buf2hexstr: properly deal with empty string

It wrote before the start of the string

found by afl

Reviewed-by: Richard Levitte <levitte@openssl.org>
MR: #2994

diff --git a/crypto/o_str.c b/crypto/o_str.c
index 29c324f4746de061a9d6b702f7130fbee479827a..beabec0ddc14a75b5ca3dab3a97aa93818695ae2 100644 (file)
--- a/crypto/o_str.c
+++ b/crypto/o_str.c
@@ -198,7 +198,12 @@ char *OPENSSL_buf2hexstr(const unsigned char *buffer, long len)
     const unsigned char *p;
     int i;
 
-    if ((tmp = OPENSSL_malloc(len * 3 + 1)) == NULL) {
+    if (len == 0)
+    {
+        return OPENSSL_zalloc(1);
+    }
+
+    if ((tmp = OPENSSL_malloc(len * 3)) == NULL) {
         CRYPTOerr(CRYPTO_F_OPENSSL_BUF2HEXSTR, ERR_R_MALLOC_FAILURE);
         return NULL;
     }

diff --git a/doc/crypto/OPENSSL_malloc.pod b/doc/crypto/OPENSSL_malloc.pod
index ba50221f1c7ef54dad246e652a0ab1f6341881f0..5d254f7b90a2f66e71d9435f4b41df69b789d8d8 100644 (file)
--- a/doc/crypto/OPENSSL_malloc.pod
+++ b/doc/crypto/OPENSSL_malloc.pod
@@ -124,7 +124,7 @@ An odd number of hex digits is an error.
 
 OPENSSL_buf2hexstr() takes the specified buffer and length, and returns
 a hex string for value, or NULL on error.
-B<Buffer> cannot be NULL; if B<len> is NULL an empty string is returned.
+B<Buffer> cannot be NULL; if B<len> is 0 an empty string is returned.
 
 OPENSSL_hexchar2int() converts a character to the hexadecimal equivalent,
 or returns -1 on error.