guoyijun163
2015-05-20 11:48:13 +08:00
A certificate can contain a special Authority Information Access extension (RFC-3280) with URL to issuer's certificate. Most browsers can use the AIA extension to download missing intermediate certificate to complete the certificate chain. This is the exact meaning of the Extra download message. But some clients (mobile browsers, OpenSSL) don't support this extension, so they report such certificate as untrusted.
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