Add a "fork" of musl as //fusl.

fusl/src/passwd/getgr_a.c

+#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;
+}