正如其他地方所见、docx、xlsx 和 pttx 是 ZIP 文件。将它们上传到我的 Web 应用程序时，file(通过libmagic和python-magic) 将它们检测为 ZIP 文件。
我将文件内容作为 blob 存储在数据库中，但自然我不想信任用户这是哪种文件类型。所以我想信任file并在下载期间自动生成文件名。
我知道可以修改，/etc/magic但格式（magic(5)）对我来说太复杂了。我发现Debian 错误中有关此问题的错误报告但由于它是 2008 年的，所以似乎无法很快得到修复。
我想我唯一的选择就是确实信任用户（但仍将内容存储为 blob）并仅根据文件名检查文件扩展名。这样我就可以禁止某些扩展名并允许其他扩展名。当用户重新下载他的文件时，他可以以他上传的任何方式获得它。但如果文件与他人共享，此解决方案是不安全的，因为您可以简单地重命名文件以允许上传它。
有任何想法吗？
最后，我发现docx 等的魔法数字列表，但我无法将它们转换为该magic(5)格式。
答案1
您可以使用
0 string PK\x03\x04\x14\x00\x06\x00 Microsoft Office Open XML Format
在 /etc/magic 中根据您提供的信息识别一般文件类型。
（但是，这可能并不普遍：PK\x03\x04\x00\x14\x08\x08在 LibreOffice 生成的 XLSX 文件开始时就已经观察到了这种情况。）
Ubuntu 的更高版本可以正确识别 .docx、.pptx 和 .xlsx 文件。在文件实用程序的源代码中挖掘后，我找到了~/file-5.09/magic/Magdir/msooxml可以进行识别的文件。您可以获取文件副本并将其添加到您的/etc/magic文件中。
包括已更新至 v 1.5 的文件副本
# $File: msooxml,v 1.5 2014/08/05 07:38:45 christos Exp $
# msooxml: file(1) magic for Microsoft Office XML
# From: Ralf Brown <[email protected]>
# .docx, .pptx, and .xlsx are XML plus other files inside a ZIP
# archive. The first member file is normally "[Content_Types].xml".
# but some libreoffice generated files put this later. Perhaps skip
# the "[Content_Types].xml" test?
# Since MSOOXML doesn't have anything like the uncompressed "mimetype"
# file of ePub or OpenDocument, we'll have to scan for a filename
# which can distinguish between the three types
# start by checking for ZIP local file header signature
0 string PK\003\004
!:strength +10
# make sure the first file is correct
>0x1E regex \\[Content_Types\\]\\.xml|_rels/\\.rels
# skip to the second local file header
# since some documents include a 520-byte extra field following the file
# header, we need to scan for the next header
>>(18.l+49) search/2000 PK\003\004
# now skip to the *third* local file header; again, we need to scan due to a
# 520-byte extra field following the file header
>>>&26 search/1000 PK\003\004
# and check the subdirectory name to determine which type of OOXML
# file we have. Correct the mimetype with the registered ones:
# http://technet.microsoft.com/en-us/library/cc179224.aspx
>>>>&26 string word/ Microsoft Word 2007+
!:mime application/vnd.openxmlformats-officedocument.wordprocessingml.document
>>>>&26 string ppt/ Microsoft PowerPoint 2007+
!:mime application/vnd.openxmlformats-officedocument.presentationml.presentation
>>>>&26 string xl/ Microsoft Excel 2007+
!:mime application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
>>>>&26 default x Microsoft OOXML
---
但将 V1.2 留在这里以供后人使用。
由于文件包更新后上述链接可能会过期，因此在此附上一份副本。
#------------------------------------------------------------------------------
# $File: msooxml,v 1.2 2013/01/25 23:04:37 christos Exp $
# msooxml: file(1) magic for Microsoft Office XML
# From: Ralf Brown <[email protected]>
# .docx, .pptx, and .xlsx are XML plus other files inside a ZIP
# archive. The first member file is normally "[Content_Types].xml".
# Since MSOOXML doesn't have anything like the uncompressed "mimetype"
# file of ePub or OpenDocument, we'll have to scan for a filename
# which can distinguish between the three types
# start by checking for ZIP local file header signature
0 string PK\003\004
# make sure the first file is correct
>0x1E string [Content_Types].xml
# skip to the second local file header
# since some documents include a 520-byte extra field following the file
# header, we need to scan for the next header
>>(18.l+49) search/2000 PK\003\004
# now skip to the *third* local file header; again, we need to scan due to a
# 520-byte extra field following the file header
>>>&26 search/1000 PK\003\004
# and check the subdirectory name to determine which type of OOXML
# file we have
# Correct the mimetype with the registered ones:
# http://technet.microsoft.com/en-us/library/cc179224.aspx
>>>>&26 string word/ Microsoft Word 2007+
!:mime application/vnd.openxmlformats-officedocument.wordprocessingml.document
>>>>&26 string ppt/ Microsoft PowerPoint 2007+
!:mime application/vnd.openxmlformats-officedocument.presentationml.presentation
>>>>&26 string xl/ Microsoft Excel 2007+
!:mime application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
>>>>&26 default x Microsoft OOXML
!:strength +10
答案2
file，5.13 之前的版本，会将 MIME 类型截断为 64 个字符。因此，使用 msooxml 的内容，file -bi 命令中的 MIME 类型变为“mime application/vnd.openxmlformats-officedocument.wordprocessingml.d; charset=binary”
答案3
如果使用libreoffice的docx，可以在/etc/magic中添加如下内容：
# start by checking for ZIP local file header signature
0 string PK\003\004
!:strength +10
>1104 search/300 PK\003\004
# and check the subdirectory name to determine which type of OOXML
# file we have. Correct the mimetype with the registered ones:
# http://technet.microsoft.com/en-us/library/cc179224.aspx
>>&26 string word/ Microsoft Word 2007+
!:mime application/vnd.openxmlformats-officedocument.wordprocessingml.document
>>&26 string ppt/ Microsoft PowerPoint 2007+
!:mime application/vnd.openxmlformats-officedocument.presentationml.presentation
>>&26 string xl/ Microsoft Excel 2007+
!:mime application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
>>&26 default x Microsoft OOXML