+
+int openssh_pem_write(const Filename *filename, struct ssh2_userkey *key,
+ char *passphrase)
+{
+ unsigned char *pubblob, *privblob, *spareblob;
+ int publen, privlen, sparelen = 0;
+ unsigned char *outblob;
+ int outlen;
+ struct mpint_pos numbers[9];
+ int nnumbers, pos, len, seqlen, i;
+ const char *header, *footer;
+ char zero[1];
+ unsigned char iv[8];
+ int ret = 0;
+ FILE *fp;
+
+ /*
+ * Fetch the key blobs.
+ */
+ pubblob = key->alg->public_blob(key->data, &publen);
+ privblob = key->alg->private_blob(key->data, &privlen);
+ spareblob = outblob = NULL;
+
+ outblob = NULL;
+ len = 0;
+
+ /*
+ * Encode the OpenSSH key blob, and also decide on the header
+ * line.
+ */
+ if (key->alg == &ssh_rsa || key->alg == &ssh_dss) {
+ /*
+ * The RSA and DSS 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 (key->alg == &ssh_rsa) {
+ int pos;
+ struct mpint_pos n, e, d, p, q, iqmp, dmp1, dmq1;
+ Bignum bd, bp, bq, bdmp1, bdmq1;
+
+ /*
+ * These blobs were generated from inside PuTTY, so we needn't
+ * treat them as untrusted.
+ */
+ pos = 4 + GET_32BIT(pubblob);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
+ pos = 0;
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
+
+ assert(e.start && iqmp.start); /* can't go wrong */
+
+ /* We also need d mod (p-1) and d mod (q-1). */
+ bd = bignum_from_bytes(d.start, d.bytes);
+ bp = bignum_from_bytes(p.start, p.bytes);
+ bq = bignum_from_bytes(q.start, q.bytes);
+ decbn(bp);
+ decbn(bq);
+ bdmp1 = bigmod(bd, bp);
+ bdmq1 = bigmod(bd, bq);
+ freebn(bd);
+ freebn(bp);
+ freebn(bq);
+
+ dmp1.bytes = (bignum_bitcount(bdmp1)+8)/8;
+ dmq1.bytes = (bignum_bitcount(bdmq1)+8)/8;
+ sparelen = dmp1.bytes + dmq1.bytes;
+ spareblob = snewn(sparelen, unsigned char);
+ dmp1.start = spareblob;
+ dmq1.start = spareblob + dmp1.bytes;
+ for (i = 0; i < dmp1.bytes; i++)
+ spareblob[i] = bignum_byte(bdmp1, dmp1.bytes-1 - i);
+ for (i = 0; i < dmq1.bytes; i++)
+ spareblob[i+dmp1.bytes] = bignum_byte(bdmq1, dmq1.bytes-1 - i);
+ freebn(bdmp1);
+ freebn(bdmq1);
+
+ numbers[0].start = zero; numbers[0].bytes = 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 */
+ int pos;
+ struct mpint_pos p, q, g, y, x;
+
+ /*
+ * These blobs were generated from inside PuTTY, so we needn't
+ * treat them as untrusted.
+ */
+ pos = 4 + GET_32BIT(pubblob);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
+ pos = 0;
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
+
+ assert(y.start && x.start); /* can't go wrong */
+
+ numbers[0].start = zero; numbers[0].bytes = 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";
+ }
+
+ /*
+ * Now count up the total size of the ASN.1 encoded integers,
+ * so as to determine the length of the containing SEQUENCE.
+ */
+ len = 0;
+ for (i = 0; i < nnumbers; i++) {
+ len += ber_write_id_len(NULL, 2, numbers[i].bytes, 0);
+ len += numbers[i].bytes;
+ }
+ seqlen = len;
+ /* Now add on the SEQUENCE header. */
+ len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
+
+ /*
+ * Now we know how big outblob needs to be. Allocate it.
+ */
+ outblob = snewn(len, unsigned char);
+
+ /*
+ * And write the data into it.
+ */
+ pos = 0;
+ pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
+ for (i = 0; i < nnumbers; i++) {
+ pos += ber_write_id_len(outblob+pos, 2, numbers[i].bytes, 0);
+ memcpy(outblob+pos, numbers[i].start, numbers[i].bytes);
+ pos += numbers[i].bytes;
+ }
+ } else if (key->alg == &ssh_ecdsa_nistp256 ||
+ key->alg == &ssh_ecdsa_nistp384 ||
+ key->alg == &ssh_ecdsa_nistp521) {
+ const unsigned char *oid;
+ int oidlen;
+ int pointlen;
+
+ /*
+ * Structure of asn1:
+ * SEQUENCE
+ * INTEGER 1
+ * OCTET STRING (private key)
+ * [0]
+ * OID (curve)
+ * [1]
+ * BIT STRING (0x00 public key point)
+ */
+ oid = ec_alg_oid(key->alg, &oidlen);
+ pointlen = (((struct ec_key *)key->data)->publicKey.curve->fieldBits
+ + 7) / 8 * 2;
+
+ len = ber_write_id_len(NULL, 2, 1, 0);
+ len += 1;
+ len += ber_write_id_len(NULL, 4, privlen - 4, 0);
+ len+= privlen - 4;
+ len += ber_write_id_len(NULL, 0, oidlen +
+ ber_write_id_len(NULL, 6, oidlen, 0),
+ ASN1_CLASS_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED);
+ len += ber_write_id_len(NULL, 6, oidlen, 0);
+ len += oidlen;
+ len += ber_write_id_len(NULL, 1, 2 + pointlen +
+ ber_write_id_len(NULL, 3, 2 + pointlen, 0),
+ ASN1_CLASS_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED);
+ len += ber_write_id_len(NULL, 3, 2 + pointlen, 0);
+ len += 2 + pointlen;
+
+ seqlen = len;
+ len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
+
+ outblob = snewn(len, unsigned char);
+ assert(outblob);
+
+ pos = 0;
+ pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
+ pos += ber_write_id_len(outblob+pos, 2, 1, 0);
+ outblob[pos++] = 1;
+ pos += ber_write_id_len(outblob+pos, 4, privlen - 4, 0);
+ memcpy(outblob+pos, privblob + 4, privlen - 4);
+ pos += privlen - 4;
+ pos += ber_write_id_len(outblob+pos, 0, oidlen +
+ ber_write_id_len(NULL, 6, oidlen, 0),
+ ASN1_CLASS_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED);
+ pos += ber_write_id_len(outblob+pos, 6, oidlen, 0);
+ memcpy(outblob+pos, oid, oidlen);
+ pos += oidlen;
+ pos += ber_write_id_len(outblob+pos, 1, 2 + pointlen +
+ ber_write_id_len(NULL, 3, 2 + pointlen, 0),
+ ASN1_CLASS_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED);
+ pos += ber_write_id_len(outblob+pos, 3, 2 + pointlen, 0);
+ outblob[pos++] = 0;
+ memcpy(outblob+pos, pubblob+39, 1 + pointlen);
+ pos += 1 + pointlen;
+
+ header = "-----BEGIN EC PRIVATE KEY-----\n";
+ footer = "-----END EC PRIVATE KEY-----\n";
+ } else {
+ assert(0); /* zoinks! */
+ exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
+ }
+
+ /*
+ * Encrypt the key.
+ *
+ * For the moment, we still encrypt our OpenSSH keys using
+ * old-style 3DES.
+ */
+ if (passphrase) {
+ struct MD5Context md5c;
+ unsigned char keybuf[32];
+
+ /*
+ * Round up to the cipher block size, ensuring we have at
+ * least one byte of padding (see below).
+ */
+ outlen = (len+8) &~ 7;
+ {
+ unsigned char *tmp = snewn(outlen, unsigned char);
+ memcpy(tmp, outblob, len);
+ smemclr(outblob, len);
+ sfree(outblob);
+ outblob = tmp;
+ }
+
+ /*
+ * 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.
+ */
+ assert(pos == len);
+ while (pos < outlen) {
+ outblob[pos++] = outlen - len;
+ }
+
+ /*
+ * Invent an iv. Then derive encryption key from 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
+ */
+ for (i = 0; i < 8; i++) iv[i] = random_byte();
+
+ MD5Init(&md5c);
+ MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
+ MD5Update(&md5c, iv, 8);
+ MD5Final(keybuf, &md5c);
+
+ MD5Init(&md5c);
+ MD5Update(&md5c, keybuf, 16);
+ MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
+ MD5Update(&md5c, iv, 8);
+ MD5Final(keybuf+16, &md5c);
+
+ /*
+ * Now encrypt the key blob.
+ */
+ des3_encrypt_pubkey_ossh(keybuf, iv, outblob, outlen);
+
+ smemclr(&md5c, sizeof(md5c));
+ smemclr(keybuf, sizeof(keybuf));
+ } else {
+ /*
+ * If no encryption, the blob has exactly its original
+ * cleartext size.
+ */
+ outlen = len;
+ }
+
+ /*
+ * 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, outblob, outlen, 64);
+ fputs(footer, fp);
+ fclose(fp);
+ ret = 1;
+
+ error:
+ if (outblob) {
+ smemclr(outblob, outlen);
+ sfree(outblob);
+ }
+ if (spareblob) {
+ smemclr(spareblob, sparelen);
+ sfree(spareblob);
+ }
+ if (privblob) {
+ smemclr(privblob, privlen);
+ sfree(privblob);
+ }
+ if (pubblob) {
+ smemclr(pubblob, publen);
+ sfree(pubblob);
+ }
+ return ret;
+}
+
+/* ----------------------------------------------------------------------
+ * Code to read and write OpenSSH private keys in the new-style format.
+ */
+
+typedef enum {
+ ON_E_NONE, ON_E_AES256CBC
+} 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 */
+ const unsigned char *salt;
+ int saltlen;
+ } bcrypt;
+ } kdfopts;
+ int nkeys, key_wanted;
+ /* This too points to a position within keyblob */
+ unsigned char *privatestr;
+ int privatelen;
+
+ unsigned char *keyblob;
+ int keyblob_len, keyblob_size;
+};
+
+static struct openssh_new_key *load_openssh_new_key(const Filename *filename,
+ const char **errmsg_p)
+{
+ struct openssh_new_key *ret;
+ FILE *fp = NULL;
+ char *line = NULL;
+ const char *errmsg;
+ char *p;
+ char base64_bit[4];
+ int base64_chars = 0;
+ const void *filedata;
+ int filelen;
+ const void *string, *kdfopts, *bcryptsalt, *pubkey;
+ int stringlen, kdfoptlen, bcryptsaltlen, pubkeylen;
+ unsigned bcryptrounds, nkeys, key_index;
+
+ ret = snew(struct openssh_new_key);
+ ret->keyblob = NULL;
+ ret->keyblob_len = ret->keyblob_size = 0;
+
+ fp = f_open(filename, "r", FALSE);
+ if (!fp) {
+ errmsg = "unable to open key file";
+ goto error;
+ }
+
+ if (!(line = fgetline(fp))) {
+ errmsg = "unexpected end of file";
+ goto error;
+ }
+ strip_crlf(line);
+ 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 = fgetline(fp))) {
+ errmsg = "unexpected end of file";
+ goto error;
+ }
+ strip_crlf(line);
+ 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;
+ }
+
+ if (ret->keyblob_len + len > ret->keyblob_size) {
+ ret->keyblob_size = ret->keyblob_len + len + 256;
+ ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
+ unsigned char);
+ }
+
+ memcpy(ret->keyblob + ret->keyblob_len, out, len);
+ ret->keyblob_len += len;
+
+ smemclr(out, sizeof(out));
+ }
+
+ p++;
+ }
+ smemclr(line, strlen(line));
+ sfree(line);
+ line = NULL;
+ }
+
+ fclose(fp);
+ fp = NULL;
+
+ if (ret->keyblob_len == 0 || !ret->keyblob) {
+ errmsg = "key body not present";
+ goto error;
+ }
+
+ filedata = ret->keyblob;
+ filelen = ret->keyblob_len;
+
+ if (filelen < 15 || 0 != memcmp(filedata, "openssh-key-v1\0", 15)) {
+ errmsg = "new-style OpenSSH magic number missing\n";
+ goto error;
+ }
+ filedata = (const char *)filedata + 15;
+ filelen -= 15;
+
+ if (!(string = get_ssh_string(&filelen, &filedata, &stringlen))) {
+ errmsg = "encountered EOF before cipher name\n";
+ goto error;
+ }
+ if (match_ssh_id(stringlen, string, "none")) {
+ ret->cipher = ON_E_NONE;
+ } else if (match_ssh_id(stringlen, string, "aes256-cbc")) {
+ ret->cipher = ON_E_AES256CBC;
+ } else {
+ errmsg = "unrecognised cipher name\n";
+ goto error;
+ }
+
+ if (!(string = get_ssh_string(&filelen, &filedata, &stringlen))) {
+ errmsg = "encountered EOF before kdf name\n";
+ goto error;
+ }
+ if (match_ssh_id(stringlen, string, "none")) {
+ ret->kdf = ON_K_NONE;
+ } else if (match_ssh_id(stringlen, string, "bcrypt")) {
+ ret->kdf = ON_K_BCRYPT;
+ } else {
+ errmsg = "unrecognised kdf name\n";
+ goto error;
+ }
+
+ if (!(kdfopts = get_ssh_string(&filelen, &filedata, &kdfoptlen))) {
+ errmsg = "encountered EOF before kdf options\n";
+ goto error;
+ }
+ switch (ret->kdf) {
+ case ON_K_NONE:
+ if (kdfoptlen != 0) {
+ errmsg = "expected empty options string for 'none' kdf";
+ goto error;
+ }
+ break;
+ case ON_K_BCRYPT:
+ if (!(bcryptsalt = get_ssh_string(&kdfoptlen, &kdfopts,
+ &bcryptsaltlen))) {
+ errmsg = "bcrypt options string did not contain salt\n";
+ goto error;
+ }
+ if (!get_ssh_uint32(&kdfoptlen, &kdfopts, &bcryptrounds)) {
+ errmsg = "bcrypt options string did not contain round count\n";
+ goto error;
+ }
+ ret->kdfopts.bcrypt.salt = bcryptsalt;
+ ret->kdfopts.bcrypt.saltlen = bcryptsaltlen;
+ ret->kdfopts.bcrypt.rounds = bcryptrounds;
+ 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.
+ */
+ if (!get_ssh_uint32(&filelen, &filedata, &nkeys)) {
+ errmsg = "encountered EOF before key count\n";
+ goto error;
+ }
+ if (nkeys != 1) {
+ errmsg = "multiple keys in new-style OpenSSH key file "
+ "not supported\n";
+ goto error;
+ }
+ ret->nkeys = nkeys;
+ ret->key_wanted = 0;
+
+ for (key_index = 0; key_index < nkeys; key_index++) {
+ if (!(pubkey = get_ssh_string(&filelen, &filedata, &pubkeylen))) {
+ errmsg = "encountered EOF before kdf options\n";
+ goto error;
+ }
+ }
+
+ /*
+ * Now we expect a string containing the encrypted part of the
+ * key file.
+ */
+ if (!(string = get_ssh_string(&filelen, &filedata, &stringlen))) {
+ errmsg = "encountered EOF before private key container\n";
+ goto error;
+ }
+ ret->privatestr = (unsigned char *)string;
+ ret->privatelen = stringlen;
+
+ /*
+ * 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) {
+ if (ret->keyblob) {
+ smemclr(ret->keyblob, ret->keyblob_size);
+ sfree(ret->keyblob);
+ }
+ smemclr(ret, sizeof(*ret));
+ sfree(ret);
+ }
+ if (errmsg_p) *errmsg_p = errmsg;
+ if (fp) fclose(fp);
+ return NULL;
+}
+
+int openssh_new_encrypted(const Filename *filename)
+{
+ struct openssh_new_key *key = load_openssh_new_key(filename, NULL);
+ int ret;
+
+ if (!key)
+ return 0;
+ ret = (key->cipher != ON_E_NONE);
+ smemclr(key->keyblob, key->keyblob_size);
+ sfree(key->keyblob);
+ smemclr(key, sizeof(*key));
+ sfree(key);
+ return ret;
+}
+
+struct ssh2_userkey *openssh_new_read(const Filename *filename,
+ char *passphrase,
+ const char **errmsg_p)
+{
+ struct openssh_new_key *key = load_openssh_new_key(filename, errmsg_p);
+ struct ssh2_userkey *retkey;
+ int i;
+ struct ssh2_userkey *retval = NULL;
+ const char *errmsg;
+ unsigned char *blob;
+ int blobsize = 0;
+ unsigned checkint0, checkint1;
+ const void *priv, *string;
+ int privlen, stringlen, key_index;
+ const struct ssh_signkey *alg;
+
+ blob = 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:
+ keysize = 48; /* 32 byte key + 16 byte IV */
+ break;
+ default:
+ assert(0 && "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(passphrase,
+ key->kdfopts.bcrypt.salt,
+ key->kdfopts.bcrypt.saltlen,
+ key->kdfopts.bcrypt.rounds,
+ keybuf, keysize);
+ break;
+ default:
+ assert(0 && "Bad kdf enumeration value");
+ }
+ switch (key->cipher) {
+ case ON_E_NONE:
+ break;
+ case ON_E_AES256CBC:
+ if (key->privatelen % 16 != 0) {
+ errmsg = "private key container length is not a"
+ " multiple of AES block size\n";
+ goto error;
+ }
+ {
+ void *ctx = aes_make_context();
+ aes256_key(ctx, keybuf);
+ aes_iv(ctx, keybuf + 32);
+ aes_ssh2_decrypt_blk(ctx, key->privatestr,
+ key->privatelen);
+ aes_free_context(ctx);
+ }
+ break;
+ default:
+ assert(0 && "Bad cipher enumeration value");
+ }
+ }
+
+ /*
+ * Now parse the entire encrypted section, and extract the key
+ * identified by key_wanted.
+ */
+ priv = key->privatestr;
+ privlen = key->privatelen;
+
+ if (!get_ssh_uint32(&privlen, &priv, &checkint0) ||
+ !get_ssh_uint32(&privlen, &priv, &checkint1) ||
+ checkint0 != checkint1) {
+ errmsg = "decryption check failed";
+ goto error;
+ }
+
+ retkey = NULL;
+ for (key_index = 0; key_index < key->nkeys; key_index++) {
+ const unsigned char *thiskey;
+ int thiskeylen;
+
+ /*
+ * Read the key type, which will tell us how to scan over
+ * the key to get to the next one.
+ */
+ if (!(string = get_ssh_string(&privlen, &priv, &stringlen))) {
+ errmsg = "expected key type in private string";
+ goto error;
+ }
+
+ /*
+ * Preliminary key type identification, and decide how
+ * many pieces of key we expect to see. Currently
+ * (conveniently) all key types can be seen as some number
+ * of strings, so we just need to know how many of them to
+ * skip over. (The numbers below exclude the key comment.)
+ */
+ {
+ /* find_pubkey_alg needs a zero-terminated copy of the
+ * algorithm name */
+ char *name_zt = dupprintf("%.*s", stringlen, (char *)string);
+ alg = find_pubkey_alg(name_zt);
+ sfree(name_zt);
+ }
+
+ if (!alg) {
+ errmsg = "private key type not recognised\n";
+ goto error;
+ }
+
+ thiskey = priv;
+
+ /*
+ * Skip over the pieces of key.
+ */
+ for (i = 0; i < alg->openssh_private_npieces; i++) {
+ if (!(string = get_ssh_string(&privlen, &priv, &stringlen))) {
+ errmsg = "ran out of data in mid-private-key";
+ goto error;
+ }
+ }
+
+ thiskeylen = (int)((const unsigned char *)priv -
+ (const unsigned char *)thiskey);
+ if (key_index == key->key_wanted) {
+ retkey = snew(struct ssh2_userkey);
+ retkey->alg = alg;
+ retkey->data = alg->openssh_createkey(alg, &thiskey, &thiskeylen);
+ if (!retkey->data) {
+ sfree(retkey);
+ errmsg = "unable to create key data structure";
+ goto error;
+ }
+ }
+
+ /*
+ * Read the key comment.
+ */
+ if (!(string = get_ssh_string(&privlen, &priv, &stringlen))) {
+ errmsg = "ran out of data at key comment";
+ goto error;
+ }
+ if (key_index == key->key_wanted) {
+ assert(retkey);
+ retkey->comment = dupprintf("%.*s", stringlen,
+ (const char *)string);
+ }
+ }
+
+ if (!retkey) {
+ errmsg = "key index out of range";
+ goto error;
+ }
+
+ /*
+ * Now we expect nothing left but padding.
+ */
+ for (i = 0; i < privlen; i++) {
+ if (((const unsigned char *)priv)[i] != (unsigned char)(i+1)) {
+ errmsg = "padding at end of private string did not match";
+ goto error;
+ }
+ }
+
+ errmsg = NULL; /* no error */
+ retval = retkey;
+
+ error:
+ if (blob) {
+ smemclr(blob, blobsize);
+ sfree(blob);
+ }
+ smemclr(key->keyblob, key->keyblob_size);
+ sfree(key->keyblob);
+ smemclr(key, sizeof(*key));
+ sfree(key);
+ if (errmsg_p) *errmsg_p = errmsg;
+ return retval;
+}
+
+int openssh_new_write(const Filename *filename, struct ssh2_userkey *key,
+ char *passphrase)
+{
+ unsigned char *pubblob, *privblob, *outblob, *p;
+ unsigned char *private_section_start, *private_section_length_field;
+ int publen, privlen, commentlen, maxsize, padvalue, i;
+ unsigned checkint;
+ int ret = 0;
+ unsigned char bcrypt_salt[16];
+ const int bcrypt_rounds = 16;
+ FILE *fp;
+
+ /*
+ * Fetch the key blobs and find out the lengths of things.
+ */
+ pubblob = key->alg->public_blob(key->data, &publen);
+ i = key->alg->openssh_fmtkey(key->data, NULL, 0);
+ privblob = snewn(i, unsigned char);
+ privlen = key->alg->openssh_fmtkey(key->data, privblob, i);
+ assert(privlen == i);
+ commentlen = strlen(key->comment);
+
+ /*
+ * Allocate enough space for the full binary key format. No need
+ * to be absolutely precise here.
+ */
+ maxsize = (16 + /* magic number */
+ 32 + /* cipher name string */
+ 32 + /* kdf name string */
+ 64 + /* kdf options string */
+ 4 + /* key count */
+ 4+publen + /* public key string */
+ 4 + /* string header for private section */
+ 8 + /* checkint x 2 */
+ 4+strlen(key->alg->name) + /* key type string */
+ privlen + /* private blob */
+ 4+commentlen + /* comment string */
+ 16); /* padding at end of private section */
+ outblob = snewn(maxsize, unsigned char);
+
+ /*
+ * Construct the cleartext version of the blob.
+ */
+ p = outblob;
+
+ /* Magic number. */
+ memcpy(p, "openssh-key-v1\0", 15);
+ p += 15;
+
+ /* Cipher and kdf names, and kdf options. */
+ if (!passphrase) {
+ memset(bcrypt_salt, 0, sizeof(bcrypt_salt)); /* prevent warnings */
+ p += put_string_z(p, "none");
+ p += put_string_z(p, "none");
+ p += put_string_z(p, "");
+ } else {
+ unsigned char *q;
+ for (i = 0; i < (int)sizeof(bcrypt_salt); i++)
+ bcrypt_salt[i] = random_byte();
+ p += put_string_z(p, "aes256-cbc");
+ p += put_string_z(p, "bcrypt");
+ q = p;
+ p += 4;
+ p += put_string(p, bcrypt_salt, sizeof(bcrypt_salt));
+ p += put_uint32(p, bcrypt_rounds);
+ PUT_32BIT_MSB_FIRST(q, (unsigned)(p - (q+4)));
+ }
+
+ /* Number of keys. */
+ p += put_uint32(p, 1);
+
+ /* Public blob. */
+ p += put_string(p, pubblob, publen);
+
+ /* Begin private section. */
+ private_section_length_field = p;
+ p += 4;
+ private_section_start = p;
+
+ /* checkint. */
+ checkint = 0;
+ for (i = 0; i < 4; i++)
+ checkint = (checkint << 8) + random_byte();
+ p += put_uint32(p, checkint);
+ p += put_uint32(p, checkint);
+
+ /* Private key. The main private blob goes inline, with no string
+ * wrapper. */
+ p += put_string_z(p, key->alg->name);
+ memcpy(p, privblob, privlen);
+ p += privlen;
+
+ /* Comment. */
+ p += put_string_z(p, key->comment);
+
+ /* Pad out the encrypted section. */
+ padvalue = 1;
+ do {
+ *p++ = padvalue++;
+ } while ((p - private_section_start) & 15);
+
+ assert(p - outblob < maxsize);
+
+ /* Go back and fill in the length field for the private section. */
+ PUT_32BIT_MSB_FIRST(private_section_length_field,
+ p - private_section_start);
+
+ if (passphrase) {
+ /*
+ * Encrypt the private section. We need 48 bytes of key
+ * material: 32 bytes AES key + 16 bytes iv.
+ */
+ unsigned char keybuf[48];
+ void *ctx;
+
+ openssh_bcrypt(passphrase,
+ bcrypt_salt, sizeof(bcrypt_salt), bcrypt_rounds,
+ keybuf, sizeof(keybuf));
+
+ ctx = aes_make_context();
+ aes256_key(ctx, keybuf);
+ aes_iv(ctx, keybuf + 32);
+ aes_ssh2_encrypt_blk(ctx, private_section_start,
+ p - private_section_start);
+ aes_free_context(ctx);
+
+ 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 OPENSSH PRIVATE KEY-----\n", fp);
+ base64_encode(fp, outblob, p - outblob, 64);
+ fputs("-----END OPENSSH PRIVATE KEY-----\n", fp);
+ fclose(fp);
+ ret = 1;
+
+ error:
+ if (outblob) {
+ smemclr(outblob, maxsize);
+ sfree(outblob);
+ }
+ if (privblob) {
+ smemclr(privblob, privlen);
+ sfree(privblob);
+ }
+ if (pubblob) {
+ smemclr(pubblob, publen);
+ sfree(pubblob);
+ }
+ return ret;
+}
+
+/* ----------------------------------------------------------------------
+ * The switch function openssh_auto_write(), which chooses one of the
+ * concrete OpenSSH output formats based on the key type.
+ */
+int openssh_auto_write(const Filename *filename, struct ssh2_userkey *key,
+ 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.
+ */
+ if (key->alg == &ssh_dss ||
+ key->alg == &ssh_rsa ||
+ key->alg == &ssh_ecdsa_nistp256 ||
+ key->alg == &ssh_ecdsa_nistp384 ||
+ key->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 */
+ unsigned char *keyblob;
+ int keyblob_len, keyblob_size;
+};
+
+static struct sshcom_key *load_sshcom_key(const Filename *filename,
+ const char **errmsg_p)
+{
+ struct sshcom_key *ret;
+ FILE *fp;
+ char *line = NULL;
+ int hdrstart, len;
+ const char *errmsg;
+ char *p;
+ int headers_done;
+ char base64_bit[4];
+ int base64_chars = 0;
+
+ ret = snew(struct sshcom_key);
+ ret->comment[0] = '\0';
+ ret->keyblob = NULL;
+ ret->keyblob_len = ret->keyblob_size = 0;
+
+ fp = f_open(filename, "r", FALSE);
+ if (!fp) {
+ errmsg = "unable to open key file";
+ goto error;
+ }
+ if (!(line = fgetline(fp))) {
+ errmsg = "unexpected end of file";
+ goto error;
+ }
+ strip_crlf(line);
+ 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 = 0;
+ while (1) {
+ if (!(line = fgetline(fp))) {
+ errmsg = "unexpected end of file";
+ goto error;
+ }
+ strip_crlf(line);
+ 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 = fgetline(fp);
+ if (!line2) {
+ errmsg = "unexpected end of file";
+ goto error;
+ }
+ strip_crlf(line2);
+
+ 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;
+ strip_crlf(p);
+ 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 = 1;
+
+ 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;
+ }
+
+ if (ret->keyblob_len + len > ret->keyblob_size) {
+ ret->keyblob_size = ret->keyblob_len + len + 256;
+ ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
+ unsigned char);
+ }
+
+ memcpy(ret->keyblob + ret->keyblob_len, out, len);
+ ret->keyblob_len += len;
+ }
+
+ p++;
+ }
+ }
+ smemclr(line, strlen(line));
+ sfree(line);
+ line = NULL;
+ }
+
+ if (ret->keyblob_len == 0 || !ret->keyblob) {
+ errmsg = "key body not present";
+ goto error;
+ }
+
+ fclose(fp);
+ if (errmsg_p) *errmsg_p = NULL;
+ return ret;
+
+ error:
+ if (fp)
+ fclose(fp);
+
+ if (line) {
+ smemclr(line, strlen(line));
+ sfree(line);
+ line = NULL;
+ }
+ if (ret) {
+ if (ret->keyblob) {
+ smemclr(ret->keyblob, ret->keyblob_size);
+ sfree(ret->keyblob);
+ }
+ smemclr(ret, sizeof(*ret));
+ sfree(ret);
+ }
+ if (errmsg_p) *errmsg_p = errmsg;
+ return NULL;
+}
+
+int sshcom_encrypted(const Filename *filename, char **comment)
+{
+ struct sshcom_key *key = load_sshcom_key(filename, NULL);
+ int pos, len, answer;
+
+ answer = 0;
+
+ *comment = NULL;
+ if (!key)
+ goto done;
+
+ /*
+ * Check magic number.
+ */
+ if (GET_32BIT(key->keyblob) != 0x3f6ff9eb) {
+ goto done; /* key is invalid */
+ }
+
+ /*
+ * Find the cipher-type string.
+ */
+ pos = 8;
+ if (key->keyblob_len < pos+4)
+ goto done; /* key is far too short */
+ len = toint(GET_32BIT(key->keyblob + pos));
+ if (len < 0 || len > key->keyblob_len - pos - 4)
+ goto done; /* key is far too short */
+ pos += 4 + len; /* skip key type */
+ len = toint(GET_32BIT(key->keyblob + pos)); /* find cipher-type length */
+ if (len < 0 || len > key->keyblob_len - pos - 4)
+ goto done; /* cipher type string is incomplete */
+ if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4))
+ answer = 1;
+
+ done:
+ if (key) {
+ *comment = dupstr(key->comment);
+ smemclr(key->keyblob, key->keyblob_size);
+ sfree(key->keyblob);
+ smemclr(key, sizeof(*key));
+ sfree(key);
+ } else {
+ *comment = dupstr("");
+ }
+ return answer;
+}
+
+static int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret)
+{
+ unsigned bits, bytes;
+ unsigned char *d = (unsigned char *) data;
+
+ if (len < 4)
+ goto error;
+ bits = GET_32BIT(d);
+
+ bytes = (bits + 7) / 8;
+ if (len < 4+bytes)
+ goto error;
+
+ ret->start = d + 4;
+ ret->bytes = bytes;
+ return bytes+4;
+
+ error:
+ ret->start = NULL;
+ ret->bytes = -1;
+ return len; /* ensure further calls fail as well */
+}
+
+static int sshcom_put_mpint(void *target, void *data, int len)
+{
+ unsigned char *d = (unsigned char *)target;
+ unsigned char *i = (unsigned char *)data;
+ int bits = len * 8 - 1;
+
+ while (bits > 0) {
+ if (*i & (1 << (bits & 7)))
+ break;
+ if (!(bits-- & 7))
+ i++, len--;
+ }
+
+ PUT_32BIT(d, bits+1);
+ memcpy(d+4, i, len);
+ return len+4;
+}
+
+struct ssh2_userkey *sshcom_read(const Filename *filename, char *passphrase,
+ const char **errmsg_p)
+{
+ struct sshcom_key *key = load_sshcom_key(filename, errmsg_p);
+ const char *errmsg;
+ int pos, len;
+ const char prefix_rsa[] = "if-modn{sign{rsa";
+ const char prefix_dsa[] = "dl-modp{sign{dsa";
+ enum { RSA, DSA } type;
+ int encrypted;
+ char *ciphertext;
+ int cipherlen;
+ struct ssh2_userkey *ret = NULL, *retkey;
+ const struct ssh_signkey *alg;
+ unsigned char *blob = NULL;
+ int blobsize = 0, publen, privlen;
+
+ if (!key)
+ return NULL;
+
+ /*
+ * Check magic number.
+ */
+ if (GET_32BIT(key->keyblob) != SSHCOM_MAGIC_NUMBER) {
+ errmsg = "key does not begin with magic number";
+ goto error;
+ }
+
+ /*
+ * Determine the key type.
+ */
+ pos = 8;
+ if (key->keyblob_len < pos+4 ||
+ (len = toint(GET_32BIT(key->keyblob + pos))) < 0 ||
+ len > key->keyblob_len - pos - 4) {
+ errmsg = "key blob does not contain a key type string";
+ goto error;
+ }
+ if (len > sizeof(prefix_rsa) - 1 &&
+ !memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) {
+ type = RSA;
+ } else if (len > sizeof(prefix_dsa) - 1 &&
+ !memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) {
+ type = DSA;
+ } else {
+ errmsg = "key is of unknown type";
+ goto error;
+ }
+ pos += 4+len;
+
+ /*
+ * Determine the cipher type.
+ */
+ if (key->keyblob_len < pos+4 ||
+ (len = toint(GET_32BIT(key->keyblob + pos))) < 0 ||
+ len > key->keyblob_len - pos - 4) {
+ errmsg = "key blob does not contain a cipher type string";
+ goto error;
+ }
+ if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4))
+ encrypted = 0;
+ else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8))
+ encrypted = 1;
+ else {
+ errmsg = "key encryption is of unknown type";
+ goto error;
+ }
+ pos += 4+len;
+
+ /*
+ * Get hold of the encrypted part of the key.
+ */
+ if (key->keyblob_len < pos+4 ||
+ (len = toint(GET_32BIT(key->keyblob + pos))) < 0 ||
+ len > key->keyblob_len - pos - 4) {
+ errmsg = "key blob does not contain actual key data";
+ goto error;
+ }
+ ciphertext = (char *)key->keyblob + pos + 4;
+ cipherlen = len;
+ if (cipherlen == 0) {
+ errmsg = "length of key data is zero";
+ 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
+ */
+ struct MD5Context md5c;
+ unsigned char keybuf[32], iv[8];
+
+ if (cipherlen % 8 != 0) {
+ errmsg = "encrypted part of key is not a multiple of cipher block"
+ " size";
+ goto error;
+ }
+
+ MD5Init(&md5c);
+ MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
+ MD5Final(keybuf, &md5c);
+
+ MD5Init(&md5c);
+ MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
+ MD5Update(&md5c, keybuf, 16);
+ MD5Final(keybuf+16, &md5c);
+
+ /*
+ * Now decrypt the key blob.
+ */
+ memset(iv, 0, sizeof(iv));
+ des3_decrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
+ cipherlen);
+
+ smemclr(&md5c, sizeof(md5c));
+ 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;
+ }
+
+ /*
+ * Strip away the containing string to get to the real meat.
+ */
+ len = toint(GET_32BIT(ciphertext));
+ if (len < 0 || len > cipherlen-4) {
+ errmsg = "containing string was ill-formed";
+ goto error;
+ }
+ ciphertext += 4;
+ cipherlen = len;
+
+ /*
+ * 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 alg->createkey().
+ */
+ blobsize = cipherlen + 256;
+ blob = snewn(blobsize, unsigned char);
+ privlen = 0;
+ if (type == RSA) {
+ struct mpint_pos n, e, d, u, p, q;
+ int pos = 0;
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e);
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d);
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n);
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u);
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
+ if (!q.start) {
+ errmsg = "key data did not contain six integers";
+ goto error;
+ }
+
+ alg = &ssh_rsa;
+ pos = 0;
+ pos += put_string(blob+pos, "ssh-rsa", 7);
+ pos += put_mp(blob+pos, e.start, e.bytes);
+ pos += put_mp(blob+pos, n.start, n.bytes);
+ publen = pos;
+ pos += put_string(blob+pos, d.start, d.bytes);
+ pos += put_mp(blob+pos, q.start, q.bytes);
+ pos += put_mp(blob+pos, p.start, p.bytes);
+ pos += put_mp(blob+pos, u.start, u.bytes);
+ privlen = pos - publen;
+ } else {
+ struct mpint_pos p, q, g, x, y;
+ int pos = 4;
+
+ assert(type == DSA); /* the only other option from the if above */
+
+ if (GET_32BIT(ciphertext) != 0) {
+ errmsg = "predefined DSA parameters not supported";
+ goto error;
+ }
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g);
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y);
+ pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x);
+ if (!x.start) {
+ errmsg = "key data did not contain five integers";
+ goto error;
+ }
+
+ alg = &ssh_dss;
+ pos = 0;
+ pos += put_string(blob+pos, "ssh-dss", 7);
+ pos += put_mp(blob+pos, p.start, p.bytes);
+ pos += put_mp(blob+pos, q.start, q.bytes);
+ pos += put_mp(blob+pos, g.start, g.bytes);
+ pos += put_mp(blob+pos, y.start, y.bytes);
+ publen = pos;
+ pos += put_mp(blob+pos, x.start, x.bytes);
+ privlen = pos - publen;
+ }
+
+ assert(privlen > 0); /* should have bombed by now if not */
+
+ retkey = snew(struct ssh2_userkey);
+ retkey->alg = alg;
+ retkey->data = alg->createkey(alg, blob, publen, blob+publen, privlen);
+ if (!retkey->data) {
+ 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) {
+ smemclr(blob, blobsize);
+ sfree(blob);
+ }
+ smemclr(key->keyblob, key->keyblob_size);
+ sfree(key->keyblob);
+ smemclr(key, sizeof(*key));
+ sfree(key);
+ if (errmsg_p) *errmsg_p = errmsg;
+ return ret;
+}
+
+int sshcom_write(const Filename *filename, struct ssh2_userkey *key,
+ char *passphrase)
+{
+ unsigned char *pubblob, *privblob;
+ int publen, privlen;
+ unsigned char *outblob;
+ int outlen;
+ struct mpint_pos numbers[6];
+ int nnumbers, initial_zero, pos, lenpos, i;
+ const char *type;
+ char *ciphertext;
+ int cipherlen;
+ int ret = 0;
+ FILE *fp;
+
+ /*
+ * Fetch the key blobs.
+ */
+ pubblob = key->alg->public_blob(key->data, &publen);
+ privblob = key->alg->private_blob(key->data, &privlen);
+ outblob = NULL;
+
+ /*
+ * Find the sequence of integers to be encoded into the OpenSSH
+ * key blob, and also decide on the header line.
+ */
+ if (key->alg == &ssh_rsa) {
+ int pos;
+ struct mpint_pos n, e, d, p, q, iqmp;
+
+ /*
+ * These blobs were generated from inside PuTTY, so we needn't
+ * treat them as untrusted.
+ */
+ pos = 4 + GET_32BIT(pubblob);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
+ pos = 0;
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
+
+ assert(e.start && iqmp.start); /* 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 = 0;
+ type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
+ } else if (key->alg == &ssh_dss) {
+ int pos;
+ struct mpint_pos p, q, g, y, x;
+
+ /*
+ * These blobs were generated from inside PuTTY, so we needn't
+ * treat them as untrusted.
+ */
+ pos = 4 + GET_32BIT(pubblob);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
+ pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
+ pos = 0;
+ pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
+
+ assert(y.start && x.start); /* can't go wrong */
+
+ numbers[0] = p;
+ numbers[1] = g;
+ numbers[2] = q;
+ numbers[3] = y;
+ numbers[4] = x;
+
+ nnumbers = 5;
+ initial_zero = 1;
+ type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
+ } else {
+ assert(0); /* zoinks! */
+ exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
+ }
+
+ /*
+ * Total size of key blob will be somewhere under 512 plus
+ * combined length of integers. We'll calculate the more
+ * precise size as we construct the blob.
+ */
+ outlen = 512;
+ for (i = 0; i < nnumbers; i++)
+ outlen += 4 + numbers[i].bytes;
+ outblob = snewn(outlen, unsigned char);
+
+ /*
+ * Create the unencrypted key blob.
+ */
+ pos = 0;
+ PUT_32BIT(outblob+pos, SSHCOM_MAGIC_NUMBER); pos += 4;
+ pos += 4; /* length field, fill in later */
+ pos += put_string(outblob+pos, type, strlen(type));
+ {
+ const char *ciphertype = passphrase ? "3des-cbc" : "none";
+ pos += put_string(outblob+pos, ciphertype, strlen(ciphertype));
+ }
+ lenpos = pos; /* remember this position */
+ pos += 4; /* encrypted-blob size */
+ pos += 4; /* encrypted-payload size */
+ if (initial_zero) {
+ PUT_32BIT(outblob+pos, 0);
+ pos += 4;
+ }
+ for (i = 0; i < nnumbers; i++)
+ pos += sshcom_put_mpint(outblob+pos,
+ numbers[i].start, numbers[i].bytes);
+ /* Now wrap up the encrypted payload. */
+ PUT_32BIT(outblob+lenpos+4, pos - (lenpos+8));
+ /* Pad encrypted blob to a multiple of cipher block size. */
+ if (passphrase) {
+ int padding = -(pos - (lenpos+4)) & 7;
+ while (padding--)
+ outblob[pos++] = random_byte();
+ }
+ ciphertext = (char *)outblob+lenpos+4;
+ cipherlen = pos - (lenpos+4);
+ assert(!passphrase || cipherlen % 8 == 0);
+ /* Wrap up the encrypted blob string. */
+ PUT_32BIT(outblob+lenpos, cipherlen);
+ /* And finally fill in the total length field. */
+ PUT_32BIT(outblob+4, pos);
+
+ assert(pos < outlen);
+
+ /*
+ * Encrypt the key.
+ */
+ if (passphrase) {
+ /*
+ * 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
+ */
+ struct MD5Context md5c;
+ unsigned char keybuf[32], iv[8];
+
+ MD5Init(&md5c);
+ MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
+ MD5Final(keybuf, &md5c);
+
+ MD5Init(&md5c);
+ MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
+ MD5Update(&md5c, keybuf, 16);
+ MD5Final(keybuf+16, &md5c);
+
+ /*
+ * Now decrypt the key blob.
+ */
+ memset(iv, 0, sizeof(iv));
+ des3_encrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
+ cipherlen);
+
+ smemclr(&md5c, sizeof(md5c));
+ 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, outblob, pos, 70);
+ fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
+ fclose(fp);
+ ret = 1;
+
+ error:
+ if (outblob) {
+ smemclr(outblob, outlen);
+ sfree(outblob);
+ }
+ if (privblob) {
+ smemclr(privblob, privlen);
+ sfree(privblob);
+ }
+ if (pubblob) {
+ smemclr(pubblob, publen);
+ sfree(pubblob);
+ }
+ return ret;
+}