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Fix bug checking pathlen on first intermediate

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Remove check on the pathLenConstraint value when looking for a parent to the
EE cert, as the constraint is on the number of intermediate certs below the
parent, and that number is always 0 at that point, so the constraint is always
satisfied.

The check was actually off-by-one, which caused valid chains to be rejected
under the following conditions:
- the parent certificate is not a trusted root, and
- it has pathLenConstraint == 0 (max_pathlen == 1 in our representation)

fixes #280
This commit is contained in:
Manuel Pégourié-Gonnard 2015-11-19 09:23:06 +01:00
parent 8b4331aa56
commit f4569b14c4
2 changed files with 7 additions and 10 deletions
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7
ChangeLog
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@ -1,5 +1,12 @@
mbed TLS ChangeLog (Sorted per branch, date)
= mbed TLS 2.x branch
Bugfix
* Fix bug in certificate validation that caused valid chains to be rejected
when the first intermediate certificate has pathLenConstraint=0. Found by
Nicholas Wilson. Introduced in mbed TLS 2.2.0. #280
= mbed TLS 2.2.0 released 2015-11-04
Security

10
library/x509_crt.c
View file

@ -2253,18 +2253,8 @@ int mbedtls_x509_crt_verify_with_profile( mbedtls_x509_crt *crt,
{
/* Look for a parent upwards the chain */
for( parent = crt->next; parent != NULL; parent = parent->next )
{
/* +2 because the current step is not yet accounted for
* and because max_pathlen is one higher than it should be */
if( parent->max_pathlen > 0 &&
parent->max_pathlen < 2 + pathlen )
{
continue;
}
if( x509_crt_check_parent( crt, parent, 0, pathlen == 0 ) == 0 )
break;
}
/* Are we part of the chain or at the top? */
if( parent != NULL )