From 110e5341eb322087c9847a9d4041692b5daecb95 Mon Sep 17 00:00:00 2001 From: David Horstmann Date: Wed, 22 Jan 2025 14:27:22 +0000 Subject: [PATCH] Add X.509 formatting validation to SECURITY.md Clarify that strict formatting of X.509 certificates is not checked by Mbed TLS and that it therefore should not be used to construct a CA. Signed-off-by: David Horstmann --- SECURITY.md | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/SECURITY.md b/SECURITY.md index 732335b233..b4d564ef44 100644 --- a/SECURITY.md +++ b/SECURITY.md @@ -135,3 +135,17 @@ Guide](docs/architecture/alternative-implementations.md) for more information. - Use cryptographic mechanisms that are not based on block ciphers. In particular, for authenticated encryption, use ChaCha20/Poly1305 instead of block cipher modes. For random generation, use HMAC\_DRBG instead of CTR\_DRBG. + +#### Formatting of X.509 certificates and certificate signing requests + +When parsing X.509 certificates and certificate signing requests (CSRs), +Mbed TLS does not check that they are strictly compliant with X.509 and other +relevant standards. In the case of signed certificates, the signing party is +assumed to have performed this validation (and the certificate is trusted to +be correctly formatted as long as the signature is correct). +Similarly, CSRs are implicitly trusted by Mbed TLS to be standards-compliant. + +**Warning!** Mbed TLS must not be used to sign untrusted CSRs unless extra +validation is performed separately to ensure that they are compliant to the +relevant specifications. This makes Mbed TLS on its own unsuitable use in a +Certificate Authority (CA).