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fix(exiftool): exclude more system tags, but keep some derived tags (safe ones)

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This commit is contained in:
Julien Neuhart
2026-03-31 19:00:49 +02:00
parent e28e2ebf0f
commit 20522fd1ac
1 changed files with 40 additions and 23 deletions
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pkg/modules/exiftool/exiftool.go
+40 -23
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@@ -23,6 +23,34 @@ func init() {
gotenberg.MustRegisterModule(new(ExifTool))
}
// systemTags lists ExifTool tags that reflect internal filesystem state
// rather than actual PDF metadata. These are stripped from both read and
// write operations.
var systemTags = []string{
"FileName", // Reflects UUID-based disk name, not original filename
"Directory", // Leaks internal temp path
"FileSize", // System attribute
"FileModifyDate", // System attribute
"FileAccessDate", // System attribute
"FileInodeChangeDate", // System attribute
"FilePermissions", // System attribute
"ExifToolVersion", // Tool metadata
"Error", // Extraction error messages
"Warning", // Extraction warning messages
}
// writeOnlyDerivedTags lists ExifTool tags that are safe to return when
// reading metadata but should not be written back (writing them can break
// PDF/A compliance or cause side effects).
var writeOnlyDerivedTags = []string{
"PageCount", // Causes prism:pageCount injection
"Linearized", // Computed status; writing it may invalidate structure
"PDFVersion", // Header version; should not be manually forced via metadata
"MIMEType", // Read-only derived
"FileType", // Read-only derived
"FileTypeExtension", // Read-only derived
}
// ExifTool abstracts the CLI tool ExifTool and implements the
// [gotenberg.PdfEngine] interface.
type ExifTool struct {
@@ -163,6 +191,12 @@ func (engine *ExifTool) ReadMetadata(ctx context.Context, logger *slog.Logger, i
return nil, err
}
// Strip system tags that reflect internal filesystem state (e.g.,
// UUID-based FileName, temp Directory) rather than actual PDF metadata.
for _, tag := range systemTags {
delete(fileMetadata[0].Fields, tag)
}
span.SetStatus(codes.Ok, "")
return fileMetadata[0].Fields, nil
}
@@ -198,30 +232,13 @@ func (engine *ExifTool) WriteMetadata(ctx context.Context, logger *slog.Logger,
return err
}
// Define a list of derived, system, or computed tags that ExifTool
// extracts but should never be written back. Writing these can break PDF/A
// compliance (e.g., PageCount -> prism:pageCount) or cause side effects
// (e.g., FileModifyDate).
derivedTags := []string{
"PageCount", // Causes prism:pageCount injection
"Linearized", // Computed status; writing it may invalidate structure
"PDFVersion", // Header version; should not be manually forced via metadata
"MIMEType", // Read-only derived
"FileType", // Read-only derived
"FileTypeExtension", // Read-only derived
"FileSize", // System attribute
"FileModifyDate", // System attribute
"FileAccessDate", // System attribute
"FileInodeChangeDate", // System attribute
"FilePermissions", // System attribute
"FileName", // Writing this triggers a file rename in ExifTool
"Directory", // System attribute
"ExifToolVersion", // Tool metadata
"Error", // Extraction error messages
"Warning", // Extraction warning messages
// Strip system and derived tags from the existing file metadata so
// they are not written back (which can break PDF/A compliance or
// cause side effects).
for _, tag := range systemTags {
delete(fileMetadata[0].Fields, tag)
}
for _, tag := range derivedTags {
for _, tag := range writeOnlyDerivedTags {
delete(fileMetadata[0].Fields, tag)
}