From adb00543413e43c4c38631a5c888fb23ce091476 Mon Sep 17 00:00:00 2001 From: Andrew Lukoshko Date: Mon, 17 Jul 2023 21:27:38 +0000 Subject: [PATCH] Improve RBT overmem cache cleaning (CVE-2023-2828) --- SOURCES/bind-9.16-CVE-2023-2828.patch | 190 ++++++++++++++++++++++++++ SPECS/bind9.16.spec | 9 +- 2 files changed, 198 insertions(+), 1 deletion(-) create mode 100644 SOURCES/bind-9.16-CVE-2023-2828.patch diff --git a/SOURCES/bind-9.16-CVE-2023-2828.patch b/SOURCES/bind-9.16-CVE-2023-2828.patch new file mode 100644 index 0000000..3cda088 --- /dev/null +++ b/SOURCES/bind-9.16-CVE-2023-2828.patch @@ -0,0 +1,190 @@ +From f1d9e9ee3859976f403914d20ad2a10855343702 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= +Date: Tue, 30 May 2023 08:46:17 +0200 +Subject: [PATCH] Improve RBT overmem cache cleaning + +When cache memory usage is over the configured cache size (overmem) and +we are cleaning unused entries, it might not be enough to clean just two +entries if the entries to be expired are smaller than the newly added +rdata. This could be abused by an attacker to cause a remote Denial of +Service by possibly running out of the operating system memory. + +Currently, the addrdataset() tries to do a single TTL-based cleaning +considering the serve-stale TTL and then optionally moves to overmem +cleaning if we are in that condition. Then the overmem_purge() tries to +do another single TTL based cleaning from the TTL heap and then continue +with LRU-based cleaning up to 2 entries cleaned. + +Squash the TTL-cleaning mechanism into single call from addrdataset(), +but ignore the serve-stale TTL if we are currently overmem. + +Then instead of having a fixed number of entries to clean, pass the size +of newly added rdatasetheader to the overmem_purge() function and +cleanup at least the size of the newly added data. This prevents the +cache going over the configured memory limit (`max-cache-size`). + +Additionally, refactor the overmem_purge() function to reduce for-loop +nesting for readability. +--- + lib/dns/rbtdb.c | 105 ++++++++++++++++++++++++++++++------------------ + 1 file changed, 65 insertions(+), 40 deletions(-) + +diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c +index c32db44cad7..ee06c51e925 100644 +--- a/lib/dns/rbtdb.c ++++ b/lib/dns/rbtdb.c +@@ -605,7 +605,7 @@ static void + expire_header(dns_rbtdb_t *rbtdb, rdatasetheader_t *header, bool tree_locked, + expire_t reason); + static void +-overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, isc_stdtime_t now, ++overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, size_t purgesize, + bool tree_locked); + static isc_result_t + resign_insert(dns_rbtdb_t *rbtdb, int idx, rdatasetheader_t *newheader); +@@ -6823,6 +6823,16 @@ cleanup: + + static dns_dbmethods_t zone_methods; + ++static size_t ++rdataset_size(rdatasetheader_t *header) { ++ if (!NONEXISTENT(header)) { ++ return (dns_rdataslab_size((unsigned char *)header, ++ sizeof(*header))); ++ } ++ ++ return (sizeof(*header)); ++} ++ + static isc_result_t + addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version, + isc_stdtime_t now, dns_rdataset_t *rdataset, unsigned int options, +@@ -6987,7 +6997,8 @@ addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version, + } + + if (cache_is_overmem) { +- overmem_purge(rbtdb, rbtnode->locknum, now, tree_locked); ++ overmem_purge(rbtdb, rbtnode->locknum, rdataset_size(newheader), ++ tree_locked); + } + + NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock, +@@ -7006,10 +7017,18 @@ addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version, + } + + header = isc_heap_element(rbtdb->heaps[rbtnode->locknum], 1); +- if (header != NULL && header->rdh_ttl + rbtdb->serve_stale_ttl < +- now - RBTDB_VIRTUAL) +- { +- expire_header(rbtdb, header, tree_locked, expire_ttl); ++ if (header != NULL) { ++ dns_ttl_t rdh_ttl = header->rdh_ttl; ++ ++ /* Only account for stale TTL if cache is not overmem */ ++ if (!cache_is_overmem) { ++ rdh_ttl += rbtdb->serve_stale_ttl; ++ } ++ ++ if (rdh_ttl < now - RBTDB_VIRTUAL) { ++ expire_header(rbtdb, header, tree_locked, ++ expire_ttl); ++ } + } + + /* +@@ -10547,52 +10566,58 @@ update_header(dns_rbtdb_t *rbtdb, rdatasetheader_t *header, isc_stdtime_t now) { + ISC_LIST_PREPEND(rbtdb->rdatasets[header->node->locknum], header, link); + } + ++static size_t ++expire_lru_headers(dns_rbtdb_t *rbtdb, unsigned int locknum, size_t purgesize, ++ bool tree_locked) { ++ rdatasetheader_t *header, *header_prev; ++ size_t purged = 0; ++ ++ for (header = ISC_LIST_TAIL(rbtdb->rdatasets[locknum]); ++ header != NULL && purged <= purgesize; header = header_prev) ++ { ++ header_prev = ISC_LIST_PREV(header, link); ++ /* ++ * Unlink the entry at this point to avoid checking it ++ * again even if it's currently used someone else and ++ * cannot be purged at this moment. This entry won't be ++ * referenced any more (so unlinking is safe) since the ++ * TTL was reset to 0. ++ */ ++ ISC_LIST_UNLINK(rbtdb->rdatasets[locknum], header, link); ++ size_t header_size = rdataset_size(header); ++ expire_header(rbtdb, header, tree_locked, expire_lru); ++ purged += header_size; ++ } ++ ++ return (purged); ++} ++ + /*% +- * Purge some expired and/or stale (i.e. unused for some period) cache entries +- * under an overmem condition. To recover from this condition quickly, up to +- * 2 entries will be purged. This process is triggered while adding a new +- * entry, and we specifically avoid purging entries in the same LRU bucket as +- * the one to which the new entry will belong. Otherwise, we might purge +- * entries of the same name of different RR types while adding RRsets from a +- * single response (consider the case where we're adding A and AAAA glue records +- * of the same NS name). ++ * Purge some stale (i.e. unused for some period - LRU based cleaning) cache ++ * entries under the overmem condition. To recover from this condition quickly, ++ * we cleanup entries up to the size of newly added rdata (passed as purgesize). ++ * ++ * This process is triggered while adding a new entry, and we specifically avoid ++ * purging entries in the same LRU bucket as the one to which the new entry will ++ * belong. Otherwise, we might purge entries of the same name of different RR ++ * types while adding RRsets from a single response (consider the case where ++ * we're adding A and AAAA glue records of the same NS name). + */ + static void +-overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, isc_stdtime_t now, ++overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, size_t purgesize, + bool tree_locked) { +- rdatasetheader_t *header, *header_prev; + unsigned int locknum; +- int purgecount = 2; ++ size_t purged = 0; + + for (locknum = (locknum_start + 1) % rbtdb->node_lock_count; +- locknum != locknum_start && purgecount > 0; ++ locknum != locknum_start && purged <= purgesize; + locknum = (locknum + 1) % rbtdb->node_lock_count) + { + NODE_LOCK(&rbtdb->node_locks[locknum].lock, + isc_rwlocktype_write); + +- header = isc_heap_element(rbtdb->heaps[locknum], 1); +- if (header && header->rdh_ttl < now - RBTDB_VIRTUAL) { +- expire_header(rbtdb, header, tree_locked, expire_ttl); +- purgecount--; +- } +- +- for (header = ISC_LIST_TAIL(rbtdb->rdatasets[locknum]); +- header != NULL && purgecount > 0; header = header_prev) +- { +- header_prev = ISC_LIST_PREV(header, link); +- /* +- * Unlink the entry at this point to avoid checking it +- * again even if it's currently used someone else and +- * cannot be purged at this moment. This entry won't be +- * referenced any more (so unlinking is safe) since the +- * TTL was reset to 0. +- */ +- ISC_LIST_UNLINK(rbtdb->rdatasets[locknum], header, +- link); +- expire_header(rbtdb, header, tree_locked, expire_lru); +- purgecount--; +- } ++ purged += expire_lru_headers(rbtdb, locknum, purgesize - purged, ++ tree_locked); + + NODE_UNLOCK(&rbtdb->node_locks[locknum].lock, + isc_rwlocktype_write); +-- +GitLab + diff --git a/SPECS/bind9.16.spec b/SPECS/bind9.16.spec index 203e39b..aa58068 100644 --- a/SPECS/bind9.16.spec +++ b/SPECS/bind9.16.spec @@ -57,7 +57,7 @@ Summary: The Berkeley Internet Name Domain (BIND) DNS (Domain Name System) serv Name: bind9.16 License: MPLv2.0 Version: 9.16.23 -Release: 0.14%{?dist} +Release: 0.14%{?dist}.1.alma Epoch: 32 Url: https://www.isc.org/downloads/bind/ # @@ -126,6 +126,9 @@ Patch185: bind-9.16-CVE-2022-3094-test.patch Patch186: bind-9.16-CVE-2022-3736.patch # https://gitlab.isc.org/isc-projects/bind9/commit/b4a65aaea19762a3712932aa2270e8a833fbde22 Patch187: bind-9.16-CVE-2022-3924.patch +# Patch is taken from bind upstream gitlab and updated to apply correctly: +# https://gitlab.isc.org/isc-projects/bind9/commit/f1d9e9ee3859976f403914d20ad2a10855343702 +Patch188: bind-9.16-CVE-2023-2828.patch %{?systemd_ordering} Requires: coreutils @@ -437,6 +440,7 @@ in HTML and PDF format. %patch185 -p1 -b .CVE-2022-3094-test %patch186 -p1 -b .CVE-2022-3736 %patch187 -p1 -b .CVE-2022-3924 +%patch188 -p1 -b .CVE-2023-2828 %if %{with PKCS11} %patch135 -p1 -b .config-pkcs11 @@ -1156,6 +1160,9 @@ fi; %endif %changelog +* Mon Jul 17 2023 Andrew Lukoshko - 32:9.16.23-0.14.1.alma +- Improve RBT overmem cache cleaning (CVE-2023-2828) + * Sat Feb 25 2023 Petr Menšík - 32:9.16.23-0.14 - Handle subtle difference between upstream and rhel (CVE-2022-3094)