On Tue, 10 May 2022 at 15:07, Łukasz Piątkowski <pion...@gmail.com> wrote: > > What I'm trying to do is to sign a mainline kernel built by ubuntu > (https://kernel.ubuntu.com/~kernel-ppa/mainline/) with my private key, that > is already enrolled to MOK, and boot it with Secure Boot. > > > the MOK key as generated by Ubuntu/Debian tooling, creates a signing > > certificate that self-limits itself to only support Kernel Module signing. > > OK, that explains why the key in `/var/lib/shim-signed/mok` doesn't work. > Still, I have created my own key as well (listed below for inspection, it has > code signing extension), enrolled that key in MOK and signed the ubuntu > mainline kernel (the kernel I'm trying to boot) with it. The result is > exactly the same. I was using exactly the same procedure a few ubuntu > editions back and it was definitely working. From what I learned so far, this > might be related to the BootHole bug > (https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-10713) that was > fixed some time ago. > > My generated key is: > > root@T495:~/mok# openssl x509 -in MOK.pem -text -noout > Certificate: > Data: > Version: 3 (0x2) > Serial Number: > 42:61:86:b2:29:3d:ca:eb:98:87:ae:3d:74:95:c7:f2:63:8f:8a:3b > Signature Algorithm: sha256WithRSAEncryption > Issuer: C = PL, ST = Poznan, L = Poznan, O = none, CN = Secure Boot > Signing, emailAddress = exam...@example.com > Validity > Not Before: Feb 18 19:28:16 2020 GMT > Not After : Jan 25 19:28:16 2120 GMT > Subject: C = PL, ST = Poznan, L = Poznan, O = none, CN = Secure Boot > Signing, emailAddress = exam...@example.com > Subject Public Key Info: > Public Key Algorithm: rsaEncryption > Public-Key: (2048 bit) > Modulus: [cut] > Exponent: 65537 (0x10001) > X509v3 extensions: > X509v3 Subject Key Identifier: > EC:57:4E:BD:DC:1A:CF:B4:55:16:4A:CE:CB:E4:9E:44:5C:C4:63:F6 > X509v3 Authority Key Identifier: > EC:57:4E:BD:DC:1A:CF:B4:55:16:4A:CE:CB:E4:9E:44:5C:C4:63:F6 > X509v3 Basic Constraints: critical > CA:FALSE > X509v3 Extended Key Usage: > Code Signing, 1.3.6.1.4.1.311.10.3.6, 1.3.6.1.4.1.2312.16.1.2
This is bad... certs that have 1.3.6.1.4.1.2312.16.1.2 cannot be used to sign kernels. Your cert must _not_ have 1.3.6.1.4.1.2312.16.1.2 EKU set on it. You cannot use the same certificate to sign both kernel and modules. > Netscape Comment: > OpenSSL Generated Certificate > Signature Algorithm: sha256WithRSAEncryption > Signature Value: [cut] > > On Tue, May 10, 2022 at 3:26 PM Dimitri John Ledkov > <dimitri.led...@canonical.com> wrote: >> >> the MOK key as generated by Ubuntu/Debian tooling, creates a signing >> certificate that self-limits itself to only support Kernel Module >> signing. >> Signatures made by such certificate, are not trusted by shim for the >> purpose of code signing of bootloaders (i.e. grub) or kernels (i.e. >> linux). >> I also responded this on stackoverflow. >> >> The automatically generated MOK key is only usable to sign kernel >> modules, i.e. self-built DKMS modules. >> >> -- >> okurrr, >> >> Dimitri >> >> On Tue, 10 May 2022 at 11:33, Łukasz Piątkowski <pion...@gmail.com> wrote: >> > >> > Hi everyone - I'm new here! >> > >> > Sorry for going with my problem directly to the grub-devel maling list, >> > but I'm pretty sure my problem is GRUB related. Still, I've spent some >> > hours trying to find a solution on the Internet and I failed :( So, here >> > it comes - if anyone has time to explain my problem to a layman, it would >> > be awesome. Even better, if you can maybe answer here on stackoverflow, >> > where it can be easier to find, I believe >> > (https://unix.stackexchange.com/questions/701612/cant-load-self-signed-kernel-with-secure-boot-on-bad-shim-signature). >> > >> > I'm running ubuntu with Secure Boot on. Everything works fine when I use a >> > kernel that comes packaged from cannonical. Still, I have issues running a >> > self-signed kernel (this is actually an externally built kernel, that I >> > have verified and want to use for my own machine). I'm pretty sure my >> > signature with MOK key is OK (verification below), but still when I try to >> > boot the kernel from grub, after selecting the correct entry, I get an >> > error that reads "Loading ... error: bad shim signature." I'm wrapping my >> > head around it and can't find a solution. Why, even though both kernels >> > are signed with MOK keys, one of them works and the other doesn't? >> > >> > Here's info about kernel signatures: >> > >> > root@T495:~# sbsign --key /var/lib/shim-signed/mok/MOK.priv --cert >> > /var/lib/shim-signed/mok/MOK.pem /boot/vmlinuz >> > Image was already signed; adding additional signature >> > >> > root@T495:~# sbverify --list /boot/vmlinuz >> > signature 1 >> > image signature issuers: >> > - /C=PL/ST=Poznan/L=Poznan/O=none/CN=Secure Boot >> > Signing/emailAddress=exam...@example.com >> > image signature certificates: >> > - subject: /C=PL/ST=yes/L=yes/O=none/CN=Secure Boot >> > Signing/emailAddress=exam...@example.com >> > issuer: /C=PL/ST=yes/L=yes/O=none/CN=Secure Boot >> > Signing/emailAddress=exam...@example.com >> > signature 2 >> > image signature issuers: >> > - /CN=ubuntu Secure Boot Module Signature key >> > image signature certificates: >> > - subject: /CN=ubuntu Secure Boot Module Signature key >> > issuer: /CN=ubuntu Secure Boot Module Signature key >> > >> > >> > And here about MOK keys: >> > >> > root@T495:~# openssl x509 -in /var/lib/shim-signed/mok/MOK.pem >> > -fingerprint -noout >> > SHA1 >> > Fingerprint=81:A2:93:CB:06:6F:52:BA:D9:E2:39:68:9D:FA:E2:2B:0C:95:3C:F7 >> > root@T495:~# mokutil --list-enrolled | grep "81:a2:93" >> > SHA1 Fingerprint: >> > 81:a2:93:cb:06:6f:52:ba:d9:e2:39:68:9d:fa:e2:2b:0c:95:3c:f7 >> > >> > If there are any docs that help understand that, I'm happy to be >> > redirected there :) >> > >> > piontec >> > _______________________________________________ >> > Grub-devel mailing list >> > Grub-devel@gnu.org >> > https://lists.gnu.org/mailman/listinfo/grub-devel >> >> _______________________________________________ >> Grub-devel mailing list >> Grub-devel@gnu.org >> https://lists.gnu.org/mailman/listinfo/grub-devel > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > https://lists.gnu.org/mailman/listinfo/grub-devel _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
