Re: [PATCH v2 5/7] efi: Import certificates from UEFI Secure Boot

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On 12/12/2018 12:17 AM, James Morris wrote:
On Sun, 9 Dec 2018, Nayna Jain wrote:

+/*
+ * Blacklist an X509 TBS hash.
+ */
+static __init void uefi_blacklist_x509_tbs(const char *source,
+					   const void *data, size_t len)
+{
+	char *hash, *p;
+
+	hash = kmalloc(4 + len * 2 + 1, GFP_KERNEL);
+	if (!hash)
+		return;
+	p = memcpy(hash, "tbs:", 4);
+	p += 4;
+	bin2hex(p, data, len);
+	p += len * 2;
+	*p = 0;
+
+	mark_hash_blacklisted(hash);
+	kfree(hash);
+}
+
+/*
+ * Blacklist the hash of an executable.
+ */
+static __init void uefi_blacklist_binary(const char *source,
+					 const void *data, size_t len)
+{
+	char *hash, *p;
+
+	hash = kmalloc(4 + len * 2 + 1, GFP_KERNEL);
+	if (!hash)
+		return;
+	p = memcpy(hash, "bin:", 4);
+	p += 4;
+	bin2hex(p, data, len);
+	p += len * 2;
+	*p = 0;
+
+	mark_hash_blacklisted(hash);
+	kfree(hash);
+}

These could be refactored into one function.



Thanks James for reviewing.

Yes, the code should be refactored.  However, I think making it a single function would require adding a new field to the function callback definitions as well. Probably, a simpler approach would be to define a common function uefi_blacklist_hash(...)  which can then be used by the two functions uefi_blacklist_x509_tbs(...) and uefi_blacklist_binary(...). These two functions now act as wrapper functions. Below is the example code:

+/*
+ * Blacklist a hash.
+ */
+static __init void uefi_blacklist_hash(const char *source, const void *data,
+                                 size_t len, 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);
+}
+
+/*
+ * Blacklist the hash of an executable.
+ */
+static __init void uefi_blacklist_binary(const char *source,
+                                        const void *data, size_t len)
+{
+       uefi_blacklist_hash(source, data, len, "bin:" , 4);
+}


Thanks & Regards,
   - Nayna




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