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Fix corruption when searching for CRLs in hashed directories 

The by_dir certificate/CRL lookup code uses an OPENSSL_STACK to track
how many sequentially numbered CRL files have been loaded for a given
X509_NAME hash which is being requested. This avoids loading already
loaded CRL files and repeated stat() calls.

This OPENSSL_STACK is searched using sk_find, however this mutates
the OPENSSL_STACK unless it is known to be sorted. This operation
therefore requires a write lock, which was not taken.

Fix this issue by sorting the OPENSSL_STACK whenever it is mutated. This
guarantees no mutation will occur during sk_find. This is chosen over
taking a write lock during sk_find as retrieving a CRL by X509_NAME is
assumed to be a hotter path than the case where a new CRL is installed.

Also optimise the code by avoiding creating the structure to track the
last CRL file sequence number in the circumstance where it would match
the initial value, namely where no CRL with the given hash is installed.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20076)
This commit is contained in:
Hugo Landau 2023-01-18 15:43:56 +00:00 committed by Pauli
parent 2fda45d5eb
commit 3147785eb2
1 changed files with 13 additions and 3 deletions
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16
crypto/x509/by_dir.c
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@ -354,9 +354,13 @@ static int get_cert_by_subject_ex(X509_LOOKUP *xl, X509_LOOKUP_TYPE type,
tmp = sk_X509_OBJECT_value(xl->store_ctx->objs, j);
X509_STORE_unlock(xl->store_ctx);
/* If a CRL, update the last file suffix added for this */
if (type == X509_LU_CRL) {
/*
* If a CRL, update the last file suffix added for this.
* We don't need to add an entry if k is 0 as this is the initial value.
* This avoids the need for a write lock and sort operation in the
* simple case where no CRL is present for a hash.
*/
if (type == X509_LU_CRL && k > 0) {
if (!CRYPTO_THREAD_write_lock(ctx->lock))
goto finish;
/*
@ -384,6 +388,12 @@ static int get_cert_by_subject_ex(X509_LOOKUP *xl, X509_LOOKUP_TYPE type,
ok = 0;
goto finish;
}
/*
* Ensure stack is sorted so that subsequent sk_BY_DIR_HASH_find
* will not mutate the stack and therefore require a write lock.
*/
sk_BY_DIR_HASH_sort(ent->hashes);
} else if (hent->suffix < k) {
hent->suffix = k;
}