When int is 32 bits wide (on 32-bit architectures like 386 and arm), an overflow could occur, causing a panic, due to malformed ASN.1 being passed to any of the ASN1 methods of String. Tested on linux/386 and darwin/amd64. This fixes CVE-2020-7919 and was found thanks to the Project Wycheproof test vectors. Change-Id: I8c9696a8bfad1b40ec877cd740dba3467d66ab54 Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/645211 Reviewed-by: Katie Hockman <katiehockman@google.com> Reviewed-by: Adam Langley <agl@google.com> Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/647740