/* * Code for PuTTY to import and export private key files in other * SSH clients' formats. */ #include #include #include #include #include "putty.h" #include "ssh.h" #include "mpint.h" #include "misc.h" static bool openssh_pem_encrypted(BinarySource *src); static bool openssh_new_encrypted(BinarySource *src); static ssh2_userkey *openssh_pem_read( BinarySource *src, const char *passphrase, const char **errmsg_p); static ssh2_userkey *openssh_new_read( BinarySource *src, const char *passphrase, const char **errmsg_p); static bool openssh_auto_write( const Filename *file, ssh2_userkey *key, const char *passphrase); static bool openssh_pem_write( const Filename *file, ssh2_userkey *key, const char *passphrase); static bool openssh_new_write( const Filename *file, ssh2_userkey *key, const char *passphrase); static bool sshcom_encrypted(BinarySource *src, char **comment); static ssh2_userkey *sshcom_read( BinarySource *src, const char *passphrase, const char **errmsg_p); static bool sshcom_write( const Filename *file, ssh2_userkey *key, const char *passphrase); /* * Given a key type, determine whether we know how to import it. */ bool import_possible(int type) { if (type == SSH_KEYTYPE_OPENSSH_PEM) return true; if (type == SSH_KEYTYPE_OPENSSH_NEW) return true; if (type == SSH_KEYTYPE_SSHCOM) return true; return false; } /* * Given a key type, determine what native key type * (SSH_KEYTYPE_SSH1 or SSH_KEYTYPE_SSH2) it will come out as once * we've imported it. */ int import_target_type(int type) { /* * There are no known foreign SSH-1 key formats. */ return SSH_KEYTYPE_SSH2; } static inline char *bsgetline(BinarySource *src) { ptrlen line = get_chomped_line(src); if (get_err(src)) return NULL; return mkstr(line); } /* * Determine whether a foreign key is encrypted. */ bool import_encrypted_s(const Filename *filename, BinarySource *src, int type, char **comment) { if (type == SSH_KEYTYPE_OPENSSH_PEM) { /* OpenSSH PEM format doesn't contain a key comment at all */ *comment = dupstr(filename_to_str(filename)); return openssh_pem_encrypted(src); } else if (type == SSH_KEYTYPE_OPENSSH_NEW) { /* OpenSSH new format does, but it's inside the encrypted * section for some reason */ *comment = dupstr(filename_to_str(filename)); return openssh_new_encrypted(src); } else if (type == SSH_KEYTYPE_SSHCOM) { return sshcom_encrypted(src, comment); } return false; } bool import_encrypted(const Filename *filename, int type, char **comment) { LoadedFile *lf = lf_load_keyfile(filename, NULL); if (!lf) return false; /* couldn't even open the file */ bool toret = import_encrypted_s(filename, BinarySource_UPCAST(lf), type, comment); lf_free(lf); return toret; } /* * Import an SSH-1 key. */ int import_ssh1_s(BinarySource *src, int type, RSAKey *key, char *passphrase, const char **errmsg_p) { return 0; } int import_ssh1(const Filename *filename, int type, RSAKey *key, char *passphrase, const char **errmsg_p) { LoadedFile *lf = lf_load_keyfile(filename, errmsg_p); if (!lf) return false; int toret = import_ssh1_s(BinarySource_UPCAST(lf), type, key, passphrase, errmsg_p); lf_free(lf); return toret; } /* * Import an SSH-2 key. */ ssh2_userkey *import_ssh2_s(BinarySource *src, int type, char *passphrase, const char **errmsg_p) { if (type == SSH_KEYTYPE_OPENSSH_PEM) return openssh_pem_read(src, passphrase, errmsg_p); else if (type == SSH_KEYTYPE_OPENSSH_NEW) return openssh_new_read(src, passphrase, errmsg_p); if (type == SSH_KEYTYPE_SSHCOM) return sshcom_read(src, passphrase, errmsg_p); return NULL; } ssh2_userkey *import_ssh2(const Filename *filename, int type, char *passphrase, const char **errmsg_p) { LoadedFile *lf = lf_load_keyfile(filename, errmsg_p); if (!lf) return false; ssh2_userkey *toret = import_ssh2_s(BinarySource_UPCAST(lf), type, passphrase, errmsg_p); lf_free(lf); return toret; } /* * Export an SSH-1 key. */ bool export_ssh1(const Filename *filename, int type, RSAKey *key, char *passphrase) { return false; } /* * Export an SSH-2 key. */ bool export_ssh2(const Filename *filename, int type, ssh2_userkey *key, char *passphrase) { if (type == SSH_KEYTYPE_OPENSSH_AUTO) return openssh_auto_write(filename, key, passphrase); if (type == SSH_KEYTYPE_OPENSSH_NEW) return openssh_new_write(filename, key, passphrase); if (type == SSH_KEYTYPE_SSHCOM) return sshcom_write(filename, key, passphrase); return false; } /* ---------------------------------------------------------------------- * Helper routines. (The base64 ones are defined in sshpubk.c.) */ #define isbase64(c) ( ((c) >= 'A' && (c) <= 'Z') || \ ((c) >= 'a' && (c) <= 'z') || \ ((c) >= '0' && (c) <= '9') || \ (c) == '+' || (c) == '/' || (c) == '=' \ ) /* * Read an ASN.1/BER identifier and length pair. * * Flags are a combination of the #defines listed below. * * Returns -1 if unsuccessful; otherwise returns the number of * bytes used out of the source data. */ /* ASN.1 tag classes. */ #define ASN1_CLASS_UNIVERSAL (0 << 6) #define ASN1_CLASS_APPLICATION (1 << 6) #define ASN1_CLASS_CONTEXT_SPECIFIC (2 << 6) #define ASN1_CLASS_PRIVATE (3 << 6) #define ASN1_CLASS_MASK (3 << 6) /* Primitive versus constructed bit. */ #define ASN1_CONSTRUCTED (1 << 5) /* * Write an ASN.1/BER identifier and length pair. Returns the * number of bytes consumed. Assumes dest contains enough space. * Will avoid writing anything if dest is NULL, but still return * amount of space required. */ static void BinarySink_put_ber_id_len(BinarySink *bs, int id, int length, int flags) { if (id <= 30) { /* * Identifier is one byte. */ put_byte(bs, id | flags); } else { int n; /* * Identifier is multiple bytes: the first byte is 11111 * plus the flags, and subsequent bytes encode the value of * the identifier, 7 bits at a time, with the top bit of * each byte 1 except the last one which is 0. */ put_byte(bs, 0x1F | flags); for (n = 1; (id >> (7*n)) > 0; n++) continue; /* count the bytes */ while (n--) put_byte(bs, (n ? 0x80 : 0) | ((id >> (7*n)) & 0x7F)); } if (length < 128) { /* * Length is one byte. */ put_byte(bs, length); } else { int n; /* * Length is multiple bytes. The first is 0x80 plus the * number of subsequent bytes, and the subsequent bytes * encode the actual length. */ for (n = 1; (length >> (8*n)) > 0; n++) continue; /* count the bytes */ put_byte(bs, 0x80 | n); while (n--) put_byte(bs, (length >> (8*n)) & 0xFF); } } #define put_ber_id_len(bs, id, len, flags) \ BinarySink_put_ber_id_len(BinarySink_UPCAST(bs), id, len, flags) typedef struct ber_item { int id; int flags; ptrlen data; } ber_item; static ber_item BinarySource_get_ber(BinarySource *src) { ber_item toret; unsigned char leadbyte, lenbyte; size_t length; leadbyte = get_byte(src); toret.flags = (leadbyte & 0xE0); if ((leadbyte & 0x1F) == 0x1F) { unsigned char idbyte; toret.id = 0; do { idbyte = get_byte(src); toret.id = (toret.id << 7) | (idbyte & 0x7F); } while (idbyte & 0x80); } else { toret.id = leadbyte & 0x1F; } lenbyte = get_byte(src); if (lenbyte & 0x80) { int nbytes = lenbyte & 0x7F; length = 0; while (nbytes-- > 0) length = (length << 8) | get_byte(src); } else { length = lenbyte; } toret.data = get_data(src, length); return toret; } #define get_ber(bs) BinarySource_get_ber(BinarySource_UPCAST(bs)) /* ---------------------------------------------------------------------- * Code to read and write OpenSSH private keys, in the old-style PEM * format. */ typedef enum { OP_DSA, OP_RSA, OP_ECDSA } openssh_pem_keytype; typedef enum { OP_E_3DES, OP_E_AES } openssh_pem_enc; struct openssh_pem_key { openssh_pem_keytype keytype; bool encrypted; openssh_pem_enc encryption; char iv[32]; strbuf *keyblob; }; static void BinarySink_put_mp_ssh2_from_string(BinarySink *bs, ptrlen str) { const unsigned char *bytes = (const unsigned char *)str.ptr; size_t nbytes = str.len; while (nbytes > 0 && bytes[0] == 0) { nbytes--; bytes++; } if (nbytes > 0 && bytes[0] & 0x80) { put_uint32(bs, nbytes + 1); put_byte(bs, 0); } else { put_uint32(bs, nbytes); } put_data(bs, bytes, nbytes); } #define put_mp_ssh2_from_string(bs, str) \ BinarySink_put_mp_ssh2_from_string(BinarySink_UPCAST(bs), str) static struct openssh_pem_key *load_openssh_pem_key(BinarySource *src, const char **errmsg_p) { struct openssh_pem_key *ret; char *line = NULL; const char *errmsg; char *p; bool headers_done; char base64_bit[4]; int base64_chars = 0; ret = snew(struct openssh_pem_key); ret->keyblob = strbuf_new_nm(); if (!(line = bsgetline(src))) { errmsg = "unexpected end of file"; goto error; } if (!strstartswith(line, "-----BEGIN ") || !strendswith(line, "PRIVATE KEY-----")) { errmsg = "file does not begin with OpenSSH key header"; goto error; } /* * Parse the BEGIN line. For old-format keys, this tells us the * type of the key; for new-format keys, all it tells us is the * format, and we'll find out the key type once we parse the * base64. */ if (!strcmp(line, "-----BEGIN RSA PRIVATE KEY-----")) { ret->keytype = OP_RSA; } else if (!strcmp(line, "-----BEGIN DSA PRIVATE KEY-----")) { ret->keytype = OP_DSA; } else if (!strcmp(line, "-----BEGIN EC PRIVATE KEY-----")) { ret->keytype = OP_ECDSA; } else if (!strcmp(line, "-----BEGIN OPENSSH PRIVATE KEY-----")) { errmsg = "this is a new-style OpenSSH key"; goto error; } else { errmsg = "unrecognised key type"; goto error; } smemclr(line, strlen(line)); sfree(line); line = NULL; ret->encrypted = false; memset(ret->iv, 0, sizeof(ret->iv)); headers_done = false; while (1) { if (!(line = bsgetline(src))) { errmsg = "unexpected end of file"; goto error; } if (strstartswith(line, "-----END ") && strendswith(line, "PRIVATE KEY-----")) { sfree(line); line = NULL; break; /* done */ } if ((p = strchr(line, ':')) != NULL) { if (headers_done) { errmsg = "header found in body of key data"; goto error; } *p++ = '\0'; while (*p && isspace((unsigned char)*p)) p++; if (!strcmp(line, "Proc-Type")) { if (p[0] != '4' || p[1] != ',') { errmsg = "Proc-Type is not 4 (only 4 is supported)"; goto error; } p += 2; if (!strcmp(p, "ENCRYPTED")) ret->encrypted = true; } else if (!strcmp(line, "DEK-Info")) { int i, ivlen; if (!strncmp(p, "DES-EDE3-CBC,", 13)) { ret->encryption = OP_E_3DES; ivlen = 8; } else if (!strncmp(p, "AES-128-CBC,", 12)) { ret->encryption = OP_E_AES; ivlen = 16; } else { errmsg = "unsupported cipher"; goto error; } p = strchr(p, ',') + 1;/* always non-NULL, by above checks */ for (i = 0; i < ivlen; i++) { unsigned j; if (1 != sscanf(p, "%2x", &j)) { errmsg = "expected more iv data in DEK-Info"; goto error; } ret->iv[i] = j; p += 2; } if (*p) { errmsg = "more iv data than expected in DEK-Info"; goto error; } } } else { headers_done = true; p = line; while (isbase64(*p)) { base64_bit[base64_chars++] = *p; if (base64_chars == 4) { unsigned char out[3]; int len; base64_chars = 0; len = base64_decode_atom(base64_bit, out); if (len <= 0) { errmsg = "invalid base64 encoding"; goto error; } put_data(ret->keyblob, out, len); smemclr(out, sizeof(out)); } p++; } } smemclr(line, strlen(line)); sfree(line); line = NULL; } if (!ret->keyblob || ret->keyblob->len == 0) { errmsg = "key body not present"; goto error; } if (ret->encrypted && ret->keyblob->len % 8 != 0) { errmsg = "encrypted key blob is not a multiple of " "cipher block size"; goto error; } smemclr(base64_bit, sizeof(base64_bit)); if (errmsg_p) *errmsg_p = NULL; return ret; error: if (line) { smemclr(line, strlen(line)); sfree(line); line = NULL; } smemclr(base64_bit, sizeof(base64_bit)); if (ret) { if (ret->keyblob) strbuf_free(ret->keyblob); smemclr(ret, sizeof(*ret)); sfree(ret); } if (errmsg_p) *errmsg_p = errmsg; return NULL; } static bool openssh_pem_encrypted(BinarySource *src) { struct openssh_pem_key *key = load_openssh_pem_key(src, NULL); bool ret; if (!key) return false; ret = key->encrypted; strbuf_free(key->keyblob); smemclr(key, sizeof(*key)); sfree(key); return ret; } static void openssh_pem_derivekey( ptrlen passphrase, const void *iv, uint8_t *keybuf) { /* * Derive the encryption key for a PEM key file from the * passphrase and iv/salt: * * - let block A equal MD5(passphrase || iv) * - let block B equal MD5(A || passphrase || iv) * - block C would be MD5(B || passphrase || iv) and so on * - encryption key is the first N bytes of A || B * * (Note that only 8 bytes of the iv are used for key * derivation, even when the key is encrypted with AES and * hence there are 16 bytes available.) */ ssh_hash *h; h = ssh_hash_new(&ssh_md5); put_datapl(h, passphrase); put_data(h, iv, 8); ssh_hash_digest(h, keybuf); ssh_hash_reset(h); put_data(h, keybuf, 16); put_datapl(h, passphrase); put_data(h, iv, 8); ssh_hash_final(h, keybuf + 16); } static ssh2_userkey *openssh_pem_read( BinarySource *filesrc, const char *passphrase, const char **errmsg_p) { struct openssh_pem_key *key = load_openssh_pem_key(filesrc, errmsg_p); ssh2_userkey *retkey; const ssh_keyalg *alg; BinarySource src[1]; int i, num_integers; ssh2_userkey *retval = NULL; const char *errmsg; strbuf *blob = strbuf_new_nm(); int privptr = 0, publen; if (!key) { strbuf_free(blob); return NULL; } if (key->encrypted) { unsigned char keybuf[32]; openssh_pem_derivekey(ptrlen_from_asciz(passphrase), key->iv, keybuf); /* * Decrypt the key blob. */ if (key->encryption == OP_E_3DES) des3_decrypt_pubkey_ossh(keybuf, key->iv, key->keyblob->u, key->keyblob->len); else { ssh_cipher *cipher = ssh_cipher_new(&ssh_aes128_cbc); ssh_cipher_setkey(cipher, keybuf); ssh_cipher_setiv(cipher, key->iv); ssh_cipher_decrypt(cipher, key->keyblob->u, key->keyblob->len); ssh_cipher_free(cipher); } smemclr(keybuf, sizeof(keybuf)); } /* * Now we have a decrypted key blob, which contains an ASN.1 * encoded private key. We must now untangle the ASN.1. * * We expect the whole key blob to be formatted as a SEQUENCE * (0x30 followed by a length code indicating that the rest of * the blob is part of the sequence). Within that SEQUENCE we * expect to see a bunch of INTEGERs. What those integers mean * depends on the key type: * * - For RSA, we expect the integers to be 0, n, e, d, p, q, * dmp1, dmq1, iqmp in that order. (The last three are d mod * (p-1), d mod (q-1), inverse of q mod p respectively.) * * - For DSA, we expect them to be 0, p, q, g, y, x in that * order. * * - In ECDSA the format is totally different: we see the * SEQUENCE, but beneath is an INTEGER 1, OCTET STRING priv * EXPLICIT [0] OID curve, EXPLICIT [1] BIT STRING pubPoint */ BinarySource_BARE_INIT(src, key->keyblob->u, key->keyblob->len); { /* Expect the SEQUENCE header. Take its absence as a failure to * decrypt, if the key was encrypted. */ ber_item seq = get_ber(src); if (get_err(src) || seq.id != 16) { errmsg = "ASN.1 decoding failure"; retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL; goto error; } /* Reinitialise our BinarySource to parse just the inside of that * SEQUENCE. */ BinarySource_BARE_INIT_PL(src, seq.data); } /* Expect a load of INTEGERs. */ if (key->keytype == OP_RSA) num_integers = 9; else if (key->keytype == OP_DSA) num_integers = 6; else num_integers = 0; /* placate compiler warnings */ if (key->keytype == OP_ECDSA) { /* And now for something completely different */ ber_item integer, privkey, sub0, sub1, oid, pubkey; const ssh_keyalg *alg; const struct ec_curve *curve; /* Parse the outer layer of things inside the containing SEQUENCE */ integer = get_ber(src); privkey = get_ber(src); sub0 = get_ber(src); sub1 = get_ber(src); /* Now look inside sub0 for the curve OID */ BinarySource_BARE_INIT_PL(src, sub0.data); oid = get_ber(src); /* And inside sub1 for the public-key BIT STRING */ BinarySource_BARE_INIT_PL(src, sub1.data); pubkey = get_ber(src); if (get_err(src) || integer.id != 2 || integer.data.len != 1 || ((const unsigned char *)integer.data.ptr)[0] != 1 || privkey.id != 4 || sub0.id != 0 || sub1.id != 1 || oid.id != 6 || pubkey.id != 3) { errmsg = "ASN.1 decoding failure"; retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL; goto error; } alg = ec_alg_by_oid(oid.data.len, oid.data.ptr, &curve); if (!alg) { errmsg = "Unsupported ECDSA curve."; retval = NULL; goto error; } if (pubkey.data.len != ((((curve->fieldBits + 7) / 8) * 2) + 2)) { errmsg = "ASN.1 decoding failure"; retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL; goto error; } /* Skip 0x00 before point */ pubkey.data.ptr = (const char *)pubkey.data.ptr + 1; pubkey.data.len -= 1; /* Construct the key */ retkey = snew(ssh2_userkey); put_stringz(blob, alg->ssh_id); put_stringz(blob, curve->name); put_stringpl(blob, pubkey.data); publen = blob->len; put_mp_ssh2_from_string(blob, privkey.data); retkey->key = ssh_key_new_priv( alg, make_ptrlen(blob->u, publen), make_ptrlen(blob->u + publen, blob->len - publen)); if (!retkey->key) { sfree(retkey); errmsg = "unable to create key data structure"; goto error; } } else if (key->keytype == OP_RSA || key->keytype == OP_DSA) { put_stringz(blob, key->keytype == OP_DSA ? "ssh-dss" : "ssh-rsa"); ptrlen rsa_modulus = PTRLEN_LITERAL(""); for (i = 0; i < num_integers; i++) { ber_item integer = get_ber(src); if (get_err(src) || integer.id != 2) { errmsg = "ASN.1 decoding failure"; retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL; goto error; } if (i == 0) { /* * The first integer should be zero always (I think * this is some sort of version indication). */ if (integer.data.len != 1 || ((const unsigned char *)integer.data.ptr)[0] != 0) { errmsg = "version number mismatch"; goto error; } } else if (key->keytype == OP_RSA) { /* * Integers 1 and 2 go into the public blob but in the * opposite order; integers 3, 4, 5 and 8 go into the * private blob. The other two (6 and 7) are ignored. */ if (i == 1) { /* Save the details for after we deal with number 2. */ rsa_modulus = integer.data; } else if (i != 6 && i != 7) { put_mp_ssh2_from_string(blob, integer.data); if (i == 2) { put_mp_ssh2_from_string(blob, rsa_modulus); privptr = blob->len; } } } else if (key->keytype == OP_DSA) { /* * Integers 1-4 go into the public blob; integer 5 goes * into the private blob. */ put_mp_ssh2_from_string(blob, integer.data); if (i == 4) privptr = blob->len; } } /* * Now put together the actual key. Simplest way to do this is * to assemble our own key blobs and feed them to the createkey * functions; this is a bit faffy but it does mean we get all * the sanity checks for free. */ assert(privptr > 0); /* should have bombed by now if not */ retkey = snew(ssh2_userkey); alg = (key->keytype == OP_RSA ? &ssh_rsa : &ssh_dsa); retkey->key = ssh_key_new_priv( alg, make_ptrlen(blob->u, privptr), make_ptrlen(blob->u+privptr, blob->len-privptr)); if (!retkey->key) { sfree(retkey); errmsg = "unable to create key data structure"; goto error; } } else { unreachable("Bad key type from load_openssh_pem_key"); errmsg = "Bad key type from load_openssh_pem_key"; goto error; } /* * The old key format doesn't include a comment in the private * key file. */ retkey->comment = dupstr("imported-openssh-key"); errmsg = NULL; /* no error */ retval = retkey; error: strbuf_free(blob); strbuf_free(key->keyblob); smemclr(key, sizeof(*key)); sfree(key); if (errmsg_p) *errmsg_p = errmsg; return retval; } static bool openssh_pem_write( const Filename *filename, ssh2_userkey *ukey, const char *passphrase) { strbuf *pubblob, *privblob, *outblob; unsigned char *spareblob; int sparelen = 0; ptrlen numbers[9]; int nnumbers, i; const char *header, *footer; char zero[1]; unsigned char iv[8]; bool ret = false; FILE *fp; BinarySource src[1]; /* OpenSSH's private key files never contain a certificate, so * revert to the underlying base key if necessary */ ssh_key *key = ssh_key_base_key(ukey->key); /* * Fetch the key blobs. */ pubblob = strbuf_new(); ssh_key_public_blob(key, BinarySink_UPCAST(pubblob)); privblob = strbuf_new_nm(); ssh_key_private_blob(key, BinarySink_UPCAST(privblob)); spareblob = NULL; outblob = strbuf_new_nm(); /* * Encode the OpenSSH key blob, and also decide on the header * line. */ if (ssh_key_alg(key) == &ssh_rsa || ssh_key_alg(key) == &ssh_dsa) { strbuf *seq; /* * The RSA and DSA handlers share some code because the two * key types have very similar ASN.1 representations, as a * plain SEQUENCE of big integers. So we set up a list of * bignums per key type and then construct the actual blob in * common code after that. */ if (ssh_key_alg(key) == &ssh_rsa) { ptrlen n, e, d, p, q, iqmp, dmp1, dmq1; mp_int *bd, *bp, *bq, *bdmp1, *bdmq1; /* * These blobs were generated from inside PuTTY, so we needn't * treat them as untrusted. */ BinarySource_BARE_INIT(src, pubblob->u, pubblob->len); get_string(src); /* skip algorithm name */ e = get_string(src); n = get_string(src); BinarySource_BARE_INIT(src, privblob->u, privblob->len); d = get_string(src); p = get_string(src); q = get_string(src); iqmp = get_string(src); assert(!get_err(src)); /* can't go wrong */ /* We also need d mod (p-1) and d mod (q-1). */ bd = mp_from_bytes_be(d); bp = mp_from_bytes_be(p); bq = mp_from_bytes_be(q); mp_sub_integer_into(bp, bp, 1); mp_sub_integer_into(bq, bq, 1); bdmp1 = mp_mod(bd, bp); bdmq1 = mp_mod(bd, bq); mp_free(bd); mp_free(bp); mp_free(bq); dmp1.len = (mp_get_nbits(bdmp1)+8)/8; dmq1.len = (mp_get_nbits(bdmq1)+8)/8; sparelen = dmp1.len + dmq1.len; spareblob = snewn(sparelen, unsigned char); dmp1.ptr = spareblob; dmq1.ptr = spareblob + dmp1.len; for (i = 0; i < dmp1.len; i++) spareblob[i] = mp_get_byte(bdmp1, dmp1.len-1 - i); for (i = 0; i < dmq1.len; i++) spareblob[i+dmp1.len] = mp_get_byte(bdmq1, dmq1.len-1 - i); mp_free(bdmp1); mp_free(bdmq1); numbers[0] = make_ptrlen(zero, 1); zero[0] = '\0'; numbers[1] = n; numbers[2] = e; numbers[3] = d; numbers[4] = p; numbers[5] = q; numbers[6] = dmp1; numbers[7] = dmq1; numbers[8] = iqmp; nnumbers = 9; header = "-----BEGIN RSA PRIVATE KEY-----\n"; footer = "-----END RSA PRIVATE KEY-----\n"; } else { /* ssh-dss */ ptrlen p, q, g, y, x; /* * These blobs were generated from inside PuTTY, so we needn't * treat them as untrusted. */ BinarySource_BARE_INIT(src, pubblob->u, pubblob->len); get_string(src); /* skip algorithm name */ p = get_string(src); q = get_string(src); g = get_string(src); y = get_string(src); BinarySource_BARE_INIT(src, privblob->u, privblob->len); x = get_string(src); assert(!get_err(src)); /* can't go wrong */ numbers[0].ptr = zero; numbers[0].len = 1; zero[0] = '\0'; numbers[1] = p; numbers[2] = q; numbers[3] = g; numbers[4] = y; numbers[5] = x; nnumbers = 6; header = "-----BEGIN DSA PRIVATE KEY-----\n"; footer = "-----END DSA PRIVATE KEY-----\n"; } seq = strbuf_new_nm(); for (i = 0; i < nnumbers; i++) { put_ber_id_len(seq, 2, numbers[i].len, 0); put_datapl(seq, numbers[i]); } put_ber_id_len(outblob, 16, seq->len, ASN1_CONSTRUCTED); put_data(outblob, seq->s, seq->len); strbuf_free(seq); } else if (ssh_key_alg(key) == &ssh_ecdsa_nistp256 || ssh_key_alg(key) == &ssh_ecdsa_nistp384 || ssh_key_alg(key) == &ssh_ecdsa_nistp521) { const unsigned char *oid; struct ecdsa_key *ec = container_of(key, struct ecdsa_key, sshk); int oidlen; int pointlen; strbuf *seq, *sub; /* * Structure of asn1: * SEQUENCE * INTEGER 1 * OCTET STRING (private key) * [0] * OID (curve) * [1] * BIT STRING (0x00 public key point) */ oid = ec_alg_oid(ssh_key_alg(key), &oidlen); pointlen = (ec->curve->fieldBits + 7) / 8 * 2; seq = strbuf_new_nm(); /* INTEGER 1 */ put_ber_id_len(seq, 2, 1, 0); put_byte(seq, 1); /* OCTET STRING private key */ put_ber_id_len(seq, 4, privblob->len - 4, 0); put_data(seq, privblob->s + 4, privblob->len - 4); /* Subsidiary OID */ sub = strbuf_new(); put_ber_id_len(sub, 6, oidlen, 0); put_data(sub, oid, oidlen); /* Append the OID to the sequence */ put_ber_id_len(seq, 0, sub->len, ASN1_CLASS_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED); put_data(seq, sub->s, sub->len); strbuf_free(sub); /* Subsidiary BIT STRING */ sub = strbuf_new(); put_ber_id_len(sub, 3, 2 + pointlen, 0); put_byte(sub, 0); put_data(sub, pubblob->s+39, 1 + pointlen); /* Append the BIT STRING to the sequence */ put_ber_id_len(seq, 1, sub->len, ASN1_CLASS_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED); put_data(seq, sub->s, sub->len); strbuf_free(sub); /* Write the full sequence with header to the output blob. */ put_ber_id_len(outblob, 16, seq->len, ASN1_CONSTRUCTED); put_data(outblob, seq->s, seq->len); strbuf_free(seq); header = "-----BEGIN EC PRIVATE KEY-----\n"; footer = "-----END EC PRIVATE KEY-----\n"; } else { unreachable("bad key alg in openssh_pem_write"); } /* * Encrypt the key. * * For the moment, we still encrypt our OpenSSH keys using * old-style 3DES. */ if (passphrase) { unsigned char keybuf[32]; int origlen, outlen, pad; /* * Padding on OpenSSH keys is deterministic. The number of * padding bytes is always more than zero, and always at most * the cipher block length. The value of each padding byte is * equal to the number of padding bytes. So a plaintext that's * an exact multiple of the block size will be padded with 08 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a * plaintext one byte less than a multiple of the block size * will be padded with just 01. * * This enables the OpenSSL key decryption function to strip * off the padding algorithmically and return the unpadded * plaintext to the next layer: it looks at the final byte, and * then expects to find that many bytes at the end of the data * with the same value. Those are all removed and the rest is * returned. */ origlen = outblob->len; outlen = (origlen + 8) &~ 7; pad = outlen - origlen; put_padding(outblob, pad, pad); /* * Invent an iv, and derive the encryption key. */ random_read(iv, 8); openssh_pem_derivekey(ptrlen_from_asciz(passphrase), iv, keybuf); /* * Now encrypt the key blob. */ des3_encrypt_pubkey_ossh(keybuf, iv, outblob->u, outlen); smemclr(keybuf, sizeof(keybuf)); } /* * And save it. We'll use Unix line endings just in case it's * subsequently transferred in binary mode. */ fp = f_open(filename, "wb", true); /* ensure Unix line endings */ if (!fp) goto error; fputs(header, fp); if (passphrase) { fprintf(fp, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,"); for (i = 0; i < 8; i++) fprintf(fp, "%02X", iv[i]); fprintf(fp, "\n\n"); } base64_encode_fp(fp, ptrlen_from_strbuf(outblob), 64); fputs(footer, fp); fclose(fp); ret = true; error: if (outblob) strbuf_free(outblob); if (spareblob) { smemclr(spareblob, sparelen); sfree(spareblob); } if (privblob) strbuf_free(privblob); if (pubblob) strbuf_free(pubblob); return ret; } /* ---------------------------------------------------------------------- * Code to read and write OpenSSH private keys in the new-style format. */ typedef enum { ON_E_NONE, ON_E_AES256CBC, ON_E_AES256CTR } openssh_new_cipher; typedef enum { ON_K_NONE, ON_K_BCRYPT } openssh_new_kdf; struct openssh_new_key { openssh_new_cipher cipher; openssh_new_kdf kdf; union { struct { int rounds; /* This points to a position within keyblob, not a * separately allocated thing */ ptrlen salt; } bcrypt; } kdfopts; int nkeys, key_wanted; /* This too points to a position within keyblob */ ptrlen private; strbuf *keyblob; }; static struct openssh_new_key *load_openssh_new_key(BinarySource *filesrc, const char **errmsg_p) { struct openssh_new_key *ret; char *line = NULL; const char *errmsg; char *p; char base64_bit[4]; int base64_chars = 0; BinarySource src[1]; ptrlen str; unsigned key_index; ret = snew(struct openssh_new_key); ret->keyblob = strbuf_new_nm(); if (!(line = bsgetline(filesrc))) { errmsg = "unexpected end of file"; goto error; } if (0 != strcmp(line, "-----BEGIN OPENSSH PRIVATE KEY-----")) { errmsg = "file does not begin with OpenSSH new-style key header"; goto error; } smemclr(line, strlen(line)); sfree(line); line = NULL; while (1) { if (!(line = bsgetline(filesrc))) { errmsg = "unexpected end of file"; goto error; } if (0 == strcmp(line, "-----END OPENSSH PRIVATE KEY-----")) { sfree(line); line = NULL; break; /* done */ } p = line; while (isbase64(*p)) { base64_bit[base64_chars++] = *p; if (base64_chars == 4) { unsigned char out[3]; int len; base64_chars = 0; len = base64_decode_atom(base64_bit, out); if (len <= 0) { errmsg = "invalid base64 encoding"; goto error; } put_data(ret->keyblob, out, len); smemclr(out, sizeof(out)); } p++; } smemclr(line, strlen(line)); sfree(line); line = NULL; } if (ret->keyblob->len == 0) { errmsg = "key body not present"; goto error; } BinarySource_BARE_INIT_PL(src, ptrlen_from_strbuf(ret->keyblob)); if (strcmp(get_asciz(src), "openssh-key-v1") != 0) { errmsg = "new-style OpenSSH magic number missing\n"; goto error; } /* Cipher name */ str = get_string(src); if (ptrlen_eq_string(str, "none")) { ret->cipher = ON_E_NONE; } else if (ptrlen_eq_string(str, "aes256-cbc")) { ret->cipher = ON_E_AES256CBC; } else if (ptrlen_eq_string(str, "aes256-ctr")) { ret->cipher = ON_E_AES256CTR; } else { errmsg = get_err(src) ? "no cipher name found" : "unrecognised cipher name\n"; goto error; } /* Key derivation function name */ str = get_string(src); if (ptrlen_eq_string(str, "none")) { ret->kdf = ON_K_NONE; } else if (ptrlen_eq_string(str, "bcrypt")) { ret->kdf = ON_K_BCRYPT; } else { errmsg = get_err(src) ? "no kdf name found" : "unrecognised kdf name\n"; goto error; } /* KDF extra options */ str = get_string(src); switch (ret->kdf) { case ON_K_NONE: if (str.len != 0) { errmsg = "expected empty options string for 'none' kdf"; goto error; } break; case ON_K_BCRYPT: { BinarySource opts[1]; BinarySource_BARE_INIT_PL(opts, str); ret->kdfopts.bcrypt.salt = get_string(opts); ret->kdfopts.bcrypt.rounds = get_uint32(opts); if (get_err(opts)) { errmsg = "failed to parse bcrypt options string"; goto error; } break; } } /* * At this point we expect a uint32 saying how many keys are * stored in this file. OpenSSH new-style key files can * contain more than one. Currently we don't have any user * interface to specify which one we're trying to extract, so * we just bomb out with an error if more than one is found in * the file. However, I've put in all the mechanism here to * extract the nth one for a given n, in case we later connect * up some UI to that mechanism. Just arrange that the * 'key_wanted' field is set to a value in the range [0, * nkeys) by some mechanism. */ ret->nkeys = toint(get_uint32(src)); if (ret->nkeys != 1) { errmsg = get_err(src) ? "no key count found" : "multiple keys in new-style OpenSSH key file not supported\n"; goto error; } ret->key_wanted = 0; /* Read and ignore a string per public key. */ for (key_index = 0; key_index < ret->nkeys; key_index++) str = get_string(src); /* * Now we expect a string containing the encrypted part of the * key file. */ ret->private = get_string(src); if (get_err(src)) { errmsg = "no private key container string found\n"; goto error; } /* * And now we're done, until asked to actually decrypt. */ smemclr(base64_bit, sizeof(base64_bit)); if (errmsg_p) *errmsg_p = NULL; return ret; error: if (line) { smemclr(line, strlen(line)); sfree(line); line = NULL; } smemclr(base64_bit, sizeof(base64_bit)); if (ret) { strbuf_free(ret->keyblob); smemclr(ret, sizeof(*ret)); sfree(ret); } if (errmsg_p) *errmsg_p = errmsg; return NULL; } static bool openssh_new_encrypted(BinarySource *src) { struct openssh_new_key *key = load_openssh_new_key(src, NULL); bool ret; if (!key) return false; ret = (key->cipher != ON_E_NONE); strbuf_free(key->keyblob); smemclr(key, sizeof(*key)); sfree(key); return ret; } static ssh2_userkey *openssh_new_read( BinarySource *filesrc, const char *passphrase, const char **errmsg_p) { struct openssh_new_key *key = load_openssh_new_key(filesrc, errmsg_p); ssh2_userkey *retkey = NULL; ssh2_userkey *retval = NULL; const char *errmsg; unsigned checkint; BinarySource src[1]; int key_index; const ssh_keyalg *alg = NULL; if (!key) return NULL; if (key->cipher != ON_E_NONE) { unsigned char keybuf[48]; int keysize; /* * Construct the decryption key, and decrypt the string. */ switch (key->cipher) { case ON_E_NONE: keysize = 0; break; case ON_E_AES256CBC: case ON_E_AES256CTR: keysize = 48; /* 32 byte key + 16 byte IV */ break; default: unreachable("Bad cipher enumeration value"); } assert(keysize <= sizeof(keybuf)); switch (key->kdf) { case ON_K_NONE: memset(keybuf, 0, keysize); break; case ON_K_BCRYPT: openssh_bcrypt(ptrlen_from_asciz(passphrase), key->kdfopts.bcrypt.salt, key->kdfopts.bcrypt.rounds, keybuf, keysize); break; default: unreachable("Bad kdf enumeration value"); } switch (key->cipher) { case ON_E_NONE: break; case ON_E_AES256CBC: case ON_E_AES256CTR: if (key->private.len % 16 != 0) { errmsg = "private key container length is not a" " multiple of AES block size\n"; goto error; } { ssh_cipher *cipher = ssh_cipher_new( key->cipher == ON_E_AES256CBC ? &ssh_aes256_cbc : &ssh_aes256_sdctr); ssh_cipher_setkey(cipher, keybuf); ssh_cipher_setiv(cipher, keybuf + 32); /* Decrypt the private section in place, casting away * the const from key->private being a ptrlen */ ssh_cipher_decrypt(cipher, (char *)key->private.ptr, key->private.len); ssh_cipher_free(cipher); } break; default: unreachable("Bad cipher enumeration value"); } } /* * Now parse the entire encrypted section, and extract the key * identified by key_wanted. */ BinarySource_BARE_INIT_PL(src, key->private); checkint = get_uint32(src); if (get_uint32(src) != checkint || get_err(src)) { errmsg = "decryption check failed"; goto error; } retkey = snew(ssh2_userkey); retkey->key = NULL; retkey->comment = NULL; for (key_index = 0; key_index < key->nkeys; key_index++) { ptrlen comment; /* * Identify the key type. */ alg = find_pubkey_alg_len(get_string(src)); if (!alg) { errmsg = "private key type not recognised\n"; goto error; } /* * Read the key. We have to do this even if it's not the one * we want, because it's the only way to find out how much * data to skip past to get to the next key in the file. */ retkey->key = ssh_key_new_priv_openssh(alg, src); if (get_err(src)) { errmsg = "unable to read entire private key"; goto error; } if (!retkey->key) { errmsg = "unable to create key data structure"; goto error; } if (key_index != key->key_wanted) { /* * If this isn't the key we're looking for, throw it away. */ ssh_key_free(retkey->key); retkey->key = NULL; } /* * Read the key comment. */ comment = get_string(src); if (get_err(src)) { errmsg = "unable to read key comment"; goto error; } if (key_index == key->key_wanted) { assert(retkey); retkey->comment = mkstr(comment); } } if (!retkey->key) { errmsg = "key index out of range"; goto error; } /* * Now we expect nothing left but padding. */ { unsigned char expected_pad_byte = 1; while (get_avail(src) > 0) if (get_byte(src) != expected_pad_byte++) { errmsg = "padding at end of private string did not match"; goto error; } } errmsg = NULL; /* no error */ retval = retkey; retkey = NULL; /* prevent the free */ error: if (retkey) { sfree(retkey->comment); if (retkey->key) ssh_key_free(retkey->key); sfree(retkey); } strbuf_free(key->keyblob); smemclr(key, sizeof(*key)); sfree(key); if (errmsg_p) *errmsg_p = errmsg; return retval; } static bool openssh_new_write( const Filename *filename, ssh2_userkey *ukey, const char *passphrase) { strbuf *pubblob, *privblob, *cblob; int padvalue; unsigned checkint; bool ret = false; unsigned char bcrypt_salt[16]; const int bcrypt_rounds = 16; FILE *fp; /* OpenSSH's private key files never contain a certificate, so * revert to the underlying base key if necessary */ ssh_key *key = ssh_key_base_key(ukey->key); /* * Fetch the key blobs and find out the lengths of things. */ pubblob = strbuf_new(); ssh_key_public_blob(key, BinarySink_UPCAST(pubblob)); privblob = strbuf_new_nm(); ssh_key_openssh_blob(key, BinarySink_UPCAST(privblob)); /* * Construct the cleartext version of the blob. */ cblob = strbuf_new_nm(); /* Magic number. */ put_asciz(cblob, "openssh-key-v1"); /* Cipher and kdf names, and kdf options. */ if (!passphrase) { memset(bcrypt_salt, 0, sizeof(bcrypt_salt)); /* prevent warnings */ put_stringz(cblob, "none"); put_stringz(cblob, "none"); put_stringz(cblob, ""); } else { strbuf *substr; random_read(bcrypt_salt, sizeof(bcrypt_salt)); put_stringz(cblob, "aes256-ctr"); put_stringz(cblob, "bcrypt"); substr = strbuf_new_nm(); put_string(substr, bcrypt_salt, sizeof(bcrypt_salt)); put_uint32(substr, bcrypt_rounds); put_stringsb(cblob, substr); } /* Number of keys. */ put_uint32(cblob, 1); /* Public blob. */ put_string(cblob, pubblob->s, pubblob->len); /* Private section. */ { strbuf *cpblob = strbuf_new_nm(); /* checkint. */ uint8_t checkint_buf[4]; random_read(checkint_buf, 4); checkint = GET_32BIT_MSB_FIRST(checkint_buf); put_uint32(cpblob, checkint); put_uint32(cpblob, checkint); /* Private key. The main private blob goes inline, with no string * wrapper. */ put_stringz(cpblob, ssh_key_ssh_id(key)); put_data(cpblob, privblob->s, privblob->len); /* Comment. */ put_stringz(cpblob, ukey->comment); /* Pad out the encrypted section. */ padvalue = 1; do { put_byte(cpblob, padvalue++); } while (cpblob->len & 15); if (passphrase) { /* * Encrypt the private section. We need 48 bytes of key * material: 32 bytes AES key + 16 bytes iv. */ unsigned char keybuf[48]; ssh_cipher *cipher; openssh_bcrypt(ptrlen_from_asciz(passphrase), make_ptrlen(bcrypt_salt, sizeof(bcrypt_salt)), bcrypt_rounds, keybuf, sizeof(keybuf)); cipher = ssh_cipher_new(&ssh_aes256_sdctr); ssh_cipher_setkey(cipher, keybuf); ssh_cipher_setiv(cipher, keybuf + 32); ssh_cipher_encrypt(cipher, cpblob->u, cpblob->len); ssh_cipher_free(cipher); smemclr(keybuf, sizeof(keybuf)); } put_stringsb(cblob, cpblob); } /* * And save it. We'll use Unix line endings just in case it's * subsequently transferred in binary mode. */ fp = f_open(filename, "wb", true); /* ensure Unix line endings */ if (!fp) goto error; fputs("-----BEGIN OPENSSH PRIVATE KEY-----\n", fp); base64_encode_fp(fp, ptrlen_from_strbuf(cblob), 64); fputs("-----END OPENSSH PRIVATE KEY-----\n", fp); fclose(fp); ret = true; error: if (cblob) strbuf_free(cblob); if (privblob) strbuf_free(privblob); if (pubblob) strbuf_free(pubblob); return ret; } /* ---------------------------------------------------------------------- * The switch function openssh_auto_write(), which chooses one of the * concrete OpenSSH output formats based on the key type. */ static bool openssh_auto_write( const Filename *filename, ssh2_userkey *key, const char *passphrase) { /* * The old OpenSSH format supports a fixed list of key types. We * assume that anything not in that fixed list is newer, and hence * will use the new format. */ const ssh_keyalg *alg = ssh_key_alg(ssh_key_base_key(key->key)); if (alg == &ssh_dsa || alg == &ssh_rsa || alg == &ssh_ecdsa_nistp256 || alg == &ssh_ecdsa_nistp384 || alg == &ssh_ecdsa_nistp521) return openssh_pem_write(filename, key, passphrase); else return openssh_new_write(filename, key, passphrase); } /* ---------------------------------------------------------------------- * Code to read ssh.com private keys. */ /* * The format of the base64 blob is largely SSH-2-packet-formatted, * except that mpints are a bit different: they're more like the * old SSH-1 mpint. You have a 32-bit bit count N, followed by * (N+7)/8 bytes of data. * * So. The blob contains: * * - uint32 0x3f6ff9eb (magic number) * - uint32 size (total blob size) * - string key-type (see below) * - string cipher-type (tells you if key is encrypted) * - string encrypted-blob * * (The first size field includes the size field itself and the * magic number before it. All other size fields are ordinary SSH-2 * strings, so the size field indicates how much data is to * _follow_.) * * The encrypted blob, once decrypted, contains a single string * which in turn contains the payload. (This allows padding to be * added after that string while still making it clear where the * real payload ends. Also it probably makes for a reasonable * decryption check.) * * The payload blob, for an RSA key, contains: * - mpint e * - mpint d * - mpint n (yes, the public and private stuff is intermixed) * - mpint u (presumably inverse of p mod q) * - mpint p (p is the smaller prime) * - mpint q (q is the larger) * * For a DSA key, the payload blob contains: * - uint32 0 * - mpint p * - mpint g * - mpint q * - mpint y * - mpint x * * Alternatively, if the parameters are `predefined', that * (0,p,g,q) sequence can be replaced by a uint32 1 and a string * containing some predefined parameter specification. *shudder*, * but I doubt we'll encounter this in real life. * * The key type strings are ghastly. The RSA key I looked at had a * type string of * * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}' * * and the DSA key wasn't much better: * * `dl-modp{sign{dsa-nist-sha1},dh{plain}}' * * It isn't clear that these will always be the same. I think it * might be wise just to look at the `if-modn{sign{rsa' and * `dl-modp{sign{dsa' prefixes. * * Finally, the encryption. The cipher-type string appears to be * either `none' or `3des-cbc'. Looks as if this is SSH-2-style * 3des-cbc (i.e. outer cbc rather than inner). The key is created * from the passphrase by means of yet another hashing faff: * * - first 16 bytes are MD5(passphrase) * - next 16 bytes are MD5(passphrase || first 16 bytes) * - if there were more, they'd be MD5(passphrase || first 32), * and so on. */ #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb struct sshcom_key { char comment[256]; /* allowing any length is overkill */ strbuf *keyblob; }; static struct sshcom_key *load_sshcom_key(BinarySource *src, const char **errmsg_p) { struct sshcom_key *ret; char *line = NULL; int hdrstart, len; const char *errmsg; char *p; bool headers_done; char base64_bit[4]; int base64_chars = 0; ret = snew(struct sshcom_key); ret->comment[0] = '\0'; ret->keyblob = strbuf_new_nm(); if (!(line = bsgetline(src))) { errmsg = "unexpected end of file"; goto error; } if (0 != strcmp(line, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----")) { errmsg = "file does not begin with ssh.com key header"; goto error; } smemclr(line, strlen(line)); sfree(line); line = NULL; headers_done = false; while (1) { if (!(line = bsgetline(src))) { errmsg = "unexpected end of file"; goto error; } if (!strcmp(line, "---- END SSH2 ENCRYPTED PRIVATE KEY ----")) { sfree(line); line = NULL; break; /* done */ } if ((p = strchr(line, ':')) != NULL) { if (headers_done) { errmsg = "header found in body of key data"; goto error; } *p++ = '\0'; while (*p && isspace((unsigned char)*p)) p++; hdrstart = p - line; /* * Header lines can end in a trailing backslash for * continuation. */ len = hdrstart + strlen(line+hdrstart); assert(!line[len]); while (line[len-1] == '\\') { char *line2; int line2len; line2 = bsgetline(src); if (!line2) { errmsg = "unexpected end of file"; goto error; } line2len = strlen(line2); line = sresize(line, len + line2len + 1, char); strcpy(line + len - 1, line2); len += line2len - 1; assert(!line[len]); smemclr(line2, strlen(line2)); sfree(line2); line2 = NULL; } p = line + hdrstart; if (!strcmp(line, "Comment")) { /* Strip quotes in comment if present. */ if (p[0] == '"' && p[strlen(p)-1] == '"') { p++; p[strlen(p)-1] = '\0'; } strncpy(ret->comment, p, sizeof(ret->comment)); ret->comment[sizeof(ret->comment)-1] = '\0'; } } else { headers_done = true; p = line; while (isbase64(*p)) { base64_bit[base64_chars++] = *p; if (base64_chars == 4) { unsigned char out[3]; base64_chars = 0; len = base64_decode_atom(base64_bit, out); if (len <= 0) { errmsg = "invalid base64 encoding"; goto error; } put_data(ret->keyblob, out, len); } p++; } } smemclr(line, strlen(line)); sfree(line); line = NULL; } if (ret->keyblob->len == 0) { errmsg = "key body not present"; goto error; } if (errmsg_p) *errmsg_p = NULL; return ret; error: if (line) { smemclr(line, strlen(line)); sfree(line); line = NULL; } if (ret) { strbuf_free(ret->keyblob); smemclr(ret, sizeof(*ret)); sfree(ret); } if (errmsg_p) *errmsg_p = errmsg; return NULL; } static bool sshcom_encrypted(BinarySource *filesrc, char **comment) { struct sshcom_key *key = load_sshcom_key(filesrc, NULL); BinarySource src[1]; ptrlen str; bool answer = false; *comment = NULL; if (!key) goto done; BinarySource_BARE_INIT_PL(src, ptrlen_from_strbuf(key->keyblob)); if (get_uint32(src) != SSHCOM_MAGIC_NUMBER) goto done; /* key is invalid */ get_uint32(src); /* skip length field */ get_string(src); /* skip key type */ str = get_string(src); /* cipher type */ if (get_err(src)) goto done; /* key is invalid */ if (!ptrlen_eq_string(str, "none")) answer = true; done: if (key) { *comment = dupstr(key->comment); strbuf_free(key->keyblob); smemclr(key, sizeof(*key)); sfree(key); } else { *comment = dupstr(""); } return answer; } static void BinarySink_put_mp_sshcom_from_string(BinarySink *bs, ptrlen str) { const unsigned char *bytes = (const unsigned char *)str.ptr; size_t nbytes = str.len; int bits = nbytes * 8 - 1; while (bits > 0) { if (*bytes & (1 << (bits & 7))) break; if (!(bits-- & 7)) bytes++, nbytes--; } put_uint32(bs, bits+1); put_data(bs, bytes, nbytes); } #define put_mp_sshcom_from_string(bs, str) \ BinarySink_put_mp_sshcom_from_string(BinarySink_UPCAST(bs), str) static ptrlen BinarySource_get_mp_sshcom_as_string(BinarySource *src) { unsigned bits = get_uint32(src); return get_data(src, (bits + 7) / 8); } #define get_mp_sshcom_as_string(bs) \ BinarySource_get_mp_sshcom_as_string(BinarySource_UPCAST(bs)) static void sshcom_derivekey(ptrlen passphrase, uint8_t *keybuf) { /* * Derive the encryption key for an ssh.com key file from the * passphrase and iv/salt: * * - let block A equal MD5(passphrase) * - let block B equal MD5(passphrase || A) * - block C would be MD5(passphrase || A || B) and so on * - encryption key is the first N bytes of A || B */ ssh_hash *h; h = ssh_hash_new(&ssh_md5); put_datapl(h, passphrase); ssh_hash_digest_nondestructive(h, keybuf); put_data(h, keybuf, 16); ssh_hash_final(h, keybuf + 16); } static ssh2_userkey *sshcom_read( BinarySource *filesrc, const char *passphrase, const char **errmsg_p) { struct sshcom_key *key = load_sshcom_key(filesrc, errmsg_p); const char *errmsg; BinarySource src[1]; ptrlen str, ciphertext; int publen; const char prefix_rsa[] = "if-modn{sign{rsa"; const char prefix_dsa[] = "dl-modp{sign{dsa"; enum { RSA, DSA } type; bool encrypted; ssh2_userkey *ret = NULL, *retkey; const ssh_keyalg *alg; strbuf *blob = NULL; if (!key) return NULL; BinarySource_BARE_INIT_PL(src, ptrlen_from_strbuf(key->keyblob)); if (get_uint32(src) != SSHCOM_MAGIC_NUMBER) { errmsg = "key does not begin with magic number"; goto error; } get_uint32(src); /* skip length field */ /* * Determine the key type. */ str = get_string(src); if (str.len > sizeof(prefix_rsa) - 1 && !memcmp(str.ptr, prefix_rsa, sizeof(prefix_rsa) - 1)) { type = RSA; } else if (str.len > sizeof(prefix_dsa) - 1 && !memcmp(str.ptr, prefix_dsa, sizeof(prefix_dsa) - 1)) { type = DSA; } else { errmsg = "key is of unknown type"; goto error; } /* * Determine the cipher type. */ str = get_string(src); if (ptrlen_eq_string(str, "none")) encrypted = false; else if (ptrlen_eq_string(str, "3des-cbc")) encrypted = true; else { errmsg = "key encryption is of unknown type"; goto error; } /* * Get hold of the encrypted part of the key. */ ciphertext = get_string(src); if (ciphertext.len == 0) { errmsg = "no key data found"; goto error; } /* * Decrypt it if necessary. */ if (encrypted) { /* * Derive encryption key from passphrase and iv/salt: * * - let block A equal MD5(passphrase) * - let block B equal MD5(passphrase || A) * - block C would be MD5(passphrase || A || B) and so on * - encryption key is the first N bytes of A || B */ unsigned char keybuf[32], iv[8]; if (ciphertext.len % 8 != 0) { errmsg = "encrypted part of key is not a multiple of cipher block" " size"; goto error; } sshcom_derivekey(ptrlen_from_asciz(passphrase), keybuf); /* * Now decrypt the key blob in place (casting away const from * ciphertext being a ptrlen). */ memset(iv, 0, sizeof(iv)); des3_decrypt_pubkey_ossh(keybuf, iv, (char *)ciphertext.ptr, ciphertext.len); smemclr(keybuf, sizeof(keybuf)); /* * Hereafter we return WRONG_PASSPHRASE for any parsing * error. (But only if we've just tried to decrypt it! * Returning WRONG_PASSPHRASE for an unencrypted key is * automatic doom.) */ if (encrypted) ret = SSH2_WRONG_PASSPHRASE; } /* * Expect the ciphertext to be formatted as a containing string, * and reinitialise src to start parsing the inside of that string. */ BinarySource_BARE_INIT_PL(src, ciphertext); str = get_string(src); if (get_err(src)) { errmsg = "containing string was ill-formed"; goto error; } BinarySource_BARE_INIT_PL(src, str); /* * Now we break down into RSA versus DSA. In either case we'll * construct public and private blobs in our own format, and * end up feeding them to ssh_key_new_priv(). */ blob = strbuf_new_nm(); if (type == RSA) { ptrlen n, e, d, u, p, q; e = get_mp_sshcom_as_string(src); d = get_mp_sshcom_as_string(src); n = get_mp_sshcom_as_string(src); u = get_mp_sshcom_as_string(src); p = get_mp_sshcom_as_string(src); q = get_mp_sshcom_as_string(src); if (get_err(src)) { errmsg = "key data did not contain six integers"; goto error; } alg = &ssh_rsa; put_stringz(blob, "ssh-rsa"); put_mp_ssh2_from_string(blob, e); put_mp_ssh2_from_string(blob, n); publen = blob->len; put_mp_ssh2_from_string(blob, d); put_mp_ssh2_from_string(blob, q); put_mp_ssh2_from_string(blob, p); put_mp_ssh2_from_string(blob, u); } else { ptrlen p, q, g, x, y; assert(type == DSA); /* the only other option from the if above */ if (get_uint32(src) != 0) { errmsg = "predefined DSA parameters not supported"; goto error; } p = get_mp_sshcom_as_string(src); g = get_mp_sshcom_as_string(src); q = get_mp_sshcom_as_string(src); y = get_mp_sshcom_as_string(src); x = get_mp_sshcom_as_string(src); if (get_err(src)) { errmsg = "key data did not contain five integers"; goto error; } alg = &ssh_dsa; put_stringz(blob, "ssh-dss"); put_mp_ssh2_from_string(blob, p); put_mp_ssh2_from_string(blob, q); put_mp_ssh2_from_string(blob, g); put_mp_ssh2_from_string(blob, y); publen = blob->len; put_mp_ssh2_from_string(blob, x); } retkey = snew(ssh2_userkey); retkey->key = ssh_key_new_priv( alg, make_ptrlen(blob->u, publen), make_ptrlen(blob->u + publen, blob->len - publen)); if (!retkey->key) { sfree(retkey); errmsg = "unable to create key data structure"; goto error; } retkey->comment = dupstr(key->comment); errmsg = NULL; /* no error */ ret = retkey; error: if (blob) { strbuf_free(blob); } strbuf_free(key->keyblob); smemclr(key, sizeof(*key)); sfree(key); if (errmsg_p) *errmsg_p = errmsg; return ret; } static bool sshcom_write( const Filename *filename, ssh2_userkey *key, const char *passphrase) { strbuf *pubblob, *privblob, *outblob; ptrlen numbers[6]; int nnumbers, lenpos, i; bool initial_zero; BinarySource src[1]; const char *type; char *ciphertext; int cipherlen; bool ret = false; FILE *fp; /* * Fetch the key blobs. */ pubblob = strbuf_new(); ssh_key_public_blob(key->key, BinarySink_UPCAST(pubblob)); privblob = strbuf_new_nm(); ssh_key_private_blob(key->key, BinarySink_UPCAST(privblob)); outblob = NULL; /* * Find the sequence of integers to be encoded into the OpenSSH * key blob, and also decide on the header line. */ if (ssh_key_alg(key->key) == &ssh_rsa) { ptrlen n, e, d, p, q, iqmp; /* * These blobs were generated from inside PuTTY, so we needn't * treat them as untrusted. */ BinarySource_BARE_INIT(src, pubblob->u, pubblob->len); get_string(src); /* skip algorithm name */ e = get_string(src); n = get_string(src); BinarySource_BARE_INIT(src, privblob->u, privblob->len); d = get_string(src); p = get_string(src); q = get_string(src); iqmp = get_string(src); assert(!get_err(src)); /* can't go wrong */ numbers[0] = e; numbers[1] = d; numbers[2] = n; numbers[3] = iqmp; numbers[4] = q; numbers[5] = p; nnumbers = 6; initial_zero = false; type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}"; } else if (ssh_key_alg(key->key) == &ssh_dsa) { ptrlen p, q, g, y, x; /* * These blobs were generated from inside PuTTY, so we needn't * treat them as untrusted. */ BinarySource_BARE_INIT(src, pubblob->u, pubblob->len); get_string(src); /* skip algorithm name */ p = get_string(src); q = get_string(src); g = get_string(src); y = get_string(src); BinarySource_BARE_INIT(src, privblob->u, privblob->len); x = get_string(src); assert(!get_err(src)); /* can't go wrong */ numbers[0] = p; numbers[1] = g; numbers[2] = q; numbers[3] = y; numbers[4] = x; nnumbers = 5; initial_zero = true; type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}"; } else { goto error; /* unsupported key type */ } outblob = strbuf_new_nm(); /* * Create the unencrypted key blob. */ put_uint32(outblob, SSHCOM_MAGIC_NUMBER); put_uint32(outblob, 0); /* length field, fill in later */ put_stringz(outblob, type); put_stringz(outblob, passphrase ? "3des-cbc" : "none"); lenpos = outblob->len; /* remember this position */ put_uint32(outblob, 0); /* encrypted-blob size */ put_uint32(outblob, 0); /* encrypted-payload size */ if (initial_zero) put_uint32(outblob, 0); for (i = 0; i < nnumbers; i++) put_mp_sshcom_from_string(outblob, numbers[i]); /* Now wrap up the encrypted payload. */ PUT_32BIT_MSB_FIRST(outblob->s + lenpos + 4, outblob->len - (lenpos + 8)); /* Pad encrypted blob to a multiple of cipher block size. */ if (passphrase) { int padding = -(outblob->len - (lenpos+4)) & 7; uint8_t padding_buf[8]; random_read(padding_buf, padding); put_data(outblob, padding_buf, padding); } ciphertext = outblob->s + lenpos + 4; cipherlen = outblob->len - (lenpos + 4); assert(!passphrase || cipherlen % 8 == 0); /* Wrap up the encrypted blob string. */ PUT_32BIT_MSB_FIRST(outblob->s + lenpos, cipherlen); /* And finally fill in the total length field. */ PUT_32BIT_MSB_FIRST(outblob->s + 4, outblob->len); /* * Encrypt the key. */ if (passphrase) { unsigned char keybuf[32], iv[8]; sshcom_derivekey(ptrlen_from_asciz(passphrase), keybuf); /* * Now decrypt the key blob. */ memset(iv, 0, sizeof(iv)); des3_encrypt_pubkey_ossh(keybuf, iv, ciphertext, cipherlen); smemclr(keybuf, sizeof(keybuf)); } /* * And save it. We'll use Unix line endings just in case it's * subsequently transferred in binary mode. */ fp = f_open(filename, "wb", true); /* ensure Unix line endings */ if (!fp) goto error; fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp); fprintf(fp, "Comment: \""); /* * Comment header is broken with backslash-newline if it goes * over 70 chars. Although it's surrounded by quotes, it * _doesn't_ escape backslashes or quotes within the string. * Don't ask me, I didn't design it. */ { int slen = 60; /* starts at 60 due to "Comment: " */ char *c = key->comment; while ((int)strlen(c) > slen) { fprintf(fp, "%.*s\\\n", slen, c); c += slen; slen = 70; /* allow 70 chars on subsequent lines */ } fprintf(fp, "%s\"\n", c); } base64_encode_fp(fp, ptrlen_from_strbuf(outblob), 70); fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp); fclose(fp); ret = true; error: if (outblob) strbuf_free(outblob); if (privblob) strbuf_free(privblob); if (pubblob) strbuf_free(pubblob); return ret; }