| Message ID | 20210524021540.18736-3-jlee@suse.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Check codeSigning extended key usage extension | expand |
Hi Joey, On 5/24/21 4:15 AM, Lee, Chun-Yi wrote: > This patch adds the logic for checking the CodeSigning extended > key usage when verifying signature of kernel module or > kexec PE binary in PKCS#7. > > Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> > --- > certs/blacklist.c | 6 +++-- > certs/system_keyring.c | 4 ++-- > crypto/asymmetric_keys/Kconfig | 9 ++++++++ > crypto/asymmetric_keys/pkcs7_trust.c | 43 +++++++++++++++++++++++++++++++++--- > include/crypto/pkcs7.h | 4 +++- > include/keys/system_keyring.h | 7 ++++-- > 6 files changed, 63 insertions(+), 10 deletions(-) > > diff --git a/certs/blacklist.c b/certs/blacklist.c > index c9a435b15af4..a4ef26286584 100644 > --- a/certs/blacklist.c > +++ b/certs/blacklist.c > @@ -16,6 +16,7 @@ > #include <linux/seq_file.h> > #include <linux/uidgid.h> > #include <keys/system_keyring.h> > +#include <keys/asymmetric-type.h> > #include "blacklist.h" > #include "common.h" > > @@ -181,11 +182,12 @@ int add_key_to_revocation_list(const char *data, size_t size) > * is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked > * @pkcs7: The PKCS#7 message to check > */ > -int is_key_on_revocation_list(struct pkcs7_message *pkcs7) > +int is_key_on_revocation_list(struct pkcs7_message *pkcs7, > + enum key_being_used_for usage) > { > int ret; > > - ret = pkcs7_validate_trust(pkcs7, blacklist_keyring); > + ret = pkcs7_validate_trust(pkcs7, blacklist_keyring, usage, false); > > if (ret == 0) > return -EKEYREJECTED; > diff --git a/certs/system_keyring.c b/certs/system_keyring.c > index 692365dee2bd..394cf4e0feed 100644 > --- a/certs/system_keyring.c > +++ b/certs/system_keyring.c > @@ -221,13 +221,13 @@ int verify_pkcs7_message_sig(const void *data, size_t len, > goto error; > } > > - ret = is_key_on_revocation_list(pkcs7); > + ret = is_key_on_revocation_list(pkcs7, usage); > if (ret != -ENOKEY) { > pr_devel("PKCS#7 platform key is on revocation list\n"); > goto error; > } > } > - ret = pkcs7_validate_trust(pkcs7, trusted_keys); > + ret = pkcs7_validate_trust(pkcs7, trusted_keys, usage, true); > 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..1754812df989 100644 > --- a/crypto/asymmetric_keys/Kconfig > +++ b/crypto/asymmetric_keys/Kconfig > @@ -96,4 +96,13 @@ 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 when verifying the signature in PKCS#7. It affects kernel > + module verification and kexec PE binary verification. > + > endif # ASYMMETRIC_KEY_TYPE > diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c > index b531df2013c4..c6ebf3e6adfd 100644 > --- a/crypto/asymmetric_keys/pkcs7_trust.c > +++ b/crypto/asymmetric_keys/pkcs7_trust.c > @@ -16,12 +16,40 @@ > #include <crypto/public_key.h> > #include "pkcs7_parser.h" > > +#ifdef CONFIG_CHECK_CODESIGN_EKU > +static bool check_eku_by_usage(struct key *key, enum key_being_used_for usage) Can this check fit into the existing find_asymmetric_key call (or, a new find_asymmetric_key_by_usage call) instead? pkcs7_validate_trust_one needs to match the signature against an EKU_codeSigning key on trust_keyring. Thanks, Varad > +{ > + struct public_key *public_key = key->payload.data[asym_crypto]; > + bool ret = true; > + > + switch (usage) { > + case VERIFYING_MODULE_SIGNATURE: > + case VERIFYING_KEXEC_PE_SIGNATURE: > + ret = !!(public_key->eku & EKU_codeSigning); > + if (!ret) > + pr_warn("The signer '%s' key is not CodeSigning\n", > + key->description); > + break; > + default: > + break; > + } > + return ret; > +} > +#else > +static bool check_eku_by_usage(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, > + bool check_eku) > { > struct public_key_signature *sig = sinfo->sig; > struct x509_certificate *x509, *last = NULL, *p; > @@ -112,6 +140,10 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7, > return -ENOKEY; > > matched: > + if (check_eku && !check_eku_by_usage(key, usage)) { > + key_put(key); > + return -ENOKEY; > + } > ret = verify_signature(key, sig); > key_put(key); > if (ret < 0) { > @@ -135,6 +167,8 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7, > * pkcs7_validate_trust - Validate PKCS#7 trust chain > * @pkcs7: The PKCS#7 certificate to validate > * @trust_keyring: Signing certificates to use as starting points > + * @usage: The use to which the key is being put. > + * @check_eku: Check EKU (Extended Key Usage) > * > * Validate that the certificate chain inside the PKCS#7 message intersects > * keys we already know and trust. > @@ -156,7 +190,9 @@ 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, > + bool check_eku) > { > struct pkcs7_signed_info *sinfo; > struct x509_certificate *p; > @@ -167,7 +203,8 @@ 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, check_eku); > switch (ret) { > case -ENOKEY: > continue; > diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h > index 38ec7f5f9041..5d87b8a02f79 100644 > --- a/include/crypto/pkcs7.h > +++ b/include/crypto/pkcs7.h > @@ -30,7 +30,9 @@ 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, > + bool check_eku); > > /* > * pkcs7_verify.c > diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h > index 6acd3cf13a18..434a9b41d3a5 100644 > --- a/include/keys/system_keyring.h > +++ b/include/keys/system_keyring.h > @@ -9,6 +9,7 @@ > #define _KEYS_SYSTEM_KEYRING_H > > #include <linux/key.h> > +#include <keys/asymmetric-type.h> > > #ifdef CONFIG_SYSTEM_TRUSTED_KEYRING > > @@ -59,13 +60,15 @@ static inline int is_binary_blacklisted(const u8 *hash, size_t hash_len) > > #ifdef CONFIG_SYSTEM_REVOCATION_LIST > extern int add_key_to_revocation_list(const char *data, size_t size); > -extern int is_key_on_revocation_list(struct pkcs7_message *pkcs7); > +extern int is_key_on_revocation_list(struct pkcs7_message *pkcs7, > + enum key_being_used_for usage); > #else > static inline int add_key_to_revocation_list(const char *data, size_t size) > { > return 0; > } > -static inline int is_key_on_revocation_list(struct pkcs7_message *pkcs7) > +static inline int is_key_on_revocation_list(struct pkcs7_message *pkcs7, > + enum key_being_used_for usage) > { > return -ENOKEY; > } >
diff --git a/certs/blacklist.c b/certs/blacklist.c index c9a435b15af4..a4ef26286584 100644 --- a/certs/blacklist.c +++ b/certs/blacklist.c @@ -16,6 +16,7 @@ #include <linux/seq_file.h> #include <linux/uidgid.h> #include <keys/system_keyring.h> +#include <keys/asymmetric-type.h> #include "blacklist.h" #include "common.h" @@ -181,11 +182,12 @@ int add_key_to_revocation_list(const char *data, size_t size) * is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked * @pkcs7: The PKCS#7 message to check */ -int is_key_on_revocation_list(struct pkcs7_message *pkcs7) +int is_key_on_revocation_list(struct pkcs7_message *pkcs7, + enum key_being_used_for usage) { int ret; - ret = pkcs7_validate_trust(pkcs7, blacklist_keyring); + ret = pkcs7_validate_trust(pkcs7, blacklist_keyring, usage, false); if (ret == 0) return -EKEYREJECTED; diff --git a/certs/system_keyring.c b/certs/system_keyring.c index 692365dee2bd..394cf4e0feed 100644 --- a/certs/system_keyring.c +++ b/certs/system_keyring.c @@ -221,13 +221,13 @@ int verify_pkcs7_message_sig(const void *data, size_t len, goto error; } - ret = is_key_on_revocation_list(pkcs7); + ret = is_key_on_revocation_list(pkcs7, usage); if (ret != -ENOKEY) { pr_devel("PKCS#7 platform key is on revocation list\n"); goto error; } } - ret = pkcs7_validate_trust(pkcs7, trusted_keys); + ret = pkcs7_validate_trust(pkcs7, trusted_keys, usage, true); 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..1754812df989 100644 --- a/crypto/asymmetric_keys/Kconfig +++ b/crypto/asymmetric_keys/Kconfig @@ -96,4 +96,13 @@ 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 when verifying the signature in PKCS#7. It affects kernel + module verification and kexec PE binary verification. + endif # ASYMMETRIC_KEY_TYPE diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c index b531df2013c4..c6ebf3e6adfd 100644 --- a/crypto/asymmetric_keys/pkcs7_trust.c +++ b/crypto/asymmetric_keys/pkcs7_trust.c @@ -16,12 +16,40 @@ #include <crypto/public_key.h> #include "pkcs7_parser.h" +#ifdef CONFIG_CHECK_CODESIGN_EKU +static bool check_eku_by_usage(struct key *key, enum key_being_used_for usage) +{ + struct public_key *public_key = key->payload.data[asym_crypto]; + bool ret = true; + + switch (usage) { + case VERIFYING_MODULE_SIGNATURE: + case VERIFYING_KEXEC_PE_SIGNATURE: + ret = !!(public_key->eku & EKU_codeSigning); + if (!ret) + pr_warn("The signer '%s' key is not CodeSigning\n", + key->description); + break; + default: + break; + } + return ret; +} +#else +static bool check_eku_by_usage(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, + bool check_eku) { struct public_key_signature *sig = sinfo->sig; struct x509_certificate *x509, *last = NULL, *p; @@ -112,6 +140,10 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7, return -ENOKEY; matched: + if (check_eku && !check_eku_by_usage(key, usage)) { + key_put(key); + return -ENOKEY; + } ret = verify_signature(key, sig); key_put(key); if (ret < 0) { @@ -135,6 +167,8 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7, * pkcs7_validate_trust - Validate PKCS#7 trust chain * @pkcs7: The PKCS#7 certificate to validate * @trust_keyring: Signing certificates to use as starting points + * @usage: The use to which the key is being put. + * @check_eku: Check EKU (Extended Key Usage) * * Validate that the certificate chain inside the PKCS#7 message intersects * keys we already know and trust. @@ -156,7 +190,9 @@ 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, + bool check_eku) { struct pkcs7_signed_info *sinfo; struct x509_certificate *p; @@ -167,7 +203,8 @@ 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, check_eku); switch (ret) { case -ENOKEY: continue; diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h index 38ec7f5f9041..5d87b8a02f79 100644 --- a/include/crypto/pkcs7.h +++ b/include/crypto/pkcs7.h @@ -30,7 +30,9 @@ 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, + bool check_eku); /* * pkcs7_verify.c diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h index 6acd3cf13a18..434a9b41d3a5 100644 --- a/include/keys/system_keyring.h +++ b/include/keys/system_keyring.h @@ -9,6 +9,7 @@ #define _KEYS_SYSTEM_KEYRING_H #include <linux/key.h> +#include <keys/asymmetric-type.h> #ifdef CONFIG_SYSTEM_TRUSTED_KEYRING @@ -59,13 +60,15 @@ static inline int is_binary_blacklisted(const u8 *hash, size_t hash_len) #ifdef CONFIG_SYSTEM_REVOCATION_LIST extern int add_key_to_revocation_list(const char *data, size_t size); -extern int is_key_on_revocation_list(struct pkcs7_message *pkcs7); +extern int is_key_on_revocation_list(struct pkcs7_message *pkcs7, + enum key_being_used_for usage); #else static inline int add_key_to_revocation_list(const char *data, size_t size) { return 0; } -static inline int is_key_on_revocation_list(struct pkcs7_message *pkcs7) +static inline int is_key_on_revocation_list(struct pkcs7_message *pkcs7, + enum key_being_used_for usage) { return -ENOKEY; }
This patch adds the logic for checking the CodeSigning extended key usage when verifying signature of kernel module or kexec PE binary in PKCS#7. Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> --- certs/blacklist.c | 6 +++-- certs/system_keyring.c | 4 ++-- crypto/asymmetric_keys/Kconfig | 9 ++++++++ crypto/asymmetric_keys/pkcs7_trust.c | 43 +++++++++++++++++++++++++++++++++--- include/crypto/pkcs7.h | 4 +++- include/keys/system_keyring.h | 7 ++++-- 6 files changed, 63 insertions(+), 10 deletions(-)