[openssl-dev] [openssl.org #4537] [PATCH] Fix a NULL dereference in chacha20_poly1305_init_key()

[Kazuki Yamaguchi via RT]

chacha20_poly1305_init_key() dereferences NULL when called with inkey !=
NULL && iv == NULL. This function is called by EVP_EncryptInit_ex()
family, whose documentation allows setting key and iv in separate calls.
---
I also created a pull request on GitHub:
- https://github.com/openssl/openssl/pull/1049

 crypto/evp/e_chacha20_poly1305.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/crypto/evp/e_chacha20_poly1305.c b/crypto/evp/e_chacha20_poly1305.c
index c3c72a1..cc3927f 100644
--- a/crypto/evp/e_chacha20_poly1305.c
+++ b/crypto/evp/e_chacha20_poly1305.c
@@ -205,7 +205,6 @@ static int chacha20_poly1305_init_key(EVP_CIPHER_CTX *ctx,
                                       const unsigned char *iv, int enc)
 {
     EVP_CHACHA_AEAD_CTX *actx = aead_data(ctx);
-    unsigned char temp[CHACHA_CTR_SIZE];
 
     if (!inkey && !iv)
         return 1;
@@ -216,16 +215,21 @@ static int chacha20_poly1305_init_key(EVP_CIPHER_CTX *ctx,
     actx->mac_inited = 0;
     actx->tls_payload_length = NO_TLS_PAYLOAD_LENGTH;
 
-    /* pad on the left */
-    memset(temp, 0, sizeof(temp));
-    if (actx->nonce_len <= CHACHA_CTR_SIZE)
-        memcpy(temp + CHACHA_CTR_SIZE - actx->nonce_len, iv, actx->nonce_len);
+    if (iv != NULL) {
+        unsigned char temp[CHACHA_CTR_SIZE] = { 0 };
 
-    chacha_init_key(ctx, inkey, temp, enc);
+        /* pad on the left */
+        if (actx->nonce_len <= CHACHA_CTR_SIZE)
+            memcpy(temp + CHACHA_CTR_SIZE - actx->nonce_len, iv, actx->nonce_len);
 
-    actx->nonce[0] = actx->key.counter[1];
-    actx->nonce[1] = actx->key.counter[2];
-    actx->nonce[2] = actx->key.counter[3];
+        chacha_init_key(ctx, inkey, temp, enc);
+
+        actx->nonce[0] = actx->key.counter[1];
+        actx->nonce[1] = actx->key.counter[2];
+        actx->nonce[2] = actx->key.counter[3];
+    } else {
+        chacha_init_key(ctx, inkey, NULL, enc);
+    }
 
     return 1;
 }
-- 
2.8.2.453.g21f6c40


-- 
Ticket here: http://rt.openssl.org/Ticket/Display.html?id=4537
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