docs/security_advisories/security-advisory-tfv-10.rst

5 | Title          | Incorrect validation of X.509 certificate extensions can    |
6 |                | result in an out-of-bounds read.                            |
16 | Affected       | downstream usages of ``get_ext()`` and/or ``auth_nvctr()``  |
19 | Impact         | Out-of-bounds read.                                         |
30 |                | - `abb8f936fd0ad085`_ "fix(auth): avoid out-of-bounds read  |
42 certificate to cause an out-of-bounds memory read.
46 different context than seen in upstream code. Details of such context is
47 described in the rest of this document.
55  - `ITU-T X.690`_, *ASN.1 encoding rules: Specification of Basic Encoding Rules
64 not check the return value of the various ``mbedtls_*()`` functions, as
66 However, it passes the end of an extension as the end pointer to these
67 functions, whereas ``cert_parse()`` passes the end of the ``TBSCertificate``.
68 Furthermore, ``cert_parse()`` does not check that the contents of the extension
70 extension block extends to the end of the ``TBSCertificate``.
77 the end of the certificate.  This could potentially access memory with dangerous
79 retrieved through some side-channel attacks as part of a more complex attack.
85 read 6 bytes, it is possible to read up to 6 bytes past the end of the buffer.
93 In upstream TF-A code, the only caller of ``auth_nvctr()`` takes its input from
97 All standard chains of trust provided in TF-A source tree (that is, under
100 Platforms taking their chain of trust from a dynamic configuration file (such as
103 case, no matter the order of the properties in the file.  Therefore, it is not
108 which greatly reduces the range of inputs it will ever receive and thus the
112  1. Retrieving a hash from an X.509 certificate to check the integrity of a
121 None of these uses authentication framework write to the out-of-bounds memory,
125 in ``auth_nvctr()`` - but neither of these can be exploited in the context of
131  - The platform uses a custom chain of trust which uses the non-volatile counter
135  - The chain of trust uses a custom authentication method that calls
141 If the platform uses a custom image parser instead of the certificate parser,