upstream commit

When generating all hostkeys (ssh-keygen -A), clobber
existing keys if they exist but are zero length. zero-length keys could
previously be made if ssh-keygen failed part way through generating them, so
avoid that case too. bz#2561 reported by Krzysztof Cieplucha; ok dtucker@

Upstream-ID: f662201c28ab8e1f086b5d43c59cddab5ade4044

1 files changed, 72 insertions, 34 deletions

diff --git a/ssh-keygen.c b/ssh-keygen.c
index d8f942f5..835f7d01 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keygen.c,v 1.306 2017/07/01 13:50:45 djm Exp $ */
+/* $OpenBSD: ssh-keygen.c,v 1.307 2017/07/07 03:53:12 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -997,20 +997,38 @@ do_gen_all_hostkeys(struct passwd *pw)
 	int first = 0;
 	struct stat st;
 	struct sshkey *private, *public;
-	char comment[1024];
+	char comment[1024], *prv_tmp, *pub_tmp, *prv_file, *pub_file;
 	int i, type, fd, r;
 	FILE *f;
 
 	for (i = 0; key_types[i].key_type; i++) {
-		if (stat(key_types[i].path, &st) == 0)
-			continue;
-		if (errno != ENOENT) {
+		public = private = NULL;
+		prv_tmp = pub_tmp = prv_file = pub_file = NULL;
+
+		xasprintf(&prv_file, "%s%s",
+		    identity_file, key_types[i].path);
+
+		/* Check whether private key exists and is not zero-length */
+		if (stat(prv_file, &st) == 0) {
+			if (st.st_size != 0)
+				goto next;
+		} else if (errno != ENOENT) {
 			error("Could not stat %s: %s", key_types[i].path,
 			    strerror(errno));
-			first = 0;
-			continue;
+			goto failnext;
 		}
 
+		/*
+		 * Private key doesn't exist or is invalid; proceed with
+		 * key generation.
+		 */
+		xasprintf(&prv_tmp, "%s%s.XXXXXXXXXX",
+		    identity_file, key_types[i].path);
+		xasprintf(&pub_tmp, "%s%s.pub.XXXXXXXXXX",
+		    identity_file, key_types[i].path);
+		xasprintf(&pub_file, "%s%s.pub",
+		    identity_file, key_types[i].path);
+
 		if (first == 0) {
 			first = 1;
 			printf("%s: generating new host keys: ", __progname);
@@ -1018,56 +1036,76 @@ do_gen_all_hostkeys(struct passwd *pw)
 		printf("%s ", key_types[i].key_type_display);
 		fflush(stdout);
 		type = sshkey_type_from_name(key_types[i].key_type);
-		strlcpy(identity_file, key_types[i].path, sizeof(identity_file));
+		if ((fd = mkstemp(prv_tmp)) == -1) {
+			error("Could not save your public key in %s: %s",
+			    prv_tmp, strerror(errno));
+			goto failnext;
+		}
+		close(fd); /* just using mkstemp() to generate/reserve a name */
 		bits = 0;
 		type_bits_valid(type, NULL, &bits);
 		if ((r = sshkey_generate(type, bits, &private)) != 0) {
 			error("sshkey_generate failed: %s", ssh_err(r));
-			first = 0;
-			continue;
+			goto failnext;
 		}
 		if ((r = sshkey_from_private(private, &public)) != 0)
 			fatal("sshkey_from_private failed: %s", ssh_err(r));
 		snprintf(comment, sizeof comment, "%s@%s", pw->pw_name,
 		    hostname);
-		if ((r = sshkey_save_private(private, identity_file, "",
+		if ((r = sshkey_save_private(private, prv_tmp, "",
 		    comment, use_new_format, new_format_cipher, rounds)) != 0) {
 			error("Saving key \"%s\" failed: %s",
-			    identity_file, ssh_err(r));
-			sshkey_free(private);
-			sshkey_free(public);
-			first = 0;
-			continue;
+			    prv_tmp, ssh_err(r));
+			goto failnext;
 		}
-		sshkey_free(private);
-		strlcat(identity_file, ".pub", sizeof(identity_file));
-		fd = open(identity_file, O_WRONLY | O_CREAT | O_TRUNC, 0644);
-		if (fd == -1) {
-			error("Could not save your public key in %s",
-			    identity_file);
-			sshkey_free(public);
-			first = 0;
-			continue;
+		if ((fd = mkstemp(pub_tmp)) == -1) {
+			error("Could not save your public key in %s: %s",
+			    pub_tmp, strerror(errno));
+			goto failnext;
 		}
+		(void)fchmod(fd, 0644);
 		f = fdopen(fd, "w");
 		if (f == NULL) {
-			error("fdopen %s failed", identity_file);
+			error("fdopen %s failed: %s", pub_tmp, strerror(errno));
 			close(fd);
-			sshkey_free(public);
-			first = 0;
-			continue;
+			goto failnext;
 		}
 		if ((r = sshkey_write(public, f)) != 0) {
 			error("write key failed: %s", ssh_err(r));
 			fclose(f);
-			sshkey_free(public);
-			first = 0;
-			continue;
+			goto failnext;
 		}
 		fprintf(f, " %s\n", comment);
-		fclose(f);
-		sshkey_free(public);
+		if (ferror(f) != 0) {
+			error("write key failed: %s", strerror(errno));
+			fclose(f);
+			goto failnext;
+		}
+		if (fclose(f) != 0) {
+			error("key close failed: %s", strerror(errno));
+			goto failnext;
+		}
 
+		/* Rename temporary files to their permanent locations. */
+		if (rename(pub_tmp, pub_file) != 0) {
+			error("Unable to move %s into position: %s",
+			    pub_file, strerror(errno));
+			goto failnext;
+		}
+		if (rename(prv_tmp, prv_file) != 0) {
+			error("Unable to move %s into position: %s",
+			    key_types[i].path, strerror(errno));
+ failnext:
+			first = 0;
+			goto next;
+		}
+ next:
+		sshkey_free(private);
+		sshkey_free(public);
+		free(prv_tmp);
+		free(pub_tmp);
+		free(prv_file);
+		free(pub_file);
 	}
 	if (first != 0)
 		printf("\n");