### Please describe the problem.

I had to migrate a special remote using hybrid encryption from an Amazon Cloud Drive-hosted rclone remote to a Google Drive-hosted rclone remote. Now I am testing it by trying to fsck a particular file.

I've left all of the special remote settings on the git annex side the same, and just changed my `.rclone.conf` to have "amazondrive", the rclone remote name, actually point to the new Google Drive location.

When I try to fsck my file, git annex generates an HMAC key, successfully downloads it from the remote, but then fails to decrypt it. After that, it looks like it retries: it generates a **different HMAC key**, which it can't find the file for.

I've compared the files in Amazon and in Google Drive and they are the same.

Using the [independent decryption script](https://git-annex.branchable.com/tips/Decrypting_files_in_special_remotes_without_git-annex/), modified to use the SHA512 MAC that my repo uses, and to not use every matching line from `remote.log`, I can generate the *second* HMAC key that git annex appears to fall back to, but not the first one. I think that this means I can't generate the decryption key either; I've had no luck manually decrypting the file with the characters after the first 256 of the decrypted shared key as the GPG passphrase.

How is Git Annex generating that first HMAC, if not by the process used in the decryption script? Why is it able to get an HMAC that exists but not a valid decryption key? What is the thinking behind trying multiple HMAC keys for the same file?

### What steps will reproduce the problem?

Have an encrypted, hybrid Git Annex repo in an Amazon Drive rclone remote.
Copy all the files over to Google Drive, and make a Google Drive rclone remote in rclone.conf with the same name that the Amazon Drive one had.
Try to retrieve files from the remote with Git Annex.

### What version of git-annex are you using? On what operating system?

`6.20170525+gitge1cf095ae-1~ndall+1` on Ubuntu 16.04

### Please provide any additional information below.

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log

$ git annex fsck info.txt --from=amazon --debug
[2017-06-03 11:24:31.368563623] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","show-ref","git-annex"]
[2017-06-03 11:24:31.373358653] process done ExitSuccess
[2017-06-03 11:24:31.373520685] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","show-ref","--hash","refs/heads/git-annex"]
[2017-06-03 11:24:31.379319755] process done ExitSuccess
[2017-06-03 11:24:31.382954929] chat: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","cat-file","--batch"]
[2017-06-03 11:24:31.386196477] chat: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","cat-file","--batch-check=%(objectname) %(objecttype) %(objectsize)"]
[2017-06-03 11:24:31.392852081] read: git ["config","--null","--list"]
[2017-06-03 11:24:31.397686571] process done ExitSuccess
[2017-06-03 11:24:31.400187312] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","ls-files","--cached","-z","--","info.txt"]
[2017-06-03 11:24:31.424951599] chat: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","check-attr","-z","--stdin","annex.backend","annex.numcopies","annex.largefiles","--"]
[2017-06-03 11:24:31.425544622] read: git ["--version"]
[2017-06-03 11:24:31.428009953] process done ExitSuccess
fsck info.txt [2017-06-03 11:24:31.479360829] chat: gpg ["--batch","--no-tty","--use-agent","--quiet","--trust-model","always","--decrypt"]
[2017-06-03 11:24:31.503040759] process done ExitSuccess
[2017-06-03 11:24:31.506638987] chat: /home/anovak/bin/git-annex-remote-rclone []
[2017-06-03 11:24:31.510094668] git-annex-remote-rclone[1] --> VERSION 1
[2017-06-03 11:24:31.510281634] git-annex-remote-rclone[1] <-- PREPARE
[2017-06-03 11:24:31.511006098] git-annex-remote-rclone[1] --> GETCONFIG prefix
[2017-06-03 11:24:31.511148645] git-annex-remote-rclone[1] <-- VALUE data/annex-rclone
[2017-06-03 11:24:31.515487261] git-annex-remote-rclone[1] --> GETCONFIG target
[2017-06-03 11:24:31.515770189] git-annex-remote-rclone[1] <-- VALUE amazondrive
[2017-06-03 11:24:31.519503001] git-annex-remote-rclone[1] --> GETCONFIG rclone_layout
[2017-06-03 11:24:31.519666709] git-annex-remote-rclone[1] <-- VALUE lower
[2017-06-03 11:24:31.523726589] git-annex-remote-rclone[1] --> PREPARE-SUCCESS
[2017-06-03 11:24:31.523902589] git-annex-remote-rclone[1] <-- CHECKPRESENT GPGHMACSHA512--4354571263cd241ac8300e0bd8fc3643c184b922500c3d9318b7ce590684e1de820d41c0b245f1595e0bd38b2844a5151192981b4f9ab41bda135d5f7a184d16
[2017-06-03 11:24:31.530946791] git-annex-remote-rclone[1] --> DIRHASH-LOWER GPGHMACSHA512--4354571263cd241ac8300e0bd8fc3643c184b922500c3d9318b7ce590684e1de820d41c0b245f1595e0bd38b2844a5151192981b4f9ab41bda135d5f7a184d16
[2017-06-03 11:24:31.531236912] git-annex-remote-rclone[1] <-- VALUE b95/785/
Total objects: 1 Total size: 119 Bytes (119 Bytes) 2017/06/03 11:24:42 Transferred: 0 Bytes (0 Bytes/s) Errors: 0 Checks: 0 Transferred: 0 Elapsed time: 10.4s
[2017-06-03 11:24:42.04576211] git-annex-remote-rclone[1] --> CHECKPRESENT-SUCCESS GPGHMACSHA512--4354571263cd241ac8300e0bd8fc3643c184b922500c3d9318b7ce590684e1de820d41c0b245f1595e0bd38b2844a5151192981b4f9ab41bda135d5f7a184d16

[2017-06-03 11:24:42.049286934] git-annex-remote-rclone[1] <-- TRANSFER RETRIEVE GPGHMACSHA512--4354571263cd241ac8300e0bd8fc3643c184b922500c3d9318b7ce590684e1de820d41c0b245f1595e0bd38b2844a5151192981b4f9ab41bda135d5f7a184d16 .git/annex/tmp/GPGHMACSHA512--4354571263cd241ac8300e0bd8fc3643c184b922500c3d9318b7ce590684e1de820d41c0b245f1595e0bd38b2844a5151192981b4f9ab41bda135d5f7a184d16
[2017-06-03 11:24:42.050298028] git-annex-remote-rclone[1] --> DIRHASH-LOWER GPGHMACSHA512--4354571263cd241ac8300e0bd8fc3643c184b922500c3d9318b7ce590684e1de820d41c0b245f1595e0bd38b2844a5151192981b4f9ab41bda135d5f7a184d16
[2017-06-03 11:24:42.05045573] git-annex-remote-rclone[1] <-- VALUE b95/785/
2017/06/03 11:24:52 Local file system at /tmp/tmp.ITXaCoES4i: Waiting for checks to finish
2017/06/03 11:24:52 Local file system at /tmp/tmp.ITXaCoES4i: Waiting for transfers to finish
2017/06/03 11:24:54 
Transferred:    119 Bytes (9 Bytes/s)
Errors:                 0
Checks:                 0
Transferred:            1
Elapsed time:         12s
[2017-06-03 11:24:54.083003717] git-annex-remote-rclone[1] --> TRANSFER-SUCCESS RETRIEVE GPGHMACSHA512--4354571263cd241ac8300e0bd8fc3643c184b922500c3d9318b7ce590684e1de820d41c0b245f1595e0bd38b2844a5151192981b4f9ab41bda135d5f7a184d16
[2017-06-03 11:24:54.083554696] chat: gpg ["--batch","--no-tty","--use-agent","--quiet","--trust-model","always","--batch","--passphrase-fd","22","--decrypt"]
gpg: decryption failed: bad key
[2017-06-03 11:24:54.086768586] process done ExitFailure 2
[2017-06-03 11:24:54.088931923] git-annex-remote-rclone[1] <-- TRANSFER RETRIEVE GPGHMACSHA512--7439fc103f30635cd914af0ce14370aef2f9a81f415ba7a652bc20454c90893bcd5701ebbed855f6a0285fce413e5c039c15a7049738cf519e2719c9d485ce28 .git/annex/tmp/GPGHMACSHA512--7439fc103f30635cd914af0ce14370aef2f9a81f415ba7a652bc20454c90893bcd5701ebbed855f6a0285fce413e5c039c15a7049738cf519e2719c9d485ce28
[2017-06-03 11:24:54.089806756] git-annex-remote-rclone[1] --> DIRHASH-LOWER GPGHMACSHA512--7439fc103f30635cd914af0ce14370aef2f9a81f415ba7a652bc20454c90893bcd5701ebbed855f6a0285fce413e5c039c15a7049738cf519e2719c9d485ce28
[2017-06-03 11:24:54.090050153] git-annex-remote-rclone[1] <-- VALUE b47/e54/
2017/06/03 11:25:03 Local file system at /tmp/tmp.5lapDbIoZy: Waiting for checks to finish
2017/06/03 11:25:03 Local file system at /tmp/tmp.5lapDbIoZy: Waiting for transfers to finish
2017/06/03 11:25:03 Attempt 1/3 failed with 0 errors and: directory not found
2017/06/03 11:25:03 Local file system at /tmp/tmp.5lapDbIoZy: Waiting for checks to finish
2017/06/03 11:25:03 Local file system at /tmp/tmp.5lapDbIoZy: Waiting for transfers to finish
2017/06/03 11:25:03 Attempt 2/3 failed with 0 errors and: directory not found
2017/06/03 11:25:04 Local file system at /tmp/tmp.5lapDbIoZy: Waiting for checks to finish
2017/06/03 11:25:04 Local file system at /tmp/tmp.5lapDbIoZy: Waiting for transfers to finish
2017/06/03 11:25:04 Attempt 3/3 failed with 0 errors and: directory not found
2017/06/03 11:25:04 Failed to copy: directory not found
[2017-06-03 11:25:04.479940212] git-annex-remote-rclone[1] --> TRANSFER-FAILURE RETRIEVE GPGHMACSHA512--7439fc103f30635cd914af0ce14370aef2f9a81f415ba7a652bc20454c90893bcd5701ebbed855f6a0285fce413e5c039c15a7049738cf519e2719c9d485ce28

  failed to download file from remote
failed
[2017-06-03 11:25:04.492702185] chat: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","hash-object","-w","--stdin-paths","--no-filters"]
[2017-06-03 11:25:04.494054942] feed: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","update-index","-z","--index-info"]
[2017-06-03 11:25:04.672344301] process done ExitSuccess
[2017-06-03 11:25:04.67255166] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","show-ref","--hash","refs/heads/git-annex"]
[2017-06-03 11:25:04.68070068] process done ExitSuccess
(recording state in git...)
[2017-06-03 11:25:04.680983817] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","write-tree"]
[2017-06-03 11:25:04.900456464] process done ExitSuccess
[2017-06-03 11:25:04.900643429] chat: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","commit-tree","a8fc26b91dab1ffac0499d3e21c0f691858d3a6a","--no-gpg-sign","-p","refs/heads/git-annex"]
[2017-06-03 11:25:04.965122443] process done ExitSuccess
[2017-06-03 11:25:04.965288386] call: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","update-ref","refs/heads/git-annex","c0b297184826849d8a24c899faa9f4f47c1f8e53"]
[2017-06-03 11:25:04.970235879] process done ExitSuccess
[2017-06-03 11:25:04.971493023] process done ExitSuccess
git-annex: fsck: 1 failed


# End of transcript or log.
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)

Yeah, it works great most of the time, and it was working great on the amazon remote before I tried to pull these migration shenanigans.
