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from fontTools.misc.textTools import bytesjoin, strjoin, tobytes, tostr, safeEval
from fontTools.misc import sstruct
from . import DefaultTable
import base64
DSIG_HeaderFormat = """
> # big endian
ulVersion: L
usNumSigs: H
usFlag: H
"""
# followed by an array of usNumSigs DSIG_Signature records
DSIG_SignatureFormat = """
> # big endian
ulFormat: L
ulLength: L # length includes DSIG_SignatureBlock header
ulOffset: L
"""
# followed by an array of usNumSigs DSIG_SignatureBlock records,
# each followed immediately by the pkcs7 bytes
DSIG_SignatureBlockFormat = """
> # big endian
usReserved1: H
usReserved2: H
cbSignature: l # length of following raw pkcs7 data
"""
#
# NOTE
# the DSIG table format allows for SignatureBlocks residing
# anywhere in the table and possibly in a different order as
# listed in the array after the first table header
#
# this implementation does not keep track of any gaps and/or data
# before or after the actual signature blocks while decompiling,
# and puts them in the same physical order as listed in the header
# on compilation with no padding whatsoever.
#
class table_D_S_I_G_(DefaultTable.DefaultTable):
def decompile(self, data, ttFont):
dummy, newData = sstruct.unpack2(DSIG_HeaderFormat, data, self)
assert self.ulVersion == 1, "DSIG ulVersion must be 1"
assert self.usFlag & ~1 == 0, "DSIG usFlag must be 0x1 or 0x0"
self.signatureRecords = sigrecs = []
for n in range(self.usNumSigs):
sigrec, newData = sstruct.unpack2(
DSIG_SignatureFormat, newData, SignatureRecord()
)
assert sigrec.ulFormat == 1, (
"DSIG signature record #%d ulFormat must be 1" % n
)
sigrecs.append(sigrec)
for sigrec in sigrecs:
dummy, newData = sstruct.unpack2(
DSIG_SignatureBlockFormat, data[sigrec.ulOffset :], sigrec
)
assert sigrec.usReserved1 == 0, (
"DSIG signature record #%d usReserverd1 must be 0" % n
)
assert sigrec.usReserved2 == 0, (
"DSIG signature record #%d usReserverd2 must be 0" % n
)
sigrec.pkcs7 = newData[: sigrec.cbSignature]
def compile(self, ttFont):
packed = sstruct.pack(DSIG_HeaderFormat, self)
headers = [packed]
offset = len(packed) + self.usNumSigs * sstruct.calcsize(DSIG_SignatureFormat)
data = []
for sigrec in self.signatureRecords:
# first pack signature block
sigrec.cbSignature = len(sigrec.pkcs7)
packed = sstruct.pack(DSIG_SignatureBlockFormat, sigrec) + sigrec.pkcs7
data.append(packed)
# update redundant length field
sigrec.ulLength = len(packed)
# update running table offset
sigrec.ulOffset = offset
headers.append(sstruct.pack(DSIG_SignatureFormat, sigrec))
offset += sigrec.ulLength
if offset % 2:
# Pad to even bytes
data.append(b"\0")
return bytesjoin(headers + data)
def toXML(self, xmlWriter, ttFont):
xmlWriter.comment(
"note that the Digital Signature will be invalid after recompilation!"
)
xmlWriter.newline()
xmlWriter.simpletag(
"tableHeader",
version=self.ulVersion,
numSigs=self.usNumSigs,
flag="0x%X" % self.usFlag,
)
for sigrec in self.signatureRecords:
xmlWriter.newline()
sigrec.toXML(xmlWriter, ttFont)
xmlWriter.newline()
def fromXML(self, name, attrs, content, ttFont):
if name == "tableHeader":
self.signatureRecords = []
self.ulVersion = safeEval(attrs["version"])
self.usNumSigs = safeEval(attrs["numSigs"])
self.usFlag = safeEval(attrs["flag"])
return
if name == "SignatureRecord":
sigrec = SignatureRecord()
sigrec.fromXML(name, attrs, content, ttFont)
self.signatureRecords.append(sigrec)
pem_spam = lambda l, spam={
"-----BEGIN PKCS7-----": True,
"-----END PKCS7-----": True,
"": True,
}: not spam.get(l.strip())
def b64encode(b):
s = base64.b64encode(b)
# Line-break at 76 chars.
items = []
while s:
items.append(tostr(s[:76]))
items.append("\n")
s = s[76:]
return strjoin(items)
class SignatureRecord(object):
def __repr__(self):
return "<%s: %s>" % (self.__class__.__name__, self.__dict__)
def toXML(self, writer, ttFont):
writer.begintag(self.__class__.__name__, format=self.ulFormat)
writer.newline()
writer.write_noindent("-----BEGIN PKCS7-----\n")
writer.write_noindent(b64encode(self.pkcs7))
writer.write_noindent("-----END PKCS7-----\n")
writer.endtag(self.__class__.__name__)
def fromXML(self, name, attrs, content, ttFont):
self.ulFormat = safeEval(attrs["format"])
self.usReserved1 = safeEval(attrs.get("reserved1", "0"))
self.usReserved2 = safeEval(attrs.get("reserved2", "0"))
self.pkcs7 = base64.b64decode(tobytes(strjoin(filter(pem_spam, content))))
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