- djm@cvs.openbsd.org 2010/11/21 10:57:07

     [authfile.c]
     Refactor internals of private key loading and saving to work on memory
     buffers rather than directly on files. This will make a few things
     easier to do in the future; ok markus@

1 files changed, 254 insertions, 193 deletions

diff --git a/authfile.c b/authfile.c
index 7f98ab547..f75c273fc 100644
--- a/authfile.c
+++ b/authfile.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: authfile.c,v 1.85 2010/10/28 11:22:09 djm Exp $ */
+/* $OpenBSD: authfile.c,v 1.86 2010/11/21 10:57:07 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -74,19 +74,18 @@ static const char authfile_id_string[] =
     "SSH PRIVATE KEY FILE FORMAT 1.1\n";
 
 /*
- * Saves the authentication (private) key in a file, encrypting it with
- * passphrase.  The identification of the file (lowest 64 bits of n) will
+ * Serialises the authentication (private) key to a blob, encrypting it with
+ * passphrase.  The identification of the blob (lowest 64 bits of n) will
  * precede the key to provide identification of the key without needing a
  * passphrase.
  */
-
 static int
-key_save_private_rsa1(Key *key, const char *filename, const char *passphrase,
+key_private_rsa1_to_blob(Key *key, Buffer *blob, const char *passphrase,
     const char *comment)
 {
         Buffer buffer, encrypted;
         u_char buf[100], *cp;
-        int fd, i, cipher_num;
+        int i, cipher_num;
         CipherContext ciphercontext;
         Cipher *cipher;
         u_int32_t rnd;
@@ -157,163 +156,222 @@ key_save_private_rsa1(Key *key, const char *filename, const char *passphrase,
         memset(buf, 0, sizeof(buf));
         buffer_free(&buffer);
 
-        fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
-        if (fd < 0) {
-                error("open %s failed: %s.", filename, strerror(errno));
-                buffer_free(&encrypted);
-                return 0;
-        }
-        if (atomicio(vwrite, fd, buffer_ptr(&encrypted),
-            buffer_len(&encrypted)) != buffer_len(&encrypted)) {
-                error("write to key file %s failed: %s", filename,
-                    strerror(errno));
-                buffer_free(&encrypted);
-                close(fd);
-                unlink(filename);
-                return 0;
-        }
-        close(fd);
+        buffer_append(blob, buffer_ptr(&encrypted), buffer_len(&encrypted));
         buffer_free(&encrypted);
+
         return 1;
 }
 
-/* save SSH v2 key in OpenSSL PEM format */
+/* convert SSH v2 key in OpenSSL PEM format */
 static int
-key_save_private_pem(Key *key, const char *filename, const char *_passphrase,
+key_private_pem_to_blob(Key *key, Buffer *blob, const char *_passphrase,
     const char *comment)
 {
-        FILE *fp;
-        int fd;
         int success = 0;
-        int len = strlen(_passphrase);
+        int blen, len = strlen(_passphrase);
         u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL;
 #if (OPENSSL_VERSION_NUMBER < 0x00907000L)
         const EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL;
 #else
         const EVP_CIPHER *cipher = (len > 0) ? EVP_aes_128_cbc() : NULL;
 #endif
+        const u_char *bptr;
+        BIO *bio;
 
         if (len > 0 && len <= 4) {
                 error("passphrase too short: have %d bytes, need > 4", len);
                 return 0;
         }
-        fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
-        if (fd < 0) {
-                error("open %s failed: %s.", filename, strerror(errno));
-                return 0;
-        }
-        fp = fdopen(fd, "w");
-        if (fp == NULL) {
-                error("fdopen %s failed: %s.", filename, strerror(errno));
-                close(fd);
+        if ((bio = BIO_new(BIO_s_mem())) == NULL) {
+                error("%s: BIO_new failed", __func__);
                 return 0;
         }
         switch (key->type) {
         case KEY_DSA:
-                success = PEM_write_DSAPrivateKey(fp, key->dsa,
+                success = PEM_write_bio_DSAPrivateKey(bio, key->dsa,
                     cipher, passphrase, len, NULL, NULL);
                 break;
 #ifdef OPENSSL_HAS_ECC
         case KEY_ECDSA:
-                success = PEM_write_ECPrivateKey(fp, key->ecdsa,
+                success = PEM_write_bio_ECPrivateKey(bio, key->ecdsa,
                     cipher, passphrase, len, NULL, NULL);
                 break;
 #endif
         case KEY_RSA:
-                success = PEM_write_RSAPrivateKey(fp, key->rsa,
+                success = PEM_write_bio_RSAPrivateKey(bio, key->rsa,
                     cipher, passphrase, len, NULL, NULL);
                 break;
         }
-        fclose(fp);
+        if (success) {
+                if ((blen = BIO_get_mem_data(bio, &bptr)) <= 0)
+                        success = 0;
+                else
+                        buffer_append(blob, bptr, blen);
+        }
+        BIO_free(bio);
         return success;
 }
 
-int
-key_save_private(Key *key, const char *filename, const char *passphrase,
+/* Save a key blob to a file */
+static int
+key_save_private_blob(Buffer *keybuf, const char *filename)
+{
+        int fd;
+
+        if ((fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600)) < 0) {
+                error("open %s failed: %s.", filename, strerror(errno));
+                return 0;
+        }
+        if (atomicio(vwrite, fd, buffer_ptr(keybuf),
+            buffer_len(keybuf)) != buffer_len(keybuf)) {
+                error("write to key file %s failed: %s", filename,
+                    strerror(errno));
+                close(fd);
+                unlink(filename);
+                return 0;
+        }
+        close(fd);
+        return 1;
+}
+
+/* Serialise "key" to buffer "blob" */
+static int
+key_private_to_blob(Key *key, Buffer *blob, const char *passphrase,
     const char *comment)
 {
         switch (key->type) {
         case KEY_RSA1:
-                return key_save_private_rsa1(key, filename, passphrase,
-                    comment);
+                return key_private_rsa1_to_blob(key, blob, passphrase, comment);
         case KEY_DSA:
         case KEY_ECDSA:
         case KEY_RSA:
-                return key_save_private_pem(key, filename, passphrase,
-                    comment);
+                return key_private_pem_to_blob(key, blob, passphrase, comment);
         default:
-                break;
+                error("%s: cannot save key type %d", __func__, key->type);
+                return 0;
         }
-        error("key_save_private: cannot save key type %d", key->type);
-        return 0;
+}
+
+int
+key_save_private(Key *key, const char *filename, const char *passphrase,
+    const char *comment)
+{
+        Buffer keyblob;
+        int success = 0;
+
+        buffer_init(&keyblob);
+        if (!key_private_to_blob(key, &keyblob, passphrase, comment))
+                goto out;
+        if (!key_save_private_blob(&keyblob, filename))
+                goto out;
+        success = 1;
+ out:
+        buffer_free(&keyblob);
+        return success;
 }
 
 /*
- * Loads the public part of the ssh v1 key file.  Returns NULL if an error was
- * encountered (the file does not exist or is not readable), and the key
- * otherwise.
+ * Parse the public, unencrypted portion of a RSA1 key.
  */
-
 static Key *
-key_load_public_rsa1(int fd, const char *filename, char **commentp)
+key_parse_public_rsa1(Buffer *blob, char **commentp)
 {
-        Buffer buffer;
         Key *pub;
-        struct stat st;
-        char *cp;
-        u_int i;
+
+        /* Check that it is at least big enough to contain the ID string. */
+        if (buffer_len(blob) < sizeof(authfile_id_string)) {
+                debug3("Truncated RSA1 identifier");
+                return NULL;
+        }
+
+        /*
+         * Make sure it begins with the id string.  Consume the id string
+         * from the buffer.
+         */
+        if (memcmp(buffer_ptr(blob), authfile_id_string,
+            sizeof(authfile_id_string)) != 0) {
+                debug3("Incorrect RSA1 identifier");
+                return NULL;
+        }
+        buffer_consume(blob, sizeof(authfile_id_string));
+
+        /* Skip cipher type and reserved data. */
+        (void) buffer_get_char(blob);   /* cipher type */
+        (void) buffer_get_int(blob);            /* reserved */
+
+        /* Read the public key from the buffer. */
+        (void) buffer_get_int(blob);
+        pub = key_new(KEY_RSA1);
+        buffer_get_bignum(blob, pub->rsa->n);
+        buffer_get_bignum(blob, pub->rsa->e);
+        if (commentp)
+                *commentp = buffer_get_string(blob, NULL);
+        /* The encrypted private part is not parsed by this function. */
+        buffer_clear(blob);
+
+        return pub;
+}
+
+/* Load the contents of a key file into a buffer */
+static int
+key_load_file(int fd, const char *filename, Buffer *blob)
+{
         size_t len;
+        u_char *cp;
+        struct stat st;
 
         if (fstat(fd, &st) < 0) {
-                error("fstat for key file %.200s failed: %.100s",
-                    filename, strerror(errno));
-                return NULL;
+                error("%s: fstat of key file %.200s%sfailed: %.100s", __func__,
+                    filename == NULL ? "" : filename,
+                    filename == NULL ? "" : " ",
+                    strerror(errno));
+                close(fd);
+                return 0;
         }
         if (st.st_size > 1*1024*1024) {
-                error("key file %.200s too large", filename);
-                return NULL;
+                error("%s: key file %.200s%stoo large", __func__,
+                    filename == NULL ? "" : filename,
+                    filename == NULL ? "" : " ");
+                close(fd);
+                return 0;
         }
         len = (size_t)st.st_size;               /* truncated */
 
-        buffer_init(&buffer);
-        cp = buffer_append_space(&buffer, len);
+        buffer_init(blob);
+        cp = buffer_append_space(blob, len);
 
         if (atomicio(read, fd, cp, len) != len) {
-                debug("Read from key file %.200s failed: %.100s", filename,
+                debug("%s: read from key file %.200s%sfailed: %.100s", __func__,
+                    filename == NULL ? "" : filename,
+                    filename == NULL ? "" : " ",
                     strerror(errno));
-                buffer_free(&buffer);
-                return NULL;
+                buffer_clear(blob);
+                close(fd);
+                return 0;
         }
+        return 1;
+}
 
-        /* Check that it is at least big enough to contain the ID string. */
-        if (len < sizeof(authfile_id_string)) {
-                debug3("Not a RSA1 key file %.200s.", filename);
+/*
+ * Loads the public part of the ssh v1 key file.  Returns NULL if an error was
+ * encountered (the file does not exist or is not readable), and the key
+ * otherwise.
+ */
+static Key *
+key_load_public_rsa1(int fd, const char *filename, char **commentp)
+{
+        Buffer buffer;
+        Key *pub;
+
+        buffer_init(&buffer);
+        if (!key_load_file(fd, filename, &buffer)) {
                 buffer_free(&buffer);
                 return NULL;
         }
-        /*
-         * Make sure it begins with the id string.  Consume the id string
-         * from the buffer.
-         */
-        for (i = 0; i < sizeof(authfile_id_string); i++)
-                if (buffer_get_char(&buffer) != authfile_id_string[i]) {
-                        debug3("Not a RSA1 key file %.200s.", filename);
-                        buffer_free(&buffer);
-                        return NULL;
-                }
-        /* Skip cipher type and reserved data. */
-        (void) buffer_get_char(&buffer);        /* cipher type */
-        (void) buffer_get_int(&buffer);         /* reserved */
-
-        /* Read the public key from the buffer. */
-        (void) buffer_get_int(&buffer);
-        pub = key_new(KEY_RSA1);
-        buffer_get_bignum(&buffer, pub->rsa->n);
-        buffer_get_bignum(&buffer, pub->rsa->e);
-        if (commentp)
-                *commentp = buffer_get_string(&buffer, NULL);
-        /* The encrypted private part is not parsed by this function. */
 
+        pub = key_parse_public_rsa1(&buffer, commentp);
+        if (pub == NULL)
+                debug3("Could not load \"%s\" as a RSA1 public key", filename);
         buffer_free(&buffer);
         return pub;
 }
@@ -336,113 +394,73 @@ key_load_public_type(int type, const char *filename, char **commentp)
         return NULL;
 }
 
-/*
- * Loads the private key from the file.  Returns 0 if an error is encountered
- * (file does not exist or is not readable, or passphrase is bad). This
- * initializes the private key.
- * Assumes we are called under uid of the owner of the file.
- */
-
 static Key *
-key_load_private_rsa1(int fd, const char *filename, const char *passphrase,
-    char **commentp)
+key_parse_private_rsa1(Buffer *blob, const char *passphrase, char **commentp)
 {
-        u_int i;
         int check1, check2, cipher_type;
-        size_t len;
-        Buffer buffer, decrypted;
+        Buffer decrypted;
         u_char *cp;
         CipherContext ciphercontext;
         Cipher *cipher;
         Key *prv = NULL;
-        struct stat st;
-
-        if (fstat(fd, &st) < 0) {
-                error("fstat for key file %.200s failed: %.100s",
-                    filename, strerror(errno));
-                close(fd);
-                return NULL;
-        }
-        if (st.st_size > 1*1024*1024) {
-                error("key file %.200s too large", filename);
-                close(fd);
-                return (NULL);
-        }
-        len = (size_t)st.st_size;               /* truncated */
-
-        buffer_init(&buffer);
-        cp = buffer_append_space(&buffer, len);
-
-        if (atomicio(read, fd, cp, len) != len) {
-                debug("Read from key file %.200s failed: %.100s", filename,
-                    strerror(errno));
-                buffer_free(&buffer);
-                close(fd);
-                return NULL;
-        }
 
         /* Check that it is at least big enough to contain the ID string. */
-        if (len < sizeof(authfile_id_string)) {
-                debug3("Not a RSA1 key file %.200s.", filename);
-                buffer_free(&buffer);
-                close(fd);
+        if (buffer_len(blob) < sizeof(authfile_id_string)) {
+                debug3("Truncated RSA1 identifier");
                 return NULL;
         }
+
         /*
          * Make sure it begins with the id string.  Consume the id string
          * from the buffer.
          */
-        for (i = 0; i < sizeof(authfile_id_string); i++)
-                if (buffer_get_char(&buffer) != authfile_id_string[i]) {
-                        debug3("Not a RSA1 key file %.200s.", filename);
-                        buffer_free(&buffer);
-                        close(fd);
-                        return NULL;
-                }
+        if (memcmp(buffer_ptr(blob), authfile_id_string,
+            sizeof(authfile_id_string)) != 0) {
+                debug3("Incorrect RSA1 identifier");
+                return NULL;
+        }
+        buffer_consume(blob, sizeof(authfile_id_string));
 
         /* Read cipher type. */
-        cipher_type = buffer_get_char(&buffer);
-        (void) buffer_get_int(&buffer); /* Reserved data. */
+        cipher_type = buffer_get_char(blob);
+        (void) buffer_get_int(blob);    /* Reserved data. */
 
         /* Read the public key from the buffer. */
-        (void) buffer_get_int(&buffer);
+        (void) buffer_get_int(blob);
         prv = key_new_private(KEY_RSA1);
 
-        buffer_get_bignum(&buffer, prv->rsa->n);
-        buffer_get_bignum(&buffer, prv->rsa->e);
+        buffer_get_bignum(blob, prv->rsa->n);
+        buffer_get_bignum(blob, prv->rsa->e);
         if (commentp)
-                *commentp = buffer_get_string(&buffer, NULL);
+                *commentp = buffer_get_string(blob, NULL);
         else
-                xfree(buffer_get_string(&buffer, NULL));
+                (void)buffer_get_string_ptr(blob, NULL);
 
         /* Check that it is a supported cipher. */
         cipher = cipher_by_number(cipher_type);
         if (cipher == NULL) {
-                debug("Unsupported cipher %d used in key file %.200s.",
-                    cipher_type, filename);
-                buffer_free(&buffer);
+                debug("Unsupported RSA1 cipher %d", cipher_type);
                 goto fail;
         }
         /* Initialize space for decrypted data. */
         buffer_init(&decrypted);
-        cp = buffer_append_space(&decrypted, buffer_len(&buffer));
+        cp = buffer_append_space(&decrypted, buffer_len(blob));
 
         /* Rest of the buffer is encrypted.  Decrypt it using the passphrase. */
         cipher_set_key_string(&ciphercontext, cipher, passphrase,
             CIPHER_DECRYPT);
         cipher_crypt(&ciphercontext, cp,
-            buffer_ptr(&buffer), buffer_len(&buffer));
+            buffer_ptr(blob), buffer_len(blob));
         cipher_cleanup(&ciphercontext);
         memset(&ciphercontext, 0, sizeof(ciphercontext));
-        buffer_free(&buffer);
+        buffer_clear(blob);
 
         check1 = buffer_get_char(&decrypted);
         check2 = buffer_get_char(&decrypted);
         if (check1 != buffer_get_char(&decrypted) ||
             check2 != buffer_get_char(&decrypted)) {
                 if (strcmp(passphrase, "") != 0)
-                        debug("Bad passphrase supplied for key file %.200s.",
-                            filename);
+                        debug("Bad passphrase supplied for RSA1 key");
                 /* Bad passphrase. */
                 buffer_free(&decrypted);
                 goto fail;
@@ -461,38 +479,37 @@ key_load_private_rsa1(int fd, const char *filename, const char *passphrase,
 
         /* enable blinding */
         if (RSA_blinding_on(prv->rsa, NULL) != 1) {
-                error("key_load_private_rsa1: RSA_blinding_on failed");
+                error("%s: RSA_blinding_on failed", __func__);
                 goto fail;
         }
-        close(fd);
         return prv;
 
 fail:
         if (commentp)
                 xfree(*commentp);
-        close(fd);
         key_free(prv);
         return NULL;
 }
 
-Key *
-key_load_private_pem(int fd, int type, const char *passphrase,
+static Key *
+key_parse_private_pem(Buffer *blob, int type, const char *passphrase,
     char **commentp)
 {
-        FILE *fp;
         EVP_PKEY *pk = NULL;
         Key *prv = NULL;
         char *name = "<no key>";
+        BIO *bio;
 
-        fp = fdopen(fd, "r");
-        if (fp == NULL) {
-                error("fdopen failed: %s", strerror(errno));
-                close(fd);
+        if ((bio = BIO_new_mem_buf(buffer_ptr(blob),
+            buffer_len(blob))) == NULL) {
+                error("%s: BIO_new_mem_buf failed", __func__);
                 return NULL;
         }
-        pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase);
+        
+        pk = PEM_read_bio_PrivateKey(bio, NULL, NULL, (char *)passphrase);
+        BIO_free(bio);
         if (pk == NULL) {
-                debug("PEM_read_PrivateKey failed");
+                debug("%s: PEM_read_PrivateKey failed", __func__);
                 (void)ERR_get_error();
         } else if (pk->type == EVP_PKEY_RSA &&
             (type == KEY_UNSPEC||type==KEY_RSA)) {
@@ -504,7 +521,7 @@ key_load_private_pem(int fd, int type, const char *passphrase,
                 RSA_print_fp(stderr, prv->rsa, 8);
 #endif
                 if (RSA_blinding_on(prv->rsa, NULL) != 1) {
-                        error("key_load_private_pem: RSA_blinding_on failed");
+                        error("%s: RSA_blinding_on failed", __func__);
                         key_free(prv);
                         prv = NULL;
                 }
@@ -539,10 +556,9 @@ key_load_private_pem(int fd, int type, const char *passphrase,
 #endif
 #endif /* OPENSSL_HAS_ECC */
         } else {
-                error("PEM_read_PrivateKey: mismatch or "
-                    "unknown EVP_PKEY save_type %d", pk->save_type);
+                error("%s: PEM_read_PrivateKey: mismatch or "
+                    "unknown EVP_PKEY save_type %d", __func__, pk->save_type);
         }
-        fclose(fp);
         if (pk != NULL)
                 EVP_PKEY_free(pk);
         if (prv != NULL && commentp)
@@ -552,6 +568,23 @@ key_load_private_pem(int fd, int type, const char *passphrase,
         return prv;
 }
 
+Key *
+key_load_private_pem(int fd, int type, const char *passphrase,
+    char **commentp)
+{
+        Buffer buffer;
+        Key *prv;
+
+        buffer_init(&buffer);
+        if (!key_load_file(fd, NULL, &buffer)) {
+                buffer_free(&buffer);
+                return NULL;
+        }
+        prv = key_parse_private_pem(&buffer, type, passphrase, commentp);
+        buffer_free(&buffer);
+        return prv;
+}
+
 int
 key_perm_ok(int fd, const char *filename)
 {
@@ -580,11 +613,31 @@ key_perm_ok(int fd, const char *filename)
         return 1;
 }
 
+static Key *
+key_parse_private_type(Buffer *blob, int type, const char *passphrase,
+    char **commentp)
+{
+        switch (type) {
+        case KEY_RSA1:
+                return key_parse_private_rsa1(blob, passphrase, commentp);
+        case KEY_DSA:
+        case KEY_ECDSA:
+        case KEY_RSA:
+        case KEY_UNSPEC:
+                return key_parse_private_pem(blob, type, passphrase, commentp);
+        default:
+                break;
+        }
+        return NULL;
+}
+
 Key *
 key_load_private_type(int type, const char *filename, const char *passphrase,
     char **commentp, int *perm_ok)
 {
         int fd;
+        Key *ret;
+        Buffer buffer;
 
         fd = open(filename, O_RDONLY);
         if (fd < 0) {
@@ -603,22 +656,17 @@ key_load_private_type(int type, const char *filename, const char *passphrase,
         }
         if (perm_ok != NULL)
                 *perm_ok = 1;
-        switch (type) {
-        case KEY_RSA1:
-                return key_load_private_rsa1(fd, filename, passphrase,
-                    commentp);
-                /* closes fd */
-        case KEY_DSA:
-        case KEY_ECDSA:
-        case KEY_RSA:
-        case KEY_UNSPEC:
-                return key_load_private_pem(fd, type, passphrase, commentp);
-                /* closes fd */
-        default:
+
+        buffer_init(&buffer);
+        if (!key_load_file(fd, filename, &buffer)) {
+                buffer_free(&buffer);
                 close(fd);
-                break;
+                return NULL;
         }
-        return NULL;
+        close(fd);
+        ret = key_parse_private_type(&buffer, type, passphrase, commentp);
+        buffer_free(&buffer);
+        return ret;
 }
 
 Key *
@@ -626,6 +674,7 @@ key_load_private(const char *filename, const char *passphrase,
     char **commentp)
 {
         Key *pub, *prv;
+        Buffer buffer, pubcopy;
         int fd;
 
         fd = open(filename, O_RDONLY);
@@ -639,20 +688,32 @@ key_load_private(const char *filename, const char *passphrase,
                 close(fd);
                 return NULL;
         }
-        pub = key_load_public_rsa1(fd, filename, commentp);
-        lseek(fd, (off_t) 0, SEEK_SET);         /* rewind */
+
+        buffer_init(&buffer);
+        if (!key_load_file(fd, filename, &buffer)) {
+                buffer_free(&buffer);
+                close(fd);
+                return NULL;
+        }
+        close(fd);
+
+        buffer_init(&pubcopy);
+        buffer_append(&pubcopy, buffer_ptr(&buffer), buffer_len(&buffer));
+        /* it's a SSH v1 key if the public key part is readable */
+        pub = key_parse_public_rsa1(&pubcopy, commentp);
+        buffer_free(&pubcopy);
         if (pub == NULL) {
-                /* closes fd */
-                prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL);
+                prv = key_parse_private_type(&buffer, KEY_UNSPEC,
+                    passphrase, NULL);
                 /* use the filename as a comment for PEM */
                 if (commentp && prv)
                         *commentp = xstrdup(filename);
         } else {
-                /* it's a SSH v1 key if the public key part is readable */
                 key_free(pub);
-                /* closes fd */
-                prv = key_load_private_rsa1(fd, filename, passphrase, NULL);
+                prv = key_parse_private_type(&buffer, KEY_RSA1, passphrase,
+                    commentp);
         }
+        buffer_free(&buffer);
         return prv;
 }