DoProtoId: case-sensitive SSH- prefix match

- Per RFC 4253 4.2 use WSTRNCMP instead of WSTRNCASECMP for
  prefix and full-ID comparisons.
- Update client tests; add server test vectors expecting
  rejection of lowercase/mixed case.

Issue: F-2865

Author: ejohnstown

src/internal.c

@@ -10923,7 +10923,7 @@ int DoProtoId(WOLFSSH* ssh)
         }
 
         if (ssh->inputBuffer.length >= 4
-            && WSTRNCASECMP((char*)ssh->inputBuffer.buffer, "SSH-", 4) == 0)
+            && WSTRNCMP((char*)ssh->inputBuffer.buffer, "SSH-", 4) == 0)
             break;
 
         if (!allowBanner) {
@@ -10952,8 +10952,8 @@ int DoProtoId(WOLFSSH* ssh)
     eolSz = (*eol == '\r') ? 2 : 1;
 
     if (ssh->inputBuffer.length >= SSH_PROTO_SZ
-        && WSTRNCASECMP((char*)ssh->inputBuffer.buffer,
-                        ssh->ctx->sshProtoIdStr, SSH_PROTO_SZ) == 0) {
+        && WSTRNCMP((char*)ssh->inputBuffer.buffer,
+                    ssh->ctx->sshProtoIdStr, SSH_PROTO_SZ) == 0) {
 
         if (ssh->ctx->side == WOLFSSH_ENDPOINT_SERVER)
             ssh->clientState = CLIENT_VERSION_DONE;

tests/unit.c

@@ -87,13 +87,21 @@ static const ProtoIdTestVector protoIdTestVectors[] = {
       "SSH-2.0-wolfSSHv" LIBWOLFSSH_VERSION_STRING "\n",
       0, WS_SUCCESS, WOLFSSH_ENDPOINT_CLIENT },
 
-    /* Case-insensitive match. DoProtoId uses WSTRNCASECMP. */
+    /* Case rejection. DoProtoId uses WSTRNCMP. */
     { "lowercase ssh prefix",
       "ssh-2.0-wolfSSHv" LIBWOLFSSH_VERSION_STRING "\r\n",
-      0, WS_SUCCESS, WOLFSSH_ENDPOINT_CLIENT },
+      0, WS_SOCKET_ERROR_E, WOLFSSH_ENDPOINT_CLIENT },
     { "mixed case SSH prefix",
       "Ssh-2.0-wolfSSHv" LIBWOLFSSH_VERSION_STRING "\r\n",
-      0, WS_SUCCESS, WOLFSSH_ENDPOINT_CLIENT },
+      0, WS_SOCKET_ERROR_E, WOLFSSH_ENDPOINT_CLIENT },
+
+    /* Case rejection. DoProtoId uses WSTRNCMP. */
+    { "lowercase ssh prefix",
+      "ssh-2.0-wolfSSHv" LIBWOLFSSH_VERSION_STRING "\r\n",
+      0, WS_VERSION_E, WOLFSSH_ENDPOINT_SERVER },
+    { "mixed case SSH prefix",
+      "Ssh-2.0-wolfSSHv" LIBWOLFSSH_VERSION_STRING "\r\n",
+      0, WS_VERSION_E, WOLFSSH_ENDPOINT_SERVER },
 
     /* OpenSSH peer identification. */
     { "OpenSSH version string",