Equinox/p2/Proposals/StoringChecksums

p2 is able to check integrity of downloaded artifacts using MD5 algorithm only. bug 423715 is going to add support for SHA-256 algorithm but the way artifact's MD5 checksum stored in artifact metadata is not ready for such minor extension (Gerrit change #59612 shows how adding SHA-256 support looks like using the same approach as MD5).

In a long run, however, this solution is not future-proof.

Separate property for every checksum type (artifact + download) and supported algorithm

Proposed implementation: Change #59612

Follows current scheme and stores SHA-256 checksums in the two new properties, artifact.sha256 and download.sha256:

 <artifact classifier='osgi.bundle' id='org.eclipse.osgi' version='3.4.3.R34x_v20081215-1030'>
   <properties>
     <property name='artifact.md5' value='58057045158895009b845b9a93f3eb6e'/>
     <property name='artifact.sha256' value='58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e'/>
     <property name='download.md5' value='58057045158895009b845b9a93f3eb6e'/>
     <property name='download.sha256' value='58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e'/>
   </properties>
 </artifact>

Problems:

• New fields should be added to org.eclipse.equinox.p2.repository.artifact.IArtifactDescriptor. Deprecating such algorithm in the future and removing these properties is an API breaking change.

Separate property for artifact and download checksums

Proposed implementation: Change #69560

Two new properties, artifact.checksums and download.checksums, store a semi-colon separated list of checksums. Each checksum is a key-value pair algotrithm,checksum separated with =:

 <artifact classifier='osgi.bundle' id='org.eclipse.osgi' version='3.4.3.R34x_v20081215-1030'>
   <properties>
     <property name='artifact.checksums' value='md5=58057045158895009b845b9a93f3eb6e;sha256=58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e'/>
     <property name='download.checksums' value='md5=58057045158895009b845b9a93f3eb6e;sha256=58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e'/>
   </properties>
 </artifact>

• Adding/removing algorithms requires no changes to the API.
• Adding implementation for the new algorithm still require code changes:
  • extend org.eclipse.equinox.internal.p2.artifact.processors.checksum.ChecksumVerifier (see MD5Verifier and SHA256Verifier)
  • register new implementation in org.eclipse.equinox.internal.p2.artifact.processors.checksum.ChecksumUtilities
• org.eclipse.equinox.internal.p2.artifact.processors.checksum.ChecksumVerifier uses java.security.MessageDigest thus limiting number of supported algorithms to MD5 and SHA-256 only.

XML

Option #1

 <artifact classifier='osgi.bundle' id='org.eclipse.osgi' version='3.4.3.R34x_v20081215-1030'>
   <checksums>
     <checksum>
       <property name='algorithm' value='md5'/>
       <property name='artifact' value='58057045158895009b845b9a93f3eb6e'/>
       <property name='download' value='58057045158895009b845b9a93f3eb6e'/>
     </checksum>
     <checksum>
       <property name='algorithm' value='sha256'/>
       <property name='artifact' value='58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e'/>
       <property name='download' value='58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e'/>
     </checksum>
   </checksums>
 </artifact>

Option #2

 <artifact classifier='osgi.bundle' id='org.eclipse.osgi' version='3.4.3.R34x_v20081215-1030'>
   <checksums>
     <checksum
       algorithm="md5"
       download="58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e"
       artifact="58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e"/>
     <checksum
       algorithm="sha256"
       download="58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e"
       artifact="58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e"/>
   </checksums>
 </artifact>

Option #3

 <artifact classifier='osgi.bundle' id='org.eclipse.osgi' version='3.4.3.R34x_v20081215-1030'>
   <checksums>
     <checksum>
       <algorithm>md5</algorithm>
       <download>58057045158895009b845b9a93f3eb6e</download>
       <artifact>58057045158895009b845b9a93f3eb6e</artifact>
     </checksum>
     <checksum>
       <algorithm>sha256</algorithm>
       <download>58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e</download>
       <artifact>58057045158895009b845b9a93f3eb6e58057045158895009b845b9a93f3eb6e</artifact>
     </checksum>
   </checksums>
 </artifact>