stir_shaken: Add the e164_max_length parameter (interop fix)

This parameter allows the 15-digit number length restriction of the E.164
format to be bypassed.  Especially useful in scenarios where various
telephony number prefixes are in use, causing some numbers to exceed
the standard maximum length.

Credits to @Integration-IT for watching over the core issue and helping
work towards the current solution!

Fixes #3202
Fixes #3182
Fixes #3181

(cherry picked from commit 2e66235)

modules/stir_shaken/doc/stir_shaken_admin.xml

@@ -164,9 +164,10 @@ modparam("stir_shaken", "crl_dir", "/stir_certs/crls")
 	<section id="param_e164_strict_mode" xreflabel="e164_strict_mode">
 	    <title><varname>e164_strict_mode</varname> (integer)</title>
 	    <para>
-		Strictly check if the originating/destination identity derived from the
-		SIP message is an E.164 telephone number. Also require the URI to either
-		be a <emphasis>tel</emphasis> URI or a <emphasis>sip</emphasis> /
+		Require a leading <emphasis>"+"</emphasis> to be present in
+		the originating/destination SHAKEN identity, on top of mandating an E.164
+		telephone number by default.  Additionally, require the URI to be either
+		a <emphasis>tel</emphasis> URI or a <emphasis>sip</emphasis> /
 		<emphasis>sips</emphasis> URI with the <emphasis>user=phone</emphasis>
 		parameter.
 	    </para>
@@ -181,6 +182,25 @@ modparam("stir_shaken", "e164_strict_mode", 1)
 	    </example>
 	</section>
 
+	<section id="param_e164_max_length" xreflabel="e164_max_length">
+	    <title><varname>e164_max_length</varname> (integer)</title>
+	    <para>
+		This parameter allows the 15-digit number length restriction of the E.164
+		format to be bypassed.  Especially useful in scenarios where various
+		telephony number prefixes are in use, causing some numbers to exceed
+		the standard maximum length.
+	    </para>
+	    <para>The default value is <emphasis>15</emphasis>.</para>
+	    <example>
+		<title>Set <varname>e164_max_length</varname> parameter</title>
+		<programlisting format="linespecific">
+...
+modparam("stir_shaken", "e164_max_length", 16)
+...
+</programlisting>
+	    </example>
+	</section>
+
 	<section id="param_require_date_hdr" xreflabel="require_date_hdr">
 	    <title><varname>require_date_hdr</varname> (integer)</title>
 	    <para>

modules/stir_shaken/stir_shaken.c

@@ -104,6 +104,7 @@ static char *crl_list;
 static char *crl_dir;
 
 static int e164_strict_mode;
+static int e164_max_length = 15;
 
 static int require_date_hdr = 1;
 
@@ -121,6 +122,7 @@ static param_export_t params[] = {
 	{"crl_list", STR_PARAM, &crl_list},
 	{"crl_dir", STR_PARAM, &crl_dir},
 	{"e164_strict_mode", INT_PARAM, &e164_strict_mode},
+	{"e164_max_length", INT_PARAM, &e164_max_length},
 	{"require_date_hdr", INT_PARAM, &require_date_hdr},
 	{0, 0, 0}
 };
@@ -940,7 +942,7 @@ static int check_passport_phonenum(str *num, int log_lev)
 		num->len--;
 	}
 
-	if (_is_e164(num, e164_strict_mode) == -1) {
+	if (_is_e164(num, e164_strict_mode, e164_max_length) == -1) {
 		LM_GEN(log_lev, "number is not in E.164 format: %.*s\n", num->len, num->s);
 		return -1;
 	}

test/test_ut.c

@@ -34,15 +34,15 @@ void test_ut(void)
 	ok(is_e164(_str("+1234567890123456")) == -1, "test-e164-7");
 	ok(is_e164(_str("+123456789x12345")) == -1, "test-e164-8");
 
-	ok(_is_e164(_str(""), 0) == -1, "test-e164-9");
-	ok(_is_e164(_str("+"), 0) == -1, "test-e164-10");
-	ok(_is_e164(_str("+1"), 0) == -1, "test-e164-11");
-	ok(_is_e164(_str("12"), 0) == 1, "test-e164-12");
-	ok(_is_e164(_str("+12"), 0) == 1, "test-e164-13");
-	ok(_is_e164(_str("123"), 0) == 1, "test-e164-14");
-	ok(_is_e164(_str("123456789012345"), 0) == 1, "test-e164-15");
-	ok(_is_e164(_str("1234567890123456"), 0) == -1, "test-e164-16");
-	ok(_is_e164(_str("+123456789012345"), 0) == 1, "test-e164-17");
-	ok(_is_e164(_str("+1234567890123456"), 0) == -1, "test-e164-18");
-	ok(_is_e164(_str("123456789x12345"), 0) == -1, "test-e164-19");
+	ok(_is_e164(_str(""), 0, 15) == -1, "test-e164-9");
+	ok(_is_e164(_str("+"), 0, 15) == -1, "test-e164-10");
+	ok(_is_e164(_str("+1"), 0, 15) == -1, "test-e164-11");
+	ok(_is_e164(_str("12"), 0, 15) == 1, "test-e164-12");
+	ok(_is_e164(_str("+12"), 0, 15) == 1, "test-e164-13");
+	ok(_is_e164(_str("123"), 0, 15) == 1, "test-e164-14");
+	ok(_is_e164(_str("123456789012345"), 0, 15) == 1, "test-e164-15");
+	ok(_is_e164(_str("1234567890123456"), 0, 15) == -1, "test-e164-16");
+	ok(_is_e164(_str("+123456789012345"), 0, 15) == 1, "test-e164-17");
+	ok(_is_e164(_str("+1234567890123456"), 0, 15) == -1, "test-e164-18");
+	ok(_is_e164(_str("123456789x12345"), 0, 15) == -1, "test-e164-19");
 }

ut.h

@@ -598,7 +598,8 @@ static inline void unescape_crlf(str *in_out)
 	}
 }
 
-static inline int _is_e164(const str* _user, int require_plus)
+/* @max_digits should be just 15, but there are exceptions to this rule! */
+static inline int _is_e164(const str* _user, int require_plus, int max_digits)
 {
 	char *d, *start, *end;
 
@@ -614,7 +615,7 @@ static inline int _is_e164(const str* _user, int require_plus)
 	}
 
 	end = _user->s + _user->len;
-	if (end - start < 2 || end - start > 15)
+	if (end - start < 2 || end - start > max_digits)
 		return -1;
 
 	for (d = start; d < end; d++)
@@ -623,7 +624,7 @@ static inline int _is_e164(const str* _user, int require_plus)
 
 	return 1;
 }
-#define is_e164(_user) _is_e164(_user, 1)
+#define is_e164(_user) _is_e164(_user, 1, 15)
 
 /*
  * Convert a string to lower case