Visual FoxPro

Validate a .pkpass Archive

See more Digital Signatures Examples

Opens a .pkpass archive (which is just a .zip renamed to .pkpass) and validates the contents. The hashes in the manifest are compared with the computed hash values for each individual file. If all computed hash values match, then the signature is verified. Visual FoxPro

LOCAL lnSuccess
LOCAL loCrypt
LOCAL loZip
LOCAL loEnt
LOCAL loBdManifest
LOCAL loJson
LOCAL lnSomeHashesFailed
LOCAL lcFilename
LOCAL loSbHashHex
LOCAL loBdFileData
LOCAL lnNumMembers
LOCAL i
LOCAL lcComputedHashHex
LOCAL loBdSignature
LOCAL lnVerified

lnSuccess = 0

* This example assumes the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

loCrypt = CreateObject('Chilkat.Crypt2')
loZip = CreateObject('Chilkat.Zip')

lnSuccess = loZip.OpenZip("qa_data/pkpass/invalid.pkpass")
IF (lnSuccess = 0) THEN
    ? loZip.LastErrorText
    RELEASE loCrypt
    RELEASE loZip
    CANCEL
ENDIF

* Get the contents of the manifest.json file, which contains something like this:

* {
*   "icon.png" : "0296b01347b3173e98438a003b0e88986340b2d8",
*   "logo.png" : "25de09e2d3b01ce1fe00c2ca9a90a2be1aaa05cf",
*   "icon@2x.png" : "5afd9585b08c65fdf105a90c8bd643407cba2787",
*   "pass.json" : "145ea5a5db784fff485126c77ecf7a1fc2a88ee7",
*   "strip@2x.png" : "468fa7bc93e6b55342b56fda09bdce7c829d7d46",
*   "strip.png" : "736d01f84cb73d06e8a9932e43076d68f19461ff"
* }

loEnt = CreateObject('Chilkat.ZipEntry')
lnSuccess = loZip.EntryOf("manifest.json",loEnt)
IF (lnSuccess = 0) THEN
    ? loZip.LastErrorText
    RELEASE loCrypt
    RELEASE loZip
    RELEASE loEnt
    CANCEL
ENDIF

* Get the exact content of the manifest.json for later signature verification.
loBdManifest = CreateObject('Chilkat.BinData')
lnSuccess = loEnt.UnzipToBd(loBdManifest)

loJson = CreateObject('Chilkat.JsonObject')
loJson.EmitCompact = 0
loJson.Load(loEnt.UnzipToString(0,"utf-8"))
? loJson.Emit()

* For each file in the JSON, get the filename and hex hash value.
loCrypt.EncodingMode = "hexlower"
loCrypt.HashAlgorithm = "sha1"

lnSomeHashesFailed = 0

loSbHashHex = CreateObject('Chilkat.StringBuilder')
loBdFileData = CreateObject('Chilkat.BinData')
lnNumMembers = loJson.Size
i = 0
DO WHILE i < lnNumMembers
    lcFilename = loJson.NameAt(i)
    loSbHashHex.Clear()
    loSbHashHex.Append(loJson.StringAt(i))

    lnSuccess = loZip.EntryOf(lcFilename,loEnt)
    IF (lnSuccess = 0) THEN
        ? loZip.LastErrorText
        RELEASE loCrypt
        RELEASE loZip
        RELEASE loEnt
        RELEASE loBdManifest
        RELEASE loJson
        RELEASE loSbHashHex
        RELEASE loBdFileData
        CANCEL
    ENDIF

    * Get the data for this file.
    loBdFileData.Clear()
    lnSuccess = loEnt.UnzipToBd(loBdFileData)

    lcComputedHashHex = loCrypt.HashBdENC(loBdFileData)
    IF (loSbHashHex.ContentsEqual(lcComputedHashHex,0) = 0) THEN
        ? "Computed hash does not match stored hash for " + lcFilename
        ? "  computed: " + lcComputedHashHex
        ? "  stored:   " + loSbHashHex.GetAsString()
        lnSomeHashesFailed = 1
    ELSE
        ? "hash verified for " + lcFilename + "(" + lcComputedHashHex + ")"
    ENDIF

    i = i + 1
ENDDO

IF (lnSomeHashesFailed = 1) THEN
    ? "Some hashes failed."
    RELEASE loCrypt
    RELEASE loZip
    RELEASE loEnt
    RELEASE loBdManifest
    RELEASE loJson
    RELEASE loSbHashHex
    RELEASE loBdFileData
    CANCEL
ENDIF

* Let's verify the signature..
* First get the signature.
lnSuccess = loZip.EntryOf("signature",loEnt)
IF (lnSuccess = 0) THEN
    ? loZip.LastErrorText
    RELEASE loCrypt
    RELEASE loZip
    RELEASE loEnt
    RELEASE loBdManifest
    RELEASE loJson
    RELEASE loSbHashHex
    RELEASE loBdFileData
    CANCEL
ENDIF

loBdSignature = CreateObject('Chilkat.BinData')
lnSuccess = loEnt.UnzipToBd(loBdSignature)

* Show the contents of the signature in base64 encoding.
? "Signature:"
? loBdSignature.GetEncoded("base64_mime")
? "----"

* Verify the signature against the manifest.json
loCrypt.EncodingMode = "base64"
lnVerified = loCrypt.VerifyBdENC(loBdManifest,loBdSignature.GetEncoded("base64"))
IF (lnVerified = 0) THEN
    ? loCrypt.LastErrorText
ENDIF

? "signature verified = " + STR(lnVerified)

RELEASE loCrypt
RELEASE loZip
RELEASE loEnt
RELEASE loBdManifest
RELEASE loJson
RELEASE loSbHashHex
RELEASE loBdFileData
RELEASE loBdSignature