diff options
author | Colin Watson <cjwatson@debian.org> | 2014-02-09 16:09:58 +0000 |
---|---|---|
committer | Colin Watson <cjwatson@debian.org> | 2016-08-07 12:18:43 +0100 |
commit | 563974a78e937c4844e1198b5f6d79b8b2b5c600 (patch) | |
tree | ab2b821031f9b3d4dac7123b677dd6e8a93ac4d3 | |
parent | 173d65e72989cba82502604da3f1336766c0cf0f (diff) |
Allow harmless group-writability
Allow secure files (~/.ssh/config, ~/.ssh/authorized_keys, etc.) to be
group-writable, provided that the group in question contains only the file's
owner. Rejected upstream for IMO incorrect reasons (e.g. a misunderstanding
about the contents of gr->gr_mem). Given that per-user groups and umask 002
are the default setup in Debian (for good reasons - this makes operating in
setgid directories with other groups much easier), we need to permit this by
default.
Bug: https://bugzilla.mindrot.org/show_bug.cgi?id=1060
Bug-Debian: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=314347
Last-Update: 2013-09-14
Patch-Name: user-group-modes.patch
-rw-r--r-- | auth-rhosts.c | 6 | ||||
-rw-r--r-- | auth.c | 9 | ||||
-rw-r--r-- | misc.c | 69 | ||||
-rw-r--r-- | misc.h | 2 | ||||
-rw-r--r-- | platform.c | 16 | ||||
-rw-r--r-- | readconf.c | 3 | ||||
-rw-r--r-- | ssh.1 | 2 | ||||
-rw-r--r-- | ssh_config.5 | 2 |
8 files changed, 80 insertions, 29 deletions
diff --git a/auth-rhosts.c b/auth-rhosts.c index 0ef344712..c17c13cc1 100644 --- a/auth-rhosts.c +++ b/auth-rhosts.c | |||
@@ -273,8 +273,7 @@ auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostnam | |||
273 | return 0; | 273 | return 0; |
274 | } | 274 | } |
275 | if (options.strict_modes && | 275 | if (options.strict_modes && |
276 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | 276 | !secure_permissions(&st, pw->pw_uid)) { |
277 | (st.st_mode & 022) != 0)) { | ||
278 | logit("Rhosts authentication refused for %.100s: " | 277 | logit("Rhosts authentication refused for %.100s: " |
279 | "bad ownership or modes for home directory.", pw->pw_name); | 278 | "bad ownership or modes for home directory.", pw->pw_name); |
280 | auth_debug_add("Rhosts authentication refused for %.100s: " | 279 | auth_debug_add("Rhosts authentication refused for %.100s: " |
@@ -300,8 +299,7 @@ auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostnam | |||
300 | * allowing access to their account by anyone. | 299 | * allowing access to their account by anyone. |
301 | */ | 300 | */ |
302 | if (options.strict_modes && | 301 | if (options.strict_modes && |
303 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | 302 | !secure_permissions(&st, pw->pw_uid)) { |
304 | (st.st_mode & 022) != 0)) { | ||
305 | logit("Rhosts authentication refused for %.100s: bad modes for %.200s", | 303 | logit("Rhosts authentication refused for %.100s: bad modes for %.200s", |
306 | pw->pw_name, buf); | 304 | pw->pw_name, buf); |
307 | auth_debug_add("Bad file modes for %.200s", buf); | 305 | auth_debug_add("Bad file modes for %.200s", buf); |
@@ -435,8 +435,7 @@ check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, | |||
435 | user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); | 435 | user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); |
436 | if (options.strict_modes && | 436 | if (options.strict_modes && |
437 | (stat(user_hostfile, &st) == 0) && | 437 | (stat(user_hostfile, &st) == 0) && |
438 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | 438 | !secure_permissions(&st, pw->pw_uid)) { |
439 | (st.st_mode & 022) != 0)) { | ||
440 | logit("Authentication refused for %.100s: " | 439 | logit("Authentication refused for %.100s: " |
441 | "bad owner or modes for %.200s", | 440 | "bad owner or modes for %.200s", |
442 | pw->pw_name, user_hostfile); | 441 | pw->pw_name, user_hostfile); |
@@ -498,8 +497,7 @@ auth_secure_path(const char *name, struct stat *stp, const char *pw_dir, | |||
498 | snprintf(err, errlen, "%s is not a regular file", buf); | 497 | snprintf(err, errlen, "%s is not a regular file", buf); |
499 | return -1; | 498 | return -1; |
500 | } | 499 | } |
501 | if ((!platform_sys_dir_uid(stp->st_uid) && stp->st_uid != uid) || | 500 | if (!secure_permissions(stp, uid)) { |
502 | (stp->st_mode & 022) != 0) { | ||
503 | snprintf(err, errlen, "bad ownership or modes for file %s", | 501 | snprintf(err, errlen, "bad ownership or modes for file %s", |
504 | buf); | 502 | buf); |
505 | return -1; | 503 | return -1; |
@@ -514,8 +512,7 @@ auth_secure_path(const char *name, struct stat *stp, const char *pw_dir, | |||
514 | strlcpy(buf, cp, sizeof(buf)); | 512 | strlcpy(buf, cp, sizeof(buf)); |
515 | 513 | ||
516 | if (stat(buf, &st) < 0 || | 514 | if (stat(buf, &st) < 0 || |
517 | (!platform_sys_dir_uid(st.st_uid) && st.st_uid != uid) || | 515 | !secure_permissions(&st, uid)) { |
518 | (st.st_mode & 022) != 0) { | ||
519 | snprintf(err, errlen, | 516 | snprintf(err, errlen, |
520 | "bad ownership or modes for directory %s", buf); | 517 | "bad ownership or modes for directory %s", buf); |
521 | return -1; | 518 | return -1; |
@@ -51,8 +51,9 @@ | |||
51 | #include <netdb.h> | 51 | #include <netdb.h> |
52 | #ifdef HAVE_PATHS_H | 52 | #ifdef HAVE_PATHS_H |
53 | # include <paths.h> | 53 | # include <paths.h> |
54 | #include <pwd.h> | ||
55 | #endif | 54 | #endif |
55 | #include <pwd.h> | ||
56 | #include <grp.h> | ||
56 | #ifdef SSH_TUN_OPENBSD | 57 | #ifdef SSH_TUN_OPENBSD |
57 | #include <net/if.h> | 58 | #include <net/if.h> |
58 | #endif | 59 | #endif |
@@ -61,6 +62,7 @@ | |||
61 | #include "misc.h" | 62 | #include "misc.h" |
62 | #include "log.h" | 63 | #include "log.h" |
63 | #include "ssh.h" | 64 | #include "ssh.h" |
65 | #include "platform.h" | ||
64 | 66 | ||
65 | /* remove newline at end of string */ | 67 | /* remove newline at end of string */ |
66 | char * | 68 | char * |
@@ -708,6 +710,71 @@ read_keyfile_line(FILE *f, const char *filename, char *buf, size_t bufsz, | |||
708 | return -1; | 710 | return -1; |
709 | } | 711 | } |
710 | 712 | ||
713 | /* | ||
714 | * return 1 if the specified uid is a uid that may own a system directory | ||
715 | * otherwise 0. | ||
716 | */ | ||
717 | int | ||
718 | platform_sys_dir_uid(uid_t uid) | ||
719 | { | ||
720 | if (uid == 0) | ||
721 | return 1; | ||
722 | #ifdef PLATFORM_SYS_DIR_UID | ||
723 | if (uid == PLATFORM_SYS_DIR_UID) | ||
724 | return 1; | ||
725 | #endif | ||
726 | return 0; | ||
727 | } | ||
728 | |||
729 | int | ||
730 | secure_permissions(struct stat *st, uid_t uid) | ||
731 | { | ||
732 | if (!platform_sys_dir_uid(st->st_uid) && st->st_uid != uid) | ||
733 | return 0; | ||
734 | if ((st->st_mode & 002) != 0) | ||
735 | return 0; | ||
736 | if ((st->st_mode & 020) != 0) { | ||
737 | /* If the file is group-writable, the group in question must | ||
738 | * have exactly one member, namely the file's owner. | ||
739 | * (Zero-member groups are typically used by setgid | ||
740 | * binaries, and are unlikely to be suitable.) | ||
741 | */ | ||
742 | struct passwd *pw; | ||
743 | struct group *gr; | ||
744 | int members = 0; | ||
745 | |||
746 | gr = getgrgid(st->st_gid); | ||
747 | if (!gr) | ||
748 | return 0; | ||
749 | |||
750 | /* Check primary group memberships. */ | ||
751 | while ((pw = getpwent()) != NULL) { | ||
752 | if (pw->pw_gid == gr->gr_gid) { | ||
753 | ++members; | ||
754 | if (pw->pw_uid != uid) | ||
755 | return 0; | ||
756 | } | ||
757 | } | ||
758 | endpwent(); | ||
759 | |||
760 | pw = getpwuid(st->st_uid); | ||
761 | if (!pw) | ||
762 | return 0; | ||
763 | |||
764 | /* Check supplementary group memberships. */ | ||
765 | if (gr->gr_mem[0]) { | ||
766 | ++members; | ||
767 | if (strcmp(pw->pw_name, gr->gr_mem[0]) || | ||
768 | gr->gr_mem[1]) | ||
769 | return 0; | ||
770 | } | ||
771 | |||
772 | if (!members) | ||
773 | return 0; | ||
774 | } | ||
775 | return 1; | ||
776 | } | ||
777 | |||
711 | int | 778 | int |
712 | tun_open(int tun, int mode) | 779 | tun_open(int tun, int mode) |
713 | { | 780 | { |
@@ -139,4 +139,6 @@ char *read_passphrase(const char *, int); | |||
139 | int ask_permission(const char *, ...) __attribute__((format(printf, 1, 2))); | 139 | int ask_permission(const char *, ...) __attribute__((format(printf, 1, 2))); |
140 | int read_keyfile_line(FILE *, const char *, char *, size_t, u_long *); | 140 | int read_keyfile_line(FILE *, const char *, char *, size_t, u_long *); |
141 | 141 | ||
142 | int secure_permissions(struct stat *st, uid_t uid); | ||
143 | |||
142 | #endif /* _MISC_H */ | 144 | #endif /* _MISC_H */ |
diff --git a/platform.c b/platform.c index 483170680..2ce4dbf81 100644 --- a/platform.c +++ b/platform.c | |||
@@ -199,19 +199,3 @@ platform_krb5_get_principal_name(const char *pw_name) | |||
199 | return NULL; | 199 | return NULL; |
200 | #endif | 200 | #endif |
201 | } | 201 | } |
202 | |||
203 | /* | ||
204 | * return 1 if the specified uid is a uid that may own a system directory | ||
205 | * otherwise 0. | ||
206 | */ | ||
207 | int | ||
208 | platform_sys_dir_uid(uid_t uid) | ||
209 | { | ||
210 | if (uid == 0) | ||
211 | return 1; | ||
212 | #ifdef PLATFORM_SYS_DIR_UID | ||
213 | if (uid == PLATFORM_SYS_DIR_UID) | ||
214 | return 1; | ||
215 | #endif | ||
216 | return 0; | ||
217 | } | ||
diff --git a/readconf.c b/readconf.c index 3a6c67ba5..f6b4c8f1e 100644 --- a/readconf.c +++ b/readconf.c | |||
@@ -1753,8 +1753,7 @@ read_config_file_depth(const char *filename, struct passwd *pw, | |||
1753 | 1753 | ||
1754 | if (fstat(fileno(f), &sb) == -1) | 1754 | if (fstat(fileno(f), &sb) == -1) |
1755 | fatal("fstat %s: %s", filename, strerror(errno)); | 1755 | fatal("fstat %s: %s", filename, strerror(errno)); |
1756 | if (((sb.st_uid != 0 && sb.st_uid != getuid()) || | 1756 | if (!secure_permissions(&sb, getuid())) |
1757 | (sb.st_mode & 022) != 0)) | ||
1758 | fatal("Bad owner or permissions on %s", filename); | 1757 | fatal("Bad owner or permissions on %s", filename); |
1759 | } | 1758 | } |
1760 | 1759 | ||
@@ -1484,6 +1484,8 @@ The file format and configuration options are described in | |||
1484 | .Xr ssh_config 5 . | 1484 | .Xr ssh_config 5 . |
1485 | Because of the potential for abuse, this file must have strict permissions: | 1485 | Because of the potential for abuse, this file must have strict permissions: |
1486 | read/write for the user, and not writable by others. | 1486 | read/write for the user, and not writable by others. |
1487 | It may be group-writable provided that the group in question contains only | ||
1488 | the user. | ||
1487 | .Pp | 1489 | .Pp |
1488 | .It Pa ~/.ssh/environment | 1490 | .It Pa ~/.ssh/environment |
1489 | Contains additional definitions for environment variables; see | 1491 | Contains additional definitions for environment variables; see |
diff --git a/ssh_config.5 b/ssh_config.5 index efc265ab7..5dd26bcaa 100644 --- a/ssh_config.5 +++ b/ssh_config.5 | |||
@@ -1903,6 +1903,8 @@ The format of this file is described above. | |||
1903 | This file is used by the SSH client. | 1903 | This file is used by the SSH client. |
1904 | Because of the potential for abuse, this file must have strict permissions: | 1904 | Because of the potential for abuse, this file must have strict permissions: |
1905 | read/write for the user, and not accessible by others. | 1905 | read/write for the user, and not accessible by others. |
1906 | It may be group-writable provided that the group in question contains only | ||
1907 | the user. | ||
1906 | .It Pa /etc/ssh/ssh_config | 1908 | .It Pa /etc/ssh/ssh_config |
1907 | Systemwide configuration file. | 1909 | Systemwide configuration file. |
1908 | This file provides defaults for those | 1910 | This file provides defaults for those |