Fork some snippets to get SANs parsing

1 files changed, 487 insertions, 0 deletions

diff --git a/internal/utils/x509.go b/internal/utils/x509.go
new file mode 100644
index 0000000..bf99334
--- /dev/null
+++ b/internal/utils/x509.go
@@ -0,0 +1,487 @@
+package utils
+
+import (
+	"fmt"
+
+	ct "github.com/google/certificate-transparency-go"
+	"github.com/google/certificate-transparency-go/asn1"
+	"github.com/google/certificate-transparency-go/x509/pkix"
+)
+
+// Mozilla Public License Version 2.0
+// ==================================
+//
+// 1. Definitions
+// --------------
+//
+// 1.1. "Contributor"
+//
+//	means each individual or legal entity that creates, contributes to
+//	the creation of, or owns Covered Software.
+//
+// 1.2. "Contributor Version"
+//
+//	means the combination of the Contributions of others (if any) used
+//	by a Contributor and that particular Contributor's Contribution.
+//
+// 1.3. "Contribution"
+//
+//	means Covered Software of a particular Contributor.
+//
+// 1.4. "Covered Software"
+//
+//	means Source Code Form to which the initial Contributor has attached
+//	the notice in Exhibit A, the Executable Form of such Source Code
+//	Form, and Modifications of such Source Code Form, in each case
+//	including portions thereof.
+//
+// 1.5. "Incompatible With Secondary Licenses"
+//
+//	means
+//
+//	(a) that the initial Contributor has attached the notice described
+//	    in Exhibit B to the Covered Software; or
+//
+//	(b) that the Covered Software was made available under the terms of
+//	    version 1.1 or earlier of the License, but not also under the
+//	    terms of a Secondary License.
+//
+// 1.6. "Executable Form"
+//
+//	means any form of the work other than Source Code Form.
+//
+// 1.7. "Larger Work"
+//
+//	means a work that combines Covered Software with other material, in
+//	a separate file or files, that is not Covered Software.
+//
+// 1.8. "License"
+//
+//	means this document.
+//
+// 1.9. "Licensable"
+//
+//	means having the right to grant, to the maximum extent possible,
+//	whether at the time of the initial grant or subsequently, any and
+//	all of the rights conveyed by this License.
+//
+// 1.10. "Modifications"
+//
+//	means any of the following:
+//
+//	(a) any file in Source Code Form that results from an addition to,
+//	    deletion from, or modification of the contents of Covered
+//	    Software; or
+//
+//	(b) any new file in Source Code Form that contains any Covered
+//	    Software.
+//
+// 1.11. "Patent Claims" of a Contributor
+//
+//	means any patent claim(s), including without limitation, method,
+//	process, and apparatus claims, in any patent Licensable by such
+//	Contributor that would be infringed, but for the grant of the
+//	License, by the making, using, selling, offering for sale, having
+//	made, import, or transfer of either its Contributions or its
+//	Contributor Version.
+//
+// 1.12. "Secondary License"
+//
+//	means either the GNU General Public License, Version 2.0, the GNU
+//	Lesser General Public License, Version 2.1, the GNU Affero General
+//	Public License, Version 3.0, or any later versions of those
+//	licenses.
+//
+// 1.13. "Source Code Form"
+//
+//	means the form of the work preferred for making modifications.
+//
+// 1.14. "You" (or "Your")
+//
+//	means an individual or a legal entity exercising rights under this
+//	License. For legal entities, "You" includes any entity that
+//	controls, is controlled by, or is under common control with You. For
+//	purposes of this definition, "control" means (a) the power, direct
+//	or indirect, to cause the direction or management of such entity,
+//	whether by contract or otherwise, or (b) ownership of more than
+//	fifty percent (50%) of the outstanding shares or beneficial
+//	ownership of such entity.
+//
+// 2. License Grants and Conditions
+// --------------------------------
+//
+// 2.1. Grants
+//
+// Each Contributor hereby grants You a world-wide, royalty-free,
+// non-exclusive license:
+//
+// (a) under intellectual property rights (other than patent or trademark)
+//
+//	Licensable by such Contributor to use, reproduce, make available,
+//	modify, display, perform, distribute, and otherwise exploit its
+//	Contributions, either on an unmodified basis, with Modifications, or
+//	as part of a Larger Work; and
+//
+// (b) under Patent Claims of such Contributor to make, use, sell, offer
+//
+//	for sale, have made, import, and otherwise transfer either its
+//	Contributions or its Contributor Version.
+//
+// 2.2. Effective Date
+//
+// The licenses granted in Section 2.1 with respect to any Contribution
+// become effective for each Contribution on the date the Contributor first
+// distributes such Contribution.
+//
+// 2.3. Limitations on Grant Scope
+//
+// The licenses granted in this Section 2 are the only rights granted under
+// this License. No additional rights or licenses will be implied from the
+// distribution or licensing of Covered Software under this License.
+// Notwithstanding Section 2.1(b) above, no patent license is granted by a
+// Contributor:
+//
+// (a) for any code that a Contributor has removed from Covered Software;
+//
+//	or
+//
+// (b) for infringements caused by: (i) Your and any other third party's
+//
+//	modifications of Covered Software, or (ii) the combination of its
+//	Contributions with other software (except as part of its Contributor
+//	Version); or
+//
+// (c) under Patent Claims infringed by Covered Software in the absence of
+//
+//	its Contributions.
+//
+// This License does not grant any rights in the trademarks, service marks,
+// or logos of any Contributor (except as may be necessary to comply with
+// the notice requirements in Section 3.4).
+//
+// 2.4. Subsequent Licenses
+//
+// No Contributor makes additional grants as a result of Your choice to
+// distribute the Covered Software under a subsequent version of this
+// License (see Section 10.2) or under the terms of a Secondary License (if
+// permitted under the terms of Section 3.3).
+//
+// 2.5. Representation
+//
+// Each Contributor represents that the Contributor believes its
+// Contributions are its original creation(s) or it has sufficient rights
+// to grant the rights to its Contributions conveyed by this License.
+//
+// 2.6. Fair Use
+//
+// This License is not intended to limit any rights You have under
+// applicable copyright doctrines of fair use, fair dealing, or other
+// equivalents.
+//
+// 2.7. Conditions
+//
+// Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted
+// in Section 2.1.
+//
+// 3. Responsibilities
+// -------------------
+//
+// 3.1. Distribution of Source Form
+//
+// All distribution of Covered Software in Source Code Form, including any
+// Modifications that You create or to which You contribute, must be under
+// the terms of this License. You must inform recipients that the Source
+// Code Form of the Covered Software is governed by the terms of this
+// License, and how they can obtain a copy of this License. You may not
+// attempt to alter or restrict the recipients' rights in the Source Code
+// Form.
+//
+// 3.2. Distribution of Executable Form
+//
+// If You distribute Covered Software in Executable Form then:
+//
+// (a) such Covered Software must also be made available in Source Code
+//
+//	Form, as described in Section 3.1, and You must inform recipients of
+//	the Executable Form how they can obtain a copy of such Source Code
+//	Form by reasonable means in a timely manner, at a charge no more
+//	than the cost of distribution to the recipient; and
+//
+// (b) You may distribute such Executable Form under the terms of this
+//
+//	License, or sublicense it under different terms, provided that the
+//	license for the Executable Form does not attempt to limit or alter
+//	the recipients' rights in the Source Code Form under this License.
+//
+// 3.3. Distribution of a Larger Work
+//
+// You may create and distribute a Larger Work under terms of Your choice,
+// provided that You also comply with the requirements of this License for
+// the Covered Software. If the Larger Work is a combination of Covered
+// Software with a work governed by one or more Secondary Licenses, and the
+// Covered Software is not Incompatible With Secondary Licenses, this
+// License permits You to additionally distribute such Covered Software
+// under the terms of such Secondary License(s), so that the recipient of
+// the Larger Work may, at their option, further distribute the Covered
+// Software under the terms of either this License or such Secondary
+// License(s).
+//
+// 3.4. Notices
+//
+// You may not remove or alter the substance of any license notices
+// (including copyright notices, patent notices, disclaimers of warranty,
+// or limitations of liability) contained within the Source Code Form of
+// the Covered Software, except that You may alter any license notices to
+// the extent required to remedy known factual inaccuracies.
+//
+// 3.5. Application of Additional Terms
+//
+// You may choose to offer, and to charge a fee for, warranty, support,
+// indemnity or liability obligations to one or more recipients of Covered
+// Software. However, You may do so only on Your own behalf, and not on
+// behalf of any Contributor. You must make it absolutely clear that any
+// such warranty, support, indemnity, or liability obligation is offered by
+// You alone, and You hereby agree to indemnify every Contributor for any
+// liability incurred by such Contributor as a result of warranty, support,
+// indemnity or liability terms You offer. You may include additional
+// disclaimers of warranty and limitations of liability specific to any
+// jurisdiction.
+//
+// 4. Inability to Comply Due to Statute or Regulation
+// ---------------------------------------------------
+//
+// If it is impossible for You to comply with any of the terms of this
+// License with respect to some or all of the Covered Software due to
+// statute, judicial order, or regulation then You must: (a) comply with
+// the terms of this License to the maximum extent possible; and (b)
+// describe the limitations and the code they affect. Such description must
+// be placed in a text file included with all distributions of the Covered
+// Software under this License. Except to the extent prohibited by statute
+// or regulation, such description must be sufficiently detailed for a
+// recipient of ordinary skill to be able to understand it.
+//
+// 5. Termination
+// --------------
+//
+// 5.1. The rights granted under this License will terminate automatically
+// if You fail to comply with any of its terms. However, if You become
+// compliant, then the rights granted under this License from a particular
+// Contributor are reinstated (a) provisionally, unless and until such
+// Contributor explicitly and finally terminates Your grants, and (b) on an
+// ongoing basis, if such Contributor fails to notify You of the
+// non-compliance by some reasonable means prior to 60 days after You have
+// come back into compliance. Moreover, Your grants from a particular
+// Contributor are reinstated on an ongoing basis if such Contributor
+// notifies You of the non-compliance by some reasonable means, this is the
+// first time You have received notice of non-compliance with this License
+// from such Contributor, and You become compliant prior to 30 days after
+// Your receipt of the notice.
+//
+// 5.2. If You initiate litigation against any entity by asserting a patent
+// infringement claim (excluding declaratory judgment actions,
+// counter-claims, and cross-claims) alleging that a Contributor Version
+// directly or indirectly infringes any patent, then the rights granted to
+// You by any and all Contributors for the Covered Software under Section
+// 2.1 of this License shall terminate.
+//
+// 5.3. In the event of termination under Sections 5.1 or 5.2 above, all
+// end user license agreements (excluding distributors and resellers) which
+// have been validly granted by You or Your distributors under this License
+// prior to termination shall survive termination.
+//
+// ************************************************************************
+// *                                                                      *
+// *  6. Disclaimer of Warranty                                           *
+// *  -------------------------                                           *
+// *                                                                      *
+// *  Covered Software is provided under this License on an "as is"       *
+// *  basis, without warranty of any kind, either expressed, implied, or  *
+// *  statutory, including, without limitation, warranties that the       *
+// *  Covered Software is free of defects, merchantable, fit for a        *
+// *  particular purpose or non-infringing. The entire risk as to the     *
+// *  quality and performance of the Covered Software is with You.        *
+// *  Should any Covered Software prove defective in any respect, You     *
+// *  (not any Contributor) assume the cost of any necessary servicing,   *
+// *  repair, or correction. This disclaimer of warranty constitutes an   *
+// *  essential part of this License. No use of any Covered Software is   *
+// *  authorized under this License except under this disclaimer.         *
+// *                                                                      *
+// ************************************************************************
+//
+// ************************************************************************
+// *                                                                      *
+// *  7. Limitation of Liability                                          *
+// *  --------------------------                                          *
+// *                                                                      *
+// *  Under no circumstances and under no legal theory, whether tort      *
+// *  (including negligence), contract, or otherwise, shall any           *
+// *  Contributor, or anyone who distributes Covered Software as          *
+// *  permitted above, be liable to You for any direct, indirect,         *
+// *  special, incidental, or consequential damages of any character      *
+// *  including, without limitation, damages for lost profits, loss of    *
+// *  goodwill, work stoppage, computer failure or malfunction, or any    *
+// *  and all other commercial damages or losses, even if such party      *
+// *  shall have been informed of the possibility of such damages. This   *
+// *  limitation of liability shall not apply to liability for death or   *
+// *  personal injury resulting from such party's negligence to the       *
+// *  extent applicable law prohibits such limitation. Some               *
+// *  jurisdictions do not allow the exclusion or limitation of           *
+// *  incidental or consequential damages, so this exclusion and          *
+// *  limitation may not apply to You.                                    *
+// *                                                                      *
+// ************************************************************************
+//
+// 8. Litigation
+// -------------
+//
+// Any litigation relating to this License may be brought only in the
+// courts of a jurisdiction where the defendant maintains its principal
+// place of business and such litigation shall be governed by laws of that
+// jurisdiction, without reference to its conflict-of-law provisions.
+// Nothing in this Section shall prevent a party's ability to bring
+// cross-claims or counter-claims.
+//
+// 9. Miscellaneous
+// ----------------
+//
+// This License represents the complete agreement concerning the subject
+// matter hereof. If any provision of this License is held to be
+// unenforceable, such provision shall be reformed only to the extent
+// necessary to make it enforceable. Any law or regulation which provides
+// that the language of a contract shall be construed against the drafter
+// shall not be used to construe this License against a Contributor.
+//
+// 10. Versions of the License
+// ---------------------------
+//
+// 10.1. New Versions
+//
+// Mozilla Foundation is the license steward. Except as provided in Section
+// 10.3, no one other than the license steward has the right to modify or
+// publish new versions of this License. Each version will be given a
+// distinguishing version number.
+//
+// 10.2. Effect of New Versions
+//
+// You may distribute the Covered Software under the terms of the version
+// of the License under which You originally received the Covered Software,
+// or under the terms of any subsequent version published by the license
+// steward.
+//
+// 10.3. Modified Versions
+//
+// If you create software not governed by this License, and you want to
+// create a new license for such software, you may create and use a
+// modified version of this License if you rename the license and remove
+// any references to the name of the license steward (except to note that
+// such modified license differs from this License).
+//
+// 10.4. Distributing Source Code Form that is Incompatible With Secondary
+// Licenses
+//
+// If You choose to distribute Source Code Form that is Incompatible With
+// Secondary Licenses under the terms of this version of the License, the
+// notice described in Exhibit B of this License must be attached.
+//
+// Exhibit A - Source Code Form License Notice
+// -------------------------------------------
+//
+//	This Source Code Form is subject to the terms of the Mozilla Public
+//	License, v. 2.0. If a copy of the MPL was not distributed with this
+//	file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+// If it is not possible or desirable to put the notice in a particular
+// file, then You may include the notice in a location (such as a LICENSE
+// file in a relevant directory) where a recipient would be likely to look
+// for such a notice.
+//
+// You may add additional accurate notices of copyright ownership.
+//
+// Exhibit B - "Incompatible With Secondary Licenses" Notice
+// ---------------------------------------------------------
+//
+//	This Source Code Form is "Incompatible With Secondary Licenses", as
+//	defined by the Mozilla Public License, v. 2.0.
+//
+// From:
+// https://gitlab.torproject.org/tpo/onion-services/sauteed-onions/monitor/-/blob/main/follow-go/main.go#L115-124
+// https://gitlab.torproject.org/tpo/onion-services/sauteed-onions/monitor/-/blob/main/follow-go/x509.go
+// https://github.com/SSLMate/certspotter/blob/54f34077d3bebe8aafce07dcfbffeb928c6e1d04/x509.go#L380
+
+func SANsFromLeafEntries(startIndex int64, leafEntries []ct.LeafEntry) (sans []string, errs []error) {
+	for offset, leafEntry := range leafEntries {
+		leafIndex := startIndex + int64(offset)
+		e, err := ct.LogEntryFromLeaf(leafIndex, &leafEntry)
+		if err != nil {
+			errs = append(errs, fmt.Errorf("leaf at index %d: %v", leafIndex, err))
+			continue
+		}
+		s, err := sansFromLogEntry(e)
+		if err != nil {
+			errs = append(errs, fmt.Errorf("leaf at index %d: %v", leafIndex, err))
+		}
+		sans = append(sans, s...)
+	}
+	return
+}
+
+func sansFromLogEntry(entry *ct.LogEntry) ([]string, error) {
+	if entry.Precert == nil && entry.X509Cert == nil {
+		return nil, fmt.Errorf("no (pre)cert in log entry")
+	}
+	if entry.Precert != nil && entry.X509Cert != nil {
+		return nil, fmt.Errorf("both precert and cert in log entry")
+	}
+
+	var exts []pkix.Extension
+	if entry.Precert != nil {
+		exts = entry.Precert.TBSCertificate.Extensions
+	}
+	if entry.X509Cert != nil {
+		exts = entry.X509Cert.Extensions
+	}
+
+	var sans []string
+	for _, ext := range exts {
+		if ext.Id.Equal(asn1.ObjectIdentifier{2, 5, 29, 17}) {
+			moreSANs, err := extract(ext)
+			if err != nil {
+				return nil, fmt.Errorf("parse: %v", err)
+			}
+
+			sans = append(sans, moreSANs...)
+		}
+	}
+	return sans, nil
+}
+
+func extract(extSAN pkix.Extension) ([]string, error) {
+	var seq asn1.RawValue
+	rest, err := asn1.Unmarshal(extSAN.Value, &seq)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse subjectAltName extension: %v", err)
+	}
+	if len(rest) != 0 {
+		// Don't complain if the SAN is followed by exactly one zero byte, which is a common error.
+		if !(len(rest) == 1 && rest[0] == 0) {
+			return nil, fmt.Errorf("trailing data in subjectAltName extension: %v", rest)
+		}
+	}
+	if !seq.IsCompound || seq.Tag != 16 || seq.Class != 0 {
+		return nil, fmt.Errorf("failed to parse subjectAltName extension: bad SAN sequence")
+	}
+
+	sans := []string{}
+	buf := seq.Bytes
+	for len(buf) > 0 {
+		var val asn1.RawValue
+		var err error
+		buf, err = asn1.Unmarshal(buf, &val)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse subjectAltName extension item: %v", err)
+		}
+
+		sans = append(sans, string(val.Bytes))
+	}
+	return sans, nil
+}