in-toto VS certificate-transparency-go

The things you mentioned are not solved by a typical "SBOM" but e.g. CycloneDX has extra fields to record provenance and pedigree and things like in-toto (https://in-toto.io/) or SLSA (https://slsa.dev/) also aim to work in this field.

I've spent the last six months in this field and people will tell you that this or that is an industry best practice or "a standard" but in my experience none of that is true. Everyone is still trying to figure out how best to protect the software supply chain security and things are still very much in flux.

in-toto is an open source project that focuses on the attestation part of software supply chain security. You use it to define a “layout” for a project, i.e., how the different components should fit together. A project ships this definition with its code, and then another user of that software can compare what they have with the attached definition to see if it matches the structure and contents they expect. If it doesn’t, then this could point to external tampering or other issues.

But it's not all doom and gloom because the industry is evolving. Companies like Google are formulating tools like scorecard to heuristically reduce risk by encouraging you to rely on trustable dependencies only. There's also more complex tools like in-toto that actually look at the integrity of your supply chain (don't ask me how this one works, I just know that people like it).

If you're talking about a certificate honored by a browser, these days they'd have to put it in a CT log, or at least obtain a "signed certificate timestamp" from a CT log: https://certificate.transparency.dev/

>This feels like this might actually be a use-case for a blockchain or a Merkle Tree.

A few years ago, this idea[0] had been explored by Google as a possible application of their Trillian[1] distributed ledger, which is based on Merkle Trees.

I don't know if they've advanced adoption of Trillian for firmware, however, the website lists Go packaging[2], Certificate Transparency [3], and SigStore[4] as current applications.

have used Trillian as the basis for their Certificate Transparency implementation.[2]

[0] https://github.com/google/trillian-examples/tree/master/bina...

[1] https://transparency.dev/

[2] https://go.googlesource.com/proposal/+/master/design/25530-s...

[3] https://certificate.transparency.dev/

[4] https://www.sigstore.dev/

You can find more about certificate monitoring and who are involved here

https://certificate.transparency.dev/

Excellent question! The sctcheck command from https://github.com/google/certificate-transparency-go/ can be used to check the signatures of embedded SCTs.

I've also got an online tool which you can use to test a site for CT policy compliance: https://sslmate.com/labs/ct_policy_analyzer/

Example of a working site: https://sslmate.com/labs/ct_policy_analyzer/?sslmate.com

Example of one of the sites affected by the Let's Encrypt incident: https://sslmate.com/labs/ct_policy_analyzer/?thecandyshake.c...

The x509 package has unfortunately burned me several times, this one included. It is too anal about non-fatal errors, that Google themselves forked it (and asn1) to improve usability.

https://github.com/google/certificate-transparency-go

ogClient, err := client.New( l.URI, &http.Client{ Timeout: 10 * time.Second, Transport: &http.Transport{ TLSHandshakeTimeout: 30 * time.Second, ResponseHeaderTimeout: 30 * time.Second, MaxIdleConnsPerHost: 10, DisableKeepAlives: false, MaxIdleConns: 100, IdleConnTimeout: 90 * time.Second, ExpectContinueTimeout: 1 * time.Second, }, }, jsonclient.Options{UserAgent: "ct-go-scanlog/1.0"}, ) if err != nil { fmt.Fprintf(os.Stderr, "%s -> Failed to create new client: %s\n", l.Name, err) return } sth, err := logClient.GetSTH(context.TODO()) if err != nil { fmt.Fprintf(os.Stderr, "%s -> Failed to get SignedTreeHead: %s\n", l.Name, err) return } fmt.Printf("%s -> Number of logs: %d\n", l.Name, sth.TreeSize) index := uint64(0) // Logs MAY return fewer than the number of leaves requested. Only complete // if we actually got all the leaves we were expecting. // See more: https://github.com/google/certificate-transparency-go/blob/52d94d8cbab94d6698621839ab1a439d17ebbfb2/scanner/fetcher.go#L263 for index <= sth.TreeSize { fmt.Printf("%s -> New fetch start with index %d-%d\n", l.Name, index, index+100) entries, err := logClient.GetRawEntries(context.TODO(), int64(index), int64(index)+100) if err != nil { fmt.Fprintf(os.Stderr, "%s -> Failed to get raw entries: %s\n", l.Name, err) return } if entries == nil { fmt.Fprintf(os.Stderr, "%s -> entries is nil", l.Name) return } if DEBUG { fmt.Printf("%s -> Got %d leaf entry\n", l.Name, len(entries.Entries)) } for i := range entries.Entries { rawLogE, err := ct.RawLogEntryFromLeaf(int64(index), &entries.Entries[i]) if err != nil { fmt.Fprintf(os.Stderr, "%s -> Failed to parse leaf to raw entry at index %d: %s\n", l.Name, index, err) index++ continue } logE, err := rawLogE.ToLogEntry() if err != nil { fmt.Printf("%s -> Failed to convert raw log to log at index %d: %s\n", l.Name, index, err) index++ continue } /* * This check is true most of the time. */ if logE.X509Cert == nil { fmt.Printf("%s -> Failed to read log cert at index %d: X509Cert is nil\n", l.Name, index) index++ continue } if DEBUG { fmt.Printf("%s -> Leaf entry at %d is parsed successfuly!\n", l.Name, index) } entryChan <- *logE index++ } }

Yes, you can use the certificate-transparency go code to pull down from the trillian API https://github.com/google/certificate-transparency-go/blob/m...

You would need to know the index, or you could just iterate over a range