X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/32874aeac8dacbca26663777b39a79efc5d8dc4b..231ee168f3732ad79bdc8772ab91393f109b8f53:/sshpubk.c diff --git a/sshpubk.c b/sshpubk.c index d5576e8b..85e0e49f 100644 --- a/sshpubk.c +++ b/sshpubk.c @@ -10,6 +10,7 @@ #include #include "ssh.h" +#include "misc.h" #define PUT_32BIT(cp, value) do { \ (cp)[3] = (value); \ @@ -31,7 +32,7 @@ (x)=='+' ? 62 : \ (x)=='/' ? 63 : 0 ) -static int loadrsakey_main(FILE * fp, struct RSAKey *key, +static int loadrsakey_main(FILE * fp, struct RSAKey *key, int pub_only, char **commentptr, char *passphrase) { unsigned char buf[16384]; @@ -75,6 +76,11 @@ static int loadrsakey_main(FILE * fp, struct RSAKey *key, if (len - i < 0) goto end; /* overran */ + if (pub_only) { + ret = 1; + goto end; + } + /* Next, the comment field. */ j = GET_32BIT(buf + i); i += 4; @@ -160,7 +166,7 @@ int loadrsakey(char *filename, struct RSAKey *key, char *passphrase) * key file. */ if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) { - return loadrsakey_main(fp, key, NULL, passphrase); + return loadrsakey_main(fp, key, FALSE, NULL, passphrase); } /* @@ -188,13 +194,50 @@ int rsakey_encrypted(char *filename, char **comment) * key file. */ if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) { - return loadrsakey_main(fp, NULL, comment, NULL); + return loadrsakey_main(fp, NULL, FALSE, comment, NULL); } fclose(fp); return 0; /* wasn't the right kind of file */ } /* + * Return a malloc'ed chunk of memory containing the public blob of + * an RSA key, as given in the agent protocol (modulus bits, + * exponent, modulus). + */ +int rsakey_pubblob(char *filename, void **blob, int *bloblen) +{ + FILE *fp; + unsigned char buf[64]; + struct RSAKey key; + int ret; + + /* Default return if we fail. */ + *blob = NULL; + *bloblen = 0; + ret = 0; + + fp = fopen(filename, "rb"); + if (!fp) + return 0; /* doesn't even exist */ + + /* + * Read the first line of the file and see if it's a v1 private + * key file. + */ + if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) { + memset(&key, 0, sizeof(key)); + if (loadrsakey_main(fp, &key, TRUE, NULL, NULL)) { + *blob = rsa_public_blob(&key, bloblen); + freersakey(&key); + ret = 1; + } + } + fclose(fp); + return ret; +} + +/* * Save an RSA key file. Return nonzero on success. */ int saversakey(char *filename, struct RSAKey *key, char *passphrase) @@ -302,64 +345,83 @@ int saversakey(char *filename, struct RSAKey *key, char *passphrase) /* * PuTTY's own format for SSH2 keys is as follows: - * + * * The file is text. Lines are terminated by CRLF, although CR-only * and LF-only are tolerated on input. - * - * The first line says "PuTTY-User-Key-File-1: " plus the name of the - * algorithm ("ssh-dss", "ssh-rsa" etc. Although, of course, this - * being PuTTY, "ssh-dss" is not supported.) - * + * + * The first line says "PuTTY-User-Key-File-2: " plus the name of the + * algorithm ("ssh-dss", "ssh-rsa" etc). + * * The next line says "Encryption: " plus an encryption type. * Currently the only supported encryption types are "aes256-cbc" * and "none". - * + * * The next line says "Comment: " plus the comment string. - * + * * Next there is a line saying "Public-Lines: " plus a number N. * The following N lines contain a base64 encoding of the public * part of the key. This is encoded as the standard SSH2 public key * blob (with no initial length): so for RSA, for example, it will * read - * + * * string "ssh-rsa" * mpint exponent * mpint modulus - * + * * Next, there is a line saying "Private-Lines: " plus a number N, * and then N lines containing the (potentially encrypted) private * part of the key. For the key type "ssh-rsa", this will be * composed of - * + * * mpint private_exponent * mpint p (the larger of the two primes) * mpint q (the smaller prime) * mpint iqmp (the inverse of q modulo p) * data padding (to reach a multiple of the cipher block size) + * + * And for "ssh-dss", it will be composed of + * + * mpint x (the private key parameter) + * [ string hash 20-byte hash of mpints p || q || g only in old format ] + * + * Finally, there is a line saying "Private-MAC: " plus a hex + * representation of a HMAC-SHA-1 of: + * + * string name of algorithm ("ssh-dss", "ssh-rsa") + * string encryption type + * string comment + * string public-blob + * string private-plaintext (the plaintext version of the + * private part, including the final + * padding) * - * Finally, there is a line saying "Private-Hash: " plus a hex - * representation of a SHA-1 hash of the plaintext version of the - * private part, including the final padding. + * The key to the MAC is itself a SHA-1 hash of: * + * data "putty-private-key-file-mac-key" + * data passphrase + * + * Encrypted keys should have a MAC, whereas unencrypted ones must + * have a hash. + * * If the key is encrypted, the encryption key is derived from the * passphrase by means of a succession of SHA-1 hashes. Each hash * is the hash of: - * + * * uint32 sequence-number - * string passphrase - * + * data passphrase + * * where the sequence-number increases from zero. As many of these * hashes are used as necessary. - * - * NOTE! It is important that all _public_ data can be verified - * with reference to the _private_ data. There exist attacks based - * on modifying the public key but leaving the private section - * intact. - * - * With RSA, this is easy: verify that n = p*q, and also verify - * that e*d == 1 modulo (p-1)(q-1). With DSA (if we were ever to - * support it), we would need to store extra data in the private - * section other than just x. + * + * For backwards compatibility with snapshots between 0.51 and + * 0.52, we also support the older key file format, which begins + * with "PuTTY-User-Key-File-1" (version number differs). In this + * format the Private-MAC: field only covers the private-plaintext + * field and nothing else (and without the 4-byte string length on + * the front too). Moreover, for RSA keys the Private-MAC: field + * can be replaced with a Private-Hash: field which is a plain + * SHA-1 hash instead of an HMAC. This is not allowable in DSA + * keys. (Yes, the old format was a mess. Guess why it changed :-) */ static int read_header(FILE * fp, char *header) @@ -514,16 +576,17 @@ struct ssh2_userkey ssh2_wrong_passphrase = { struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) { FILE *fp; - char header[40], *b, *comment, *hash; + char header[40], *b, *encryption, *comment, *mac; const struct ssh_signkey *alg; struct ssh2_userkey *ret; int cipher, cipherblk; unsigned char *public_blob, *private_blob; int public_blob_len, private_blob_len; - int i; + int i, is_mac, old_fmt; + int passlen = passphrase ? strlen(passphrase) : 0; ret = NULL; /* return NULL for most errors */ - comment = hash = NULL; + comment = mac = NULL; public_blob = private_blob = NULL; fp = fopen(filename, "rb"); @@ -531,14 +594,23 @@ struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) goto error; /* Read the first header line which contains the key type. */ - if (!read_header(fp, header) - || 0 != strcmp(header, "PuTTY-User-Key-File-1")) + if (!read_header(fp, header)) + goto error; + if (0 == strcmp(header, "PuTTY-User-Key-File-2")) { + old_fmt = 0; + } else if (0 == strcmp(header, "PuTTY-User-Key-File-1")) { + /* this is an old key file; warn and then continue */ + old_keyfile_warning(); + old_fmt = 1; + } else goto error; if ((b = read_body(fp)) == NULL) goto error; - /* Select key algorithm structure. Currently only ssh-rsa. */ + /* Select key algorithm structure. */ if (!strcmp(b, "ssh-rsa")) alg = &ssh_rsa; + else if (!strcmp(b, "ssh-dss")) + alg = &ssh_dss; else { sfree(b); goto error; @@ -548,19 +620,18 @@ struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) /* Read the Encryption header line. */ if (!read_header(fp, header) || 0 != strcmp(header, "Encryption")) goto error; - if ((b = read_body(fp)) == NULL) + if ((encryption = read_body(fp)) == NULL) goto error; - if (!strcmp(b, "aes256-cbc")) { + if (!strcmp(encryption, "aes256-cbc")) { cipher = 1; cipherblk = 16; - } else if (!strcmp(b, "none")) { + } else if (!strcmp(encryption, "none")) { cipher = 0; cipherblk = 1; } else { - sfree(b); + sfree(encryption); goto error; } - sfree(b); /* Read the Comment header line. */ if (!read_header(fp, header) || 0 != strcmp(header, "Comment")) @@ -588,10 +659,19 @@ struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) if ((private_blob = read_blob(fp, i, &private_blob_len)) == NULL) goto error; - /* Read the Private-Hash header line. */ - if (!read_header(fp, header) || 0 != strcmp(header, "Private-Hash")) + /* Read the Private-MAC or Private-Hash header line. */ + if (!read_header(fp, header)) goto error; - if ((hash = read_body(fp)) == NULL) + if (0 == strcmp(header, "Private-MAC")) { + if ((mac = read_body(fp)) == NULL) + goto error; + is_mac = 1; + } else if (0 == strcmp(header, "Private-Hash") && + alg == &ssh_rsa && old_fmt) { + if ((mac = read_body(fp)) == NULL) + goto error; + is_mac = 0; + } else goto error; fclose(fp); @@ -603,15 +683,12 @@ struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) if (cipher) { unsigned char key[40]; SHA_State s; - int passlen; if (!passphrase) goto error; if (private_blob_len % cipherblk) goto error; - passlen = strlen(passphrase); - SHA_Init(&s); SHA_Bytes(&s, "\0\0\0\0", 4); SHA_Bytes(&s, passphrase, passlen); @@ -624,24 +701,77 @@ struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) } /* - * Verify the private hash. + * Verify the MAC. */ { - char realhash[41]; + char realmac[41]; unsigned char binary[20]; + unsigned char *macdata; + int maclen; + int free_macdata; + + if (old_fmt) { + /* MAC (or hash) only covers the private blob. */ + macdata = private_blob; + maclen = private_blob_len; + free_macdata = 0; + } else { + unsigned char *p; + int namelen = strlen(alg->name); + int enclen = strlen(encryption); + int commlen = strlen(comment); + maclen = (4 + namelen + + 4 + enclen + + 4 + commlen + + 4 + public_blob_len + + 4 + private_blob_len); + macdata = smalloc(maclen); + p = macdata; +#define DO_STR(s,len) PUT_32BIT(p,(len));memcpy(p+4,(s),(len));p+=4+(len) + DO_STR(alg->name, namelen); + DO_STR(encryption, enclen); + DO_STR(comment, commlen); + DO_STR(public_blob, public_blob_len); + DO_STR(private_blob, private_blob_len); + + free_macdata = 1; + } + + if (is_mac) { + SHA_State s; + unsigned char mackey[20]; + char header[] = "putty-private-key-file-mac-key"; + + SHA_Init(&s); + SHA_Bytes(&s, header, sizeof(header)-1); + if (passphrase) + SHA_Bytes(&s, passphrase, passlen); + SHA_Final(&s, mackey); + + hmac_sha1_simple(mackey, 20, macdata, maclen, binary); + + memset(mackey, 0, sizeof(mackey)); + memset(&s, 0, sizeof(s)); + } else { + SHA_Simple(macdata, maclen, binary); + } + + if (free_macdata) { + memset(macdata, 0, maclen); + sfree(macdata); + } - SHA_Simple(private_blob, private_blob_len, binary); for (i = 0; i < 20; i++) - sprintf(realhash + 2 * i, "%02x", binary[i]); + sprintf(realmac + 2 * i, "%02x", binary[i]); - if (strcmp(hash, realhash)) { - /* An incorrect hash is an unconditional Error if the key is + if (strcmp(mac, realmac)) { + /* An incorrect MAC is an unconditional Error if the key is * unencrypted. Otherwise, it means Wrong Passphrase. */ ret = cipher ? SSH2_WRONG_PASSPHRASE : NULL; goto error; } } - sfree(hash); + sfree(mac); /* * Create and return the key. @@ -658,6 +788,7 @@ struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) } sfree(public_blob); sfree(private_blob); + sfree(encryption); return ret; /* @@ -668,8 +799,10 @@ struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) fclose(fp); if (comment) sfree(comment); - if (hash) - sfree(hash); + if (encryption) + sfree(encryption); + if (mac) + sfree(mac); if (public_blob) sfree(public_blob); if (private_blob) @@ -695,13 +828,16 @@ char *ssh2_userkey_loadpub(char *filename, char **algorithm, /* Read the first header line which contains the key type. */ if (!read_header(fp, header) - || 0 != strcmp(header, "PuTTY-User-Key-File-1")) + || (0 != strcmp(header, "PuTTY-User-Key-File-2") && + 0 != strcmp(header, "PuTTY-User-Key-File-1"))) goto error; if ((b = read_body(fp)) == NULL) goto error; /* Select key algorithm structure. Currently only ssh-rsa. */ if (!strcmp(b, "ssh-rsa")) alg = &ssh_rsa; + else if (!strcmp(b, "ssh-dss")) + alg = &ssh_dss; else { sfree(b); goto error; @@ -733,8 +869,10 @@ char *ssh2_userkey_loadpub(char *filename, char **algorithm, goto error; fclose(fp); - *pub_blob_len = public_blob_len; - *algorithm = alg->name; + if (pub_blob_len) + *pub_blob_len = public_blob_len; + if (algorithm) + *algorithm = alg->name; return public_blob; /* @@ -761,7 +899,8 @@ int ssh2_userkey_encrypted(char *filename, char **commentptr) if (!fp) return 0; if (!read_header(fp, header) - || 0 != strcmp(header, "PuTTY-User-Key-File-1")) { + || (0 != strcmp(header, "PuTTY-User-Key-File-2") && + 0 != strcmp(header, "PuTTY-User-Key-File-1"))) { fclose(fp); return 0; } @@ -865,7 +1004,7 @@ int ssh2_save_userkey(char *filename, struct ssh2_userkey *key, int cipherblk; int i; char *cipherstr; - unsigned char priv_hash[20]; + unsigned char priv_mac[20]; /* * Fetch the key component blobs. @@ -895,13 +1034,48 @@ int ssh2_save_userkey(char *filename, struct ssh2_userkey *key, memcpy(priv_blob_encrypted, priv_blob, priv_blob_len); /* Create padding based on the SHA hash of the unpadded blob. This prevents * too easy a known-plaintext attack on the last block. */ - SHA_Simple(priv_blob, priv_blob_len, priv_hash); + SHA_Simple(priv_blob, priv_blob_len, priv_mac); assert(priv_encrypted_len - priv_blob_len < 20); - memcpy(priv_blob_encrypted + priv_blob_len, priv_hash, + memcpy(priv_blob_encrypted + priv_blob_len, priv_mac, priv_encrypted_len - priv_blob_len); - /* Now create the _real_ private hash. */ - SHA_Simple(priv_blob_encrypted, priv_encrypted_len, priv_hash); + /* Now create the MAC. */ + { + unsigned char *macdata; + int maclen; + unsigned char *p; + int namelen = strlen(key->alg->name); + int enclen = strlen(cipherstr); + int commlen = strlen(key->comment); + SHA_State s; + unsigned char mackey[20]; + char header[] = "putty-private-key-file-mac-key"; + + maclen = (4 + namelen + + 4 + enclen + + 4 + commlen + + 4 + pub_blob_len + + 4 + priv_encrypted_len); + macdata = smalloc(maclen); + p = macdata; +#define DO_STR(s,len) PUT_32BIT(p,(len));memcpy(p+4,(s),(len));p+=4+(len) + DO_STR(key->alg->name, namelen); + DO_STR(cipherstr, enclen); + DO_STR(key->comment, commlen); + DO_STR(pub_blob, pub_blob_len); + DO_STR(priv_blob_encrypted, priv_encrypted_len); + + SHA_Init(&s); + SHA_Bytes(&s, header, sizeof(header)-1); + if (passphrase) + SHA_Bytes(&s, passphrase, strlen(passphrase)); + SHA_Final(&s, mackey); + hmac_sha1_simple(mackey, 20, macdata, maclen, priv_mac); + memset(macdata, 0, maclen); + sfree(macdata); + memset(mackey, 0, sizeof(mackey)); + memset(&s, 0, sizeof(s)); + } if (passphrase) { char key[40]; @@ -919,43 +1093,80 @@ int ssh2_save_userkey(char *filename, struct ssh2_userkey *key, SHA_Final(&s, key + 20); aes256_encrypt_pubkey(key, priv_blob_encrypted, priv_encrypted_len); + + memset(key, 0, sizeof(key)); + memset(&s, 0, sizeof(s)); } fp = fopen(filename, "w"); if (!fp) return 0; - fprintf(fp, "PuTTY-User-Key-File-1: %s\n", key->alg->name); + fprintf(fp, "PuTTY-User-Key-File-2: %s\n", key->alg->name); fprintf(fp, "Encryption: %s\n", cipherstr); fprintf(fp, "Comment: %s\n", key->comment); fprintf(fp, "Public-Lines: %d\n", base64_lines(pub_blob_len)); base64_encode(fp, pub_blob, pub_blob_len); fprintf(fp, "Private-Lines: %d\n", base64_lines(priv_encrypted_len)); base64_encode(fp, priv_blob_encrypted, priv_encrypted_len); - fprintf(fp, "Private-Hash: "); + fprintf(fp, "Private-MAC: "); for (i = 0; i < 20; i++) - fprintf(fp, "%02x", priv_hash[i]); + fprintf(fp, "%02x", priv_mac[i]); fprintf(fp, "\n"); fclose(fp); + + sfree(pub_blob); + memset(priv_blob, 0, priv_blob_len); + sfree(priv_blob); + sfree(priv_blob_encrypted); return 1; } /* ---------------------------------------------------------------------- - * A function to determine which version of SSH to try on a private - * key file. Returns 0 on failure, 1 or 2 on success. + * A function to determine the type of a private key file. Returns + * 0 on failure, 1 or 2 on success. */ -int keyfile_version(char *filename) +int key_type(char *filename) { FILE *fp; + char buf[32]; + const char putty2_sig[] = "PuTTY-User-Key-File-"; + const char sshcom_sig[] = "---- BEGIN SSH2 ENCRYPTED PRIVAT"; + const char openssh_sig[] = "-----BEGIN "; int i; fp = fopen(filename, "r"); if (!fp) - return 0; - i = fgetc(fp); + return SSH_KEYTYPE_UNOPENABLE; + i = fread(buf, 1, sizeof(buf), fp); fclose(fp); - if (i == 'S') - return 1; /* "SSH PRIVATE KEY FORMAT" etc */ - if (i == 'P') /* "PuTTY-User-Key-File" etc */ - return 2; - return 0; /* unrecognised or EOF */ + if (i < 0) + return SSH_KEYTYPE_UNOPENABLE; + if (i < 32) + return SSH_KEYTYPE_UNKNOWN; + if (!memcmp(buf, rsa_signature, sizeof(rsa_signature)-1)) + return SSH_KEYTYPE_SSH1; + if (!memcmp(buf, putty2_sig, sizeof(putty2_sig)-1)) + return SSH_KEYTYPE_SSH2; + if (!memcmp(buf, openssh_sig, sizeof(openssh_sig)-1)) + return SSH_KEYTYPE_OPENSSH; + if (!memcmp(buf, sshcom_sig, sizeof(sshcom_sig)-1)) + return SSH_KEYTYPE_SSHCOM; + return SSH_KEYTYPE_UNKNOWN; /* unrecognised or EOF */ +} + +/* + * Convert the type word to a string, for `wrong type' error + * messages. + */ +char *key_type_to_str(int type) +{ + switch (type) { + case SSH_KEYTYPE_UNOPENABLE: return "unable to open file"; break; + case SSH_KEYTYPE_UNKNOWN: return "not a private key"; break; + case SSH_KEYTYPE_SSH1: return "SSH1 private key"; break; + case SSH_KEYTYPE_SSH2: return "PuTTY SSH2 private key"; break; + case SSH_KEYTYPE_OPENSSH: return "OpenSSH SSH2 private key"; break; + case SSH_KEYTYPE_SSHCOM: return "ssh.com SSH2 private key"; break; + default: return "INTERNAL ERROR"; break; + } }