crypto/x509, x/crypto/cryptobyte: panic in certificate parsing

[katiehockman]

On 32-bit architectures, a malformed input to crypto/x509 or the ASN.1 parsing functions of golang.org/x/crypto/cryptobyte can lead to a panic.

The malformed certificate can be delivered via a crypto/tls connection to a client, or to a server that accepts client certificates. net/http clients can be made to crash by an HTTPS server, while net/http servers that accept client certificates will recover the panic and are unaffected.

Thanks to Project Wycheproof for providing the test cases that led to the discovery of this issue.

The issue is CVE-2020-7919.

This is also fixed in version v0.0.0-20200124225646-8b5121be2f68 of golang.org/x/crypto/cryptobyte.

[dmitshur]

The crypto/x509 part is fixed in master (which will become Go 1.14) in commit b13ce14.