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-rw-r--r--debian/patches/user-group-modes.patch210
1 files changed, 210 insertions, 0 deletions
diff --git a/debian/patches/user-group-modes.patch b/debian/patches/user-group-modes.patch
new file mode 100644
index 000000000..8f5a8a383
--- /dev/null
+++ b/debian/patches/user-group-modes.patch
@@ -0,0 +1,210 @@
1From d08cd2b0cfbedf3ccd2ec3adaef850b8d9a87e85 Mon Sep 17 00:00:00 2001
2From: Colin Watson <cjwatson@debian.org>
3Date: Sun, 9 Feb 2014 16:09:58 +0000
4Subject: Allow harmless group-writability
5
6Allow secure files (~/.ssh/config, ~/.ssh/authorized_keys, etc.) to be
7group-writable, provided that the group in question contains only the file's
8owner. Rejected upstream for IMO incorrect reasons (e.g. a misunderstanding
9about the contents of gr->gr_mem). Given that per-user groups and umask 002
10are the default setup in Debian (for good reasons - this makes operating in
11setgid directories with other groups much easier), we need to permit this by
12default.
13
14Bug: https://bugzilla.mindrot.org/show_bug.cgi?id=1060
15Bug-Debian: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=314347
16Last-Update: 2019-10-09
17
18Patch-Name: user-group-modes.patch
19---
20 auth-rhosts.c | 6 ++----
21 auth.c | 3 +--
22 misc.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++-----
23 misc.h | 2 ++
24 readconf.c | 3 +--
25 ssh.1 | 2 ++
26 ssh_config.5 | 2 ++
27 7 files changed, 63 insertions(+), 13 deletions(-)
28
29diff --git a/auth-rhosts.c b/auth-rhosts.c
30index e81321b49..3bcc73766 100644
31--- a/auth-rhosts.c
32+++ b/auth-rhosts.c
33@@ -260,8 +260,7 @@ auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
34 return 0;
35 }
36 if (options.strict_modes &&
37- ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
38- (st.st_mode & 022) != 0)) {
39+ !secure_permissions(&st, pw->pw_uid)) {
40 logit("Rhosts authentication refused for %.100s: "
41 "bad ownership or modes for home directory.", pw->pw_name);
42 auth_debug_add("Rhosts authentication refused for %.100s: "
43@@ -287,8 +286,7 @@ auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
44 * allowing access to their account by anyone.
45 */
46 if (options.strict_modes &&
47- ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
48- (st.st_mode & 022) != 0)) {
49+ !secure_permissions(&st, pw->pw_uid)) {
50 logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
51 pw->pw_name, buf);
52 auth_debug_add("Bad file modes for %.200s", buf);
53diff --git a/auth.c b/auth.c
54index 3d31ec860..4152d9c44 100644
55--- a/auth.c
56+++ b/auth.c
57@@ -474,8 +474,7 @@ check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
58 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
59 if (options.strict_modes &&
60 (stat(user_hostfile, &st) == 0) &&
61- ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
62- (st.st_mode & 022) != 0)) {
63+ !secure_permissions(&st, pw->pw_uid)) {
64 logit("Authentication refused for %.100s: "
65 "bad owner or modes for %.200s",
66 pw->pw_name, user_hostfile);
67diff --git a/misc.c b/misc.c
68index 4623b5755..c75a795c2 100644
69--- a/misc.c
70+++ b/misc.c
71@@ -55,8 +55,9 @@
72 #include <netdb.h>
73 #ifdef HAVE_PATHS_H
74 # include <paths.h>
75-#include <pwd.h>
76 #endif
77+#include <pwd.h>
78+#include <grp.h>
79 #ifdef SSH_TUN_OPENBSD
80 #include <net/if.h>
81 #endif
82@@ -1271,6 +1272,55 @@ percent_dollar_expand(const char *string, ...)
83 return ret;
84 }
85
86+int
87+secure_permissions(struct stat *st, uid_t uid)
88+{
89+ if (!platform_sys_dir_uid(st->st_uid) && st->st_uid != uid)
90+ return 0;
91+ if ((st->st_mode & 002) != 0)
92+ return 0;
93+ if ((st->st_mode & 020) != 0) {
94+ /* If the file is group-writable, the group in question must
95+ * have exactly one member, namely the file's owner.
96+ * (Zero-member groups are typically used by setgid
97+ * binaries, and are unlikely to be suitable.)
98+ */
99+ struct passwd *pw;
100+ struct group *gr;
101+ int members = 0;
102+
103+ gr = getgrgid(st->st_gid);
104+ if (!gr)
105+ return 0;
106+
107+ /* Check primary group memberships. */
108+ while ((pw = getpwent()) != NULL) {
109+ if (pw->pw_gid == gr->gr_gid) {
110+ ++members;
111+ if (pw->pw_uid != uid)
112+ return 0;
113+ }
114+ }
115+ endpwent();
116+
117+ pw = getpwuid(st->st_uid);
118+ if (!pw)
119+ return 0;
120+
121+ /* Check supplementary group memberships. */
122+ if (gr->gr_mem[0]) {
123+ ++members;
124+ if (strcmp(pw->pw_name, gr->gr_mem[0]) ||
125+ gr->gr_mem[1])
126+ return 0;
127+ }
128+
129+ if (!members)
130+ return 0;
131+ }
132+ return 1;
133+}
134+
135 int
136 tun_open(int tun, int mode, char **ifname)
137 {
138@@ -2056,8 +2106,7 @@ safe_path(const char *name, struct stat *stp, const char *pw_dir,
139 snprintf(err, errlen, "%s is not a regular file", buf);
140 return -1;
141 }
142- if ((!platform_sys_dir_uid(stp->st_uid) && stp->st_uid != uid) ||
143- (stp->st_mode & 022) != 0) {
144+ if (!secure_permissions(stp, uid)) {
145 snprintf(err, errlen, "bad ownership or modes for file %s",
146 buf);
147 return -1;
148@@ -2072,8 +2121,7 @@ safe_path(const char *name, struct stat *stp, const char *pw_dir,
149 strlcpy(buf, cp, sizeof(buf));
150
151 if (stat(buf, &st) == -1 ||
152- (!platform_sys_dir_uid(st.st_uid) && st.st_uid != uid) ||
153- (st.st_mode & 022) != 0) {
154+ !secure_permissions(&st, uid)) {
155 snprintf(err, errlen,
156 "bad ownership or modes for directory %s", buf);
157 return -1;
158diff --git a/misc.h b/misc.h
159index ab94a79c0..b34c798e7 100644
160--- a/misc.h
161+++ b/misc.h
162@@ -192,6 +192,8 @@ struct notifier_ctx *notify_start(int, const char *, ...)
163 __attribute__((format(printf, 2, 3)));
164 void notify_complete(struct notifier_ctx *);
165
166+int secure_permissions(struct stat *st, uid_t uid);
167+
168 #define MINIMUM(a, b) (((a) < (b)) ? (a) : (b))
169 #define MAXIMUM(a, b) (((a) > (b)) ? (a) : (b))
170 #define ROUNDUP(x, y) ((((x)+((y)-1))/(y))*(y))
171diff --git a/readconf.c b/readconf.c
172index 3d0a812b3..f4f273c96 100644
173--- a/readconf.c
174+++ b/readconf.c
175@@ -1967,8 +1967,7 @@ read_config_file_depth(const char *filename, struct passwd *pw,
176
177 if (fstat(fileno(f), &sb) == -1)
178 fatal("fstat %s: %s", filename, strerror(errno));
179- if (((sb.st_uid != 0 && sb.st_uid != getuid()) ||
180- (sb.st_mode & 022) != 0))
181+ if (!secure_permissions(&sb, getuid()))
182 fatal("Bad owner or permissions on %s", filename);
183 }
184
185diff --git a/ssh.1 b/ssh.1
186index be8e964f0..5d613076c 100644
187--- a/ssh.1
188+++ b/ssh.1
189@@ -1528,6 +1528,8 @@ The file format and configuration options are described in
190 .Xr ssh_config 5 .
191 Because of the potential for abuse, this file must have strict permissions:
192 read/write for the user, and not writable by others.
193+It may be group-writable provided that the group in question contains only
194+the user.
195 .Pp
196 .It Pa ~/.ssh/environment
197 Contains additional definitions for environment variables; see
198diff --git a/ssh_config.5 b/ssh_config.5
199index 3ceb800ba..190e1d927 100644
200--- a/ssh_config.5
201+++ b/ssh_config.5
202@@ -2010,6 +2010,8 @@ The format of this file is described above.
203 This file is used by the SSH client.
204 Because of the potential for abuse, this file must have strict permissions:
205 read/write for the user, and not writable by others.
206+It may be group-writable provided that the group in question contains only
207+the user.
208 .It Pa /etc/ssh/ssh_config
209 Systemwide configuration file.
210 This file provides defaults for those
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-10 12:02:12 +0000