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Message-Id: <1424660290-25921-1-git-send-email-josiahw@gmail.com>
Date: Sun, 22 Feb 2015 20:58:10 -0600
From: Josiah Worcester <josiahw@...il.com>
To: musl@...ts.openwall.com
Cc: Josiah Worcester <josiahw@...il.com>
Subject: [PATCH] support alternate backends for the passwd and group dbs
when we fail to find the entry in the commonly accepted files, we
query a server over a Unix domain socket on /var/run/nscd/socket.
the protocol used here is compatible with glibc's nscd protocol on
most systems (all that use 32-bit numbers for all the protocol fields,
which appears to be everything but Alpha).
---
src/passwd/getgr_a.c | 140 +++++++++++++++++++++++++++++++++++++++++++++++-
src/passwd/getpw_a.c | 114 ++++++++++++++++++++++++++++++++++++++-
src/passwd/nscd.h | 38 +++++++++++++
src/passwd/nscd_query.c | 125 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 415 insertions(+), 2 deletions(-)
create mode 100644 src/passwd/nscd.h
create mode 100644 src/passwd/nscd_query.c
diff --git a/src/passwd/getgr_a.c b/src/passwd/getgr_a.c
index 805e28c..2d3ed1d 100644
--- a/src/passwd/getgr_a.c
+++ b/src/passwd/getgr_a.c
@@ -1,5 +1,21 @@
#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)
{
@@ -10,7 +26,6 @@ int __getgr_a(const char *name, gid_t gid, struct group *gr, char **buf, size_t
*res = 0;
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
-
f = fopen("/etc/group", "rbe");
if (!f) {
rv = errno;
@@ -25,6 +40,129 @@ int __getgr_a(const char *name, gid_t gid, struct group *gr, char **buf, size_t
}
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 (f == (FILE*)-1) { rv = 0; 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) {
+ char *tmp = realloc(*buf, len);
+ if (!tmp) {
+ rv = errno;
+ goto cleanup_f;
+ }
+ *buf = tmp;
+ *size = len;
+ }
+
+ if (fread(*buf, 1, len, f) < len) {
+ 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;
diff --git a/src/passwd/getpw_a.c b/src/passwd/getpw_a.c
index 21efc5c..9af6cab 100644
--- a/src/passwd/getpw_a.c
+++ b/src/passwd/getpw_a.c
@@ -1,5 +1,21 @@
-#include "pwf.h"
#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 __getpw_a(const char *name, uid_t uid, struct passwd *pw, char **buf, size_t *size, struct passwd **res)
{
@@ -24,6 +40,102 @@ int __getpw_a(const char *name, uid_t uid, struct passwd *pw, char **buf, size_t
}
fclose(f);
+ if (!*res && (rv == 0 || rv == ENOENT || rv == ENOTDIR)) {
+ int32_t req = name ? GETPWBYNAME : GETPWBYUID;
+ const char *key;
+ int32_t passwdbuf[PW_LEN] = {0};
+ size_t len = 0;
+ char uidbuf[11] = {0};
+
+ if (name) {
+ key = name;
+ } else {
+ /* uid outside of this range can't be queried with the
+ * nscd interface, but might happen if uid_t ever
+ * happens to be a larger type (this is not true as of
+ * now)
+ */
+ if(uid < 0 || uid > UINT32_MAX) {
+ rv = 0;
+ goto done;
+ }
+ key = itoa(uidbuf, uid);
+ }
+
+ f = __nscd_query(req, key, passwdbuf, sizeof passwdbuf, (int[]){0});
+ if (!f) { rv = errno; goto done; }
+ if (f == (FILE*)-1) { rv = 0; goto done; }
+
+ if(!passwdbuf[PWFOUND]) { rv = 0; goto cleanup_f; }
+
+ /* A zero length response from nscd is invalid. We ignore
+ * invalid responses and just report an error, rather than
+ * trying to do something with them.
+ */
+ if (!passwdbuf[PWNAMELEN] || !passwdbuf[PWPASSWDLEN]
+ || !passwdbuf[PWGECOSLEN] || !passwdbuf[PWDIRLEN]
+ || !passwdbuf[PWSHELLLEN]) {
+ rv = EIO;
+ goto cleanup_f;
+ }
+
+ if ((passwdbuf[PWNAMELEN]|passwdbuf[PWPASSWDLEN]
+ |passwdbuf[PWGECOSLEN]|passwdbuf[PWDIRLEN]
+ |passwdbuf[PWSHELLLEN]) >= SIZE_MAX/8) {
+ rv = ENOMEM;
+ goto cleanup_f;
+ }
+
+ len = passwdbuf[PWNAMELEN] + passwdbuf[PWPASSWDLEN]
+ + passwdbuf[PWGECOSLEN] + passwdbuf[PWDIRLEN]
+ + passwdbuf[PWSHELLLEN];
+
+ if (len > *size) {
+ char *tmp = realloc(*buf, len);
+ if (!tmp) {
+ rv = errno;
+ goto cleanup_f;
+ }
+ *buf = tmp;
+ *size = len;
+ }
+
+ if (fread(*buf, 1, len, f) < len) {
+ rv = ferror(f) ? errno : EIO;
+ goto cleanup_f;
+ }
+
+ pw->pw_name = *buf;
+ pw->pw_passwd = pw->pw_name + passwdbuf[PWNAMELEN];
+ pw->pw_gecos = pw->pw_passwd + passwdbuf[PWPASSWDLEN];
+ pw->pw_dir = pw->pw_gecos + passwdbuf[PWGECOSLEN];
+ pw->pw_shell = pw->pw_dir + passwdbuf[PWDIRLEN];
+ pw->pw_uid = passwdbuf[PWUID];
+ pw->pw_gid = passwdbuf[PWGID];
+
+ /* Don't assume that nscd made sure to null terminate strings.
+ * It's supposed to, but malicious nscd should be ignored
+ * rather than causing a crash.
+ */
+ if (pw->pw_passwd[-1] || pw->pw_gecos[-1] || pw->pw_dir[-1]
+ || pw->pw_shell[passwdbuf[PWSHELLLEN]-1]) {
+ rv = EIO;
+ goto cleanup_f;
+ }
+
+ if (name && strcmp(name, pw->pw_name)
+ || !name && uid != pw->pw_uid) {
+ rv = EIO;
+ goto cleanup_f;
+ }
+
+
+ *res = pw;
+cleanup_f:
+ fclose(f);
+ goto done;
+ }
+
done:
pthread_setcancelstate(cs, 0);
if (rv) errno = rv;
diff --git a/src/passwd/nscd.h b/src/passwd/nscd.h
new file mode 100644
index 0000000..102f0b4
--- /dev/null
+++ b/src/passwd/nscd.h
@@ -0,0 +1,38 @@
+#ifndef NSCD_H
+#define NSCD_H
+
+#include <stdint.h>
+
+#define NSCDVERSION 2
+#define GETPWBYNAME 0
+#define GETPWBYUID 1
+#define GETGRBYNAME 2
+#define GETGRBYGID 3
+
+#define REQVERSION 0
+#define REQTYPE 1
+#define REQKEYLEN 2
+#define REQ_LEN 3
+
+#define PWVERSION 0
+#define PWFOUND 1
+#define PWNAMELEN 2
+#define PWPASSWDLEN 3
+#define PWUID 4
+#define PWGID 5
+#define PWGECOSLEN 6
+#define PWDIRLEN 7
+#define PWSHELLLEN 8
+#define PW_LEN 9
+
+#define GRVERSION 0
+#define GRFOUND 1
+#define GRNAMELEN 2
+#define GRPASSWDLEN 3
+#define GRGID 4
+#define GRMEMCNT 5
+#define GR_LEN 6
+
+FILE *__nscd_query(int32_t req, const char *key, int32_t *buf, size_t len, int *swap);
+
+#endif
diff --git a/src/passwd/nscd_query.c b/src/passwd/nscd_query.c
new file mode 100644
index 0000000..539cc2a
--- /dev/null
+++ b/src/passwd/nscd_query.c
@@ -0,0 +1,125 @@
+#include <sys/socket.h>
+#include <byteswap.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include "nscd.h"
+
+static const struct {
+ short sun_family;
+ char sun_path[21];
+} addr = {
+ AF_UNIX,
+ "/var/run/nscd/socket"
+};
+
+static ssize_t full_sendmsg(int fd, struct msghdr *m, int flags)
+{
+ ssize_t n, count = 0;
+
+ while (m->msg_iovlen) {
+ n = sendmsg(fd, m, flags);
+ if(n < 0) return n;
+ count += n;
+
+ while (n) {
+ if (n >= m->msg_iov[0].iov_len) {
+ n -= m->msg_iov[0].iov_len;
+ m->msg_iov++;
+ m->msg_iovlen--;
+ } else {
+ m->msg_iov[0].iov_len -= n;
+ n = 0;
+ }
+ }
+ }
+ return count;
+}
+
+FILE *__nscd_query(int32_t req, const char *key, int32_t *buf, size_t len, int *swap)
+{
+ size_t i;
+ int fd;
+ int res = 0;
+ FILE *f = 0;
+ int32_t req_buf[REQ_LEN] = {
+ NSCDVERSION,
+ req,
+ strlen(key)+1
+ };
+ struct msghdr msg = {
+ .msg_iov = (struct iovec[]){
+ {&req_buf, sizeof(req_buf)},
+ {(char*)key, strlen(key)+1}
+ },
+ .msg_iovlen = 2
+ };
+
+ if (strlen(key) > INT32_MAX - 1) {
+ return (FILE*)-1;
+ }
+
+ *swap = 0;
+retry:
+
+ fd = socket(PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+ if (fd < 0) return NULL;
+
+ if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
+ /* If there isn't a running nscd we return -1 to indicate that
+ * that is precisely what happened
+ */
+ if (errno == EACCES || errno == ECONNREFUSED || errno == ENOENT) {
+ res = -1;
+ }
+ goto error;
+ }
+
+ if (full_sendmsg(fd, &msg, MSG_NOSIGNAL) < 0)
+ goto error;
+
+ f = fdopen(fd, "r");
+
+ if (fread(buf, 1, len, f) < len) {
+ /* If the VERSION entry mismatches nscd will disconnect. The
+ * most likely cause is that the endianness mismatched. So, we
+ * byteswap and try once more. (if we already swapped, just
+ * fail out)
+ */
+ if (!feof(f)) goto error;
+ if (!*swap) {
+ fclose(f);
+ for (i = 0; i < sizeof(req_buf)/sizeof(req_buf[0]); i++) {
+ req_buf[i] = bswap_32(req_buf[i]);
+ }
+ *swap = 1;
+ goto retry;
+ } else {
+ fclose(f);
+ res = -1;
+ goto error;
+ }
+ }
+
+ if (*swap) {
+ for (i = 0; i < len/sizeof(buf[0]); i++) {
+ buf[i] = bswap_32(buf[i]);
+ }
+ }
+
+ /* The first entry in every nscd response is the version number. This
+ * really shouldn't happen, and is evidence of some form of malformed
+ * response.
+ */
+ if(buf[0] != NSCDVERSION) {
+ res = -1;
+ errno = EIO;
+ goto error;
+ }
+
+ return f;
+error:
+ fclose(f);
+ return (FILE*)res;
+}
--
2.1.4
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