diff options
Diffstat (limited to 'meta/recipes-extended/shadow/files')
-rw-r--r-- | meta/recipes-extended/shadow/files/CVE-2018-7169.patch | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/meta/recipes-extended/shadow/files/CVE-2018-7169.patch b/meta/recipes-extended/shadow/files/CVE-2018-7169.patch new file mode 100644 index 0000000000..36887d44ee --- /dev/null +++ b/meta/recipes-extended/shadow/files/CVE-2018-7169.patch | |||
@@ -0,0 +1,186 @@ | |||
1 | From fb28c99b8a66ff2605c5cb96abc0a4d975f92de0 Mon Sep 17 00:00:00 2001 | ||
2 | From: Aleksa Sarai <asarai@suse.de> | ||
3 | Date: Thu, 15 Feb 2018 23:49:40 +1100 | ||
4 | Subject: [PATCH] newgidmap: enforce setgroups=deny if self-mapping a group | ||
5 | |||
6 | This is necessary to match the kernel-side policy of "self-mapping in a | ||
7 | user namespace is fine, but you cannot drop groups" -- a policy that was | ||
8 | created in order to stop user namespaces from allowing trivial privilege | ||
9 | escalation by dropping supplementary groups that were "blacklisted" from | ||
10 | certain paths. | ||
11 | |||
12 | This is the simplest fix for the underlying issue, and effectively makes | ||
13 | it so that unless a user has a valid mapping set in /etc/subgid (which | ||
14 | only administrators can modify) -- and they are currently trying to use | ||
15 | that mapping -- then /proc/$pid/setgroups will be set to deny. This | ||
16 | workaround is only partial, because ideally it should be possible to set | ||
17 | an "allow_setgroups" or "deny_setgroups" flag in /etc/subgid to allow | ||
18 | administrators to further restrict newgidmap(1). | ||
19 | |||
20 | We also don't write anything in the "allow" case because "allow" is the | ||
21 | default, and users may have already written "deny" even if they | ||
22 | technically are allowed to use setgroups. And we don't write anything if | ||
23 | the setgroups policy is already "deny". | ||
24 | |||
25 | Ref: https://bugs.launchpad.net/ubuntu/+source/shadow/+bug/1729357 | ||
26 | Fixes: CVE-2018-7169 | ||
27 | |||
28 | Upstream-Status: Backport [https://github.com/shadow-maint/shadow/commit/fb28c99b8a66ff2605c5cb96abc0a4d975f92de0] | ||
29 | Reported-by: Craig Furman <craig.furman89@gmail.com> | ||
30 | Signed-off-by: Aleksa Sarai <asarai@suse.de> | ||
31 | Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.com> | ||
32 | --- | ||
33 | src/newgidmap.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++------ | ||
34 | 1 file changed, 80 insertions(+), 9 deletions(-) | ||
35 | |||
36 | diff --git a/src/newgidmap.c b/src/newgidmap.c | ||
37 | index b1e33513..59a2e75c 100644 | ||
38 | --- a/src/newgidmap.c | ||
39 | +++ b/src/newgidmap.c | ||
40 | @@ -46,32 +46,37 @@ | ||
41 | */ | ||
42 | const char *Prog; | ||
43 | |||
44 | -static bool verify_range(struct passwd *pw, struct map_range *range) | ||
45 | + | ||
46 | +static bool verify_range(struct passwd *pw, struct map_range *range, bool *allow_setgroups) | ||
47 | { | ||
48 | /* An empty range is invalid */ | ||
49 | if (range->count == 0) | ||
50 | return false; | ||
51 | |||
52 | - /* Test /etc/subgid */ | ||
53 | - if (have_sub_gids(pw->pw_name, range->lower, range->count)) | ||
54 | + /* Test /etc/subgid. If the mapping is valid then we allow setgroups. */ | ||
55 | + if (have_sub_gids(pw->pw_name, range->lower, range->count)) { | ||
56 | + *allow_setgroups = true; | ||
57 | return true; | ||
58 | + } | ||
59 | |||
60 | - /* Allow a process to map it's own gid */ | ||
61 | - if ((range->count == 1) && (pw->pw_gid == range->lower)) | ||
62 | + /* Allow a process to map its own gid. */ | ||
63 | + if ((range->count == 1) && (pw->pw_gid == range->lower)) { | ||
64 | + /* noop -- if setgroups is enabled already we won't disable it. */ | ||
65 | return true; | ||
66 | + } | ||
67 | |||
68 | return false; | ||
69 | } | ||
70 | |||
71 | static void verify_ranges(struct passwd *pw, int ranges, | ||
72 | - struct map_range *mappings) | ||
73 | + struct map_range *mappings, bool *allow_setgroups) | ||
74 | { | ||
75 | struct map_range *mapping; | ||
76 | int idx; | ||
77 | |||
78 | mapping = mappings; | ||
79 | for (idx = 0; idx < ranges; idx++, mapping++) { | ||
80 | - if (!verify_range(pw, mapping)) { | ||
81 | + if (!verify_range(pw, mapping, allow_setgroups)) { | ||
82 | fprintf(stderr, _( "%s: gid range [%lu-%lu) -> [%lu-%lu) not allowed\n"), | ||
83 | Prog, | ||
84 | mapping->upper, | ||
85 | @@ -89,6 +94,70 @@ static void usage(void) | ||
86 | exit(EXIT_FAILURE); | ||
87 | } | ||
88 | |||
89 | +void write_setgroups(int proc_dir_fd, bool allow_setgroups) | ||
90 | +{ | ||
91 | + int setgroups_fd; | ||
92 | + char *policy, policy_buffer[4096]; | ||
93 | + | ||
94 | + /* | ||
95 | + * Default is "deny", and any "allow" will out-rank a "deny". We don't | ||
96 | + * forcefully write an "allow" here because the process we are writing | ||
97 | + * mappings for may have already set themselves to "deny" (and "allow" | ||
98 | + * is the default anyway). So allow_setgroups == true is a noop. | ||
99 | + */ | ||
100 | + policy = "deny\n"; | ||
101 | + if (allow_setgroups) | ||
102 | + return; | ||
103 | + | ||
104 | + setgroups_fd = openat(proc_dir_fd, "setgroups", O_RDWR|O_CLOEXEC); | ||
105 | + if (setgroups_fd < 0) { | ||
106 | + /* | ||
107 | + * If it's an ENOENT then we are on too old a kernel for the setgroups | ||
108 | + * code to exist. Emit a warning and bail on this. | ||
109 | + */ | ||
110 | + if (ENOENT == errno) { | ||
111 | + fprintf(stderr, _("%s: kernel doesn't support setgroups restrictions\n"), Prog); | ||
112 | + goto out; | ||
113 | + } | ||
114 | + fprintf(stderr, _("%s: couldn't open process setgroups: %s\n"), | ||
115 | + Prog, | ||
116 | + strerror(errno)); | ||
117 | + exit(EXIT_FAILURE); | ||
118 | + } | ||
119 | + | ||
120 | + /* | ||
121 | + * Check whether the policy is already what we want. /proc/self/setgroups | ||
122 | + * is write-once, so attempting to write after it's already written to will | ||
123 | + * fail. | ||
124 | + */ | ||
125 | + if (read(setgroups_fd, policy_buffer, sizeof(policy_buffer)) < 0) { | ||
126 | + fprintf(stderr, _("%s: failed to read setgroups: %s\n"), | ||
127 | + Prog, | ||
128 | + strerror(errno)); | ||
129 | + exit(EXIT_FAILURE); | ||
130 | + } | ||
131 | + if (!strncmp(policy_buffer, policy, strlen(policy))) | ||
132 | + goto out; | ||
133 | + | ||
134 | + /* Write the policy. */ | ||
135 | + if (lseek(setgroups_fd, 0, SEEK_SET) < 0) { | ||
136 | + fprintf(stderr, _("%s: failed to seek setgroups: %s\n"), | ||
137 | + Prog, | ||
138 | + strerror(errno)); | ||
139 | + exit(EXIT_FAILURE); | ||
140 | + } | ||
141 | + if (dprintf(setgroups_fd, "%s", policy) < 0) { | ||
142 | + fprintf(stderr, _("%s: failed to setgroups %s policy: %s\n"), | ||
143 | + Prog, | ||
144 | + policy, | ||
145 | + strerror(errno)); | ||
146 | + exit(EXIT_FAILURE); | ||
147 | + } | ||
148 | + | ||
149 | +out: | ||
150 | + close(setgroups_fd); | ||
151 | +} | ||
152 | + | ||
153 | /* | ||
154 | * newgidmap - Set the gid_map for the specified process | ||
155 | */ | ||
156 | @@ -103,6 +172,7 @@ int main(int argc, char **argv) | ||
157 | struct stat st; | ||
158 | struct passwd *pw; | ||
159 | int written; | ||
160 | + bool allow_setgroups = false; | ||
161 | |||
162 | Prog = Basename (argv[0]); | ||
163 | |||
164 | @@ -145,7 +215,7 @@ int main(int argc, char **argv) | ||
165 | (unsigned long) getuid ())); | ||
166 | return EXIT_FAILURE; | ||
167 | } | ||
168 | - | ||
169 | + | ||
170 | /* Get the effective uid and effective gid of the target process */ | ||
171 | if (fstat(proc_dir_fd, &st) < 0) { | ||
172 | fprintf(stderr, _("%s: Could not stat directory for target %u\n"), | ||
173 | @@ -177,8 +247,9 @@ int main(int argc, char **argv) | ||
174 | if (!mappings) | ||
175 | usage(); | ||
176 | |||
177 | - verify_ranges(pw, ranges, mappings); | ||
178 | + verify_ranges(pw, ranges, mappings, &allow_setgroups); | ||
179 | |||
180 | + write_setgroups(proc_dir_fd, allow_setgroups); | ||
181 | write_mapping(proc_dir_fd, ranges, mappings, "gid_map"); | ||
182 | sub_gid_close(); | ||
183 | |||
184 | -- | ||
185 | 2.13.3 | ||
186 | |||