inet_ntop bug in 1.1.19

[Philip Homburg <philip.homburg@ripe.net>]

[-- Attachment #1: Type: text/plain, Size: 389 bytes --]

(Please CC me on any replies, I'm not subscribed to the list)

inet_ntop doesn't conform to RFC 5952 (A Recommendation for IPv6 Address
Text Representation).

I attached a test program to demonstrate the issue and a patch:
$ cc inet_ntop_test.c musl-1.1.19/src/network/inet_ntop.c
$ ./a.out
Section 4.2.2 test failed: got 2001:db8::1:1:1:1:1, expected
2001:db8:0:1:1:1:1:1
Found 1 error.


[-- Attachment #2: inet_ntop_test.c --]
[-- Type: text/plain, Size: 2273 bytes --]

/*
Check if inet_ntop is according to RFC 5952
*/

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>

/* Section 4.1: Handling Leading Zeros in a 16-Bit Field */
struct in6_addr s41_input = { {
			0x20, 0x01, 0x0d, 0xb8, 0x00, 0x00, 0x00, 0x00,
			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } };
char *s41_str = "2001:db8::1";

/* Section 4.2.1: Shorten as Much as Possible */
struct in6_addr s421_input = { {
			0x20, 0x01, 0x0d, 0xb8, 0x00, 0x00, 0x00, 0x00,
			0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x01 } };
char *s421_str = "2001:db8::2:1";

/* Section 4.2.2: Handling One 16-Bit 0 Field */
struct in6_addr s422_input = { {
			0x20, 0x01, 0x0d, 0xb8, 0x00, 0x00, 0x00, 0x01,
			0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01 } };
char *s422_str = "2001:db8:0:1:1:1:1:1";

/* Section 4.2.3a: Choice in Placement of "::" */
struct in6_addr s423a_input = { {
			0x20, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } };
char *s423a_str = "2001:0:0:1::1";

/* Section 4.2.3b: Choice in Placement of "::" */
struct in6_addr s423b_input = { {
			0x20, 0x01, 0x0d, 0xb8, 0x00, 0x00, 0x00, 0x00,
			0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } };
char *s423b_str = "2001:db8::1:0:0:1";

struct tests {
	char *label;
	struct in6_addr *addrp;
	char **strp;
} tests[] = {
	{ "Section 4.1", &s41_input, &s41_str },
	{ "Section 4.2.1", &s421_input, &s421_str },
	{ "Section 4.2.2", &s422_input, &s422_str },
	{ "Section 4.2.3a", &s423a_input, &s423a_str },
	{ "Section 4.2.3b", &s423b_input, &s423b_str },
	{ NULL, NULL, NULL }
};

int main(void)
{
	int i, errors;
	char buf[INET6_ADDRSTRLEN];

	errors= 0;
	for (i= 0; tests[i].label != NULL; i++)
	{
		if (inet_ntop(AF_INET6, tests[i].addrp, buf, sizeof(buf)) ==
			NULL)
		{
			fprintf(stderr, "inet_ntop failed for test %s: %s\n",
				tests[i].label, strerror(errno));
			exit(1);
		}
		if (strcmp(buf, *tests[i].strp) != 0)
		{
			fprintf(stderr, "%s test failed: got %s, expected %s\n",
				tests[i].label, buf, *tests[i].strp);
			errors++;
		}
	}
	if (errors)
	{
		fprintf(stderr, "Found %d error%s.\n",
			errors, errors == 1 ? "" : "s");
		exit(1);
	}
	exit(0);
}
	

[-- Attachment #3: inet_ntop.c.patch --]
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--- musl-1.1.19/src/network/inet_ntop.c	2018-02-22 19:39:19.000000000 +0100
+++ inet_ntop.c	2018-06-04 15:51:23.192207973 +0200
@@ -34,6 +34,7 @@
 		for (i=best=0, max=2; buf[i]; i++) {
 			if (i && buf[i] != ':') continue;
 			j = strspn(buf+i, ":0");
+			if (j<4) continue;
 			if (j>max) best=i, max=j;
 		}
 		if (max>2) {