From: Dr. David von Oheimb <David.von.Oheimb@siemens.com>
Date: Wed, 20 May 2020 06:11:47 +0000 (+0200)
Subject: Check expected sender not only for signature-protected CMP messages
X-Git-Tag: openssl-3.0.0-alpha4~124
X-Git-Url: https://git.librecmc.org/?p=oweals%2Fopenssl.git;a=commitdiff_plain;h=6d934add347c7d07fbe0e7a0ced1fdc9813ad640

Check expected sender not only for signature-protected CMP messages

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11998)
---

diff --git a/crypto/cmp/cmp_vfy.c b/crypto/cmp/cmp_vfy.c
index 289402d829..45b2e0010c 100644
--- a/crypto/cmp/cmp_vfy.c
+++ b/crypto/cmp/cmp_vfy.c
@@ -567,6 +567,25 @@ int OSSL_CMP_validate_msg(OSSL_CMP_CTX *ctx, const OSSL_CMP_MSG *msg)
         return 0;
     }
 
+    /* validate sender name of received msg */
+    if (msg->header->sender->type != GEN_DIRNAME) {
+        CMPerr(0, CMP_R_SENDER_GENERALNAME_TYPE_NOT_SUPPORTED);
+        return 0; /* TODO FR#42: support for more than X509_NAME */
+    }
+    /*
+     * Compare actual sender name of response with expected sender name.
+     * Mitigates risk to accept misused PBM secret
+     * or misused certificate of an unauthorized entity of a trusted hierarchy.
+     */
+    expected_sender = ctx->expected_sender;
+    if (expected_sender == NULL && ctx->srvCert != NULL)
+        expected_sender = X509_get_subject_name(ctx->srvCert);
+    if (!check_name(ctx, "sender DN field",
+                    msg->header->sender->d.directoryName,
+                    "expected sender", expected_sender))
+        return 0;
+    /* Note: if recipient was NULL-DN it could be learned here if needed */
+
     if ((alg = msg->header->protectionAlg) == NULL /* unprotected message */
             || msg->protection == NULL || msg->protection->data == NULL) {
         CMPerr(0, CMP_R_MISSING_PROTECTION);
@@ -632,26 +651,6 @@ int OSSL_CMP_validate_msg(OSSL_CMP_CTX *ctx, const OSSL_CMP_MSG *msg)
             CMPerr(0, CMP_R_UNKNOWN_ALGORITHM_ID);
             break;
         }
-        /* validate sender name of received msg */
-        if (msg->header->sender->type != GEN_DIRNAME) {
-            CMPerr(0, CMP_R_SENDER_GENERALNAME_TYPE_NOT_SUPPORTED);
-            break; /* FR#42: support for more than X509_NAME */
-        }
-        /*
-         * Compare actual sender name of response with expected sender name.
-         * Expected name can be set explicitly or the subject of ctx->srvCert.
-         * Mitigates risk to accept misused certificate of an unauthorized
-         * entity of a trusted hierarchy.
-         */
-        expected_sender = ctx->expected_sender;
-        if (expected_sender == NULL && ctx->srvCert != NULL)
-            expected_sender = X509_get_subject_name(ctx->srvCert);
-        if (!check_name(ctx, "sender DN field",
-                        msg->header->sender->d.directoryName,
-                        "expected sender", expected_sender))
-            break;
-        /* Note: if recipient was NULL-DN it could be learned here if needed */
-
         scrt = ctx->srvCert;
         if (scrt == NULL) {
             if (check_msg_find_cert(ctx, msg))
diff --git a/doc/man1/openssl-cmp.pod.in b/doc/man1/openssl-cmp.pod.in
index e6cfe00bfc..aac322b528 100644
--- a/doc/man1/openssl-cmp.pod.in
+++ b/doc/man1/openssl-cmp.pod.in
@@ -521,8 +521,7 @@ as far as any of those is present, else the NULL-DN as last resort.
 
 =item B<-expect_sender> I<name>
 
-Distinguished Name (DN)
-expected in the sender field of signature-protected response messages.
+Distinguished Name (DN) expected in the sender field of CMP response messages.
 Defaults to the subject DN of the pinned B<-srvcert>, if any.
 
 The argument must be formatted as I</type0=value0/type1=value1/type2=...>,
diff --git a/doc/man3/OSSL_CMP_CTX_new.pod b/doc/man3/OSSL_CMP_CTX_new.pod
index b8acf692f8..f8fee277e2 100644
--- a/doc/man3/OSSL_CMP_CTX_new.pod
+++ b/doc/man3/OSSL_CMP_CTX_new.pod
@@ -391,7 +391,7 @@ as default value for the recipient of CMP requests
 and as default value for the expected sender of CMP responses.
 
 OSSL_CMP_CTX_set1_expected_sender() sets the Distinguished Name (DN)
-expected in the sender field of signature-protected response messages.
+expected in the sender field of CMP response messages.
 Defaults to the subject of the pinned server certificate B<-srvcert>, if any.
 This can be used to make sure that only a particular entity is accepted as
 CMP message signer, and attackers are not able to use arbitrary certificates