Fix potential buffer overflow in asn1write
Ref: IOTSSL-519
diff --git a/ChangeLog b/ChangeLog
index 6529b66..2abdf1e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,10 @@
* Fix potential heap corruption on Windows when
x509_crt_parse_path() is passed a path longer than 2GB. Cannot be
triggered remotely. Found by Guido Vranken, Interlworks.
+ * Fix potential buffer overflow in some asn1_write_xxx() functions.
+ Cannot be triggered remotely unless you create X.509 certificates based
+ on untrusted input or write keys of untrusted origin. Found by Guido
+ Vranken, Interlworks.
= Version 1.2.17 released 2015-10-06
diff --git a/library/asn1write.c b/library/asn1write.c
index 3d6f101..6c520dc 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -78,7 +78,7 @@
//
len = mpi_size( X );
- if( *p - start < (int) len )
+ if( *p < start || (size_t)( *p - start ) < len )
return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
(*p) -= len;
@@ -127,7 +127,7 @@
//
len = strlen( oid );
- if( *p - start < (int) len )
+ if( *p < start || (size_t)( *p - start ) < len )
return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
(*p) -= len;
@@ -203,7 +203,7 @@
//
len = strlen( text );
- if( *p - start < (int) len )
+ if( *p < start || (size_t)( *p - start ) < len )
return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
(*p) -= len;
@@ -225,7 +225,7 @@
//
len = strlen( text );
- if( *p - start < (int) len )
+ if( *p < start || (size_t)( *p - start ) < len )
return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
(*p) -= len;