From bbb71507b7bab52002f9b1e0880bed6a32834511 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Fri, 23 Apr 2021 10:54:10 +0200
Subject: [PATCH] schannel: don't use static to store selected ciphers

CVE-2021-22897

Bug: https://curl.se/docs/CVE-2021-22897.html
---
 lib/vtls/schannel.c | 9 +++++----
 lib/vtls/schannel.h | 3 +++
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/lib/vtls/schannel.c b/lib/vtls/schannel.c
index 8c25ac5dd5a5..dba7072273a9 100644
--- a/lib/vtls/schannel.c
+++ b/lib/vtls/schannel.c
@@ -328,12 +328,12 @@ get_alg_id_by_name(char *name)
 }
 
 static CURLcode
-set_ssl_ciphers(SCHANNEL_CRED *schannel_cred, char *ciphers)
+set_ssl_ciphers(SCHANNEL_CRED *schannel_cred, char *ciphers,
+                int *algIds)
 {
   char *startCur = ciphers;
   int algCount = 0;
-  static ALG_ID algIds[45]; /*There are 45 listed in the MS headers*/
-  while(startCur && (0 != *startCur) && (algCount < 45)) {
+  while(startCur && (0 != *startCur) && (algCount < NUMOF_CIPHERS)) {
     long alg = strtol(startCur, 0, 0);
     if(!alg)
       alg = get_alg_id_by_name(startCur);
@@ -593,7 +593,8 @@ schannel_connect_step1(struct Curl_easy *data, struct connectdata *conn,
     }
 
     if(SSL_CONN_CONFIG(cipher_list)) {
-      result = set_ssl_ciphers(&schannel_cred, SSL_CONN_CONFIG(cipher_list));
+      result = set_ssl_ciphers(&schannel_cred, SSL_CONN_CONFIG(cipher_list),
+                               BACKEND->algIds);
       if(CURLE_OK != result) {
         failf(data, "Unable to set ciphers to passed via SSL_CONN_CONFIG");
         return result;
diff --git a/lib/vtls/schannel.h b/lib/vtls/schannel.h
index 2952caa1a5a1..77853aa30f96 100644
--- a/lib/vtls/schannel.h
+++ b/lib/vtls/schannel.h
@@ -71,6 +71,8 @@ CURLcode Curl_verify_certificate(struct Curl_easy *data,
 #endif
 #endif
 
+#define NUMOF_CIPHERS 45 /* There are 45 listed in the MS headers */
+
 struct Curl_schannel_cred {
   CredHandle cred_handle;
   TimeStamp time_stamp;
@@ -102,6 +104,7 @@ struct ssl_backend_data {
 #ifdef HAS_MANUAL_VERIFY_API
   bool use_manual_cred_validation; /* true if manual cred validation is used */
 #endif
+  ALG_ID algIds[NUMOF_CIPHERS];
 };
 #endif /* EXPOSE_SCHANNEL_INTERNAL_STRUCTS */