Description: Fix CVE-2017-14032: authentication bypass
 If a malicious peer supplies an X.509 certificate chain that has more
 than MBEDTLS_X509_MAX_INTERMEDIATE_CA intermediates (which by default is
 8), it could bypass authentication of the certificates, when the
 authentication mode was set to 'optional' eg.
 MBEDTLS_SSL_VERIFY_OPTIONAL. The issue could be triggered remotely by
 both the client and server sides.
 .
 Fix by backporting two patches from the upstream 2.6 branch:
  d15795acd507 = Improve behaviour on fatal errors
  31458a18788b = Only return VERIFY_FAILED from a single point
Author: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
Origin: backport, https://github.com/ARMmbed/mbedtls/commit/d15795acd5074e0b44e71f7ede8bdfe1b48591fc
Origin: backport, https://github.com/ARMmbed/mbedtls/commit/31458a18788b0cf0b722acda9bb2f2fe13a3fb32
Bug-Debian: https://bugs.debian.org/873557
---
This patch header follows DEP-3: http://dep.debian.net/deps/dep3/

--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -2055,8 +2055,8 @@ static int x509_crt_verify_child(
     /* path_cnt is 0 for the first intermediate CA */
     if( 1 + path_cnt > MBEDTLS_X509_MAX_INTERMEDIATE_CA )
     {
-        *flags |= MBEDTLS_X509_BADCERT_NOT_TRUSTED;
-        return( MBEDTLS_ERR_X509_CERT_VERIFY_FAILED );
+        /* return immediately as the goal is to avoid unbounded recursion */
+        return( MBEDTLS_ERR_X509_FATAL_ERROR );
     }
 
     if( mbedtls_x509_time_is_past( &child->valid_to ) )
@@ -2200,11 +2200,14 @@ int mbedtls_x509_crt_verify_with_profile
     mbedtls_x509_sequence *cur = NULL;
     mbedtls_pk_type_t pk_type;
 
-    if( profile == NULL )
-        return( MBEDTLS_ERR_X509_BAD_INPUT_DATA );
-
     *flags = 0;
 
+    if( profile == NULL )
+    {
+        ret = MBEDTLS_ERR_X509_BAD_INPUT_DATA;
+        goto exit;
+    }
+
     if( cn != NULL )
     {
         name = &crt->subject;
@@ -2278,7 +2281,7 @@ int mbedtls_x509_crt_verify_with_profile
         ret = x509_crt_verify_top( crt, parent, ca_crl, profile,
                                    pathlen, selfsigned, flags, f_vrfy, p_vrfy );
         if( ret != 0 )
-            return( ret );
+            goto exit;
     }
     else
     {
@@ -2293,17 +2296,28 @@ int mbedtls_x509_crt_verify_with_profile
             ret = x509_crt_verify_child( crt, parent, trust_ca, ca_crl, profile,
                                          pathlen, selfsigned, flags, f_vrfy, p_vrfy );
             if( ret != 0 )
-                return( ret );
+                goto exit;
         }
         else
         {
             ret = x509_crt_verify_top( crt, trust_ca, ca_crl, profile,
                                        pathlen, selfsigned, flags, f_vrfy, p_vrfy );
             if( ret != 0 )
-                return( ret );
+                goto exit;
         }
     }
 
+exit:
+    /* prevent misuse of the vrfy callback */
+    if( ret == MBEDTLS_ERR_X509_CERT_VERIFY_FAILED )
+        ret = MBEDTLS_ERR_X509_FATAL_ERROR;
+
+    if( ret != 0 )
+    {
+        *flags = (uint32_t) -1;
+        return( ret );
+    }
+
     if( *flags != 0 )
         return( MBEDTLS_ERR_X509_CERT_VERIFY_FAILED );
 
--- a/include/mbedtls/error.h
+++ b/include/mbedtls/error.h
@@ -71,7 +71,7 @@
  * Name      ID  Nr of Errors
  * PEM       1   9
  * PKCS#12   1   4 (Started from top)
- * X509      2   19
+ * X509      2   20
  * PKCS5     2   4 (Started from top)
  * DHM       3   9
  * PK        3   14 (Started from top)
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1042,7 +1042,7 @@ void mbedtls_ssl_conf_authmode( mbedtls_
  *
  *                 If set, the verify callback is called for each
  *                 certificate in the chain. For implementation
- *                 information, please see \c x509parse_verify()
+ *                 information, please see \c mbedtls_x509_crt_verify()
  *
  * \param conf     SSL configuration
  * \param f_vrfy   verification function
--- a/include/mbedtls/x509.h
+++ b/include/mbedtls/x509.h
@@ -76,6 +76,7 @@
 #define MBEDTLS_ERR_X509_ALLOC_FAILED                     -0x2880  /**< Allocation of memory failed. */
 #define MBEDTLS_ERR_X509_FILE_IO_ERROR                    -0x2900  /**< Read/write of file failed. */
 #define MBEDTLS_ERR_X509_BUFFER_TOO_SMALL                 -0x2980  /**< Destination buffer is too small. */
+#define MBEDTLS_ERR_X509_FATAL_ERROR                      -0x3000  /**< A fatal error occured, eg the chain is too long or the vrfy callback failed. */
 /* \} name */
 
 /**
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -267,7 +267,13 @@ int mbedtls_x509_crt_verify_info( char *
  *
  *                 All flags left after returning from the callback
  *                 are also returned to the application. The function should
- *                 return 0 for anything but a fatal error.
+ *                 return 0 for anything (including invalid certificates)
+ *                 other than fatal error, as a non-zero return code
+ *                 immediately aborts the verification process. For fatal
+ *                 errors, a specific error code should be used (different
+ *                 from MBEDTLS_ERR_X509_CERT_VERIFY_FAILED which should not
+ *                 be returned at this point), or MBEDTLS_ERR_X509_FATAL_ERROR
+ *                 can be used if no better code is available.
  *
  * \note           In case verification failed, the results can be displayed
  *                 using \c mbedtls_x509_crt_verify_info()
--- a/library/error.c
+++ b/library/error.c
@@ -480,6 +480,8 @@ void mbedtls_strerror( int ret, char *bu
             mbedtls_snprintf( buf, buflen, "X509 - Read/write of file failed" );
         if( use_ret == -(MBEDTLS_ERR_X509_BUFFER_TOO_SMALL) )
             mbedtls_snprintf( buf, buflen, "X509 - Destination buffer is too small" );
+        if( use_ret == -(MBEDTLS_ERR_X509_FATAL_ERROR) )
+            mbedtls_snprintf( buf, buflen, "X509 - A fatal error occured, eg the chain is too long or the vrfy callback failed" );
 #endif /* MBEDTLS_X509_USE_C || MBEDTLS_X509_CREATE_C */
         // END generated code