[PATCH 2/3] ecryptfs: Replace strcpy with strscpy in ecryptfs_cipher_code_to_string

[Thorsten Blum <thorsten.blum@linux.dev>]

strcpy() has been deprecated [1] because it performs no bounds checking
on the destination buffer, which can lead to buffer overflows. Since
the parameter 'char *str' is just a pointer with no size information,
extend the function with a 'size' parameter to pass the destination
buffer's size as an additional argument. Adjust the call sites
accordingly.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy [1]
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 fs/ecryptfs/crypto.c          | 6 ++++--
 fs/ecryptfs/ecryptfs_kernel.h | 2 +-
 fs/ecryptfs/keystore.c        | 9 +++++++--
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index 2c37ee6a8be1..c99fc60a4e3b 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -934,11 +934,12 @@ u8 ecryptfs_code_for_cipher_string(char *cipher_name, size_t key_bytes)
 /**
  * ecryptfs_cipher_code_to_string
  * @str: Destination to write out the cipher name
+ * @size: Destination buffer size
  * @cipher_code: The code to convert to cipher name string
  *
  * Returns zero on success
  */
-int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code)
+int ecryptfs_cipher_code_to_string(char *str, size_t size, u8 cipher_code)
 {
 	int rc = 0;
 	int i;
@@ -946,7 +947,8 @@ int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code)
 	str[0] = '\0';
 	for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
 		if (cipher_code == ecryptfs_cipher_code_str_map[i].cipher_code)
-			strcpy(str, ecryptfs_cipher_code_str_map[i].cipher_str);
+			strscpy(str, ecryptfs_cipher_code_str_map[i].cipher_str,
+				size);
 	if (str[0] == '\0') {
 		ecryptfs_printk(KERN_WARNING, "Cipher code not recognized: "
 				"[%d]\n", cipher_code);
diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index 9e6ab0b41337..0d824350f31a 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -577,7 +577,7 @@ int ecryptfs_read_and_validate_header_region(struct inode *inode);
 int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
 					    struct inode *inode);
 u8 ecryptfs_code_for_cipher_string(char *cipher_name, size_t key_bytes);
-int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code);
+int ecryptfs_cipher_code_to_string(char *str, size_t size, u8 cipher_code);
 void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat);
 int ecryptfs_generate_key_packet_set(char *dest_base,
 				     struct ecryptfs_crypt_stat *crypt_stat,
diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index 7f9f68c00ef6..b5204ab3150d 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -954,7 +954,9 @@ ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
 	s->fnek_sig_hex[ECRYPTFS_SIG_SIZE_HEX] = '\0';
 	(*packet_size) += ECRYPTFS_SIG_SIZE;
 	s->cipher_code = data[(*packet_size)++];
-	rc = ecryptfs_cipher_code_to_string(s->cipher_string, s->cipher_code);
+	rc = ecryptfs_cipher_code_to_string(s->cipher_string,
+					    sizeof(s->cipher_string),
+					    s->cipher_code);
 	if (rc) {
 		printk(KERN_WARNING "%s: Cipher code [%d] is invalid\n",
 		       __func__, s->cipher_code);
@@ -1172,7 +1174,9 @@ decrypt_pki_encrypted_session_key(struct ecryptfs_auth_tok *auth_tok,
 	memcpy(crypt_stat->key, auth_tok->session_key.decrypted_key,
 	       auth_tok->session_key.decrypted_key_size);
 	crypt_stat->key_size = auth_tok->session_key.decrypted_key_size;
-	rc = ecryptfs_cipher_code_to_string(crypt_stat->cipher, cipher_code);
+	rc = ecryptfs_cipher_code_to_string(crypt_stat->cipher,
+					    sizeof(crypt_stat->cipher),
+					    cipher_code);
 	if (rc) {
 		ecryptfs_printk(KERN_ERR, "Cipher code [%d] is invalid\n",
 				cipher_code);
@@ -1438,6 +1442,7 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
 		goto out_free;
 	}
 	rc = ecryptfs_cipher_code_to_string(crypt_stat->cipher,
+					    sizeof(crypt_stat->cipher),
 					    (u16)data[(*packet_size)]);
 	if (rc)
 		goto out_free;
-- 
Thorsten Blum <thorsten.blum@linux.dev>
GPG: 1D60 735E 8AEF 3BE4 73B6  9D84 7336 78FD 8DFE EAD4