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3.1. Log Entries

3.1. Log Entries​

Anyone can submit a certificate to any log. In order to enable attribution of each logged certificate to its issuer, the log SHALL publish a list of acceptable root certificates (this list might usefully be the union of root certificates trusted by major browser vendors). Each submitted certificate MUST be accompanied by all additional certificates required to verify the certificate chain up to an accepted root certificate. The root certificate itself MAY be omitted from the chain submitted to the log server.

Alternatively, (root as well as intermediate) certificate authorities may submit a certificate to logs prior to issuance. To do so, the CA submits a Precertificate that the log can use to create an entry that will be valid against the issued certificate. The Precertificate is constructed from the certificate to be issued by adding a special critical poison extension (OID 1.3.6.1.4.1.11129.2.4.3, whose extnValue OCTET STRING contains ASN.1 NULL data (0x05 0x00)) to the end-entity TBSCertificate (this extension is to ensure that the Precertificate cannot be validated by a standard X.509v3 client) and signing the resulting TBSCertificate [RFC5280] with either

  • a special-purpose (CA:true, Extended Key Usage: Certificate Transparency, OID 1.3.6.1.4.1.11129.2.4.4) Precertificate Signing Certificate. The Precertificate Signing Certificate MUST be directly certified by the (root or intermediate) CA certificate that will ultimately sign the end-entity TBSCertificate yielding the end-entity certificate (note that the log may relax standard validation rules to allow this, so long as the issued certificate will be valid),

  • or, the CA certificate that will sign the final certificate.

As above, the Precertificate submission MUST be accompanied by the Precertificate Signing Certificate, if used, and all additional certificates required to verify the chain up to an accepted root certificate. The signature on the TBSCertificate indicates the certificate authority's intent to issue a certificate. This intent is considered binding (i.e., misissuance of the Precertificate is considered equal to misissuance of the final certificate). Each log verifies the Precertificate signature chain and issues a Signed Certificate Timestamp on the corresponding TBSCertificate.

Logs MUST verify that the submitted end-entity certificate or Precertificate has a valid signature chain leading back to a trusted root CA certificate, using the chain of intermediate CA certificates provided by the submitter. Logs MAY accept certificates that have expired, are not yet valid, have been revoked, or are otherwise not fully valid according to X.509 verification rules in order to accommodate quirks of CA certificate-issuing software. However, logs MUST refuse to publish certificates without a valid chain to a known root CA. If a certificate is accepted and an SCT issued, the accepting log MUST store the entire chain used for verification, including the certificate or Precertificate itself and including the root certificate used to verify the chain (even if it was omitted from the submission), and MUST present this chain for auditing upon request. This chain is required to prevent a CA from avoiding blame by logging a partial or empty chain. (Note: This effectively excludes self-signed and DANE-based certificates until some mechanism to control spam for those certificates is found. The authors welcome suggestions.)

Each certificate entry in a log MUST include the following components:

    enum { x509_entry(0), precert_entry(1), (65535) } LogEntryType;

    struct {
        LogEntryType entry_type;
        select (entry_type) {
            case x509_entry: X509ChainEntry;
            case precert_entry: PrecertChainEntry;
        } entry;
    } LogEntry;

    opaque ASN.1Cert<1..2^24-1>;

    struct {
        ASN.1Cert leaf_certificate;
        ASN.1Cert certificate_chain<0..2^24-1>;
    } X509ChainEntry;

    struct {
        ASN.1Cert pre_certificate;
        ASN.1Cert precertificate_chain<0..2^24-1>;
    } PrecertChainEntry;

Logs MAY limit the length of chain they will accept.

"entry_type" is the type of this entry. Future revisions of this protocol version may add new LogEntryType values. Section 4 explains how clients should handle unknown entry types.

"leaf_certificate" is the end-entity certificate submitted for auditing.

"certificate_chain" is a chain of additional certificates required to verify the end-entity certificate. The first certificate MUST certify the end-entity certificate. Each following certificate MUST directly certify the one preceding it. The final certificate MUST be a root certificate accepted by the log.

"pre_certificate" is the Precertificate submitted for auditing.

"precertificate_chain" is a chain of additional certificates required to verify the Precertificate submission. The first certificate MAY be a valid Precertificate Signing Certificate and MUST certify the first certificate. Each following certificate MUST directly certify the one preceding it. The final certificate MUST be a root certificate accepted by the log.

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