OpenSSH can forward TCP sockets and UNIX domain sockets. If privilege separation is disabled, then on the server side, the forwarding is handled by a child of sshd that has root privileges. For TCP server sockets, sshd explicitly checks whether an attempt is made to bind to a low port (below IPPORT_RESERVED) and, if so, requires the client to authenticate as root. However, for UNIX domain sockets, no such security measures are implemented. This means that, using “ssh -L”, an attacker who is permitted to log in as a normal user over SSH can effectively connect to non-abstract unix domain sockets with root privileges. On systems that run systemd, this can for example be exploited by asking systemd to add an LD_PRELOAD environment variable for all following daemon launches and then asking it to restart cron or so. The attached exploit demonstrates this – if it is executed on a system with systemd where the user is allowed to ssh to his own account and where privsep is disabled, it yields a root shell.<\/p>\n","protected":false},"excerpt":{"rendered":"
OpenSSH can forward TCP sockets and UNIX domain sockets. If privilege separation is disabled, then on the server side, the forwarding is handled by a child of sshd that has…<\/p>\n","protected":false},"author":439,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[43],"tags":[],"class_list":["post-27341","post","type-post","status-publish","format-standard","hentry","category-exploit"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p4bBYZ-76Z","_links":{"self":[{"href":"https:\/\/deepquest.code511.com\/blog\/wp-json\/wp\/v2\/posts\/27341","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/deepquest.code511.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/deepquest.code511.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/deepquest.code511.com\/blog\/wp-json\/wp\/v2\/users\/439"}],"replies":[{"embeddable":true,"href":"https:\/\/deepquest.code511.com\/blog\/wp-json\/wp\/v2\/comments?post=27341"}],"version-history":[{"count":0,"href":"https:\/\/deepquest.code511.com\/blog\/wp-json\/wp\/v2\/posts\/27341\/revisions"}],"wp:attachment":[{"href":"https:\/\/deepquest.code511.com\/blog\/wp-json\/wp\/v2\/media?parent=27341"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/deepquest.code511.com\/blog\/wp-json\/wp\/v2\/categories?post=27341"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/deepquest.code511.com\/blog\/wp-json\/wp\/v2\/tags?post=27341"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}