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Prevent signed integer overflow in CSR parsing

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Modify the function 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.
This commit is contained in:
Andres AG 2017-03-01 14:59:02 +00:00 committed by Simon Butcher
parent 47f3059780
commit 3df4e4e1d0
2 changed files with 7 additions and 3 deletions
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4
ChangeLog
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@ -20,6 +20,10 @@ Bugfix
* Fix a potential integer overflow in the version verification for DER * Fix a potential integer overflow in the version verification for DER
encoded X509 certificates. The overflow would enable maliciously encoded X509 certificates. The overflow would enable maliciously
constructed certificates to bypass the certificate verification check. constructed certificates to bypass the certificate verification check.
* 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
= mbed TLS 1.3.20 branch released 2017-06-21 = mbed TLS 1.3.20 branch released 2017-06-21

6
library/x509_csr.c
View file

@ -169,14 +169,14 @@ int x509_csr_parse_der( x509_csr *csr,
return( ret ); return( ret );
} }
csr->version++; if( csr->version != 0 )
if( csr->version != 1 )
{ {
x509_csr_free( csr ); x509_csr_free( csr );
return( POLARSSL_ERR_X509_UNKNOWN_VERSION ); return( POLARSSL_ERR_X509_UNKNOWN_VERSION );
} }
csr->version++;
/* /*
* subject Name * subject Name
*/ */