X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/98ba26b92452911f8f6b9cfccd134a4836218904..65a22376e5875181e41108028091018cdcd4fdae:/sshpubk.c diff --git a/sshpubk.c b/sshpubk.c index 377be3a0..ce237b9d 100644 --- a/sshpubk.c +++ b/sshpubk.c @@ -7,6 +7,7 @@ #include #include +#include #include "ssh.h" @@ -30,7 +31,7 @@ (x)=='+' ? 62 : \ (x)=='/' ? 63 : 0 ) -static int loadrsakey_main(FILE *fp, struct RSAKey *key, struct RSAAux *aux, +static int loadrsakey_main(FILE *fp, struct RSAKey *key, char **commentptr, char *passphrase) { unsigned char buf[16384]; unsigned char keybuf[16]; @@ -117,14 +118,12 @@ static int loadrsakey_main(FILE *fp, struct RSAKey *key, struct RSAAux *aux, */ i += makeprivate(buf+i, key); if (len-i < 0) goto end; - if (aux) { - i += ssh1_read_bignum(buf+i, &aux->iqmp); - if (len-i < 0) goto end; - i += ssh1_read_bignum(buf+i, &aux->q); - if (len-i < 0) goto end; - i += ssh1_read_bignum(buf+i, &aux->p); - if (len-i < 0) goto end; - } + i += ssh1_read_bignum(buf+i, &key->iqmp); + if (len-i < 0) goto end; + i += ssh1_read_bignum(buf+i, &key->q); + if (len-i < 0) goto end; + i += ssh1_read_bignum(buf+i, &key->p); + if (len-i < 0) goto end; ret = 1; end: @@ -132,8 +131,7 @@ static int loadrsakey_main(FILE *fp, struct RSAKey *key, struct RSAAux *aux, return ret; } -int loadrsakey(char *filename, struct RSAKey *key, struct RSAAux *aux, - char *passphrase) { +int loadrsakey(char *filename, struct RSAKey *key, char *passphrase) { FILE *fp; unsigned char buf[64]; @@ -147,7 +145,7 @@ int loadrsakey(char *filename, struct RSAKey *key, struct RSAAux *aux, */ if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) { - return loadrsakey_main(fp, key, aux, NULL, passphrase); + return loadrsakey_main(fp, key, NULL, passphrase); } /* @@ -175,7 +173,7 @@ int rsakey_encrypted(char *filename, char **comment) { */ if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) { - return loadrsakey_main(fp, NULL, NULL, comment, NULL); + return loadrsakey_main(fp, NULL, comment, NULL); } fclose(fp); return 0; /* wasn't the right kind of file */ @@ -184,8 +182,7 @@ int rsakey_encrypted(char *filename, char **comment) { /* * Save an RSA key file. Return nonzero on success. */ -int saversakey(char *filename, struct RSAKey *key, struct RSAAux *aux, - char *passphrase) { +int saversakey(char *filename, struct RSAKey *key, char *passphrase) { unsigned char buf[16384]; unsigned char keybuf[16]; struct MD5Context md5c; @@ -243,9 +240,9 @@ int saversakey(char *filename, struct RSAKey *key, struct RSAAux *aux, * q, then p. */ p += ssh1_write_bignum(p, key->private_exponent); - p += ssh1_write_bignum(p, aux->iqmp); - p += ssh1_write_bignum(p, aux->q); - p += ssh1_write_bignum(p, aux->p); + p += ssh1_write_bignum(p, key->iqmp); + p += ssh1_write_bignum(p, key->q); + p += ssh1_write_bignum(p, key->p); /* * Now write zeros until the encrypted portion is a multiple of @@ -276,3 +273,619 @@ int saversakey(char *filename, struct RSAKey *key, struct RSAAux *aux, } else return 0; } + +/* ---------------------------------------------------------------------- + * SSH2 private key load/store functions. + */ + +/* + * 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 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) + * + * 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. + * + * 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 + * + * where the sequence-number increases from zero. As many of these + * hashes are used as necessary. + */ + +static int read_header(FILE *fp, char *header) { + int len = 39; + int c; + + while (len > 0) { + c = fgetc(fp); + if (c == '\n' || c == '\r' || c == EOF) + return 0; /* failure */ + if (c == ':') { + c = fgetc(fp); + if (c != ' ') + return 0; + *header = '\0'; + return 1; /* success! */ + } + if (len == 0) + return 0; /* failure */ + *header++ = c; + len--; + } + return 0; /* failure */ +} + +static char *read_body(FILE *fp) { + char *text; + int len; + int size; + int c; + + size = 128; + text = smalloc(size); + len = 0; + text[len] = '\0'; + + while (1) { + c = fgetc(fp); + if (c == '\r' || c == '\n') { + c = fgetc(fp); + if (c != '\r' && c != '\n' && c != EOF) + ungetc(c, fp); + return text; + } + if (c == EOF) { + sfree(text); + return NULL; + } + if (len + 1 > size) { + size += 128; + text = srealloc(text, size); + } + text[len++] = c; + text[len] = '\0'; + } +} + +int base64_decode_atom(char *atom, unsigned char *out) { + int vals[4]; + int i, v, len; + unsigned word; + char c; + + for (i = 0; i < 4; i++) { + c = atom[i]; + if (c >= 'A' && c <= 'Z') + v = c - 'A'; + else if (c >= 'a' && c <= 'z') + v = c - 'a' + 26; + else if (c >= '0' && c <= '9') + v = c - '0' + 52; + else if (c == '+') + v = 62; + else if (c == '/') + v = 63; + else if (c == '=') + v = -1; + else + return 0; /* invalid atom */ + vals[i] = v; + } + + if (vals[0] == -1 || vals[1] == -1) + return 0; + if (vals[2] == -1 && vals[3] != -1) + return 0; + + if (vals[3] != -1) + len = 3; + else if (vals[2] != -1) + len = 2; + else + len = 1; + + word = ((vals[0] << 18) | + (vals[1] << 12) | + ((vals[2] & 0x3F) << 6) | + (vals[3] & 0x3F)); + out[0] = (word >> 16) & 0xFF; + if (len > 1) + out[1] = (word >> 8) & 0xFF; + if (len > 2) + out[2] = word & 0xFF; + return len; +} + +static char *read_blob(FILE *fp, int nlines, int *bloblen) { + unsigned char *blob; + char *line; + int linelen, len; + int i, j, k; + + /* We expect at most 64 base64 characters, ie 48 real bytes, per line. */ + blob = smalloc(48 * nlines); + len = 0; + for (i = 0; i < nlines; i++) { + line = read_body(fp); + if (!line) { + sfree(blob); + return NULL; + } + linelen = strlen(line); + if (linelen % 4 != 0 || linelen > 64) { + sfree(blob); + sfree(line); + return NULL; + } + for (j = 0; j < linelen; j += 4) { + k = base64_decode_atom(line+j, blob+len); + if (!k) { + sfree(line); + sfree(blob); + return NULL; + } + len += k; + } + sfree(line); + } + *bloblen = len; + return blob; +} + +/* + * Magic error return value for when the passphrase is wrong. + */ +struct ssh2_userkey ssh2_wrong_passphrase = { + NULL, NULL, NULL +}; + +struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) { + FILE *fp; + char header[40], *b, *comment, *hash; + 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; + + ret = NULL; /* return NULL for most errors */ + comment = hash = NULL; + public_blob = private_blob = NULL; + + fp = fopen(filename, "rb"); + if (!fp) + 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")) + 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 { + sfree(b); + goto error; + } + sfree(b); + + /* Read the Encryption header line. */ + if (!read_header(fp, header) || 0!=strcmp(header, "Encryption")) + goto error; + if ((b = read_body(fp)) == NULL) + goto error; + if (!strcmp(b, "aes256-cbc")) { + cipher = 1; cipherblk = 16; + } else if (!strcmp(b, "none")) { + cipher = 0; cipherblk = 1; + } else { + sfree(b); + goto error; + } + sfree(b); + + /* Read the Comment header line. */ + if (!read_header(fp, header) || 0!=strcmp(header, "Comment")) + goto error; + if ((comment = read_body(fp)) == NULL) + goto error; + + /* Read the Public-Lines header line and the public blob. */ + if (!read_header(fp, header) || 0!=strcmp(header, "Public-Lines")) + goto error; + if ((b = read_body(fp)) == NULL) + goto error; + i = atoi(b); + sfree(b); + if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL) + goto error; + + /* Read the Private-Lines header line and the Private blob. */ + if (!read_header(fp, header) || 0!=strcmp(header, "Private-Lines")) + goto error; + if ((b = read_body(fp)) == NULL) + goto error; + i = atoi(b); + sfree(b); + 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")) + goto error; + if ((hash = read_body(fp)) == NULL) + goto error; + + fclose(fp); + fp = NULL; + + /* + * Decrypt the private blob. + */ + 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); + SHA_Final(&s, key+0); + SHA_Init(&s); + SHA_Bytes(&s, "\0\0\0\1", 4); + SHA_Bytes(&s, passphrase, passlen); + SHA_Final(&s, key+20); + aes256_decrypt_pubkey(key, private_blob, private_blob_len); + } + + /* + * Verify the private hash. + */ + { + char realhash[41]; + unsigned char binary[20]; + SHA_State s; + + SHA_Simple(private_blob, private_blob_len, binary); + for (i = 0; i < 20; i++) + sprintf(realhash+2*i, "%02x", binary[i]); + + if (strcmp(hash, realhash)) { + /* An incorrect hash is an unconditional Error if the key is + * unencrypted. Otherwise, it means Wrong Passphrase. */ + ret = cipher ? SSH2_WRONG_PASSPHRASE : NULL; + goto error; + } + } + sfree(hash); + + /* + * Create and return the key. + */ + ret = smalloc(sizeof(struct ssh2_userkey)); + ret->alg = alg; + ret->comment = comment; + ret->data = alg->createkey(public_blob, public_blob_len, + private_blob, private_blob_len); + sfree(public_blob); + sfree(private_blob); + return ret; + + /* + * Error processing. + */ + error: + if (fp) fclose(fp); + if (comment) sfree(comment); + if (hash) sfree(hash); + if (public_blob) sfree(public_blob); + if (private_blob) sfree(private_blob); + return ret; +} + +char *ssh2_userkey_loadpub(char *filename, char **algorithm, int *pub_blob_len) { + FILE *fp; + char header[40], *b; + const struct ssh_signkey *alg; + int cipher, cipherblk; + unsigned char *public_blob; + int public_blob_len; + int i; + + public_blob = NULL; + + fp = fopen(filename, "rb"); + if (!fp) + 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")) + 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 { + sfree(b); + goto error; + } + sfree(b); + + /* Read the Encryption header line. */ + if (!read_header(fp, header) || 0!=strcmp(header, "Encryption")) + goto error; + if ((b = read_body(fp)) == NULL) + goto error; + sfree(b); /* we don't care */ + + /* Read the Comment header line. */ + if (!read_header(fp, header) || 0!=strcmp(header, "Comment")) + goto error; + if ((b = read_body(fp)) == NULL) + goto error; + sfree(b); /* we don't care */ + + /* Read the Public-Lines header line and the public blob. */ + if (!read_header(fp, header) || 0!=strcmp(header, "Public-Lines")) + goto error; + if ((b = read_body(fp)) == NULL) + goto error; + i = atoi(b); + sfree(b); + if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL) + goto error; + + fclose(fp); + *pub_blob_len = public_blob_len; + *algorithm = alg->name; + return public_blob; + + /* + * Error processing. + */ + error: + if (fp) fclose(fp); + if (public_blob) sfree(public_blob); + return NULL; +} + +int ssh2_userkey_encrypted(char *filename, char **commentptr) { + FILE *fp; + char header[40], *b, *comment; + int ret; + + if (commentptr) *commentptr = NULL; + + fp = fopen(filename, "rb"); + if (!fp) + return 0; + if (!read_header(fp, header) || 0!=strcmp(header, "PuTTY-User-Key-File-1")) { + fclose(fp); return 0; + } + if ((b = read_body(fp)) == NULL) { + fclose(fp); return 0; + } + sfree(b); /* we don't care about key type here */ + /* Read the Encryption header line. */ + if (!read_header(fp, header) || 0!=strcmp(header, "Encryption")) { + fclose(fp); return 0; + } + if ((b = read_body(fp)) == NULL) { + fclose(fp); return 0; + } + + /* Read the Comment header line. */ + if (!read_header(fp, header) || 0!=strcmp(header, "Comment")) { + fclose(fp); sfree(b); return 1; + } + if ((comment = read_body(fp)) == NULL) { + fclose(fp); sfree(b); return 1; + } + + if (commentptr) *commentptr = comment; + + fclose(fp); + if (!strcmp(b, "aes256-cbc")) + ret = 1; + else + ret = 0; + sfree(b); + return ret; +} + +int base64_lines(int datalen) { + /* When encoding, we use 64 chars/line, which equals 48 real chars. */ + return (datalen+47) / 48; +} + +void base64_encode_atom(unsigned char *data, int n, char *out) { + static const char base64_chars[] = + "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; + + unsigned word; + + word = data[0] << 16; + if (n > 1) + word |= data[1] << 8; + if (n > 2) + word |= data[2]; + out[0] = base64_chars[(word >> 18) & 0x3F]; + out[1] = base64_chars[(word >> 12) & 0x3F]; + if (n > 1) + out[2] = base64_chars[(word >> 6) & 0x3F]; + else + out[2] = '='; + if (n > 2) + out[3] = base64_chars[word & 0x3F]; + else + out[3] = '='; +} + +void base64_encode(FILE *fp, unsigned char *data, int datalen) { + int linelen = 0; + char out[4]; + int n; + + while (datalen > 0) { + if (linelen >= 64) { + linelen = 0; + fputc('\n', fp); + } + n = (datalen < 3 ? datalen : 3); + base64_encode_atom(data, n, out); + data += n; + datalen -= n; + fwrite(out, 1, 4, fp); + linelen += 4; + } + fputc('\n', fp); +} + +int ssh2_save_userkey(char *filename, struct ssh2_userkey *key, char *passphrase) { + FILE *fp; + unsigned char *pub_blob, *priv_blob, *priv_blob_encrypted; + int pub_blob_len, priv_blob_len, priv_encrypted_len; + int passlen; + int cipherblk; + int i; + char *cipherstr; + unsigned char priv_hash[20]; + + /* + * Fetch the key component blobs. + */ + pub_blob = key->alg->public_blob(key->data, &pub_blob_len); + priv_blob = key->alg->private_blob(key->data, &priv_blob_len); + if (!pub_blob || !priv_blob) { + sfree(pub_blob); + sfree(priv_blob); + return 0; + } + + /* + * Determine encryption details, and encrypt the private blob. + */ + if (passphrase) { + cipherstr = "aes256-cbc"; + cipherblk = 16; + } else { + cipherstr = "none"; + cipherblk = 1; + } + priv_encrypted_len = priv_blob_len + cipherblk - 1; + priv_encrypted_len -= priv_encrypted_len % cipherblk; + priv_blob_encrypted = smalloc(priv_encrypted_len); + memset(priv_blob_encrypted, 0, priv_encrypted_len); + 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); + assert(priv_encrypted_len - priv_blob_len < 20); + memcpy(priv_blob_encrypted + priv_blob_len, priv_hash, + priv_encrypted_len - priv_blob_len); + + /* Now create the _real_ private hash. */ + SHA_Simple(priv_blob_encrypted, priv_encrypted_len, priv_hash); + + if (passphrase) { + char key[40]; + SHA_State s; + + passlen = strlen(passphrase); + + SHA_Init(&s); + SHA_Bytes(&s, "\0\0\0\0", 4); + SHA_Bytes(&s, passphrase, passlen); + SHA_Final(&s, key+0); + SHA_Init(&s); + SHA_Bytes(&s, "\0\0\0\1", 4); + SHA_Bytes(&s, passphrase, passlen); + SHA_Final(&s, key+20); + aes256_encrypt_pubkey(key, priv_blob_encrypted, priv_encrypted_len); + } + + fp = fopen(filename, "w"); + if (!fp) + return 0; + fprintf(fp, "PuTTY-User-Key-File-1: %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: "); + for (i = 0; i < 20; i++) + fprintf(fp, "%02x", priv_hash[i]); + fprintf(fp, "\n"); + fclose(fp); + 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. + */ +int keyfile_version(char *filename) { + FILE *fp; + int i; + + fp = fopen(filename, "r"); + if (!fp) + return 0; + i = fgetc(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 */ +}