{"id":49079,"date":"2025-09-01T15:43:16","date_gmt":"2025-09-01T19:43:16","guid":{"rendered":"https:\/\/mjtsai.com\/blog\/?p=49079"},"modified":"2025-09-01T15:43:16","modified_gmt":"2025-09-01T19:43:16","slug":"the-anatomy-of-a-mach-o","status":"publish","type":"post","link":"https:\/\/mjtsai.com\/blog\/2025\/09\/01\/the-anatomy-of-a-mach-o\/","title":{"rendered":"The Anatomy of a Mach-O"},"content":{"rendered":"<p><a href=\"https:\/\/oliviagallucci.com\/the-anatomy-of-a-mach-o-structure-code-signing-and-pac\/\">Olivia A. Gallucci<\/a>:<\/p>\n<blockquote cite=\"https:\/\/oliviagallucci.com\/the-anatomy-of-a-mach-o-structure-code-signing-and-pac\/\"><p>The Mach Object (Mach-O) is the binary format used on Apple&rsquo;s operating systems for executables, libraries, and object code. It was created for the Mach kernel (hence the name) and introduced in NeXTSTEP, the predecessor to macOS, as a replacement for the <a href=\"https:\/\/stackoverflow.com\/questions\/37415177\/what-is-use-of-creating-many-executable-file-formats\">a.out format<\/a>. <\/p><p>[&#8230;]<\/p><p>In this post, we&rsquo;ll explore Mach-O&rsquo;s layout and history. Then, we will examine how macs use Mach-O for code signing integrity and for Pointer Authentication Codes (PAC) on ARM64e systems.<\/p><\/blockquote>\n\n<p>Previously:<\/p>\n<ul>\n<li><a href=\"https:\/\/mjtsai.com\/blog\/2025\/08\/27\/archaeology-1-4\/\">Archaeology 1.4<\/a><\/li>\n<li><a href=\"https:\/\/mjtsai.com\/blog\/2022\/07\/05\/pacman-attack-on-m1-processor\/\">PACMAN Attack on M1 Processor<\/a><\/li>\n<li><a href=\"https:\/\/mjtsai.com\/blog\/2020\/09\/04\/auto-linking-in-macho-explorer\/\">Auto Linking in MachO-Explorer<\/a><\/li>\n<li><a href=\"https:\/\/mjtsai.com\/blog\/2015\/09\/15\/parsing-mach-o-files\/\">Parsing Mach-O Files<\/a><\/li>\n<li><a href=\"https:\/\/mjtsai.com\/blog\/2003\/04\/09\/machoview\/\">MachOView<\/a><\/li>\n<li><a href=\"https:\/\/mjtsai.com\/blog\/2002\/10\/19\/mach_o_vs_cfm\/\">Mach-O vs. CFM<\/a><\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"<p>Olivia A. Gallucci: The Mach Object (Mach-O) is the binary format used on Apple&rsquo;s operating systems for executables, libraries, and object code. It was created for the Mach kernel (hence the name) and introduced in NeXTSTEP, the predecessor to macOS, as a replacement for the a.out format. [&#8230;]In this post, we&rsquo;ll explore Mach-O&rsquo;s layout and [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"apple_news_api_created_at":"2025-09-01T19:43:19Z","apple_news_api_id":"418798d8-d714-4289-ae2f-9ccb1a76becf","apple_news_api_modified_at":"2025-09-01T19:43:19Z","apple_news_api_revision":"AAAAAAAAAAD\/\/\/\/\/\/\/\/\/\/w==","apple_news_api_share_url":"https:\/\/apple.news\/AQYeY2NcUQomuL5zLGna-zw","apple_news_coverimage":0,"apple_news_coverimage_caption":"","apple_news_is_hidden":false,"apple_news_is_paid":false,"apple_news_is_preview":false,"apple_news_is_sponsored":false,"apple_news_maturity_rating":"","apple_news_metadata":"\"\"","apple_news_pullquote":"","apple_news_pullquote_position":"","apple_news_slug":"","apple_news_sections":"\"\"","apple_news_suppress_video_url":false,"apple_news_use_image_component":false,"footnotes":""},"categories":[4],"tags":[262,466,31,2586,30,2792,2598,71],"class_list":["post-49079","post","type-post","status-publish","format-standard","hentry","category-programming-category","tag-arm","tag-codesigning","tag-ios","tag-ios-18","tag-mac","tag-mach-o","tag-macos-15-sequoia","tag-programming"],"apple_news_notices":[],"_links":{"self":[{"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/posts\/49079","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/comments?post=49079"}],"version-history":[{"count":1,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/posts\/49079\/revisions"}],"predecessor-version":[{"id":49080,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/posts\/49079\/revisions\/49080"}],"wp:attachment":[{"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/media?parent=49079"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/categories?post=49079"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/tags?post=49079"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}