| Message ID | 20201020065001.13836-3-jlee@suse.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Check codeSigning extended key usage extension | expand |
On Tue, Oct 20, 2020 at 14:50:01 +0800, Lee, Chun-Yi wrote: > +config CHECK_CODESIGN_EKU > + bool "Check codeSigning extended key usage" > + depends on PKCS7_MESSAGE_PARSER=y > + depends on SYSTEM_DATA_VERIFICATION > + help > + This option provides support for checking the codeSigning extended > + key usage extension when verifying the signature in PKCS#7. It > + affects kernel module verification and kexec PE binary verification > + now. Is the "now" necessary? Isn't it implied by the option's existence? --Ben
On 10/20/20 6:42 AM, Ben Boeckel wrote: > On Tue, Oct 20, 2020 at 14:50:01 +0800, Lee, Chun-Yi wrote: >> +config CHECK_CODESIGN_EKU >> + bool "Check codeSigning extended key usage" >> + depends on PKCS7_MESSAGE_PARSER=y >> + depends on SYSTEM_DATA_VERIFICATION >> + help >> + This option provides support for checking the codeSigning extended >> + key usage extension when verifying the signature in PKCS#7. It extended ... extension. Can we drop one of those or reword it? >> + affects kernel module verification and kexec PE binary verification >> + now. > > Is the "now" necessary? Isn't it implied by the option's existence?
Hi Ben, On Tue, Oct 20, 2020 at 09:42:08AM -0400, Ben Boeckel wrote: > On Tue, Oct 20, 2020 at 14:50:01 +0800, Lee, Chun-Yi wrote: > > +config CHECK_CODESIGN_EKU > > + bool "Check codeSigning extended key usage" > > + depends on PKCS7_MESSAGE_PARSER=y > > + depends on SYSTEM_DATA_VERIFICATION > > + help > > + This option provides support for checking the codeSigning extended > > + key usage extension when verifying the signature in PKCS#7. It > > + affects kernel module verification and kexec PE binary verification > > + now. > > Is the "now" necessary? Isn't it implied by the option's existence? Thanks for your review. I will remove the "now" in next version. Joey Lee
Hi Randy, On Tue, Oct 20, 2020 at 07:56:29AM -0700, Randy Dunlap wrote: > On 10/20/20 6:42 AM, Ben Boeckel wrote: > > On Tue, Oct 20, 2020 at 14:50:01 +0800, Lee, Chun-Yi wrote: > >> +config CHECK_CODESIGN_EKU > >> + bool "Check codeSigning extended key usage" > >> + depends on PKCS7_MESSAGE_PARSER=y > >> + depends on SYSTEM_DATA_VERIFICATION > >> + help > >> + This option provides support for checking the codeSigning extended > >> + key usage extension when verifying the signature in PKCS#7. It > > extended ... extension. > Can we drop one of those or reword it? I will remove the _extension_ word in next version. Thanks for your review! Joey Lee
diff --git a/certs/system_keyring.c b/certs/system_keyring.c index 798291177186..4104f5465d8a 100644 --- a/certs/system_keyring.c +++ b/certs/system_keyring.c @@ -242,7 +242,7 @@ int verify_pkcs7_message_sig(const void *data, size_t len, goto error; } } - ret = pkcs7_validate_trust(pkcs7, trusted_keys); + ret = pkcs7_validate_trust(pkcs7, trusted_keys, usage); if (ret < 0) { if (ret == -ENOKEY) pr_devel("PKCS#7 signature not signed with a trusted key\n"); diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig index 1f1f004dc757..6e3de0c3b5f0 100644 --- a/crypto/asymmetric_keys/Kconfig +++ b/crypto/asymmetric_keys/Kconfig @@ -96,4 +96,14 @@ config SIGNED_PE_FILE_VERIFICATION This option provides support for verifying the signature(s) on a signed PE binary. +config CHECK_CODESIGN_EKU + bool "Check codeSigning extended key usage" + depends on PKCS7_MESSAGE_PARSER=y + depends on SYSTEM_DATA_VERIFICATION + help + This option provides support for checking the codeSigning extended + key usage extension when verifying the signature in PKCS#7. It + affects kernel module verification and kexec PE binary verification + now. + endif # ASYMMETRIC_KEY_TYPE diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c index 61af3c4d82cc..1d2318ff63db 100644 --- a/crypto/asymmetric_keys/pkcs7_trust.c +++ b/crypto/asymmetric_keys/pkcs7_trust.c @@ -16,12 +16,36 @@ #include <crypto/public_key.h> #include "pkcs7_parser.h" +#ifdef CONFIG_CHECK_CODESIGN_EKU +static bool check_codesign_eku(struct key *key, + enum key_being_used_for usage) +{ + struct public_key *public_key = key->payload.data[asym_crypto]; + + switch (usage) { + case VERIFYING_MODULE_SIGNATURE: + case VERIFYING_KEXEC_PE_SIGNATURE: + return !!(public_key->eku & EKU_codeSigning); + default: + break; + } + return true; +} +#else +static bool check_codesign_eku(struct key *key, + enum key_being_used_for usage) +{ + return true; +} +#endif + /** * Check the trust on one PKCS#7 SignedInfo block. */ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7, struct pkcs7_signed_info *sinfo, - struct key *trust_keyring) + struct key *trust_keyring, + enum key_being_used_for usage) { struct public_key_signature *sig = sinfo->sig; struct x509_certificate *x509, *last = NULL, *p; @@ -112,6 +136,12 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7, return -ENOKEY; matched: + if (!check_codesign_eku(key, usage)) { + pr_warn("sinfo %u: The signer %x key is not CodeSigning\n", + sinfo->index, key_serial(key)); + key_put(key); + return -ENOKEY; + } ret = verify_signature(key, sig); key_put(key); if (ret < 0) { @@ -156,7 +186,8 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7, * May also return -ENOMEM. */ int pkcs7_validate_trust(struct pkcs7_message *pkcs7, - struct key *trust_keyring) + struct key *trust_keyring, + enum key_being_used_for usage) { struct pkcs7_signed_info *sinfo; struct x509_certificate *p; @@ -167,7 +198,7 @@ int pkcs7_validate_trust(struct pkcs7_message *pkcs7, p->seen = false; for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) { - ret = pkcs7_validate_trust_one(pkcs7, sinfo, trust_keyring); + ret = pkcs7_validate_trust_one(pkcs7, sinfo, trust_keyring, usage); switch (ret) { case -ENOKEY: continue; diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h index 38ec7f5f9041..b3b48240ba73 100644 --- a/include/crypto/pkcs7.h +++ b/include/crypto/pkcs7.h @@ -30,7 +30,8 @@ extern int pkcs7_get_content_data(const struct pkcs7_message *pkcs7, * pkcs7_trust.c */ extern int pkcs7_validate_trust(struct pkcs7_message *pkcs7, - struct key *trust_keyring); + struct key *trust_keyring, + enum key_being_used_for usage); /* * pkcs7_verify.c
This patch adds the logic for checking the CodeSigning extended key usage extenstion when verifying signature of kernel module or kexec PE binary in PKCS#7. Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> --- certs/system_keyring.c | 2 +- crypto/asymmetric_keys/Kconfig | 10 ++++++++++ crypto/asymmetric_keys/pkcs7_trust.c | 37 +++++++++++++++++++++++++++++++++--- include/crypto/pkcs7.h | 3 ++- 4 files changed, 47 insertions(+), 5 deletions(-)