| /* $OpenBSD: authfile.c,v 1.77 2009/10/22 22:26:13 djm Exp $ */ |
| /* |
| * Author: Tatu Ylonen <ylo@cs.hut.fi> |
| * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| * All rights reserved |
| * This file contains functions for reading and writing identity files, and |
| * for reading the passphrase from the user. |
| * |
| * As far as I am concerned, the code I have written for this software |
| * can be used freely for any purpose. Any derived versions of this |
| * software must be clearly marked as such, and if the derived work is |
| * incompatible with the protocol description in the RFC file, it must be |
| * called by a name other than "ssh" or "Secure Shell". |
| * |
| * |
| * Copyright (c) 2000 Markus Friedl. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #include "includes.h" |
| |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| #include <sys/param.h> |
| #include <sys/uio.h> |
| |
| #include <openssl/err.h> |
| #include <openssl/evp.h> |
| #include <openssl/pem.h> |
| |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <stdarg.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <unistd.h> |
| |
| #include "xmalloc.h" |
| #include "cipher.h" |
| #include "buffer.h" |
| #include "key.h" |
| #include "ssh.h" |
| #include "log.h" |
| #include "authfile.h" |
| #include "rsa.h" |
| #include "misc.h" |
| #include "atomicio.h" |
| |
| /* Version identification string for SSH v1 identity files. */ |
| static const char authfile_id_string[] = |
| "SSH PRIVATE KEY FILE FORMAT 1.1\n"; |
| |
| /* |
| * Saves the authentication (private) key in a file, encrypting it with |
| * passphrase. The identification of the file (lowest 64 bits of n) will |
| * precede the key to provide identification of the key without needing a |
| * passphrase. |
| */ |
| |
| static int |
| key_save_private_rsa1(Key *key, const char *filename, const char *passphrase, |
| const char *comment) |
| { |
| Buffer buffer, encrypted; |
| u_char buf[100], *cp; |
| int fd, i, cipher_num; |
| CipherContext ciphercontext; |
| Cipher *cipher; |
| u_int32_t rnd; |
| |
| /* |
| * If the passphrase is empty, use SSH_CIPHER_NONE to ease converting |
| * to another cipher; otherwise use SSH_AUTHFILE_CIPHER. |
| */ |
| cipher_num = (strcmp(passphrase, "") == 0) ? |
| SSH_CIPHER_NONE : SSH_AUTHFILE_CIPHER; |
| if ((cipher = cipher_by_number(cipher_num)) == NULL) |
| fatal("save_private_key_rsa: bad cipher"); |
| |
| /* This buffer is used to built the secret part of the private key. */ |
| buffer_init(&buffer); |
| |
| /* Put checkbytes for checking passphrase validity. */ |
| rnd = arc4random(); |
| buf[0] = rnd & 0xff; |
| buf[1] = (rnd >> 8) & 0xff; |
| buf[2] = buf[0]; |
| buf[3] = buf[1]; |
| buffer_append(&buffer, buf, 4); |
| |
| /* |
| * Store the private key (n and e will not be stored because they |
| * will be stored in plain text, and storing them also in encrypted |
| * format would just give known plaintext). |
| */ |
| buffer_put_bignum(&buffer, key->rsa->d); |
| buffer_put_bignum(&buffer, key->rsa->iqmp); |
| buffer_put_bignum(&buffer, key->rsa->q); /* reverse from SSL p */ |
| buffer_put_bignum(&buffer, key->rsa->p); /* reverse from SSL q */ |
| |
| /* Pad the part to be encrypted until its size is a multiple of 8. */ |
| while (buffer_len(&buffer) % 8 != 0) |
| buffer_put_char(&buffer, 0); |
| |
| /* This buffer will be used to contain the data in the file. */ |
| buffer_init(&encrypted); |
| |
| /* First store keyfile id string. */ |
| for (i = 0; authfile_id_string[i]; i++) |
| buffer_put_char(&encrypted, authfile_id_string[i]); |
| buffer_put_char(&encrypted, 0); |
| |
| /* Store cipher type. */ |
| buffer_put_char(&encrypted, cipher_num); |
| buffer_put_int(&encrypted, 0); /* For future extension */ |
| |
| /* Store public key. This will be in plain text. */ |
| buffer_put_int(&encrypted, BN_num_bits(key->rsa->n)); |
| buffer_put_bignum(&encrypted, key->rsa->n); |
| buffer_put_bignum(&encrypted, key->rsa->e); |
| buffer_put_cstring(&encrypted, comment); |
| |
| /* Allocate space for the private part of the key in the buffer. */ |
| cp = buffer_append_space(&encrypted, buffer_len(&buffer)); |
| |
| cipher_set_key_string(&ciphercontext, cipher, passphrase, |
| CIPHER_ENCRYPT); |
| cipher_crypt(&ciphercontext, cp, |
| buffer_ptr(&buffer), buffer_len(&buffer)); |
| cipher_cleanup(&ciphercontext); |
| memset(&ciphercontext, 0, sizeof(ciphercontext)); |
| |
| /* Destroy temporary data. */ |
| memset(buf, 0, sizeof(buf)); |
| buffer_free(&buffer); |
| |
| fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); |
| if (fd < 0) { |
| error("open %s failed: %s.", filename, strerror(errno)); |
| buffer_free(&encrypted); |
| return 0; |
| } |
| if (atomicio(vwrite, fd, buffer_ptr(&encrypted), |
| buffer_len(&encrypted)) != buffer_len(&encrypted)) { |
| error("write to key file %s failed: %s", filename, |
| strerror(errno)); |
| buffer_free(&encrypted); |
| close(fd); |
| unlink(filename); |
| return 0; |
| } |
| close(fd); |
| buffer_free(&encrypted); |
| return 1; |
| } |
| |
| /* save SSH v2 key in OpenSSL PEM format */ |
| static int |
| key_save_private_pem(Key *key, const char *filename, const char *_passphrase, |
| const char *comment) |
| { |
| FILE *fp; |
| int fd; |
| int success = 0; |
| int len = strlen(_passphrase); |
| u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL; |
| const EVP_CIPHER *cipher = (len > 0) ? EVP_aes_128_cbc() : NULL; |
| |
| if (len > 0 && len <= 4) { |
| error("passphrase too short: have %d bytes, need > 4", len); |
| return 0; |
| } |
| fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); |
| if (fd < 0) { |
| error("open %s failed: %s.", filename, strerror(errno)); |
| return 0; |
| } |
| fp = fdopen(fd, "w"); |
| if (fp == NULL) { |
| error("fdopen %s failed: %s.", filename, strerror(errno)); |
| close(fd); |
| return 0; |
| } |
| switch (key->type) { |
| case KEY_DSA: |
| success = PEM_write_DSAPrivateKey(fp, key->dsa, |
| cipher, passphrase, len, NULL, NULL); |
| break; |
| case KEY_RSA: |
| success = PEM_write_RSAPrivateKey(fp, key->rsa, |
| cipher, passphrase, len, NULL, NULL); |
| break; |
| } |
| fclose(fp); |
| return success; |
| } |
| |
| int |
| key_save_private(Key *key, const char *filename, const char *passphrase, |
| const char *comment) |
| { |
| switch (key->type) { |
| case KEY_RSA1: |
| return key_save_private_rsa1(key, filename, passphrase, |
| comment); |
| case KEY_DSA: |
| case KEY_RSA: |
| return key_save_private_pem(key, filename, passphrase, |
| comment); |
| default: |
| break; |
| } |
| error("key_save_private: cannot save key type %d", key->type); |
| return 0; |
| } |
| |
| /* |
| * Loads the public part of the ssh v1 key file. Returns NULL if an error was |
| * encountered (the file does not exist or is not readable), and the key |
| * otherwise. |
| */ |
| |
| static Key * |
| key_load_public_rsa1(int fd, const char *filename, char **commentp) |
| { |
| Buffer buffer; |
| Key *pub; |
| struct stat st; |
| char *cp; |
| u_int i; |
| size_t len; |
| |
| if (fstat(fd, &st) < 0) { |
| error("fstat for key file %.200s failed: %.100s", |
| filename, strerror(errno)); |
| return NULL; |
| } |
| if (st.st_size > 1*1024*1024) { |
| error("key file %.200s too large", filename); |
| return NULL; |
| } |
| len = (size_t)st.st_size; /* truncated */ |
| |
| buffer_init(&buffer); |
| cp = buffer_append_space(&buffer, len); |
| |
| if (atomicio(read, fd, cp, len) != len) { |
| debug("Read from key file %.200s failed: %.100s", filename, |
| strerror(errno)); |
| buffer_free(&buffer); |
| return NULL; |
| } |
| |
| /* Check that it is at least big enough to contain the ID string. */ |
| if (len < sizeof(authfile_id_string)) { |
| debug3("Not a RSA1 key file %.200s.", filename); |
| buffer_free(&buffer); |
| return NULL; |
| } |
| /* |
| * Make sure it begins with the id string. Consume the id string |
| * from the buffer. |
| */ |
| for (i = 0; i < sizeof(authfile_id_string); i++) |
| if (buffer_get_char(&buffer) != authfile_id_string[i]) { |
| debug3("Not a RSA1 key file %.200s.", filename); |
| buffer_free(&buffer); |
| return NULL; |
| } |
| /* Skip cipher type and reserved data. */ |
| (void) buffer_get_char(&buffer); /* cipher type */ |
| (void) buffer_get_int(&buffer); /* reserved */ |
| |
| /* Read the public key from the buffer. */ |
| (void) buffer_get_int(&buffer); |
| pub = key_new(KEY_RSA1); |
| buffer_get_bignum(&buffer, pub->rsa->n); |
| buffer_get_bignum(&buffer, pub->rsa->e); |
| if (commentp) |
| *commentp = buffer_get_string(&buffer, NULL); |
| /* The encrypted private part is not parsed by this function. */ |
| |
| buffer_free(&buffer); |
| return pub; |
| } |
| |
| /* load public key from private-key file, works only for SSH v1 */ |
| Key * |
| key_load_public_type(int type, const char *filename, char **commentp) |
| { |
| Key *pub; |
| int fd; |
| |
| if (type == KEY_RSA1) { |
| fd = open(filename, O_RDONLY); |
| if (fd < 0) |
| return NULL; |
| pub = key_load_public_rsa1(fd, filename, commentp); |
| close(fd); |
| return pub; |
| } |
| return NULL; |
| } |
| |
| /* |
| * Loads the private key from the file. Returns 0 if an error is encountered |
| * (file does not exist or is not readable, or passphrase is bad). This |
| * initializes the private key. |
| * Assumes we are called under uid of the owner of the file. |
| */ |
| |
| static Key * |
| key_load_private_rsa1(int fd, const char *filename, const char *passphrase, |
| char **commentp) |
| { |
| u_int i; |
| int check1, check2, cipher_type; |
| size_t len; |
| Buffer buffer, decrypted; |
| u_char *cp; |
| CipherContext ciphercontext; |
| Cipher *cipher; |
| Key *prv = NULL; |
| struct stat st; |
| |
| if (fstat(fd, &st) < 0) { |
| error("fstat for key file %.200s failed: %.100s", |
| filename, strerror(errno)); |
| close(fd); |
| return NULL; |
| } |
| if (st.st_size > 1*1024*1024) { |
| error("key file %.200s too large", filename); |
| close(fd); |
| return (NULL); |
| } |
| len = (size_t)st.st_size; /* truncated */ |
| |
| buffer_init(&buffer); |
| cp = buffer_append_space(&buffer, len); |
| |
| if (atomicio(read, fd, cp, len) != len) { |
| debug("Read from key file %.200s failed: %.100s", filename, |
| strerror(errno)); |
| buffer_free(&buffer); |
| close(fd); |
| return NULL; |
| } |
| |
| /* Check that it is at least big enough to contain the ID string. */ |
| if (len < sizeof(authfile_id_string)) { |
| debug3("Not a RSA1 key file %.200s.", filename); |
| buffer_free(&buffer); |
| close(fd); |
| return NULL; |
| } |
| /* |
| * Make sure it begins with the id string. Consume the id string |
| * from the buffer. |
| */ |
| for (i = 0; i < sizeof(authfile_id_string); i++) |
| if (buffer_get_char(&buffer) != authfile_id_string[i]) { |
| debug3("Not a RSA1 key file %.200s.", filename); |
| buffer_free(&buffer); |
| close(fd); |
| return NULL; |
| } |
| |
| /* Read cipher type. */ |
| cipher_type = buffer_get_char(&buffer); |
| (void) buffer_get_int(&buffer); /* Reserved data. */ |
| |
| /* Read the public key from the buffer. */ |
| (void) buffer_get_int(&buffer); |
| prv = key_new_private(KEY_RSA1); |
| |
| buffer_get_bignum(&buffer, prv->rsa->n); |
| buffer_get_bignum(&buffer, prv->rsa->e); |
| if (commentp) |
| *commentp = buffer_get_string(&buffer, NULL); |
| else |
| xfree(buffer_get_string(&buffer, NULL)); |
| |
| /* Check that it is a supported cipher. */ |
| cipher = cipher_by_number(cipher_type); |
| if (cipher == NULL) { |
| debug("Unsupported cipher %d used in key file %.200s.", |
| cipher_type, filename); |
| buffer_free(&buffer); |
| goto fail; |
| } |
| /* Initialize space for decrypted data. */ |
| buffer_init(&decrypted); |
| cp = buffer_append_space(&decrypted, buffer_len(&buffer)); |
| |
| /* Rest of the buffer is encrypted. Decrypt it using the passphrase. */ |
| cipher_set_key_string(&ciphercontext, cipher, passphrase, |
| CIPHER_DECRYPT); |
| cipher_crypt(&ciphercontext, cp, |
| buffer_ptr(&buffer), buffer_len(&buffer)); |
| cipher_cleanup(&ciphercontext); |
| memset(&ciphercontext, 0, sizeof(ciphercontext)); |
| buffer_free(&buffer); |
| |
| check1 = buffer_get_char(&decrypted); |
| check2 = buffer_get_char(&decrypted); |
| if (check1 != buffer_get_char(&decrypted) || |
| check2 != buffer_get_char(&decrypted)) { |
| if (strcmp(passphrase, "") != 0) |
| debug("Bad passphrase supplied for key file %.200s.", |
| filename); |
| /* Bad passphrase. */ |
| buffer_free(&decrypted); |
| goto fail; |
| } |
| /* Read the rest of the private key. */ |
| buffer_get_bignum(&decrypted, prv->rsa->d); |
| buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */ |
| /* in SSL and SSH v1 p and q are exchanged */ |
| buffer_get_bignum(&decrypted, prv->rsa->q); /* p */ |
| buffer_get_bignum(&decrypted, prv->rsa->p); /* q */ |
| |
| /* calculate p-1 and q-1 */ |
| rsa_generate_additional_parameters(prv->rsa); |
| |
| buffer_free(&decrypted); |
| |
| /* enable blinding */ |
| if (RSA_blinding_on(prv->rsa, NULL) != 1) { |
| error("key_load_private_rsa1: RSA_blinding_on failed"); |
| goto fail; |
| } |
| close(fd); |
| return prv; |
| |
| fail: |
| if (commentp) |
| xfree(*commentp); |
| close(fd); |
| key_free(prv); |
| return NULL; |
| } |
| |
| Key * |
| key_load_private_pem(int fd, int type, const char *passphrase, |
| char **commentp) |
| { |
| FILE *fp; |
| EVP_PKEY *pk = NULL; |
| Key *prv = NULL; |
| char *name = "<no key>"; |
| |
| fp = fdopen(fd, "r"); |
| if (fp == NULL) { |
| error("fdopen failed: %s", strerror(errno)); |
| close(fd); |
| return NULL; |
| } |
| pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase); |
| if (pk == NULL) { |
| debug("PEM_read_PrivateKey failed"); |
| (void)ERR_get_error(); |
| } else if (pk->type == EVP_PKEY_RSA && |
| (type == KEY_UNSPEC||type==KEY_RSA)) { |
| prv = key_new(KEY_UNSPEC); |
| prv->rsa = EVP_PKEY_get1_RSA(pk); |
| prv->type = KEY_RSA; |
| name = "rsa w/o comment"; |
| #ifdef DEBUG_PK |
| RSA_print_fp(stderr, prv->rsa, 8); |
| #endif |
| if (RSA_blinding_on(prv->rsa, NULL) != 1) { |
| error("key_load_private_pem: RSA_blinding_on failed"); |
| key_free(prv); |
| prv = NULL; |
| } |
| } else if (pk->type == EVP_PKEY_DSA && |
| (type == KEY_UNSPEC||type==KEY_DSA)) { |
| prv = key_new(KEY_UNSPEC); |
| prv->dsa = EVP_PKEY_get1_DSA(pk); |
| prv->type = KEY_DSA; |
| name = "dsa w/o comment"; |
| #ifdef DEBUG_PK |
| DSA_print_fp(stderr, prv->dsa, 8); |
| #endif |
| } else { |
| error("PEM_read_PrivateKey: mismatch or " |
| "unknown EVP_PKEY save_type %d", pk->save_type); |
| } |
| fclose(fp); |
| if (pk != NULL) |
| EVP_PKEY_free(pk); |
| if (prv != NULL && commentp) |
| *commentp = xstrdup(name); |
| debug("read PEM private key done: type %s", |
| prv ? key_type(prv) : "<unknown>"); |
| return prv; |
| } |
| |
| int |
| key_perm_ok(int fd, const char *filename) |
| { |
| struct stat st; |
| |
| if (fstat(fd, &st) < 0) |
| return 0; |
| /* |
| * if a key owned by the user is accessed, then we check the |
| * permissions of the file. if the key owned by a different user, |
| * then we don't care. |
| */ |
| #ifdef HAVE_CYGWIN |
| if (check_ntsec(filename)) |
| #endif |
| if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) { |
| error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); |
| error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @"); |
| error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); |
| error("Permissions 0%3.3o for '%s' are too open.", |
| (u_int)st.st_mode & 0777, filename); |
| error("It is recommended that your private key files are NOT accessible by others."); |
| error("This private key will be ignored."); |
| return 0; |
| } |
| return 1; |
| } |
| |
| Key * |
| key_load_private_type(int type, const char *filename, const char *passphrase, |
| char **commentp, int *perm_ok) |
| { |
| int fd; |
| |
| fd = open(filename, O_RDONLY); |
| if (fd < 0) |
| return NULL; |
| if (!key_perm_ok(fd, filename)) { |
| if (perm_ok != NULL) |
| *perm_ok = 0; |
| error("bad permissions: ignore key: %s", filename); |
| close(fd); |
| return NULL; |
| } |
| if (perm_ok != NULL) |
| *perm_ok = 1; |
| switch (type) { |
| case KEY_RSA1: |
| return key_load_private_rsa1(fd, filename, passphrase, |
| commentp); |
| /* closes fd */ |
| case KEY_DSA: |
| case KEY_RSA: |
| case KEY_UNSPEC: |
| return key_load_private_pem(fd, type, passphrase, commentp); |
| /* closes fd */ |
| default: |
| close(fd); |
| break; |
| } |
| return NULL; |
| } |
| |
| Key * |
| key_load_private(const char *filename, const char *passphrase, |
| char **commentp) |
| { |
| Key *pub, *prv; |
| int fd; |
| |
| fd = open(filename, O_RDONLY); |
| if (fd < 0) |
| return NULL; |
| if (!key_perm_ok(fd, filename)) { |
| error("bad permissions: ignore key: %s", filename); |
| close(fd); |
| return NULL; |
| } |
| pub = key_load_public_rsa1(fd, filename, commentp); |
| lseek(fd, (off_t) 0, SEEK_SET); /* rewind */ |
| if (pub == NULL) { |
| /* closes fd */ |
| prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL); |
| /* use the filename as a comment for PEM */ |
| if (commentp && prv) |
| *commentp = xstrdup(filename); |
| } else { |
| /* it's a SSH v1 key if the public key part is readable */ |
| key_free(pub); |
| /* closes fd */ |
| prv = key_load_private_rsa1(fd, filename, passphrase, NULL); |
| } |
| return prv; |
| } |
| |
| static int |
| key_try_load_public(Key *k, const char *filename, char **commentp) |
| { |
| FILE *f; |
| char line[SSH_MAX_PUBKEY_BYTES]; |
| char *cp; |
| u_long linenum = 0; |
| |
| f = fopen(filename, "r"); |
| if (f != NULL) { |
| while (read_keyfile_line(f, filename, line, sizeof(line), |
| &linenum) != -1) { |
| cp = line; |
| switch (*cp) { |
| case '#': |
| case '\n': |
| case '\0': |
| continue; |
| } |
| /* Skip leading whitespace. */ |
| for (; *cp && (*cp == ' ' || *cp == '\t'); cp++) |
| ; |
| if (*cp) { |
| if (key_read(k, &cp) == 1) { |
| if (commentp) |
| *commentp=xstrdup(filename); |
| fclose(f); |
| return 1; |
| } |
| } |
| } |
| fclose(f); |
| } |
| return 0; |
| } |
| |
| /* load public key from ssh v1 private or any pubkey file */ |
| Key * |
| key_load_public(const char *filename, char **commentp) |
| { |
| Key *pub; |
| char file[MAXPATHLEN]; |
| |
| /* try rsa1 private key */ |
| pub = key_load_public_type(KEY_RSA1, filename, commentp); |
| if (pub != NULL) |
| return pub; |
| |
| /* try rsa1 public key */ |
| pub = key_new(KEY_RSA1); |
| if (key_try_load_public(pub, filename, commentp) == 1) |
| return pub; |
| key_free(pub); |
| |
| /* try ssh2 public key */ |
| pub = key_new(KEY_UNSPEC); |
| if (key_try_load_public(pub, filename, commentp) == 1) |
| return pub; |
| if ((strlcpy(file, filename, sizeof file) < sizeof(file)) && |
| (strlcat(file, ".pub", sizeof file) < sizeof(file)) && |
| (key_try_load_public(pub, file, commentp) == 1)) |
| return pub; |
| key_free(pub); |
| return NULL; |
| } |