From 2e3ddfac5fedaf9f05b086c3e0a8ae69ea432e42 Mon Sep 17 00:00:00 2001 From: Andres AG Date: Fri, 17 Feb 2017 13:54:43 +0000 Subject: [PATCH] Prevent signed integer overflow in CSR parsing Modify the function mbedtls_x509_csr_parse_der() so that it checks the parsed CSR version integer before it increments the value. This prevents a potential signed integer overflow, as these have undefined behaviour in the C standard. --- ChangeLog | 4 ++++ library/x509_csr.c | 6 +++--- 2 files changed, 7 insertions(+), 3 deletions(-) diff --git a/ChangeLog b/ChangeLog index 567e98883c..eea691958f 100644 --- a/ChangeLog +++ b/ChangeLog @@ -46,6 +46,10 @@ Bugfix Reported and fix suggested by guidovranken in #740 * Fix conditional preprocessor directives in bignum.h to enable 64-bit compilation when using ARM Compiler 6. + * Fix potential integer overflow in the version verification for DER + encoded X509 CSRs. The overflow would enable maliciously constructed CSRs + to bypass the version verification check. Found by Peng Li/Yueh-Hsun Lin, + KNOX Security, Samsung Research America Security * Fix authentication bypass in SSL/TLS: when auth_mode is set to optional, diff --git a/library/x509_csr.c b/library/x509_csr.c index f92b66c58f..26a06db4f6 100644 --- a/library/x509_csr.c +++ b/library/x509_csr.c @@ -168,14 +168,14 @@ int mbedtls_x509_csr_parse_der( mbedtls_x509_csr *csr, return( ret ); } - csr->version++; - - if( csr->version != 1 ) + if( csr->version != 0 ) { mbedtls_x509_csr_free( csr ); return( MBEDTLS_ERR_X509_UNKNOWN_VERSION ); } + csr->version++; + /* * subject Name */