source: azure_iot_hub/trunk/musl-1.1.18/src/passwd/getgr_a.c@ 389

#include <pthread.h>
#include <byteswap.h>
#include <string.h>
#include <unistd.h>
#include "pwf.h"
#include "nscd.h"

static char *itoa(char *p, uint32_t x)
{
        // number of digits in a uint32_t + NUL
        p += 11;
        *--p = 0;
        do {
                *--p = '0' + x % 10;
                x /= 10;
        } while (x);
        return p;
}

int __getgr_a(const char *name, gid_t gid, struct group *gr, char **buf, size_t *size, char ***mem, size_t *nmem, struct group **res)
{
        FILE *f;
        int rv = 0;
        int cs;

        *res = 0;

        pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
        f = fopen("/etc/group", "rbe");
        if (!f) {
                rv = errno;
                goto done;
        }

        while (!(rv = __getgrent_a(f, gr, buf, size, mem, nmem, res)) && *res) {
                if (name && !strcmp(name, (*res)->gr_name)
                || !name && (*res)->gr_gid == gid) {
                        break;
                }
        }
        fclose(f);

        if (!*res && (rv == 0 || rv == ENOENT || rv == ENOTDIR)) {
                int32_t req = name ? GETGRBYNAME : GETGRBYGID;
                int32_t i;
                const char *key;
                int32_t groupbuf[GR_LEN] = {0};
                size_t len = 0;
                size_t grlist_len = 0;
                char gidbuf[11] = {0};
                int swap = 0;
                char *ptr;

                if (name) {
                        key = name;
                } else {
                        if (gid < 0 || gid > UINT32_MAX) {
                                rv = 0;
                                goto done;
                        }
                        key = itoa(gidbuf, gid);
                }

                f = __nscd_query(req, key, groupbuf, sizeof groupbuf, &swap);
                if (!f) { rv = errno; goto done; }

                if (!groupbuf[GRFOUND]) { rv = 0; goto cleanup_f; }

                if (!groupbuf[GRNAMELEN] || !groupbuf[GRPASSWDLEN]) {
                        rv = EIO;
                        goto cleanup_f;
                }

                if (groupbuf[GRNAMELEN] > SIZE_MAX - groupbuf[GRPASSWDLEN]) {
                        rv = ENOMEM;
                        goto cleanup_f;
                }
                len = groupbuf[GRNAMELEN] + groupbuf[GRPASSWDLEN];

                for (i = 0; i < groupbuf[GRMEMCNT]; i++) {
                        uint32_t name_len;
                        if (fread(&name_len, sizeof name_len, 1, f) < 1) {
                                rv = ferror(f) ? errno : EIO;
                                goto cleanup_f;
                        }
                        if (swap) {
                                name_len = bswap_32(name_len);
                        }
                        if (name_len > SIZE_MAX - grlist_len
                        || name_len > SIZE_MAX - len) {
                                rv = ENOMEM;
                                goto cleanup_f;
                        }
                        len += name_len;
                        grlist_len += name_len;
                }

                if (len > *size || !*buf) {
                        char *tmp = realloc(*buf, len);
                        if (!tmp) {
                                rv = errno;
                                goto cleanup_f;
                        }
                        *buf = tmp;
                        *size = len;
                }

                if (!fread(*buf, len, 1, f)) {
                        rv = ferror(f) ? errno : EIO;
                        goto cleanup_f;
                }

                if (groupbuf[GRMEMCNT] + 1 > *nmem) {
                        if (groupbuf[GRMEMCNT] + 1 > SIZE_MAX/sizeof(char*)) {
                                rv = ENOMEM;
                                goto cleanup_f;
                        }
                        char **tmp = realloc(*mem, (groupbuf[GRMEMCNT]+1)*sizeof(char*));
                        if (!tmp) {
                                rv = errno;
                                goto cleanup_f;
                        }
                        *mem = tmp;
                        *nmem = groupbuf[GRMEMCNT] + 1;
                }

                if (groupbuf[GRMEMCNT]) {
                        mem[0][0] = *buf + groupbuf[GRNAMELEN] + groupbuf[GRPASSWDLEN];
                        for (ptr = mem[0][0], i = 0; ptr != mem[0][0]+grlist_len; ptr++)
                                if (!*ptr) mem[0][++i] = ptr+1;
                        mem[0][i] = 0;

                        if (i != groupbuf[GRMEMCNT]) {
                                rv = EIO;
                                goto cleanup_f;
                        }
                } else {
                        mem[0][0] = 0;
                }

                gr->gr_name = *buf;
                gr->gr_passwd = gr->gr_name + groupbuf[GRNAMELEN];
                gr->gr_gid = groupbuf[GRGID];
                gr->gr_mem = *mem;

                if (gr->gr_passwd[-1]
                || gr->gr_passwd[groupbuf[GRPASSWDLEN]-1]) {
                        rv = EIO;
                        goto cleanup_f;
                }

                if (name && strcmp(name, gr->gr_name)
                || !name && gid != gr->gr_gid) {
                        rv = EIO;
                        goto cleanup_f;
                }

                *res = gr;

cleanup_f:
                fclose(f);
                goto done;
        }

done:
        pthread_setcancelstate(cs, 0);
        if (rv) errno = rv;
        return rv;
}