From 041a7b5bc79367297d4e7d340176b4b096a1c835 Mon Sep 17 00:00:00 2001
From: Liviu Chircu <liviu@opensips.org>
Date: Tue, 9 Jan 2024 15:15:05 +0200
Subject: [PATCH] transformations: Fix edge-cases with {param.value} and
 {uri.param}

For inputs containing only the parameter part, these transformations
would return a bogus {NULL, 0} value (flagged as PV_VAL_STR), which
cannot be used in assignments or conditional checks:

Credits to Bogdan-Andrei Iancu for finding this issue!

(cherry picked from commit b7c4f2a3bb3307b3c505f7017934a52bef8762fd)
---
 str.h             |  2 ++
 transformations.c | 10 ++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/str.h b/str.h
index 3629778ea95..5229928f42c 100644
--- a/str.h
+++ b/str.h
@@ -69,6 +69,8 @@ typedef struct __str_const str_const;
 /* str initialization */
 #define STR_NULL (str){NULL, 0}
 #define STR_NULL_const (str_const){NULL, 0}
+#define STR_EMPTY ((str){"", 0})
+#define STR_EMPTY_const ((str_const){"", 0})
 #define str_init(_string)  (str){_string, sizeof(_string) - 1}
 #define str_const_init(_string)  (str_const){_string, sizeof(_string) - 1}
 
diff --git a/transformations.c b/transformations.c
index 7b37300ee09..3c7dad652e1 100644
--- a/transformations.c
+++ b/transformations.c
@@ -1204,7 +1204,10 @@ int tr_eval_uri(struct sip_msg *msg, tr_param_t *tp, int subtype,
 				if (pit->name.len==sv.len
 						&& strncasecmp(pit->name.s, sv.s, sv.len)==0)
 				{
-					val->rs = pit->body;
+					if (ZSTR(pit->body))
+						val->rs = STR_EMPTY;
+					else
+						val->rs = pit->body;
 					goto done;
 				}
 			}
@@ -2226,7 +2229,10 @@ int tr_eval_paramlist(struct sip_msg *msg, tr_param_t *tp, int subtype,
 				if (pit->name.len==sv.len
 						&& strncasecmp(pit->name.s, sv.s, sv.len)==0)
 				{
-					val->rs = pit->body;
+					if (ZSTR(pit->body))
+						val->rs = STR_EMPTY;
+					else
+						val->rs = pit->body;
 					goto done;
 				}
 			}