What version of Go are you using (go version)?

$ go version
go version go1.14.2 darwin/amd64

Does this issue reproduce with the latest release?

What operating system and processor architecture are you using (go env)?

$ go env
mac

What did you do?

try to parse a CA file:

block, _ := pem.Decode(certBits)
ca, _ := x509.ParseCertificate(block.Bytes) 

What did you expect to see?

success

What did you see instead?

asn1: syntax error: PrintableString contains invalid character

this ca has special character, like "_" "@"

but encoding.asn1.isPrintable() not support .

current code:

// isPrintable reports whether the given b is in the ASN.1 PrintableString set.
// If asterisk is allowAsterisk then '*' is also allowed, reflecting existing
// practice. If ampersand is allowAmpersand then '&' is allowed as well.
func isPrintable(b byte, asterisk asteriskFlag, ampersand ampersandFlag) bool {
	return 'a' <= b && b <= 'z' ||
		'A' <= b && b <= 'Z' ||
		'0' <= b && b <= '9' ||
		'\'' <= b && b <= ')' ||
		'+' <= b && b <= '/' ||
		b == ' ' ||
		b == ':' ||
		b == '=' ||
		b == '?' ||
		// This is technically not allowed in a PrintableString.
		// However, x509 certificates with wildcard strings don't
		// always use the correct string type so we permit it.
		(bool(asterisk) && b == '*') ||
		// This is not technically allowed either. However, not
		// only is it relatively common, but there are also a
		// handful of CA certificates that contain it. At least
		// one of which will not expire until 2027.
		(bool(ampersand) && b == '&')
}