a release in place is not very good... Upon further digging, the issue was already reported and discussed[3][4]. Note: they are moving to Github and in the furure the releases will be offered directly through Github. Patch will follow. [1] https://web.archive.org/web/20170606065325/http://exiv2.org/download.html [2] http://exiv2.org/download.html [3] http://dev.exiv2.org/issues/1299 [4] https://github.com/Exiv2/exiv2/issues/19
