Mercurial > dropbear
view gensignkey.c @ 1930:299f4f19ba19
Add /usr/sbin and /sbin to default root PATH
When dropbear is used in a very restricted environment (such as in a
initrd), the default user shell is often also very restricted
and doesn't take care of setting the PATH so the user ends up
with the PATH set by dropbear. Unfortunately, dropbear always
sets "/usr/bin:/bin" as default PATH even for the root user
which should have /usr/sbin and /sbin too.
For a concrete instance of this problem, see the "Remote Unlocking"
section in this tutorial: https://paxswill.com/blog/2013/11/04/encrypted-raspberry-pi/
It speaks of a bug in the initramfs script because it's written "blkid"
instead of "/sbin/blkid"... this is just because the scripts from the
initramfs do not expect to have a PATH without the sbin directories and
because dropbear is not setting the PATH appropriately for the root user.
I'm thus suggesting to use the attached patch to fix this misbehaviour (I
did not test it, but it's easy enough). It might seem anecdotic but
multiple Kali users have been bitten by this.
From https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=903403
author | Raphael Hertzog <hertzog@debian.org> |
---|---|
date | Mon, 09 Jul 2018 16:27:53 +0200 |
parents | 8b4274d34fe8 |
children |
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#include "includes.h" #include "dbutil.h" #include "buffer.h" #include "ecdsa.h" #include "genrsa.h" #include "gendss.h" #include "gened25519.h" #include "signkey.h" #include "dbrandom.h" /* Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */ static int buf_writefile(buffer * buf, const char * filename, int skip_exist) { int ret = DROPBEAR_FAILURE; int fd = -1; fd = open(filename, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); if (fd < 0) { /* If generating keys on connection (skip_exist) it's OK to get EEXIST - we probably just lost a race with another connection to generate the key */ if (skip_exist && errno == EEXIST) { ret = DROPBEAR_SUCCESS; } else { dropbear_log(LOG_ERR, "Couldn't create new file %s: %s", filename, strerror(errno)); } goto out; } /* write the file now */ while (buf->pos != buf->len) { int len = write(fd, buf_getptr(buf, buf->len - buf->pos), buf->len - buf->pos); if (len == -1 && errno == EINTR) { continue; } if (len <= 0) { dropbear_log(LOG_ERR, "Failed writing file %s: %s", filename, strerror(errno)); goto out; } buf_incrpos(buf, len); } ret = DROPBEAR_SUCCESS; out: if (fd >= 0) { if (fsync(fd) != 0) { dropbear_log(LOG_ERR, "fsync of %s failed: %s", filename, strerror(errno)); } m_close(fd); } return ret; } /* returns 0 on failure */ static int get_default_bits(enum signkey_type keytype) { switch (keytype) { #if DROPBEAR_RSA case DROPBEAR_SIGNKEY_RSA: return DROPBEAR_DEFAULT_RSA_SIZE; #endif #if DROPBEAR_DSS case DROPBEAR_SIGNKEY_DSS: /* DSS for SSH only defines 1024 bits */ return 1024; #endif #if DROPBEAR_ECDSA case DROPBEAR_SIGNKEY_ECDSA_KEYGEN: return ECDSA_DEFAULT_SIZE; case DROPBEAR_SIGNKEY_ECDSA_NISTP521: return 521; case DROPBEAR_SIGNKEY_ECDSA_NISTP384: return 384; case DROPBEAR_SIGNKEY_ECDSA_NISTP256: return 256; #endif #if DROPBEAR_ED25519 case DROPBEAR_SIGNKEY_ED25519: return 256; #endif default: return 0; } } int signkey_generate_get_bits(enum signkey_type keytype, int bits) { if (bits == 0) { bits = get_default_bits(keytype); } return bits; } /* if skip_exist is set it will silently return if the key file exists */ int signkey_generate(enum signkey_type keytype, int bits, const char* filename, int skip_exist) { sign_key * key = NULL; buffer *buf = NULL; char *fn_temp = NULL; int ret = DROPBEAR_FAILURE; bits = signkey_generate_get_bits(keytype, bits); /* now we can generate the key */ key = new_sign_key(); seedrandom(); switch(keytype) { #if DROPBEAR_RSA case DROPBEAR_SIGNKEY_RSA: key->rsakey = gen_rsa_priv_key(bits); break; #endif #if DROPBEAR_DSS case DROPBEAR_SIGNKEY_DSS: key->dsskey = gen_dss_priv_key(bits); break; #endif #if DROPBEAR_ECDSA case DROPBEAR_SIGNKEY_ECDSA_KEYGEN: case DROPBEAR_SIGNKEY_ECDSA_NISTP521: case DROPBEAR_SIGNKEY_ECDSA_NISTP384: case DROPBEAR_SIGNKEY_ECDSA_NISTP256: { ecc_key *ecckey = gen_ecdsa_priv_key(bits); keytype = ecdsa_signkey_type(ecckey); *signkey_key_ptr(key, keytype) = ecckey; } break; #endif #if DROPBEAR_ED25519 case DROPBEAR_SIGNKEY_ED25519: key->ed25519key = gen_ed25519_priv_key(bits); break; #endif default: dropbear_exit("Internal error"); } seedrandom(); buf = buf_new(MAX_PRIVKEY_SIZE); buf_put_priv_key(buf, key, keytype); sign_key_free(key); key = NULL; buf_setpos(buf, 0); fn_temp = m_malloc(strlen(filename) + 30); snprintf(fn_temp, strlen(filename)+30, "%s.tmp%d", filename, getpid()); ret = buf_writefile(buf, fn_temp, 0); if (ret == DROPBEAR_FAILURE) { goto out; } if (link(fn_temp, filename) < 0) { /* If generating keys on connection (skipexist) it's OK to get EEXIST - we probably just lost a race with another connection to generate the key */ if (!(skip_exist && errno == EEXIST)) { if (errno == EPERM || errno == EACCES) { /* Non-atomic fallback when hard-links not allowed or unsupported */ buf_setpos(buf, 0); ret = buf_writefile(buf, filename, skip_exist); } else { dropbear_log(LOG_ERR, "Failed moving key file to %s: %s", filename, strerror(errno)); ret = DROPBEAR_FAILURE; } goto out; } } /* ensure directory update is flushed to disk, otherwise we can end up with zero-byte hostkey files if the power goes off */ fsync_parent_dir(filename); out: if (buf) { buf_burn_free(buf); } if (fn_temp) { unlink(fn_temp); m_free(fn_temp); } return ret; }