thodg/libgit2/tests/checkout/nasty.c
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Hash : 3f7851ea
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Date : 2019-09-18T14:32:05
Disallow NTFS Alternate Data Stream attacks, even on Linux/macOS A little-known feature of NTFS is that it offers to store metadata in so-called "Alternate Data Streams" (inspired by Apple's "resource forks") that are copied together with the file they are associated with. These Alternate Data Streams can be accessed via `<file name>:<stream name>:<stream type>`. Directories, too, have Alternate Data Streams, and they even have a default stream type `$INDEX_ALLOCATION`. Which means that `abc/` and `abc::$INDEX_ALLOCATION/` are actually equivalent. This is of course another attack vector on the Git directory that we definitely want to prevent. On Windows, we already do this incidentally, by disallowing colons in file/directory names. While it looks as if files'/directories' Alternate Data Streams are not accessible in the Windows Subsystem for Linux, and neither via CIFS/SMB-mounted network shares in Linux, it _is_ possible to access them on SMB-mounted network shares on macOS. Therefore, let's go the extra mile and prevent this particular attack _everywhere_. To keep things simple, let's just disallow *any* Alternate Data Stream of `.git`. This is libgit2's variant of CVE-2019-1352. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
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tests/checkout/nasty.c
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#include "clar_libgit2.h" #include "checkout_helpers.h" #include "git2/checkout.h" #include "repository.h" #include "buffer.h" #include "futils.h" static const char *repo_name = "nasty"; static git_repository *repo; static git_checkout_options checkout_opts; void test_checkout_nasty__initialize(void) { repo = cl_git_sandbox_init(repo_name); GIT_INIT_STRUCTURE(&checkout_opts, GIT_CHECKOUT_OPTIONS_VERSION); checkout_opts.checkout_strategy = GIT_CHECKOUT_FORCE; } void test_checkout_nasty__cleanup(void) { cl_git_sandbox_cleanup(); } static void test_checkout_passes(const char *refname, const char *filename) { git_oid commit_id; git_commit *commit; git_checkout_options opts = GIT_CHECKOUT_OPTIONS_INIT; git_buf path = GIT_BUF_INIT; cl_git_pass(git_buf_joinpath(&path, repo_name, filename)); cl_git_pass(git_reference_name_to_id(&commit_id, repo, refname)); cl_git_pass(git_commit_lookup(&commit, repo, &commit_id)); opts.checkout_strategy = GIT_CHECKOUT_FORCE | GIT_CHECKOUT_DONT_UPDATE_INDEX; cl_git_pass(git_checkout_tree(repo, (const git_object *)commit, &opts)); cl_assert(!git_path_exists(path.ptr)); git_commit_free(commit); git_buf_dispose(&path); } static void test_checkout_fails(const char *refname, const char *filename) { git_oid commit_id; git_commit *commit; git_checkout_options opts = GIT_CHECKOUT_OPTIONS_INIT; git_buf path = GIT_BUF_INIT; cl_git_pass(git_buf_joinpath(&path, repo_name, filename)); cl_git_pass(git_reference_name_to_id(&commit_id, repo, refname)); cl_git_pass(git_commit_lookup(&commit, repo, &commit_id)); opts.checkout_strategy = GIT_CHECKOUT_FORCE; cl_git_fail(git_checkout_tree(repo, (const git_object *)commit, &opts)); cl_assert(!git_path_exists(path.ptr)); git_commit_free(commit); git_buf_dispose(&path); } /* A tree that contains ".git" as a tree, with a blob inside * (".git/foobar"). */ void test_checkout_nasty__dotgit_tree(void) { test_checkout_fails("refs/heads/dotgit_tree", ".git/foobar"); } /* A tree that contains ".GIT" as a tree, with a blob inside * (".GIT/foobar"). */ void test_checkout_nasty__dotcapitalgit_tree(void) { test_checkout_fails("refs/heads/dotcapitalgit_tree", ".GIT/foobar"); } /* A tree that contains a tree ".", with a blob inside ("./foobar"). */ void test_checkout_nasty__dot_tree(void) { test_checkout_fails("refs/heads/dot_tree", "foobar"); } /* A tree that contains a tree ".", with a tree ".git", with a blob * inside ("./.git/foobar"). */ void test_checkout_nasty__dot_dotgit_tree(void) { test_checkout_fails("refs/heads/dot_dotgit_tree", ".git/foobar"); } /* A tree that contains a tree, with a tree "..", with a tree ".git", with a * blob inside ("foo/../.git/foobar"). */ void test_checkout_nasty__dotdot_dotgit_tree(void) { test_checkout_fails("refs/heads/dotdot_dotgit_tree", ".git/foobar"); } /* A tree that contains a tree, with a tree "..", with a blob inside * ("foo/../foobar"). */ void test_checkout_nasty__dotdot_tree(void) { test_checkout_fails("refs/heads/dotdot_tree", "foobar"); } /* A tree that contains a blob with the rogue name ".git/foobar" */ void test_checkout_nasty__dotgit_path(void) { test_checkout_fails("refs/heads/dotgit_path", ".git/foobar"); } /* A tree that contains a blob with the rogue name ".GIT/foobar" */ void test_checkout_nasty__dotcapitalgit_path(void) { test_checkout_fails("refs/heads/dotcapitalgit_path", ".GIT/foobar"); } /* A tree that contains a blob with the rogue name "./.git/foobar" */ void test_checkout_nasty__dot_dotgit_path(void) { test_checkout_fails("refs/heads/dot_dotgit_path", ".git/foobar"); } /* A tree that contains a blob with the rogue name "./.GIT/foobar" */ void test_checkout_nasty__dot_dotcapitalgit_path(void) { test_checkout_fails("refs/heads/dot_dotcapitalgit_path", ".GIT/foobar"); } /* A tree that contains a blob with the rogue name "foo/../.git/foobar" */ void test_checkout_nasty__dotdot_dotgit_path(void) { test_checkout_fails("refs/heads/dotdot_dotgit_path", ".git/foobar"); } /* A tree that contains a blob with the rogue name "foo/../.GIT/foobar" */ void test_checkout_nasty__dotdot_dotcapitalgit_path(void) { test_checkout_fails("refs/heads/dotdot_dotcapitalgit_path", ".GIT/foobar"); } /* A tree that contains a blob with the rogue name "foo/." */ void test_checkout_nasty__dot_path(void) { test_checkout_fails("refs/heads/dot_path", "./foobar"); } /* A tree that contains a blob with the rogue name "foo/." */ void test_checkout_nasty__dot_path_two(void) { test_checkout_fails("refs/heads/dot_path_two", "foo/."); } /* A tree that contains a blob with the rogue name "foo/../foobar" */ void test_checkout_nasty__dotdot_path(void) { test_checkout_fails("refs/heads/dotdot_path", "foobar"); } /* A tree that contains an entry with a backslash ".git\foobar" */ void test_checkout_nasty__dotgit_backslash_path(void) { #ifdef GIT_WIN32 test_checkout_fails("refs/heads/dotgit_backslash_path", ".git/foobar"); #endif } /* A tree that contains an entry with a backslash ".GIT\foobar" */ void test_checkout_nasty__dotcapitalgit_backslash_path(void) { #ifdef GIT_WIN32 test_checkout_fails("refs/heads/dotcapitalgit_backslash_path", ".GIT/foobar"); #endif } /* A tree that contains an entry with a backslash ".\.GIT\foobar" */ void test_checkout_nasty__dot_backslash_dotcapitalgit_path(void) { #ifdef GIT_WIN32 test_checkout_fails("refs/heads/dot_backslash_dotcapitalgit_path", ".GIT/foobar"); #endif } /* A tree that contains an entry ".git.", because Win32 APIs will drop the * trailing slash. */ void test_checkout_nasty__dot_git_dot(void) { #ifdef GIT_WIN32 test_checkout_fails("refs/heads/dot_git_dot", ".git/foobar"); #endif } /* A tree that contains an entry "git~1", because that is typically the * short name for ".git". */ void test_checkout_nasty__git_tilde1(void) { test_checkout_fails("refs/heads/git_tilde1", ".git/foobar"); test_checkout_fails("refs/heads/git_tilde1", "git~1/foobar"); } /* A tree that contains an entry "git~2", when we have forced the short * name for ".git" into "GIT~2". */ void test_checkout_nasty__git_custom_shortname(void) { #ifdef GIT_WIN32 if (!cl_sandbox_supports_8dot3()) clar__skip(); cl_must_pass(p_rename("nasty/.git", "nasty/_temp")); cl_git_write2file("nasty/git~1", "", 0, O_RDWR|O_CREAT, 0666); cl_must_pass(p_rename("nasty/_temp", "nasty/.git")); test_checkout_fails("refs/heads/git_tilde2", ".git/foobar"); #endif } /* A tree that contains an entry "git~3", which should be allowed, since * it is not the typical short name ("GIT~1") or the actual short name * ("GIT~2") for ".git". */ void test_checkout_nasty__only_looks_like_a_git_shortname(void) { #ifdef GIT_WIN32 git_oid commit_id; git_commit *commit; git_checkout_options opts = GIT_CHECKOUT_OPTIONS_INIT; cl_must_pass(p_rename("nasty/.git", "nasty/_temp")); cl_git_write2file("nasty/git~1", "", 0, O_RDWR|O_CREAT, 0666); cl_must_pass(p_rename("nasty/_temp", "nasty/.git")); cl_git_pass(git_reference_name_to_id(&commit_id, repo, "refs/heads/git_tilde3")); cl_git_pass(git_commit_lookup(&commit, repo, &commit_id)); opts.checkout_strategy = GIT_CHECKOUT_FORCE; cl_git_pass(git_checkout_tree(repo, (const git_object *)commit, &opts)); cl_assert(git_path_exists("nasty/git~3/foobar")); git_commit_free(commit); #endif } /* A tree that contains an entry "git:", because Win32 APIs will reject * that as looking too similar to a drive letter. */ void test_checkout_nasty__dot_git_colon(void) { #ifdef GIT_WIN32 test_checkout_fails("refs/heads/dot_git_colon", ".git/foobar"); #endif } /* A tree that contains an entry "git:foo", because Win32 APIs will turn * that into ".git". */ void test_checkout_nasty__dot_git_colon_stuff(void) { #ifdef GIT_WIN32 test_checkout_fails("refs/heads/dot_git_colon_stuff", ".git/foobar"); #endif } /* A tree that contains an entry ".git::$INDEX_ALLOCATION" because NTFS * will interpret that as a synonym to ".git", even when mounted via SMB * on macOS. */ void test_checkout_nasty__dotgit_alternate_data_stream(void) { test_checkout_fails("refs/heads/dotgit_alternate_data_stream", ".git/dummy-file"); test_checkout_fails("refs/heads/dotgit_alternate_data_stream", ".git::$INDEX_ALLOCATION/dummy-file"); } /* Trees that contains entries with a tree ".git" that contain * byte sequences: * { 0xe2, 0x80, 0x8c } * { 0xe2, 0x80, 0x8d } * { 0xe2, 0x80, 0x8e } * { 0xe2, 0x80, 0x8f } * { 0xe2, 0x80, 0xaa } * { 0xe2, 0x80, 0xab } * { 0xe2, 0x80, 0xac } * { 0xe2, 0x80, 0xad } * { 0xe2, 0x81, 0xae } * { 0xe2, 0x81, 0xaa } * { 0xe2, 0x81, 0xab } * { 0xe2, 0x81, 0xac } * { 0xe2, 0x81, 0xad } * { 0xe2, 0x81, 0xae } * { 0xe2, 0x81, 0xaf } * { 0xef, 0xbb, 0xbf } * Because these map to characters that HFS filesystems "ignore". Thus * ".git<U+200C>" will map to ".git". */ void test_checkout_nasty__dot_git_hfs_ignorable(void) { #ifdef __APPLE__ test_checkout_fails("refs/heads/dotgit_hfs_ignorable_1", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_2", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_3", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_4", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_5", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_6", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_7", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_8", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_9", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_10", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_11", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_12", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_13", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_14", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_15", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_16", ".git/foobar"); #endif } void test_checkout_nasty__honors_core_protecthfs(void) { cl_repo_set_bool(repo, "core.protectHFS", true); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_1", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_2", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_3", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_4", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_5", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_6", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_7", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_8", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_9", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_10", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_11", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_12", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_13", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_14", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_15", ".git/foobar"); test_checkout_fails("refs/heads/dotgit_hfs_ignorable_16", ".git/foobar"); } void test_checkout_nasty__honors_core_protectntfs(void) { cl_repo_set_bool(repo, "core.protectNTFS", true); test_checkout_fails("refs/heads/dotgit_backslash_path", ".git/foobar"); test_checkout_fails("refs/heads/dotcapitalgit_backslash_path", ".GIT/foobar"); test_checkout_fails("refs/heads/dot_git_dot", ".git/foobar"); test_checkout_fails("refs/heads/git_tilde1", ".git/foobar"); } void test_checkout_nasty__symlink1(void) { test_checkout_passes("refs/heads/symlink1", ".git/foobar"); } void test_checkout_nasty__symlink2(void) { test_checkout_passes("refs/heads/symlink2", ".git/foobar"); } void test_checkout_nasty__symlink3(void) { test_checkout_passes("refs/heads/symlink3", ".git/foobar"); } void test_checkout_nasty__gitmodules_symlink(void) { cl_repo_set_bool(repo, "core.protectHFS", true); test_checkout_fails("refs/heads/gitmodules-symlink", ".gitmodules"); cl_repo_set_bool(repo, "core.protectHFS", false); cl_repo_set_bool(repo, "core.protectNTFS", true); test_checkout_fails("refs/heads/gitmodules-symlink", ".gitmodules"); cl_repo_set_bool(repo, "core.protectNTFS", false); test_checkout_fails("refs/heads/gitmodules-symlink", ".gitmodules"); }