strings.h: Fix issues with escape string functions.

Fixes for issues with the ASTERISK-24934 patch.

* Fixed ast_escape_alloc() and ast_escape_c_alloc() if the s parameter is
an empty string.  If it were an empty string the functions returned NULL
as if there were a memory allocation failure.  This failure caused the AMI
VarSet event to not get posted if the new value was an empty string.

* Fixed dest buffer overwrite potential in ast_escape() and
ast_escape_c().  If the dest buffer size is smaller than the space needed
by the escaped s parameter string then the dest buffer would be written
beyond the end by the nul string terminator.  The num parameter was really
the dest buffer size parameter so I renamed it to size.

* Made nul terminate the dest buffer if the source string parameter s was
an empty string in ast_escape() and ast_escape_c().

* Updated ast_escape() and ast_escape_c() doxygen function description
comments to reflect reality.

* Added some more unit test cases to /main/strings/escape to cover the
empty source string issues.

ASTERISK-25255 #close
Reported by: Richard Mudgett

Change-Id: Id77fc704600ebcce81615c1200296f74de254104

1 files changed, 41 insertions, 5 deletions

diff --git a/tests/test_strings.c b/tests/test_strings.c
index ab65037ee..5e3446d99 100644
--- a/tests/test_strings.c
+++ b/tests/test_strings.c
@@ -460,7 +460,32 @@ AST_TEST_DEFINE(escape_test)
 	char buf[128];
 
 #define TEST_ESCAPE(s, to_escape, expected) \
-	!strcmp(ast_escape(buf, s, sizeof(buf) / sizeof(char), to_escape), expected)
+	!strcmp(ast_escape(buf, s, ARRAY_LEN(buf), to_escape), expected)
+
+#define TEST_ESCAPE_C(s, expected) \
+	!strcmp(ast_escape_c(buf, s, ARRAY_LEN(buf)), expected)
+
+#define TEST_ESCAPE_ALLOC(s, to_escape, expected)		\
+	({													\
+		int res = 0;									\
+		char *a_buf = ast_escape_alloc(s, to_escape);	\
+		if (a_buf) {									\
+			res = !strcmp(a_buf, expected);				\
+			ast_free(a_buf);							\
+		}												\
+		res;											\
+	})
+
+#define TEST_ESCAPE_C_ALLOC(s, expected)				\
+	({													\
+		int res = 0;									\
+		char *a_buf = ast_escape_c_alloc(s);			\
+		if (a_buf) {									\
+			res = !strcmp(a_buf, expected);				\
+			ast_free(a_buf);							\
+		}												\
+		res;											\
+	})
 
 	switch (cmd) {
 	case TEST_INIT:
@@ -474,16 +499,27 @@ AST_TEST_DEFINE(escape_test)
 	}
 
 	ast_test_validate(test, TEST_ESCAPE("null escape", NULL, "null escape"));
+	ast_test_validate(test, TEST_ESCAPE("empty escape", "", "empty escape"));
+	ast_test_validate(test, TEST_ESCAPE("", "Z", ""));
 	ast_test_validate(test, TEST_ESCAPE("no matching escape", "Z", "no matching escape"));
 	ast_test_validate(test, TEST_ESCAPE("escape Z", "Z", "escape \\Z"));
 	ast_test_validate(test, TEST_ESCAPE("Z", "Z", "\\Z"));
-	ast_test_validate(test, TEST_ESCAPE(";;", ";;", "\\;\\;"));
+	ast_test_validate(test, TEST_ESCAPE(";;", ";", "\\;\\;"));
 	ast_test_validate(test, TEST_ESCAPE("escape \n", "\n", "escape \\n"));
 	ast_test_validate(test, TEST_ESCAPE("escape \n again \n", "\n", "escape \\n again \\n"));
 
-	ast_test_validate(test, !strcmp(ast_escape_c(buf, "escape \a\b\f\n\r\t\v\\\'\"\?",
-						     sizeof(buf) / sizeof(char)),
-					"escape \\a\\b\\f\\n\\r\\t\\v\\\\\\\'\\\"\\?"));
+	ast_test_validate(test, TEST_ESCAPE_C("", ""));
+	ast_test_validate(test, TEST_ESCAPE_C("escape \a\b\f\n\r\t\v\\\'\"\?",
+		"escape \\a\\b\\f\\n\\r\\t\\v\\\\\\\'\\\"\\?"));
+
+	ast_test_validate(test, TEST_ESCAPE_ALLOC("", "Z", ""));
+	ast_test_validate(test, TEST_ESCAPE_ALLOC("Z", "Z", "\\Z"));
+	ast_test_validate(test, TEST_ESCAPE_ALLOC("a", "Z", "a"));
+
+	ast_test_validate(test, TEST_ESCAPE_C_ALLOC("", ""));
+	ast_test_validate(test, TEST_ESCAPE_C_ALLOC("\n", "\\n"));
+	ast_test_validate(test, TEST_ESCAPE_C_ALLOC("a", "a"));
+
 	return AST_TEST_PASS;
 }