[PATCH 1/2] mkfs.ubifs: fscrypt: bail from encrypt_block if gen_essiv_salt fails

[David Oberhollenzer <david.oberhollenzer@xxxxxxxxxxxxx>]

What originally cought my attention was that gen_essiv_salt has a
size_t return type and error paths that return -1 on failure.
Further investigation revealed that the error value is never checked
for. The encrypt_block function doesn't use the return value in any
way and simply continues onward.

Furthermore, the gen_essiv_salt function has an error case that emits
an error message but returns success state.

This patch modifes gen_essiv_salt to return an error status in all
error branches, changes the return type to ssize_t and adds a check
to encrypt_block if gen_essiv_salt fails.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@xxxxxxxxxxxxx>
---
 ubifs-utils/mkfs.ubifs/crypto.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/ubifs-utils/mkfs.ubifs/crypto.c b/ubifs-utils/mkfs.ubifs/crypto.c
index cd68e37..d31bd2a 100644
--- a/ubifs-utils/mkfs.ubifs/crypto.c
+++ b/ubifs-utils/mkfs.ubifs/crypto.c
@@ -109,7 +109,7 @@ fail:
 	return -1;
 }
 
-static size_t gen_essiv_salt(const void *iv, size_t iv_len, const void *key, size_t key_len, void *salt)
+static ssize_t gen_essiv_salt(const void *iv, size_t iv_len, const void *key, size_t key_len, void *salt)
 {
 	size_t ret;
 	const EVP_CIPHER *cipher;
@@ -127,8 +127,10 @@ static size_t gen_essiv_salt(const void *iv, size_t iv_len, const void *key, siz
 	}
 
 	ret = do_encrypt(cipher, iv, iv_len, sha256, EVP_MD_size(EVP_sha256()), NULL, 0, salt);
-	if (ret != iv_len)
+	if (ret != iv_len) {
 		errmsg("Unable to compute ESSIV salt, return value %zi instead of %zi", ret, iv_len);
+		return -1;
+	}
 
 	free(sha256);
 
@@ -154,7 +156,8 @@ static ssize_t encrypt_block(const void *plaintext, size_t size,
 
 	if (cipher == EVP_aes_128_cbc()) {
 		tweak = alloca(ivsize);
-		gen_essiv_salt(&iv, FS_IV_SIZE, key, key_len, tweak);
+		if (gen_essiv_salt(&iv, FS_IV_SIZE, key, key_len, tweak) < 0)
+			return -1;
 	} else {
 		tweak = &iv;
 	}
-- 
2.21.0


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