Deprecate Asn1StringRef::as_utf8 in favor of a NUL-safe to_string#2652
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as_utf8 calls ASN1_STRING_to_UTF8, which returns an explicit length, but discards it: the result is read back through CStr::from_ptr (in OpensslStringRef's Deref), dropping everything after the first NUL byte. X.509 name entries can legally contain interior NULs, and seeing them matters for detecting the classic NUL-byte-CN spoofing trick (e.g. "example.com\0evil.com"). The truncation can't be fixed in place because OpensslString's representation is inherently NUL-terminated. Add Asn1StringRef::to_string, which preserves the full contents using the length reported for the conversion. For string types whose UTF-8 conversion is the identity (UTF8String already containing valid UTF-8, and the Latin-1 family when ASCII-only), it copies directly out of the underlying buffer with a single allocation; otherwise it converts through ASN1_STRING_to_UTF8 and copies the result (replacing any invalid UTF-8 with U+FFFD rather than assuming validity unchecked). The Debug impl now uses to_string, so interior NULs show up there too. https://claude.ai/code/session_01JS5sEpf4jRcbgsqsfNnMPs
botovq
approved these changes
Jun 8, 2026
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as_utf8 calls ASN1_STRING_to_UTF8, which returns an explicit length, but discards it: the result is read back through CStr::from_ptr (in OpensslStringRef's Deref), dropping everything after the first NUL byte. X.509 name entries can legally contain interior NULs, and seeing them matters for detecting the classic NUL-byte-CN spoofing trick (e.g. "example.com\0evil.com"). The truncation can't be fixed in place because OpensslString's representation is inherently NUL-terminated.
Add Asn1StringRef::to_string, which preserves the full contents using the length reported for the conversion. For string types whose UTF-8 conversion is the identity (UTF8String already containing valid UTF-8, and the Latin-1 family when ASCII-only), it copies directly out of the underlying buffer with a single allocation; otherwise it converts through ASN1_STRING_to_UTF8 and copies the result (replacing any invalid UTF-8 with U+FFFD rather than assuming validity unchecked). The Debug impl now uses to_string, so interior NULs show up there too.
https://claude.ai/code/session_01JS5sEpf4jRcbgsqsfNnMPs