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Relax the check on the length of the PKCS#7 cert as it appears that the PE
file wrapper size gets rounded up to the nearest 8.
The debugging output looks like this:
PEFILE: ==> verify_pefile_signature()
PEFILE: ==> pefile_parse_binary()
PEFILE: checksum @ 110
PEFILE: header size = 200
PEFILE: cert = 968 @547be0 [68 09 00 00 00 02 02 00 30 82 09 56 ]
PEFILE: sig wrapper = { 968, 200, 2 }
PEFILE: Signature data not PKCS#7
The wrapper is the first 8 bytes of the hex dump inside []. This indicates a
length of 0x968 bytes, including the wrapper header - so 0x960 bytes of
payload.
The ASN.1 wrapper begins [ ... 30 82 09 56 ]. That indicates an object of size
0x956 - a four byte discrepency, presumably just padding for alignment
purposes.
So we just check that the ASN.1 container is no bigger than the payload and
reduce the recorded size appropriately.
Whilst we're at it, allow shorter PKCS#7 objects that manage to squeeze within
127 or 255 bytes. It's just about conceivable if no X.509 certs are included
in the PKCS#7 message.
Reported-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Peter Jones <pjones@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
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Validate the PKCS#7 trust chain against the contents of the system keyring.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
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Digest the signed parts of the PE binary, canonicalising the section table
before we need it, and then compare the the resulting digest to the one in the
PKCS#7 signed content.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
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The PKCS#7 certificate should contain a "Microsoft individual code signing"
data blob as its signed content. This blob contains a digest of the signed
content of the PE binary and the OID of the digest algorithm used (typically
SHA256).
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
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Parse the content of the certificate blob, presuming it to be PKCS#7 format.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
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The certificate data block in a PE binary has a wrapper around the PKCS#7
signature we actually want to get at. Strip this off and check that we've got
something that appears to be a PKCS#7 signature.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
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Parse a PE binary to find a key and a signature contained therein. Later
patches will check the signature and add the key if the signature checks out.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
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