Date: Thu, 22 Apr 2021 13:33:39 -0700 From: Mark Millard <marklmi@yahoo.com> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Gleb Popov <arrowd@freebsd.org>, freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Re: A bug with getsockopt(SOL_LOCAL, LOCAL_PEERCRED) ? Message-ID: <445774BD-D68B-48A1-856D-F8DC9A480C68@yahoo.com> In-Reply-To: <YIHPzqgjRwDtrMrM@kib.kiev.ua> References: <CALH631kLCApctk4iQJj6br0Pzeb6qsh9g3jz_SA8hH91ftQGDQ@mail.gmail.com> <YHiQ6qEjS2w8uYpS@kib.kiev.ua> <CALH631=3hqvfraume467OM%2BqGqp854sGJFfhO8b61mF%2BkbsJ2Q@mail.gmail.com> <E6626DFC-2014-412C-AEA2-ECE57835B058@yahoo.com> <CALH631mi0xOQGjd6F3Beu_BQdqAx8RYCrbkUi524F8S4rwo1aA@mail.gmail.com> <40116716-D8D9-438D-A168-B26A112D199E@yahoo.com> <CALH631nrhyY%2BK3tPSwt1wuYHoZkz371UtjK%2BdG844RybtA2yKw@mail.gmail.com> <YIFQ/U34i1Jbxjv7@kib.kiev.ua> <CALH631maNoe_x%2BippbRTE3s8XarZ32Nrb%2BfXWUz-NMFeCre_-w@mail.gmail.com> <YIHPzqgjRwDtrMrM@kib.kiev.ua>
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On 2021-Apr-22, at 12:34, Konstantin Belousov <kostikbel@gmail.com> = wrote: > On Thu, Apr 22, 2021 at 09:49:15PM +0300, Gleb Popov wrote: >> On Thu, Apr 22, 2021 at 1:33 PM Konstantin Belousov = <kostikbel@gmail.com> >> wrote: >>=20 >>> There is no peer for listening socket. >>>=20 >>> Show minimal code that works for you on Linux. >>>=20 >>=20 >> Here you go: http://arrowd.name/un_linux.cpp >> It is almost identical to FreeBSD one, but works for me on ArchLinux. >=20 > Of course it works because it uses s2, that is, connected and not = listening > socket, for getsockopt(), same as the working FreeBSD version. I made a variant that tries s2 and then s, printing the peercred uid, group id, and pid fields, and built it on Fedora 34. The result was: # ./a.out & ncat -U foobar [1] 18646 s2 data is uid field: 0 groups[0] field: 0 pid field: 18647 s data is uid field: 0 groups[0] field: 0 pid field: 18646 [1]+ Done ./a.out On FreeBSD: # ./a.out & nc -U foobar s2 data is uid field: 0 groups[0] field: 0 pid field: 6984 getsockopt for s failed with Socket is not connected [1] Done ./a.out The code is: #ifndef __FreeBSD__ #define _GNU_SOURCE #endif #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #ifdef __FreeBSD__ #define FOR_PEERCRED 0 #define CR_GROUP_ID cr_groups[0] #else // Linux #define xucred ucred #define FOR_PEERCRED SOL_SOCKET #define LOCAL_PEERCRED SO_PEERCRED #define cr_uid uid #define CR_GROUP_ID gid #define cr_pid pid #endif #include <sys/socket.h> #include <sys/un.h> #ifdef __FreeBSD__ #include <sys/ucred.h> #endif #include <netinet/in.h> #include <netinet/tcp.h> void failure(char const * err) { puts(err); puts("failed with"); puts(strerror(errno)); } void die(char const * err) { failure(err); unlink("foobar"); exit(1); } int main() { int s =3D socket(PF_LOCAL, SOCK_STREAM, 0); if(s < 0) die("socket"); struct sockaddr_un addrunix; memset(&addrunix, 0, sizeof(addrunix)); addrunix.sun_family =3D AF_UNIX; memcpy(addrunix.sun_path, "foobar", 6); int r =3D bind(s, (const struct sockaddr *)&addrunix, sizeof(struct = sockaddr_un)); if(r < 0) die("bind"); listen(s, 64); int s2; do { s2 =3D accept4(s, 0, 0, 0); } while (s2 < 0 && errno =3D=3D EAGAIN); if(s2 < 0) die("accept4"); struct xucred s2_creds; socklen_t s2_credSize =3D sizeof(struct xucred); r =3D getsockopt(s2, FOR_PEERCRED, LOCAL_PEERCRED, &s2_creds, = &s2_credSize); if(r < 0) failure("getsockopt for s2"); else printf("s2 data is uid field: %jd groups[0] field: %jd pid = field: %jd\n", (uintmax_t) s2_creds.cr_uid, (uintmax_t) = s2_creds.CR_GROUP_ID, (uintmax_t) s2_creds.cr_pid); struct xucred s_creds; socklen_t s_credSize =3D sizeof(struct xucred); r =3D getsockopt(s, FOR_PEERCRED, LOCAL_PEERCRED, &s_creds, = &s_credSize); if(r < 0) failure("getsockopt for s"); else printf("s data is uid field: %jd groups[0] field: %jd pid field: = %jd\n", (uintmax_t) s_creds.cr_uid, (uintmax_t) s_creds.CR_GROUP_ID, = (uintmax_t) s_creds.cr_pid); unlink("foobar"); return 0; } =3D=3D=3D Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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