Fixing rclone Proton Drive uploads — block verification, retry, draft cleanup (March 2026)

proton-drive-backup-fix.md

Fixing rclone Proton Drive Uploads (March 2026)

Proton Drive uploads via rclone have been broken since ~November 2025. This documents the root causes, fixes, and testing.

Problem

Three issues combine to break uploads:

1. Missing block verification tokens — Proton's storage backend now requires a Verifier.Token per block in POST /drive/blocks. Without it, every block upload fails with 422 / Code=200501. This is the primary cause.
2. Broken shouldRetry() — backend/protondrive/protondrive.go:248 always returns (false, err), disabling rclone's pacer retry logic entirely.
3. Orphaned draft accumulation — Failed uploads leave draft links on Proton's servers. Subsequent uploads hit Code=2500 ("already exists") and GetRevisions returns Code=2501 ("not found") for the broken draft, causing an unrecoverable error loop.

Solution

Changes across three repos in the rclone ecosystem:

go-proton-api (fix/block-verification branch)

• Added Verifier struct and VerificationRes struct to block_types.go
• Added Verifier field to BlockUploadInfo
• Added Verification() API endpoint to block.go — GET /drive/shares/{shareID}/links/{linkID}/revisions/{revisionID}/verification

Proton-API-Bridge (fix/upload-retry branch)

• Block verification (uploadAndCollectBlockData): fetches VerificationCode + ContentKeyPacket from the verification endpoint, derives a verifier session key, and generates per-block verification tokens via XOR of the verification code with leading bytes of each block's ciphertext (algorithm sourced from ProtonDriveApps/sdk)
• Block-level retry (uploadBlockWrapper): 5 attempts with exponential backoff (2s→32s) for transient errors (Code=200501, Status=429, 5xx)
• Orphaned draft cleanup (handleRevisionConflict): when GetRevisions fails with 2501 and link is in draft state, deletes the orphaned draft and signals retry

rclone (fix/protondrive-backups branch)

Cherry-picked from existing PRs/commits:

• shouldRetry fix (from PR #9080): properly retries Code=200501, Status=429, 5xx errors
• shouldRetry tests: 10 table-driven test cases
• Crash fix (from issue #9117): o.Size() instead of *o.originalSize nil deref in Open()

Testing

1. Cross-compiled static linux/amd64 binary (CGO_ENABLED=0)
2. Injected into running gitea-backup container on VPS
3. Small file upload — succeeded
4. Full 1.39 GiB Gitea backup upload — succeeded in 5m32s, SHA1 verified
5. Rebuilt Docker image with patched binary, deployed via docker compose
6. Next cron backup scheduled for Saturday 2026-03-07 15:00 UTC

Related PRs & Issues

Repo	PR/Issue	Status	Description
rclone/rclone	#9080	Open	shouldRetry fix
rclone/rclone	#9081	Open	Block verification + draft cleanup (rclone-level)
rclone/rclone	#9117	Open	nil originalSize crash
rclone/Proton-API-Bridge	#1	Open	Draft cleanup + verification (Bridge-level)
rclone/go-proton-api	#2	Open	Verification endpoint + Verifier types
henrybear327/Proton-API-Bridge	#34	Open	Verification API (LouisBrunner)
henrybear327/go-proton-api	#5	Open	Verification endpoint (LouisBrunner)