buffer: Create ssh_buffer_validate_length()

This functions allows if a given length can be obtained from the buffer.

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>

1 files changed, 21 insertions, 3 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 61b07e9a..0c776698 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -526,8 +526,8 @@ uint32_t ssh_buffer_get_data(struct ssh_buffer_struct *buffer, void *data, uint3
      * Check for a integer overflow first, then check if not enough data is in
      * the buffer.
      */
-    if (buffer->pos + len < len || buffer->pos + len > buffer->used) {
-      return 0;
+    if (!ssh_buffer_validate_length(buffer, len)) {
+        return 0;
     }
     memcpy(data,buffer->data+buffer->pos,len);
     buffer->pos+=len;
@@ -581,6 +581,24 @@ int ssh_buffer_get_u64(struct ssh_buffer_struct *buffer, uint64_t *data){
 }
 
 /**
+ * @brief Valdiates that the given length can be obtained from the buffer.
+ *
+ * @param[in]  buffer  The buffer to read from.
+ *
+ * @param[in]  len     The length to be checked.
+ *
+ * @return             SSH_OK if the length is valid, SSH_ERROR otherwise.
+ */
+int ssh_buffer_validate_length(struct ssh_buffer_struct *buffer, size_t len)
+{
+    if (buffer->pos + len < len || buffer->pos + len > buffer->used) {
+        return SSH_ERROR;
+    }
+
+    return SSH_OK;
+}
+
+/**
  * @internal
  *
  * @brief Get a SSH String out of the buffer and adjusts the read pointer.
@@ -599,7 +617,7 @@ struct ssh_string_struct *ssh_buffer_get_ssh_string(struct ssh_buffer_struct *bu
   }
   hostlen = ntohl(stringlen);
   /* verify if there is enough space in buffer to get it */
-  if (buffer->pos + hostlen < hostlen || buffer->pos + hostlen > buffer->used) {
+  if (!ssh_buffer_validate_length(buffer, hostlen) {
     return NULL; /* it is indeed */
   }
   str = ssh_string_new(hostlen);