2 files changed, 19 insertions, 13 deletions

diff --git a/src/lib/libcrypto/lhash/lhash.c b/src/lib/libcrypto/lhash/lhash.c
index 3adec71ed6..81660419c7 100644
--- a/src/lib/libcrypto/lhash/lhash.c
+++ b/src/lib/libcrypto/lhash/lhash.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: lhash.c,v 1.20 2023/07/07 13:40:44 beck Exp $ */
+/* $OpenBSD: lhash.c,v 1.21 2024/01/24 14:02:52 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -250,12 +250,21 @@ static void
 doall_util_fn(_LHASH *lh, int use_arg, LHASH_DOALL_FN_TYPE func,
     LHASH_DOALL_ARG_FN_TYPE func_arg, void *arg)
 {
-        int i;
         LHASH_NODE *a, *n;
+        int down_load;
+        int i;
 
         if (lh == NULL)
                 return;
 
+        /*
+         * Disable contraction of the hash while walking, as some consumers use
+         * it to delete hash entries. A better option would be to snapshot the
+         * hash, making it insert safe as well.
+         */
+        down_load = lh->down_load;
+        lh->down_load = 0;
+
         /* reverse the order so we search from 'top to bottom'
          * We were having memory leaks otherwise */
         for (i = lh->num_nodes - 1; i >= 0; i--) {
@@ -273,6 +282,10 @@ doall_util_fn(_LHASH *lh, int use_arg, LHASH_DOALL_FN_TYPE func,
                         a = n;
                 }
         }
+
+        /* Restore down load factor and trigger contraction. */
+        lh->down_load = down_load;
+        contract(lh);
 }
 
 void
diff --git a/src/lib/libcrypto/man/lh_new.3 b/src/lib/libcrypto/man/lh_new.3
index c848eed825..d672b4d2d8 100644
--- a/src/lib/libcrypto/man/lh_new.3
+++ b/src/lib/libcrypto/man/lh_new.3
@@ -1,4 +1,4 @@
-.\" $OpenBSD: lh_new.3,v 1.9 2022/03/31 17:27:17 naddy Exp $
+.\" $OpenBSD: lh_new.3,v 1.10 2024/01/24 14:02:52 jsing Exp $
 .\" full merge up to:
 .\" OpenSSL doc/crypto/lhash.pod 1bc74519 May 20 08:11:46 2016 -0400
 .\" selective merge up to:
@@ -118,7 +118,7 @@
 .\" copied and put under another distribution licence
 .\" [including the GNU Public Licence.]
 .\"
-.Dd $Mdocdate: March 31 2022 $
+.Dd $Mdocdate: January 24 2024 $
 .Dt LH_NEW 3
 .Os
 .Sh NAME
@@ -342,15 +342,8 @@ lh_STUFF_doall(hashtable, LHASH_DOALL_FN(STUFF_cleanup));
 lh_STUFF_free(hashtable);
 .Ed
 .Pp
-When doing this, be careful if you delete entries from the hash table in
-your callbacks: the table may decrease in size, moving the item that you
-are currently on down lower in the hash table \(em this could cause some
-entries to be skipped during the iteration.
-The second best solution to this problem is to set hash->down_load=0
-before you start (which will stop the hash table ever decreasing in
-size).
-The best solution is probably to avoid deleting items from the hash
-table inside a doall callback!
+A callback may delete entries from the hash table, however, it is
+not safe to insert new entries.
 .Pp
 .Fn lh_<type>_doall_arg
 is the same as