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nhormanjogme
nhorman
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Fix unbounded cert cache growth in cmp
If a remote user sends cmp messages to a server with a list of extraCerts and the message is rejected, the extraCerts from the message remain in the server contexts untrusted certificate stack. This exposes servers with long lived ctx objects to denial of service attacks in which an attacker sends messages intending to be rejected with a large list of additional cerificated repeatedly, forcing the server to store them indefinately. Fix it by rolling back the added extra certs if the message is rejected, using the same method we do when the context is configured to not do caching at all. Fixes openssl/srt#224 Fixes CVE-2026-63074 Reviewed-by: Milan Broz <mbroz@openssl.org> Reviewed-by: Tomas Mraz <tomas@openssl.foundation> Reviewed-by: Igor Ustinov <igus@openssl.foundation> Merge-date: Mon Aug 24 12:45:55 2026
1 parent 9f2b852 commit 21a5d96

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Lines changed: 14 additions & 1 deletion

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‎crypto/cmp/cmp_vfy.c‎

Lines changed: 14 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -666,6 +666,7 @@ int ossl_cmp_msg_check_update(OSSL_CMP_CTX *ctx, const OSSL_CMP_MSG *msg,
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{
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OSSL_CMP_PKIHEADER *hdr;
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const X509_NAME *expected_sender;
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int num_extra_before, num_extra_after, num_added;
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if (!ossl_assert(ctx != NULL && msg != NULL && msg->header != NULL))
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return 0;
@@ -700,17 +701,27 @@ int ossl_cmp_msg_check_update(OSSL_CMP_CTX *ctx, const OSSL_CMP_MSG *msg,
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* extraCerts because they do not belong to the protected msg part anyway.
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* For efficiency, the extraCerts are prepended so they get used first.
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*/
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num_extra_before = sk_X509_num(ctx->untrusted);
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if (!X509_add_certs(ctx->untrusted, msg->extraCerts,
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/* this allows self-signed certs */
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X509_ADD_FLAG_UP_REF | X509_ADD_FLAG_NO_DUP
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| X509_ADD_FLAG_PREPEND))
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return 0;
708-
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num_extra_after = sk_X509_num(ctx->untrusted);
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num_added = num_extra_after - num_extra_before;
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/* validate message protection */
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if (hdr->protectionAlg != NULL) {
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/* detect explicitly permitted exceptions for invalid protection */
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if (!OSSL_CMP_validate_msg(ctx, msg)
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&& (cb == NULL || (*cb)(ctx, msg, 1, cb_arg) <= 0)) {
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/*
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* remove extraCerts again if not caching
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* or if we failed validation above, lest a remote user
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* starts sending us lots of certificate in invalid messages
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* leading to a DOS from unbounded certificate stack growth
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*/
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while (num_added-- > 0)
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X509_free(sk_X509_shift(ctx->untrusted));
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#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
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ERR_raise(ERR_LIB_CMP, CMP_R_ERROR_VALIDATING_PROTECTION);
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return 0;
@@ -719,6 +730,8 @@ int ossl_cmp_msg_check_update(OSSL_CMP_CTX *ctx, const OSSL_CMP_MSG *msg,
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} else {
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/* detect explicitly permitted exceptions for missing protection */
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if (cb == NULL || (*cb)(ctx, msg, 0, cb_arg) <= 0) {
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while (num_added-- > 0)
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X509_free(sk_X509_shift(ctx->untrusted));
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#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
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ERR_raise(ERR_LIB_CMP, CMP_R_MISSING_PROTECTION);
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return 0;

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