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Issue #243: Cannot look up group "shellinabox" at service start

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_SC_GETGR_R_SIZE_MAX was treated as a maximum buffer size while
it should only be a proposition for an initial size.

The buffer size is now increased dynamically if the initial size
is not sufficient.
This commit is contained in:
tickelton 2015-05-08 09:03:16 +02:00
parent 5372964801
commit 5f1aaea6f1
1 changed files with 42 additions and 20 deletions
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26
shellinabox/privileges.c
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@ -363,8 +363,12 @@ static int getgrnam_r(const char *name, struct group *grp, char *buf,
#endif #endif
gid_t getGroupId(const char *name) { gid_t getGroupId(const char *name) {
static const long gr_max = 64 * 1024;
struct group grbuf, *gr; struct group grbuf, *gr;
char *temp;
char *buf; char *buf;
int ret;
int gr_baselen;
#ifdef _SC_GETGR_R_SIZE_MAX #ifdef _SC_GETGR_R_SIZE_MAX
int gr_len = sysconf(_SC_GETGR_R_SIZE_MAX); int gr_len = sysconf(_SC_GETGR_R_SIZE_MAX);
if (gr_len <= 0) { if (gr_len <= 0) {
@ -373,11 +377,17 @@ gid_t getGroupId(const char *name) {
#else #else
int gr_len = 4096; int gr_len = 4096;
#endif #endif
gr_baselen = gr_len;
check(buf = malloc(gr_len)); check(buf = malloc(gr_len));
if (getgrnam_r(name, &grbuf, buf, gr_len, &gr) || !gr) { for(;;) {
errno = 0;
ret = getgrnam_r(name, &grbuf, buf, gr_len, &gr);
if(!ret) {
if(gr) {
break;
} else if(!strcmp(name, "nogroup")) {
// Maybe, this system does not have a "nogroup" group. Substitute the // Maybe, this system does not have a "nogroup" group. Substitute the
// group of the "nobody" user. // group of the "nobody" user.
if (!strcmp(name, "nogroup")) {
struct passwd pwbuf, *pw; struct passwd pwbuf, *pw;
#ifdef _SC_GETPW_R_SIZE_MAX #ifdef _SC_GETPW_R_SIZE_MAX
int pw_len = sysconf(_SC_GETPW_R_SIZE_MAX); int pw_len = sysconf(_SC_GETPW_R_SIZE_MAX);
@ -397,6 +407,18 @@ gid_t getGroupId(const char *name) {
return gid; return gid;
} }
} }
}
if(ret && errno == ERANGE) {
if ((gr_len + gr_baselen) < gr_len || (gr_len + gr_baselen) > gr_max) {
fatal("Cannot look up group \"%s\": buffer limit reached", name);
break;
}
// grow the buffer by 'gr_baselen' each time getgrnam_r fails
gr_len += gr_baselen;
check(temp = realloc (buf, gr_len));
buf = temp;
continue;
}
fatal("Cannot look up group \"%s\"", name); fatal("Cannot look up group \"%s\"", name);
} }
gid_t gid = gr->gr_gid; gid_t gid = gr->gr_gid;