From 2470bc91f62cc9b0ab1deac60a67f87b7cc95f6e Mon Sep 17 00:00:00 2001

From: Daniel Stenberg <daniel@haxx.se>

Date: Wed, 2 Dec 2020 23:01:11 +0100

Subject: [PATCH] openssl: make the OCSP verification verify the certificate id

CVE-2020-8286

Reported by anonymous

Bug: https://curl.se/docs/CVE-2020-8286.html

Upstream-commit: d9d01672785b8ac04aab1abb6de95fe3072ae199

Signed-off-by: Kamil Dudka <kdudka@redhat.com>

---

 lib/vtls/openssl.c | 83 ++++++++++++++++++++++++++++++----------------

 1 file changed, 54 insertions(+), 29 deletions(-)

diff --git a/lib/vtls/openssl.c b/lib/vtls/openssl.c

index 9476773..35cd652 100644

--- a/lib/vtls/openssl.c

+++ b/lib/vtls/openssl.c

@@ -1659,6 +1659,11 @@ static CURLcode verifystatus(struct connectdata *conn,

   OCSP_BASICRESP *br = NULL;

   X509_STORE     *st = NULL;

   STACK_OF(X509) *ch = NULL;

+  X509 *cert;

+  OCSP_CERTID *id = NULL;

+  int cert_status, crl_reason;

+  ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;

+  int ret;

   long len = SSL_get_tlsext_status_ocsp_resp(BACKEND->handle, &p);

@@ -1727,43 +1732,63 @@ static CURLcode verifystatus(struct connectdata *conn,

     goto end;

   }

-  for(i = 0; i < OCSP_resp_count(br); i++) {

-    int cert_status, crl_reason;

-    OCSP_SINGLERESP *single = NULL;

-

-    ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;

+  /* Compute the certificate's ID */

+  cert = SSL_get_peer_certificate(BACKEND->handle);

+  if(!cert) {

+    failf(data, "Error getting peer certficate");

+    result = CURLE_SSL_INVALIDCERTSTATUS;

+    goto end;

+  }

-    single = OCSP_resp_get0(br, i);

-    if(!single)

-      continue;

+  for(i = 0; i < sk_X509_num(ch); i++) {

+    X509 *issuer = sk_X509_value(ch, i);

+    if(X509_check_issued(issuer, cert) == X509_V_OK) {

+      id = OCSP_cert_to_id(EVP_sha1(), cert, issuer);

+      break;

+    }

+  }

+  X509_free(cert);

-    cert_status = OCSP_single_get0_status(single, &crl_reason, &rev,

-                                          &thisupd, &nextupd);

+  if(!id) {

+    failf(data, "Error computing OCSP ID");

+    result = CURLE_SSL_INVALIDCERTSTATUS;

+    goto end;

+  }

-    if(!OCSP_check_validity(thisupd, nextupd, 300L, -1L)) {

-      failf(data, "OCSP response has expired");

-      result = CURLE_SSL_INVALIDCERTSTATUS;

-      goto end;

-    }

+  /* Find the single OCSP response corresponding to the certificate ID */

+  ret = OCSP_resp_find_status(br, id, &cert_status, &crl_reason, &rev,

+                              &thisupd, &nextupd);

+  OCSP_CERTID_free(id);

+  if(ret != 1) {

+    failf(data, "Could not find certificate ID in OCSP response");

+    result = CURLE_SSL_INVALIDCERTSTATUS;

+    goto end;

+  }

-    infof(data, "SSL certificate status: %s (%d)\n",

-          OCSP_cert_status_str(cert_status), cert_status);

+  /* Validate the corresponding single OCSP response */

+  if(!OCSP_check_validity(thisupd, nextupd, 300L, -1L)) {

+    failf(data, "OCSP response has expired");

+    result = CURLE_SSL_INVALIDCERTSTATUS;

+    goto end;

+  }

-    switch(cert_status) {

-      case V_OCSP_CERTSTATUS_GOOD:

-        break;

+  infof(data, "SSL certificate status: %s (%d)\n",

+        OCSP_cert_status_str(cert_status), cert_status);

-      case V_OCSP_CERTSTATUS_REVOKED:

-        result = CURLE_SSL_INVALIDCERTSTATUS;

+  switch(cert_status) {

+  case V_OCSP_CERTSTATUS_GOOD:

+    break;

-        failf(data, "SSL certificate revocation reason: %s (%d)",

-              OCSP_crl_reason_str(crl_reason), crl_reason);

-        goto end;

+  case V_OCSP_CERTSTATUS_REVOKED:

+    result = CURLE_SSL_INVALIDCERTSTATUS;

+    failf(data, "SSL certificate revocation reason: %s (%d)",

+          OCSP_crl_reason_str(crl_reason), crl_reason);

+    goto end;

-      case V_OCSP_CERTSTATUS_UNKNOWN:

-        result = CURLE_SSL_INVALIDCERTSTATUS;

-        goto end;

-    }

+  case V_OCSP_CERTSTATUS_UNKNOWN:

+  default:

+    result = CURLE_SSL_INVALIDCERTSTATUS;

+    goto end;

   }

 end:

-- 

2.26.2