/* * 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 "misc.h" int openssh_encrypted(const Filename *filename); struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase, const char **errmsg_p); int openssh_write(const Filename *filename, struct ssh2_userkey *key, char *passphrase); int sshcom_encrypted(const Filename *filename, char **comment); struct ssh2_userkey *sshcom_read(const Filename *filename, char *passphrase, const char **errmsg_p); int sshcom_write(const Filename *filename, struct ssh2_userkey *key, char *passphrase); /* * Given a key type, determine whether we know how to import it. */ int import_possible(int type) { if (type == SSH_KEYTYPE_OPENSSH) return 1; if (type == SSH_KEYTYPE_SSHCOM) return 1; return 0; } /* * 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; } /* * Determine whether a foreign key is encrypted. */ int import_encrypted(const Filename *filename, int type, char **comment) { if (type == SSH_KEYTYPE_OPENSSH) { /* OpenSSH doesn't do key comments */ *comment = dupstr(filename_to_str(filename)); return openssh_encrypted(filename); } if (type == SSH_KEYTYPE_SSHCOM) { return sshcom_encrypted(filename, comment); } return 0; } /* * Import an SSH-1 key. */ int import_ssh1(const Filename *filename, int type, struct RSAKey *key, char *passphrase, const char **errmsg_p) { return 0; } /* * Import an SSH-2 key. */ struct ssh2_userkey *import_ssh2(const Filename *filename, int type, char *passphrase, const char **errmsg_p) { if (type == SSH_KEYTYPE_OPENSSH) return openssh_read(filename, passphrase, errmsg_p); if (type == SSH_KEYTYPE_SSHCOM) return sshcom_read(filename, passphrase, errmsg_p); return NULL; } /* * Export an SSH-1 key. */ int export_ssh1(const Filename *filename, int type, struct RSAKey *key, char *passphrase) { return 0; } /* * Export an SSH-2 key. */ int export_ssh2(const Filename *filename, int type, struct ssh2_userkey *key, char *passphrase) { if (type == SSH_KEYTYPE_OPENSSH) return openssh_write(filename, key, passphrase); if (type == SSH_KEYTYPE_SSHCOM) return sshcom_write(filename, key, passphrase); return 0; } /* * Strip trailing CRs and LFs at the end of a line of text. */ void strip_crlf(char *str) { char *p = str + strlen(str); while (p > str && (p[-1] == '\r' || p[-1] == '\n')) *--p = '\0'; } /* ---------------------------------------------------------------------- * 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) static int ber_read_id_len(void *source, int sourcelen, int *id, int *length, int *flags) { unsigned char *p = (unsigned char *) source; if (sourcelen == 0) return -1; *flags = (*p & 0xE0); if ((*p & 0x1F) == 0x1F) { *id = 0; while (*p & 0x80) { p++, sourcelen--; if (sourcelen == 0) return -1; *id = (*id << 7) | (*p & 0x7F); } p++, sourcelen--; } else { *id = *p & 0x1F; p++, sourcelen--; } if (sourcelen == 0) return -1; if (*p & 0x80) { int n = *p & 0x7F; p++, sourcelen--; if (sourcelen < n) return -1; *length = 0; while (n--) *length = (*length << 8) | (*p++); sourcelen -= n; } else { *length = *p; p++, sourcelen--; } return p - (unsigned char *) source; } /* * 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 int ber_write_id_len(void *dest, int id, int length, int flags) { unsigned char *d = (unsigned char *)dest; int len = 0; if (id <= 30) { /* * Identifier is one byte. */ len++; if (d) *d++ = 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. */ len++; if (d) *d++ = 0x1F | flags; for (n = 1; (id >> (7*n)) > 0; n++) continue; /* count the bytes */ while (n--) { len++; if (d) *d++ = (n ? 0x80 : 0) | ((id >> (7*n)) & 0x7F); } } if (length < 128) { /* * Length is one byte. */ len++; if (d) *d++ = 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 */ len++; if (d) *d++ = 0x80 | n; while (n--) { len++; if (d) *d++ = (length >> (8*n)) & 0xFF; } } return len; } static int put_string(void *target, void *data, int len) { unsigned char *d = (unsigned char *)target; PUT_32BIT(d, len); memcpy(d+4, data, len); return len+4; } static int put_mp(void *target, void *data, int len) { unsigned char *d = (unsigned char *)target; unsigned char *i = (unsigned char *)data; if (*i & 0x80) { PUT_32BIT(d, len+1); d[4] = 0; memcpy(d+5, data, len); return len+5; } else { PUT_32BIT(d, len); memcpy(d+4, data, len); return len+4; } } /* Simple structure to point to an mp-int within a blob. */ struct mpint_pos { void *start; int bytes; }; static int ssh2_read_mpint(void *data, int len, struct mpint_pos *ret) { int bytes; unsigned char *d = (unsigned char *) data; if (len < 4) goto error; bytes = GET_32BIT(d); 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 */ } /* ---------------------------------------------------------------------- * Code to read and write OpenSSH private keys. */ enum { OSSH_DSA, OSSH_RSA }; enum { OSSH_ENC_3DES, OSSH_ENC_AES }; struct openssh_key { int type; int encrypted, encryption; char iv[32]; unsigned char *keyblob; int keyblob_len, keyblob_size; }; static struct openssh_key *load_openssh_key(const Filename *filename, const char **errmsg_p) { struct openssh_key *ret; FILE *fp; char *line = NULL; char *errmsg, *p; int headers_done; char base64_bit[4]; int base64_chars = 0; ret = snew(struct openssh_key); ret->keyblob = NULL; ret->keyblob_len = ret->keyblob_size = 0; ret->encrypted = 0; memset(ret->iv, 0, sizeof(ret->iv)); 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 != strncmp(line, "-----BEGIN ", 11) || 0 != strcmp(line+strlen(line)-16, "PRIVATE KEY-----")) { errmsg = "file does not begin with OpenSSH key header"; goto error; } if (!strcmp(line, "-----BEGIN RSA PRIVATE KEY-----")) ret->type = OSSH_RSA; else if (!strcmp(line, "-----BEGIN DSA PRIVATE KEY-----")) ret->type = OSSH_DSA; else { errmsg = "unrecognised key type"; goto error; } memset(line, 0, 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 (0 == strncmp(line, "-----END ", 9) && 0 == strcmp(line+strlen(line)-16, "PRIVATE KEY-----")) 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 = 1; } else if (!strcmp(line, "DEK-Info")) { int i, j, ivlen; if (!strncmp(p, "DES-EDE3-CBC,", 13)) { ret->encryption = OSSH_ENC_3DES; ivlen = 8; } else if (!strncmp(p, "AES-128-CBC,", 12)) { ret->encryption = OSSH_ENC_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++) { 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 = 1; 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; memset(out, 0, sizeof(out)); } p++; } } memset(line, 0, strlen(line)); sfree(line); line = NULL; } if (ret->keyblob_len == 0 || !ret->keyblob) { 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; } memset(base64_bit, 0, sizeof(base64_bit)); if (errmsg_p) *errmsg_p = NULL; return ret; error: if (line) { memset(line, 0, strlen(line)); sfree(line); line = NULL; } memset(base64_bit, 0, sizeof(base64_bit)); if (ret) { if (ret->keyblob) { memset(ret->keyblob, 0, ret->keyblob_size); sfree(ret->keyblob); } memset(ret, 0, sizeof(*ret)); sfree(ret); } if (errmsg_p) *errmsg_p = errmsg; return NULL; } int openssh_encrypted(const Filename *filename) { struct openssh_key *key = load_openssh_key(filename, NULL); int ret; if (!key) return 0; ret = key->encrypted; memset(key->keyblob, 0, key->keyblob_size); sfree(key->keyblob); memset(key, 0, sizeof(*key)); sfree(key); return ret; } struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase, const char **errmsg_p) { struct openssh_key *key = load_openssh_key(filename, errmsg_p); struct ssh2_userkey *retkey; unsigned char *p; int ret, id, len, flags; int i, num_integers; struct ssh2_userkey *retval = NULL; char *errmsg; unsigned char *blob; int blobsize = 0, blobptr, privptr; char *modptr = NULL; int modlen = 0; blob = NULL; if (!key) return NULL; if (key->encrypted) { /* * 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 * * (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.) */ struct MD5Context md5c; unsigned char keybuf[32]; MD5Init(&md5c); MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase)); MD5Update(&md5c, (unsigned char *)key->iv, 8); MD5Final(keybuf, &md5c); MD5Init(&md5c); MD5Update(&md5c, keybuf, 16); MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase)); MD5Update(&md5c, (unsigned char *)key->iv, 8); MD5Final(keybuf+16, &md5c); /* * Now decrypt the key blob. */ if (key->encryption == OSSH_ENC_3DES) des3_decrypt_pubkey_ossh(keybuf, (unsigned char *)key->iv, key->keyblob, key->keyblob_len); else { void *ctx; assert(key->encryption == OSSH_ENC_AES); ctx = aes_make_context(); aes128_key(ctx, keybuf); aes_iv(ctx, (unsigned char *)key->iv); aes_ssh2_decrypt_blk(ctx, key->keyblob, key->keyblob_len); aes_free_context(ctx); } memset(&md5c, 0, sizeof(md5c)); memset(keybuf, 0, 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. */ p = key->keyblob; /* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */ ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags); p += ret; if (ret < 0 || id != 16) { errmsg = "ASN.1 decoding failure"; retval = SSH2_WRONG_PASSPHRASE; goto error; } /* Expect a load of INTEGERs. */ if (key->type == OSSH_RSA) num_integers = 9; else if (key->type == OSSH_DSA) num_integers = 6; else num_integers = 0; /* placate compiler warnings */ /* * Space to create key blob in. */ blobsize = 256+key->keyblob_len; blob = snewn(blobsize, unsigned char); PUT_32BIT(blob, 7); if (key->type == OSSH_DSA) memcpy(blob+4, "ssh-dss", 7); else if (key->type == OSSH_RSA) memcpy(blob+4, "ssh-rsa", 7); blobptr = 4+7; privptr = -1; for (i = 0; i < num_integers; i++) { ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p, &id, &len, &flags); p += ret; if (ret < 0 || id != 2 || key->keyblob+key->keyblob_len-p < len) { errmsg = "ASN.1 decoding failure"; retval = SSH2_WRONG_PASSPHRASE; goto error; } if (i == 0) { /* * The first integer should be zero always (I think * this is some sort of version indication). */ if (len != 1 || p[0] != 0) { errmsg = "version number mismatch"; goto error; } } else if (key->type == OSSH_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. */ modptr = (char *)p; modlen = len; } else if (i != 6 && i != 7) { PUT_32BIT(blob+blobptr, len); memcpy(blob+blobptr+4, p, len); blobptr += 4+len; if (i == 2) { PUT_32BIT(blob+blobptr, modlen); memcpy(blob+blobptr+4, modptr, modlen); blobptr += 4+modlen; privptr = blobptr; } } } else if (key->type == OSSH_DSA) { /* * Integers 1-4 go into the public blob; integer 5 goes * into the private blob. */ PUT_32BIT(blob+blobptr, len); memcpy(blob+blobptr+4, p, len); blobptr += 4+len; if (i == 4) privptr = blobptr; } /* Skip past the number. */ p += 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(struct ssh2_userkey); retkey->alg = (key->type == OSSH_RSA ? &ssh_rsa : &ssh_dss); retkey->data = retkey->alg->createkey(blob, privptr, blob+privptr, blobptr-privptr); if (!retkey->data) { sfree(retkey); errmsg = "unable to create key data structure"; goto error; } retkey->comment = dupstr("imported-openssh-key"); errmsg = NULL; /* no error */ retval = retkey; error: if (blob) { memset(blob, 0, blobsize); sfree(blob); } memset(key->keyblob, 0, key->keyblob_size); sfree(key->keyblob); memset(key, 0, sizeof(*key)); sfree(key); if (errmsg_p) *errmsg_p = errmsg; return retval; } int openssh_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; 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; /* * 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, dmp1, dmq1; Bignum bd, bp, bq, bdmp1, bdmq1; 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 if (key->alg == &ssh_dss) { int pos; struct mpint_pos p, q, g, y, x; 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"; } else { assert(0); /* zoinks! */ exit(1); /* XXX: GCC doesn't understand assert() on some systems. */ } /* * 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); /* Round up to the cipher block size, ensuring we have at least one * byte of padding (see below). */ outlen = len; if (passphrase) outlen = (outlen+8) &~ 7; /* * Now we know how big outblob needs to be. Allocate it. */ outblob = snewn(outlen, 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; } /* * 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; } /* * Encrypt the key. * * For the moment, we still encrypt our OpenSSH keys using * old-style 3DES. */ if (passphrase) { /* * 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 */ struct MD5Context md5c; unsigned char keybuf[32]; 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); memset(&md5c, 0, sizeof(md5c)); memset(keybuf, 0, 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, outblob, outlen, 64); fputs(footer, fp); fclose(fp); ret = 1; error: if (outblob) { memset(outblob, 0, outlen); sfree(outblob); } if (spareblob) { memset(spareblob, 0, sparelen); sfree(spareblob); } if (privblob) { memset(privblob, 0, privlen); sfree(privblob); } if (pubblob) { memset(pubblob, 0, publen); sfree(pubblob); } return ret; } /* ---------------------------------------------------------------------- * 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; char *errmsg, *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; } memset(line, 0, 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 ----")) 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]); memset(line2, 0, 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++; } } memset(line, 0, strlen(line)); sfree(line); line = NULL; } if (ret->keyblob_len == 0 || !ret->keyblob) { errmsg = "key body not present"; goto error; } if (errmsg_p) *errmsg_p = NULL; return ret; error: if (line) { memset(line, 0, strlen(line)); sfree(line); line = NULL; } if (ret) { if (ret->keyblob) { memset(ret->keyblob, 0, ret->keyblob_size); sfree(ret->keyblob); } memset(ret, 0, 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; *comment = NULL; if (!key) return 0; /* * Check magic number. */ if (GET_32BIT(key->keyblob) != 0x3f6ff9eb) return 0; /* key is invalid */ /* * Find the cipher-type string. */ answer = 0; pos = 8; if (key->keyblob_len < pos+4) goto done; /* key is far too short */ pos += 4 + GET_32BIT(key->keyblob + pos); /* skip key type */ if (key->keyblob_len < pos+4) goto done; /* key is far too short */ len = GET_32BIT(key->keyblob + pos); /* find cipher-type length */ if (key->keyblob_len < pos+4+len) goto done; /* cipher type string is incomplete */ if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4)) answer = 1; done: *comment = dupstr(key->comment); memset(key->keyblob, 0, key->keyblob_size); sfree(key->keyblob); memset(key, 0, sizeof(*key)); sfree(key); return answer; } static int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret) { int bits; int 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); 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 = GET_32BIT(key->keyblob + pos)) > 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 = GET_32BIT(key->keyblob + pos)) > 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 = GET_32BIT(key->keyblob + pos)) > 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); memset(&md5c, 0, sizeof(md5c)); memset(keybuf, 0, 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 = 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 if (type == DSA) { struct mpint_pos p, q, g, x, y; int pos = 4; 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; } else return NULL; assert(privlen > 0); /* should have bombed by now if not */ retkey = snew(struct ssh2_userkey); retkey->alg = alg; retkey->data = alg->createkey(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) { memset(blob, 0, blobsize); sfree(blob); } memset(key->keyblob, 0, key->keyblob_size); sfree(key->keyblob); memset(key, 0, 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; 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; 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; 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)); { 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); memset(&md5c, 0, sizeof(md5c)); memset(keybuf, 0, 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) { memset(outblob, 0, outlen); sfree(outblob); } if (privblob) { memset(privblob, 0, privlen); sfree(privblob); } if (pubblob) { memset(pubblob, 0, publen); sfree(pubblob); } return ret; }