encoding/asn1: prevent memory exhaustion when parsing using internal/saferio
Within parseSequenceOf, reflect.MakeSlice is being used to pre-allocate
a slice that is needed in order to fully validate the given DER payload.
The size of the slice allocated are also multiple times larger than the
input DER:
- When using asn1.Unmarshal directly, the allocated slice is ~28x
larger.
- When passing in DER using x509.ParseCertificateRequest, the allocated
slice is ~48x larger.
- When passing in DER using ocsp.ParseResponse, the allocated slice is
~137x larger.
As a result, a malicious actor can craft a big empty DER payload,
resulting in an unnecessary large allocation of memories. This can be a
way to cause memory exhaustion.
To prevent this, we now use SliceCapWithSize within internal/saferio to
enforce a memory allocation cap.
Thanks to Jakub Ciolek for reporting this issue.
For #75671
Fixes CVE-2025-58185
Change-Id: Id50e76187eda43f594be75e516b9ca1d2ae6f428
Reviewed-on: https://go-internal-review.googlesource.com/c/go/+/2700 Reviewed-by: Roland Shoemaker <bracewell@google.com> Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/709856 Reviewed-by: Carlos Amedee <carlos@golang.org>
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