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author | Karolin Seeger <kseeger@samba.org> | 2021-04-29 11:12:26 +0200 |
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committer | Karolin Seeger <kseeger@samba.org> | 2021-04-29 11:12:26 +0200 |
commit | 5ab7bbd30bd8cdd4510c07b37577f6c4d78ee187 (patch) | |
tree | c7fe64e93264066f63f34321d4076ae169ef36d9 | |
parent | deb7b32b4372625211a4d6ba26e3d00223e903ca (diff) | |
parent | 703c6301013f78e80882abfe8375d6a45a176b7f (diff) | |
download | samba-5ab7bbd30bd8cdd4510c07b37577f6c4d78ee187.tar.gz |
Merge tag 'samba-4.12.15' into v4-12-test
samba: tag release samba-4.12.15
-rw-r--r-- | WHATSNEW.txt | 68 | ||||
-rw-r--r-- | source3/passdb/lookup_sid.c | 140 |
2 files changed, 184 insertions, 24 deletions
diff --git a/WHATSNEW.txt b/WHATSNEW.txt index f3c64a7050c..d77b074f2a7 100644 --- a/WHATSNEW.txt +++ b/WHATSNEW.txt @@ -1,4 +1,69 @@ =============================== + Release Notes for Samba 4.12.15 + April 29, 2021 + =============================== + + +This is a security release in order to address the following defect: + +o CVE-2021-20254: Negative idmap cache entries can cause incorrect group entries + in the Samba file server process token. + + +======= +Details +======= + +o CVE-2021-20254: + The Samba smbd file server must map Windows group identities (SIDs) into unix + group ids (gids). The code that performs this had a flaw that could allow it + to read data beyond the end of the array in the case where a negative cache + entry had been added to the mapping cache. This could cause the calling code + to return those values into the process token that stores the group + membership for a user. + + Most commonly this flaw caused the calling code to crash, but an alert user + (Peter Eriksson, IT Department, Linköping University) found this flaw by + noticing an unprivileged user was able to delete a file within a network + share that they should have been disallowed access to. + + Analysis of the code paths has not allowed us to discover a way for a + remote user to be able to trigger this flaw reproducibly or on demand, + but this CVE has been issued out of an abundance of caution. + + +Changes since 4.12.14 +--------------------- + +o Volker Lendecke <vl@samba.org> + * BUG 14571: CVE-2021-20254: Fix buffer overrun in sids_to_unixids(). + + +####################################### +Reporting bugs & Development Discussion +####################################### + +Please discuss this release on the samba-technical mailing list or by +joining the #samba-technical IRC channel on irc.freenode.net. + +If you do report problems then please try to send high quality +feedback. If you don't provide vital information to help us track down +the problem then you will probably be ignored. All bug reports should +be filed under the Samba 4.1 and newer product in the project's Bugzilla +database (https://bugzilla.samba.org/). + + +====================================================================== +== Our Code, Our Bugs, Our Responsibility. +== The Samba Team +====================================================================== + + +Release notes for older releases follow: +---------------------------------------- + + + =============================== Release Notes for Samba 4.12.14 March 24, 2021 =============================== @@ -55,8 +120,7 @@ database (https://bugzilla.samba.org/). ====================================================================== -Release notes for older releases follow: ----------------------------------------- +---------------------------------------------------------------------- =============================== diff --git a/source3/passdb/lookup_sid.c b/source3/passdb/lookup_sid.c index 82c47b3145b..6887b6ebb62 100644 --- a/source3/passdb/lookup_sid.c +++ b/source3/passdb/lookup_sid.c @@ -29,6 +29,7 @@ #include "../libcli/security/security.h" #include "lib/winbind_util.h" #include "../librpc/gen_ndr/idmap.h" +#include "lib/util/bitmap.h" static bool lookup_unix_user_name(const char *name, struct dom_sid *sid) { @@ -1247,7 +1248,9 @@ bool sids_to_unixids(const struct dom_sid *sids, uint32_t num_sids, { struct wbcDomainSid *wbc_sids = NULL; struct wbcUnixId *wbc_ids = NULL; + struct bitmap *found = NULL; uint32_t i, num_not_cached; + uint32_t wbc_ids_size = 0; wbcErr err; bool ret = false; @@ -1255,6 +1258,20 @@ bool sids_to_unixids(const struct dom_sid *sids, uint32_t num_sids, if (wbc_sids == NULL) { return false; } + found = bitmap_talloc(wbc_sids, num_sids); + if (found == NULL) { + goto fail; + } + + /* + * We go through the requested SID array three times. + * First time to look for global_sid_Unix_Users + * and global_sid_Unix_Groups SIDS, and to look + * for mappings cached in the idmap_cache. + * + * Use bitmap_set() to mark an ids[] array entry as + * being mapped. + */ num_not_cached = 0; @@ -1266,17 +1283,20 @@ bool sids_to_unixids(const struct dom_sid *sids, uint32_t num_sids, &sids[i], &rid)) { ids[i].type = ID_TYPE_UID; ids[i].id = rid; + bitmap_set(found, i); continue; } if (sid_peek_check_rid(&global_sid_Unix_Groups, &sids[i], &rid)) { ids[i].type = ID_TYPE_GID; ids[i].id = rid; + bitmap_set(found, i); continue; } if (idmap_cache_find_sid2unixid(&sids[i], &ids[i], &expired) && !expired) { + bitmap_set(found, i); continue; } ids[i].type = ID_TYPE_NOT_SPECIFIED; @@ -1287,62 +1307,138 @@ bool sids_to_unixids(const struct dom_sid *sids, uint32_t num_sids, if (num_not_cached == 0) { goto done; } - wbc_ids = talloc_array(talloc_tos(), struct wbcUnixId, num_not_cached); + + /* + * For the ones that we couldn't map in the loop above, query winbindd + * via wbcSidsToUnixIds(). + */ + + wbc_ids_size = num_not_cached; + wbc_ids = talloc_array(talloc_tos(), struct wbcUnixId, wbc_ids_size); if (wbc_ids == NULL) { goto fail; } - for (i=0; i<num_not_cached; i++) { + for (i=0; i<wbc_ids_size; i++) { wbc_ids[i].type = WBC_ID_TYPE_NOT_SPECIFIED; } - err = wbcSidsToUnixIds(wbc_sids, num_not_cached, wbc_ids); + /* + * gcc versions at least 5.x -> 6.x have a bug + * with initializing the wbc_ids[i].type and + * wbc_ids[i].id.gid to (uint32_t)-1 in the + * same loop when using [-Werror=strict-overflow]. + * The error is: + * + * ../../source3/passdb/lookup_sid.c:1246:6: error: assuming + * pointer wraparound does not occur when comparing P +- C1 + * with P +- C2 [-Werror=strict-overflow] + * + * Doing this loop twice fixes the compiler error. + * As wbc_ids_size isn't large this isn't too much + * of a performance burden. + */ + for (i=0; i<wbc_ids_size; i++) { + wbc_ids[i].id.gid = (uint32_t)-1; + } + err = wbcSidsToUnixIds(wbc_sids, wbc_ids_size, wbc_ids); if (!WBC_ERROR_IS_OK(err)) { DEBUG(10, ("wbcSidsToUnixIds returned %s\n", wbcErrorString(err))); } + /* + * Second time through the SID array, replace + * the ids[] entries that wbcSidsToUnixIds() was able to + * map. + * + * Use bitmap_set() to mark an ids[] array entry as + * being mapped. + */ + num_not_cached = 0; for (i=0; i<num_sids; i++) { - if (ids[i].type == ID_TYPE_NOT_SPECIFIED) { - switch (wbc_ids[num_not_cached].type) { - case WBC_ID_TYPE_UID: - ids[i].type = ID_TYPE_UID; - ids[i].id = wbc_ids[num_not_cached].id.uid; - break; - case WBC_ID_TYPE_GID: - ids[i].type = ID_TYPE_GID; - ids[i].id = wbc_ids[num_not_cached].id.gid; - break; - default: - /* The types match, and wbcUnixId -> id is a union anyway */ - ids[i].type = (enum id_type)wbc_ids[num_not_cached].type; - ids[i].id = wbc_ids[num_not_cached].id.gid; - break; - } - num_not_cached += 1; + if (bitmap_query(found, i)) { + continue; } + + SMB_ASSERT(num_not_cached < wbc_ids_size); + + switch (wbc_ids[num_not_cached].type) { + case WBC_ID_TYPE_UID: + ids[i].type = ID_TYPE_UID; + ids[i].id = wbc_ids[num_not_cached].id.uid; + bitmap_set(found, i); + break; + case WBC_ID_TYPE_GID: + ids[i].type = ID_TYPE_GID; + ids[i].id = wbc_ids[num_not_cached].id.gid; + bitmap_set(found, i); + break; + case WBC_ID_TYPE_BOTH: + ids[i].type = ID_TYPE_BOTH; + ids[i].id = wbc_ids[num_not_cached].id.uid; + bitmap_set(found, i); + break; + case WBC_ID_TYPE_NOT_SPECIFIED: + /* + * wbcSidsToUnixIds() wasn't able to map this + * so we still need to check legacy_sid_to_XXX() + * below. Don't mark the bitmap entry + * as being found so the final loop knows + * to try and map this entry. + */ + ids[i].type = ID_TYPE_NOT_SPECIFIED; + ids[i].id = (uint32_t)-1; + break; + default: + /* + * A successful return from wbcSidsToUnixIds() + * cannot return anything other than the values + * checked for above. Ensure this is so. + */ + smb_panic(__location__); + break; + } + num_not_cached += 1; } + /* + * Third and final time through the SID array, + * try legacy_sid_to_gid()/legacy_sid_to_uid() + * for entries we haven't already been able to + * map. + * + * Use bitmap_set() to mark an ids[] array entry as + * being mapped. + */ + for (i=0; i<num_sids; i++) { - if (ids[i].type != ID_TYPE_NOT_SPECIFIED) { + if (bitmap_query(found, i)) { continue; } if (legacy_sid_to_gid(&sids[i], &ids[i].id)) { ids[i].type = ID_TYPE_GID; + bitmap_set(found, i); continue; } if (legacy_sid_to_uid(&sids[i], &ids[i].id)) { ids[i].type = ID_TYPE_UID; + bitmap_set(found, i); continue; } } done: + /* + * Pass through the return array for consistency. + * Any ids[].id mapped to (uint32_t)-1 must be returned + * as ID_TYPE_NOT_SPECIFIED. + */ for (i=0; i<num_sids; i++) { switch(ids[i].type) { case WBC_ID_TYPE_GID: case WBC_ID_TYPE_UID: case WBC_ID_TYPE_BOTH: - if (ids[i].id == -1) { + if (ids[i].id == (uint32_t)-1) { ids[i].type = ID_TYPE_NOT_SPECIFIED; } break; |