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encoding/asn1: allow lengths up to the maximum int value.

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Previously we capped lengths at 2**24 rather than 2**31.

R=golang-dev, r, r
CC=golang-dev
https://golang.org/cl/6050050
This commit is contained in:
Adam Langley 2012-04-18 13:41:11 -04:00
parent b65c9a633e
commit 6742d0a085
2 changed files with 17 additions and 5 deletions
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16
src/pkg/encoding/asn1/asn1.go
View File

@ -377,11 +377,6 @@ func parseTagAndLength(bytes []byte, initOffset int) (ret tagAndLength, offset i
} else {
// Bottom 7 bits give the number of length bytes to follow.
numBytes := int(b & 0x7f)
// We risk overflowing a signed 32-bit number if we accept more than 3 bytes.
if numBytes > 3 {
err = StructuralError{"length too large"}
return
}
if numBytes == 0 {
err = SyntaxError{"indefinite length found (not DER)"}
return
@ -394,8 +389,19 @@ func parseTagAndLength(bytes []byte, initOffset int) (ret tagAndLength, offset i
}
b = bytes[offset]
offset++
if ret.length >= 1<<23 {
// We can't shift ret.length up without
// overflowing.
err = StructuralError{"length too large"}
return
}
ret.length <<= 8
ret.length |= int(b)
if ret.length == 0 {
// DER requires that lengths be minimal.
err = StructuralError{"superfluous leading zeros in length"}
return
}
}
}

6
src/pkg/encoding/asn1/asn1_test.go
View File

@ -283,6 +283,12 @@ var tagAndLengthData = []tagAndLengthTest{
{[]byte{0x00, 0x83, 0x01, 0x00}, false, tagAndLength{}},
{[]byte{0x1f, 0x85}, false, tagAndLength{}},
{[]byte{0x30, 0x80}, false, tagAndLength{}},
// Superfluous zeros in the length should be an error.
{[]byte{0xa0, 0x82, 0x00, 0x01}, false, tagAndLength{}},
// Lengths up to the maximum size of an int should work.
{[]byte{0xa0, 0x84, 0x7f, 0xff, 0xff, 0xff}, true, tagAndLength{2, 0, 0x7fffffff, true}},
// Lengths that would overflow an int should be rejected.
{[]byte{0xa0, 0x84, 0x80, 0x00, 0x00, 0x00}, false, tagAndLength{}},
}
func TestParseTagAndLength(t *testing.T) {