{"record":{"id":"2fa252f174668cd6","repo":"JuliusBrussee/caveman","slug":"native-session-key-chmod-w","errorCode":null,"errorMessage":"native session key chmod: %w","messagePattern":"native session key chmod: %w","errorType":"console","errorClass":null,"httpStatus":null,"severity":"error","filePath":"proxy/internal/nativeruntime/marker.go","lineNumber":64,"sourceCode":"\t\t\treturn nil, fmt.Errorf(\"native session key sync: %w\", syncErr)\n\t\t}\n\t\tif closeErr := file.Close(); closeErr != nil {\n\t\t\treturn nil, fmt.Errorf(\"native session key close: %w\", closeErr)\n\t\t}\n\t\treturn key, nil\n\t}\n\tif !errors.Is(err, os.ErrExist) {\n\t\treturn nil, fmt.Errorf(\"native session key create: %w\", err)\n\t}\n\tkey, err = os.ReadFile(path)\n\tif err != nil {\n\t\treturn nil, fmt.Errorf(\"native session key read: %w\", err)\n\t}\n\tif len(key) != sessionKeyBytes {\n\t\treturn nil, fmt.Errorf(\"native session key length = %d, want %d\", len(key), sessionKeyBytes)\n\t}\n\tif err := os.Chmod(path, 0o600); err != nil {\n\t\treturn nil, fmt.Errorf(\"native session key chmod: %w\", err)\n\t}\n\treturn key, nil\n}\n\n// SessionMarker builds model-temporary correlation context. Local proxy removes\n// valid markers byte-surgically before provider inspection or forwarding.\nfunc SessionMarker(key []byte, sessionID string) (string, error) {\n\tif len(key) != sessionKeyBytes || sessionID == \"\" || len(sessionID) > 256 {\n\t\treturn \"\", errors.New(\"native session marker: invalid key or session id\")\n\t}\n\tencoded := base64.RawURLEncoding.EncodeToString([]byte(sessionID))\n\tsig := markerMAC(key, encoded)\n\treturn fmt.Sprintf(`[[caveman-session-v1 sid=\"%s\" sig=\"%s\"]]`, encoded, sig), nil\n}\n\n// StripSessionMarkers removes only valid HMAC-signed markers. Invalid marker-\n// shaped user text remains byte-identical. Conflicting valid session IDs are\n// stripped but return no correlation identity.","sourceCodeStart":46,"sourceCodeEnd":82,"githubUrl":"https://github.com/JuliusBrussee/caveman/blob/27d5a3981a347890211bb1bf2439e5c821a63bc9/proxy/internal/nativeruntime/marker.go#L46-L82","documentation":"After reading an existing 32-byte session.key, LoadOrCreateSessionKey Chmods it to 0600 to guarantee user-only access even if it was provisioned with looser modes. Failure indicates the running user does not own the file or the filesystem rejects chmod — the key would potentially be readable by others, so the operation refuses to continue with it.","triggerScenarios":"Key file created by root or another user; key on a chmod-ignoring filesystem (FAT, some CIFS mounts); immutable attribute set (chattr +i).","commonSituations":"Mixed sudo/user operation; keys copied between machines preserving foreign ownership; provisioning pipelines running as root.","solutions":["chown the key (and runtime dir) to the running user, then retry","Remove the immutable flag if set: sudo chattr -i <home>/runtime/session.key","Store home on a POSIX-permission filesystem"],"exampleFix":"# before\nsession.key owned by root -> Error[1075]\n\n# after\nsudo chown $(id -un):$(id -gn) ~/.caveman/runtime/session.key && chmod 600 ~/.caveman/runtime/session.key","handlingStrategy":"validation","validationCode":"func keyOwnedAndTight(path string) bool {\n    fi, err := os.Stat(path)\n    return err == nil && fi.Mode().Perm() == 0o600 &&\n        int(fi.Sys().(*syscall.Stat_t).Uid) == os.Geteuid()\n}","typeGuard":null,"tryCatchPattern":null,"preventionTips":["chown key material to the service user during provisioning","Do not copy keys between users/machines with foreign ownership","Skip chattr +i on files the runtime must chmod"],"tags":["permissions","session-key","security","filesystem"],"backgroundTag":null,"analyzedSha":"27d5a3981a347890211bb1bf2439e5c821a63bc9","analyzedAt":"2026-08-15T09:26:11.751Z","schemaVersion":2},"datasetVersion":"2026-08-15T17:31:12.345Z"}