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Message-ID: <YE0KTAfElytCNh0M@kernel.org>
Date: Sat, 13 Mar 2021 20:54:04 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Mickaël Salaün <mic@...ikod.net>
Cc: David Howells <dhowells@...hat.com>,
David Woodhouse <dwmw2@...radead.org>,
"David S . Miller" <davem@...emloft.net>,
Eric Snowberg <eric.snowberg@...cle.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
James Morris <jmorris@...ei.org>,
Mickaël Salaün <mic@...ux.microsoft.com>,
Mimi Zohar <zohar@...ux.ibm.com>,
"Serge E . Hallyn" <serge@...lyn.com>,
Tyler Hicks <tyhicks@...ux.microsoft.com>,
keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org
Subject: Re: [PATCH v7 4/5] certs: Factor out the blacklist hash creation
On Fri, Mar 12, 2021 at 06:12:31PM +0100, Mickaël Salaün wrote:
> From: Mickaël Salaün <mic@...ux.microsoft.com>
>
> Factor out the blacklist hash creation with the get_raw_hash() helper.
> This also centralize the "tbs" and "bin" prefixes and make them private,
> which help to manage them consistently.
>
> Cc: David Howells <dhowells@...hat.com>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: David Woodhouse <dwmw2@...radead.org>
> Cc: Eric Snowberg <eric.snowberg@...cle.com>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: Jarkko Sakkinen <jarkko@...nel.org>
> Signed-off-by: Mickaël Salaün <mic@...ux.microsoft.com>
> Link: https://lore.kernel.org/r/20210312171232.2681989-5-mic@digikod.net
Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
/Jarkko
> ---
>
> Changes since v6:
> * Rebase on keys-cve-2020-26541-v3: commit ebd9c2ae369a ("integrity:
> Load mokx variables into the blacklist keyring").
>
> Changes since v5:
> * Rebase on keys-next and fix conflict as previously done by David
> Howells.
> * Fix missing part to effectively handle UEFI DBX blacklisting.
> * Remove Jarkko's Acked-by because of the above changes.
>
> Changes since v2:
> * Add Jarkko's Acked-by.
> ---
> certs/blacklist.c | 76 ++++++++++++++-----
> crypto/asymmetric_keys/x509_public_key.c | 3 +-
> include/keys/system_keyring.h | 14 +++-
> .../platform_certs/keyring_handler.c | 26 +------
> 4 files changed, 73 insertions(+), 46 deletions(-)
>
> diff --git a/certs/blacklist.c b/certs/blacklist.c
> index 97a35cf9a62c..b254c87ceb3a 100644
> --- a/certs/blacklist.c
> +++ b/certs/blacklist.c
> @@ -109,11 +109,43 @@ static struct key_type key_type_blacklist = {
> .describe = blacklist_describe,
> };
>
> +static char *get_raw_hash(const u8 *hash, size_t hash_len,
> + enum blacklist_hash_type hash_type)
> +{
> + size_t type_len;
> + const char *type_prefix;
> + char *buffer, *p;
> +
> + switch (hash_type) {
> + case BLACKLIST_HASH_X509_TBS:
> + type_len = sizeof(tbs_prefix) - 1;
> + type_prefix = tbs_prefix;
> + break;
> + case BLACKLIST_HASH_BINARY:
> + type_len = sizeof(bin_prefix) - 1;
> + type_prefix = bin_prefix;
> + break;
> + default:
> + WARN_ON_ONCE(1);
> + return ERR_PTR(-EINVAL);
> + }
> + buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL);
> + if (!buffer)
> + return ERR_PTR(-ENOMEM);
> + p = memcpy(buffer, type_prefix, type_len);
> + p += type_len;
> + *p++ = ':';
> + bin2hex(p, hash, hash_len);
> + p += hash_len * 2;
> + *p = '\0';
> + return buffer;
> +}
> +
> /**
> - * mark_hash_blacklisted - Add a hash to the system blacklist
> + * mark_raw_hash_blacklisted - Add a hash to the system blacklist
> * @hash: The hash as a hex string with a type prefix (eg. "tbs:23aa429783")
> */
> -int mark_hash_blacklisted(const char *hash)
> +static int mark_raw_hash_blacklisted(const char *hash)
> {
> key_ref_t key;
>
> @@ -133,29 +165,36 @@ int mark_hash_blacklisted(const char *hash)
> return 0;
> }
>
> +int mark_hash_blacklisted(const u8 *hash, size_t hash_len,
> + enum blacklist_hash_type hash_type)
> +{
> + const char *buffer;
> + int err;
> +
> + buffer = get_raw_hash(hash, hash_len, hash_type);
> + if (IS_ERR(buffer))
> + return PTR_ERR(buffer);
> + err = mark_raw_hash_blacklisted(buffer);
> + kfree(buffer);
> + return err;
> +}
> +
> /**
> * is_hash_blacklisted - Determine if a hash is blacklisted
> * @hash: The hash to be checked as a binary blob
> * @hash_len: The length of the binary hash
> - * @type: Type of hash
> + * @hash_type: Type of hash
> */
> -int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type)
> +int is_hash_blacklisted(const u8 *hash, size_t hash_len,
> + enum blacklist_hash_type hash_type)
> {
> key_ref_t kref;
> - size_t type_len = strlen(type);
> - char *buffer, *p;
> + const char *buffer;
> int ret = 0;
>
> - buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL);
> - if (!buffer)
> - return -ENOMEM;
> - p = memcpy(buffer, type, type_len);
> - p += type_len;
> - *p++ = ':';
> - bin2hex(p, hash, hash_len);
> - p += hash_len * 2;
> - *p = 0;
> -
> + buffer = get_raw_hash(hash, hash_len, hash_type);
> + if (IS_ERR(buffer))
> + return PTR_ERR(buffer);
> kref = keyring_search(make_key_ref(blacklist_keyring, true),
> &key_type_blacklist, buffer, false);
> if (!IS_ERR(kref)) {
> @@ -170,7 +209,8 @@ EXPORT_SYMBOL_GPL(is_hash_blacklisted);
>
> int is_binary_blacklisted(const u8 *hash, size_t hash_len)
> {
> - if (is_hash_blacklisted(hash, hash_len, "bin") == -EKEYREJECTED)
> + if (is_hash_blacklisted(hash, hash_len, BLACKLIST_HASH_BINARY) ==
> + -EKEYREJECTED)
> return -EPERM;
>
> return 0;
> @@ -243,7 +283,7 @@ static int __init blacklist_init(void)
> panic("Can't allocate system blacklist keyring\n");
>
> for (bl = blacklist_hashes; *bl; bl++)
> - if (mark_hash_blacklisted(*bl) < 0)
> + if (mark_raw_hash_blacklisted(*bl) < 0)
> pr_err("- blacklisting failed\n");
> return 0;
> }
> diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
> index ae450eb8be14..3b7dba5e4cd9 100644
> --- a/crypto/asymmetric_keys/x509_public_key.c
> +++ b/crypto/asymmetric_keys/x509_public_key.c
> @@ -81,7 +81,8 @@ int x509_get_sig_params(struct x509_certificate *cert)
> if (ret < 0)
> goto error_2;
>
> - ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
> + ret = is_hash_blacklisted(sig->digest, sig->digest_size,
> + BLACKLIST_HASH_X509_TBS);
> if (ret == -EKEYREJECTED) {
> pr_err("Cert %*phN is blacklisted\n",
> sig->digest_size, sig->digest);
> diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
> index 875e002a4180..d2597f8d6d7e 100644
> --- a/include/keys/system_keyring.h
> +++ b/include/keys/system_keyring.h
> @@ -10,6 +10,13 @@
>
> #include <linux/key.h>
>
> +enum blacklist_hash_type {
> + /* TBSCertificate hash */
> + BLACKLIST_HASH_X509_TBS = 1,
> + /* Raw data hash */
> + BLACKLIST_HASH_BINARY = 2,
> +};
> +
> #ifdef CONFIG_SYSTEM_TRUSTED_KEYRING
>
> extern int restrict_link_by_builtin_trusted(struct key *keyring,
> @@ -33,13 +40,14 @@ extern int restrict_link_by_builtin_and_secondary_trusted(
>
> extern struct pkcs7_message *pkcs7;
> #ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
> -extern int mark_hash_blacklisted(const char *hash);
> +extern int mark_hash_blacklisted(const u8 *hash, size_t hash_len,
> + enum blacklist_hash_type hash_type);
> extern int is_hash_blacklisted(const u8 *hash, size_t hash_len,
> - const char *type);
> + enum blacklist_hash_type hash_type);
> extern int is_binary_blacklisted(const u8 *hash, size_t hash_len);
> #else
> static inline int is_hash_blacklisted(const u8 *hash, size_t hash_len,
> - const char *type)
> + enum blacklist_hash_type hash_type)
> {
> return 0;
> }
> diff --git a/security/integrity/platform_certs/keyring_handler.c b/security/integrity/platform_certs/keyring_handler.c
> index 5604bd57c990..9e4f156b356e 100644
> --- a/security/integrity/platform_certs/keyring_handler.c
> +++ b/security/integrity/platform_certs/keyring_handler.c
> @@ -15,35 +15,13 @@ static efi_guid_t efi_cert_x509_sha256_guid __initdata =
> EFI_CERT_X509_SHA256_GUID;
> static efi_guid_t efi_cert_sha256_guid __initdata = EFI_CERT_SHA256_GUID;
>
> -/*
> - * Blacklist a hash.
> - */
> -static __init void uefi_blacklist_hash(const char *source, const void *data,
> - size_t len, const char *type,
> - size_t type_len)
> -{
> - char *hash, *p;
> -
> - hash = kmalloc(type_len + len * 2 + 1, GFP_KERNEL);
> - if (!hash)
> - return;
> - p = memcpy(hash, type, type_len);
> - p += type_len;
> - bin2hex(p, data, len);
> - p += len * 2;
> - *p = 0;
> -
> - mark_hash_blacklisted(hash);
> - kfree(hash);
> -}
> -
> /*
> * Blacklist an X509 TBS hash.
> */
> static __init void uefi_blacklist_x509_tbs(const char *source,
> const void *data, size_t len)
> {
> - uefi_blacklist_hash(source, data, len, "tbs:", 4);
> + mark_hash_blacklisted(data, len, BLACKLIST_HASH_X509_TBS);
> }
>
> /*
> @@ -52,7 +30,7 @@ static __init void uefi_blacklist_x509_tbs(const char *source,
> static __init void uefi_blacklist_binary(const char *source,
> const void *data, size_t len)
> {
> - uefi_blacklist_hash(source, data, len, "bin:", 4);
> + mark_hash_blacklisted(data, len, BLACKLIST_HASH_BINARY);
> }
>
> /*
> --
> 2.30.2
>
>
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