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ranap_transp_layer_addr_decode2(): Fix decoding X.213 IPv4 address len=7 

It was found in the field that some peers sends an X.213 IP address
consisting of 7 bytes (1byte IDP/AFI, 2byte ICP, 4 byte IPv4 address) insetad
of 20 bytes.

This is indeed possible when reading ITU Rec X.213 A.5.2.3, where it
states that Table A5 defining the 17 bytes DSP len for IANA ICP
"gives the maximum length of the DSP". So smaller values are still
possible/acceptable.

Related: SYS#6623
Change-Id: I507fb1605d976bd8573162e4fa81721245330184
This commit is contained in:
Pau Espin 2023-11-03 16:51:28 +01:00
parent 20b9eeb310
commit 5484d958c6
1 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/iu_helpers.c
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@ -140,14 +140,21 @@ int ranap_transp_layer_addr_decode2(struct osmo_sockaddr *addr, bool *uses_x213_
memset(addr, 0, sizeof(*addr));
if (len == 20 && buf[0] == 0x35) {
/* For an X.213 NSAP encoded address we expect a buffer of exactly 20 bytes (3 bytes IDP + 17 bytes
* DSP). we also expect AFI = 0x35, which means that two byte IDI and an IP address follows. (see also
* comments in function ranap_new_transp_layer_addr below) */
if ((len == 7 || len == 20) && buf[0] == 0x35) {
/* ITU-T Rec. X.213 A.5.2.1.2.7, RFC 1888 section 6
* For an X.213 NSAP encoded address we expect:
* 3 bytes IDP (first byte AFI = 0x35, which means that two byte IDI and an IP address follows)
* Either 4 or 17 bytes of DSP containing the IP address.
* (see also comments in function ranap_new_transp_layer_addr below) */
x213_nsap = true;
icp = osmo_load16be(&buf[1]);
switch (icp) {
case 0x0000:
/* "RFC 1888 provides guidance on how to embed an IPv6 address within the DSP of an NSAP
* address. The IPv6 address is carried in the first 16 octets of the DSP.
* Octet 17 of the DSP is set to zero, but has no significance for IPv6." */
if (len != 20)
return -EINVAL;
addr->u.sa.sa_family = AF_INET6;
memcpy(addr->u.sin6.sin6_addr.s6_addr, buf + 3, sizeof(addr->u.sin6.sin6_addr.s6_addr));
break;