main/dropbear: backport security fix (CVE-2018-15599)

fixes #9347

2 files changed, 232 insertions, 3 deletions

diff --git a/main/dropbear/APKBUILD b/main/dropbear/APKBUILD
index d3991417dc..f9c274cd99 100644
--- a/main/dropbear/APKBUILD
+++ b/main/dropbear/APKBUILD
@@ -3,7 +3,7 @@
 # Maintainer: Natanael Copa <ncopa@alpinelinux.org>
 pkgname=dropbear
 pkgver=2018.76
-pkgrel=1
+pkgrel=2
 pkgdesc="small SSH 2 client/server designed for small memory environments"
 url="http://matt.ucc.asn.au/dropbear/dropbear.html"
 arch="all"
@@ -21,7 +21,13 @@ source="http://matt.ucc.asn.au/dropbear/releases/${pkgname}-${pkgver}.tar.bz2
 	dropbear.initd
 	dropbear.confd
 	dropbear-0.53.1-static_build_fix.patch
-	dropbear-options_sftp-server_path.patch"
+	dropbear-options_sftp-server_path.patch
+	CVE-2018-15599.patch
+	"
+
+# secfixes:
+#   2018.76-r2:
+#     - CVE-2018-15599
 
 _progs="dropbear dropbearkey dbclient dropbearconvert scp"
 
@@ -82,4 +88,5 @@ sha512sums="82323279f7e78c366ba1ea07ff242259132b2576122429f54326518dd6092aba8ae5
 9c55ab3d8b61955cde1ccc1b8acbd3d2ef123feb9489e92737304c35315d07b7f85fad8a12ac7b0ec2c1dcee3d76b8bc4aa18518f4ddd963917805db33e48826  dropbear.initd
 83f2c1eaf7687917a4b2bae7d599d4378c4bd64f9126ba42fc5d235f2b3c9a474d1b3168d70ed64bb4101cc251d30bc9ae20604da9b5d819fcd635ee4d0ebb0f  dropbear.confd
 c9b0f28eb9653de21da4e8646fc27870a156112bce3d8a13baa6154ebf4baada3dee4f75bd5fdf5b6cd24a43fb80fb009e917d139d9e65d35118b082de0ebfbf  dropbear-0.53.1-static_build_fix.patch
-e11456ec3bc7e1265727c8921a6eb6151712a9a498c7768e2d4b7f9043256099457cebf29b2d47dd61eb260746d97f4b19e9429443bda1c3e441ea50ced79b48  dropbear-options_sftp-server_path.patch"
+e11456ec3bc7e1265727c8921a6eb6151712a9a498c7768e2d4b7f9043256099457cebf29b2d47dd61eb260746d97f4b19e9429443bda1c3e441ea50ced79b48  dropbear-options_sftp-server_path.patch
+f204c2ee5aea8c0962573c4c49479ac17e9f6a9ab9ce21060a252b449323be841c1e64460f0e191fc72c6e213ffe829544418715d120a8f6c40de7b6374428e0  CVE-2018-15599.patch"
diff --git a/main/dropbear/CVE-2018-15599.patch b/main/dropbear/CVE-2018-15599.patch
new file mode 100644
index 0000000000..963ed35bb9
--- /dev/null
+++ b/main/dropbear/CVE-2018-15599.patch
@@ -0,0 +1,222 @@
+
+# HG changeset patch
+# User Matt Johnston <matt@ucc.asn.au>
+# Date 1535038992 -28800
+# Node ID 5d2d1021ca0006337af58859c861f2349715b73b
+# Parent  cd23631dab5c653c66fe697e24f026aefbfcecb3
+Wait to fail invalid usernames
+
+diff -r cd23631dab5c -r 5d2d1021ca00 auth.h
+--- a/auth.h	Thu Aug 23 22:10:07 2018 +0800
++++ b/auth.h	Thu Aug 23 23:43:12 2018 +0800
+@@ -37,9 +37,9 @@
+ void send_msg_userauth_failure(int partial, int incrfail);
+ void send_msg_userauth_success(void);
+ void send_msg_userauth_banner(const buffer *msg);
+-void svr_auth_password(void);
+-void svr_auth_pubkey(void);
+-void svr_auth_pam(void);
++void svr_auth_password(int valid_user);
++void svr_auth_pubkey(int valid_user);
++void svr_auth_pam(int valid_user);
+ 
+ #if DROPBEAR_SVR_PUBKEY_OPTIONS_BUILT
+ int svr_pubkey_allows_agentfwd(void);
+diff -r cd23631dab5c -r 5d2d1021ca00 svr-auth.c
+--- a/svr-auth.c	Thu Aug 23 22:10:07 2018 +0800
++++ b/svr-auth.c	Thu Aug 23 23:43:12 2018 +0800
+@@ -149,10 +149,8 @@
+ 		if (methodlen == AUTH_METHOD_PASSWORD_LEN &&
+ 				strncmp(methodname, AUTH_METHOD_PASSWORD,
+ 					AUTH_METHOD_PASSWORD_LEN) == 0) {
+-			if (valid_user) {
+-				svr_auth_password();
+-				goto out;
+-			}
++			svr_auth_password(valid_user);
++			goto out;
+ 		}
+ 	}
+ #endif
+@@ -164,10 +162,8 @@
+ 		if (methodlen == AUTH_METHOD_PASSWORD_LEN &&
+ 				strncmp(methodname, AUTH_METHOD_PASSWORD,
+ 					AUTH_METHOD_PASSWORD_LEN) == 0) {
+-			if (valid_user) {
+-				svr_auth_pam();
+-				goto out;
+-			}
++			svr_auth_pam(valid_user);
++			goto out;
+ 		}
+ 	}
+ #endif
+@@ -177,12 +173,7 @@
+ 	if (methodlen == AUTH_METHOD_PUBKEY_LEN &&
+ 			strncmp(methodname, AUTH_METHOD_PUBKEY,
+ 				AUTH_METHOD_PUBKEY_LEN) == 0) {
+-		if (valid_user) {
+-			svr_auth_pubkey();
+-		} else {
+-			/* pubkey has no failure delay */
+-			send_msg_userauth_failure(0, 0);
+-		}
++		svr_auth_pubkey(valid_user);
+ 		goto out;
+ 	}
+ #endif
+diff -r cd23631dab5c -r 5d2d1021ca00 svr-authpam.c
+--- a/svr-authpam.c	Thu Aug 23 22:10:07 2018 +0800
++++ b/svr-authpam.c	Thu Aug 23 23:43:12 2018 +0800
+@@ -178,13 +178,14 @@
+  * Keyboard interactive would be a lot nicer, but since PAM is synchronous, it
+  * gets very messy trying to send the interactive challenges, and read the
+  * interactive responses, over the network. */
+-void svr_auth_pam() {
++void svr_auth_pam(int valid_user) {
+ 
+ 	struct UserDataS userData = {NULL, NULL};
+ 	struct pam_conv pamConv = {
+ 		pamConvFunc,
+ 		&userData /* submitted to pamvConvFunc as appdata_ptr */ 
+ 	};
++	const char* printable_user = NULL;
+ 
+ 	pam_handle_t* pamHandlep = NULL;
+ 
+@@ -204,12 +205,23 @@
+ 
+ 	password = buf_getstring(ses.payload, &passwordlen);
+ 
++	/* We run the PAM conversation regardless of whether the username is valid
++	in case the conversation function has an inherent delay.
++	Use ses.authstate.username rather than ses.authstate.pw_name.
++	After PAM succeeds we then check the valid_user flag too */
++
+ 	/* used to pass data to the PAM conversation function - don't bother with
+ 	 * strdup() etc since these are touched only by our own conversation
+ 	 * function (above) which takes care of it */
+-	userData.user = ses.authstate.pw_name;
++	userData.user = ses.authstate.username;
+ 	userData.passwd = password;
+ 
++	if (ses.authstate.pw_name) {
++		printable_user = ses.authstate.pw_name;
++	} else {
++		printable_user = "<invalid username>";
++	}
++
+ 	/* Init pam */
+ 	if ((rc = pam_start("sshd", NULL, &pamConv, &pamHandlep)) != PAM_SUCCESS) {
+ 		dropbear_log(LOG_WARNING, "pam_start() failed, rc=%d, %s", 
+@@ -242,7 +254,7 @@
+ 				rc, pam_strerror(pamHandlep, rc));
+ 		dropbear_log(LOG_WARNING,
+ 				"Bad PAM password attempt for '%s' from %s",
+-				ses.authstate.pw_name,
++				printable_user,
+ 				svr_ses.addrstring);
+ 		send_msg_userauth_failure(0, 1);
+ 		goto cleanup;
+@@ -253,12 +265,18 @@
+ 				rc, pam_strerror(pamHandlep, rc));
+ 		dropbear_log(LOG_WARNING,
+ 				"Bad PAM password attempt for '%s' from %s",
+-				ses.authstate.pw_name,
++				printable_user,
+ 				svr_ses.addrstring);
+ 		send_msg_userauth_failure(0, 1);
+ 		goto cleanup;
+ 	}
+ 
++	if (!valid_user) {
++		/* PAM auth succeeded but the username isn't allowed in for another reason
++		(checkusername() failed) */
++		send_msg_userauth_failure(0, 1);
++	}
++
+ 	/* successful authentication */
+ 	dropbear_log(LOG_NOTICE, "PAM password auth succeeded for '%s' from %s",
+ 			ses.authstate.pw_name,
+diff -r cd23631dab5c -r 5d2d1021ca00 svr-authpasswd.c
+--- a/svr-authpasswd.c	Thu Aug 23 22:10:07 2018 +0800
++++ b/svr-authpasswd.c	Thu Aug 23 23:43:12 2018 +0800
+@@ -48,22 +48,14 @@
+ 
+ /* Process a password auth request, sending success or failure messages as
+  * appropriate */
+-void svr_auth_password() {
++void svr_auth_password(int valid_user) {
+ 	
+ 	char * passwdcrypt = NULL; /* the crypt from /etc/passwd or /etc/shadow */
+ 	char * testcrypt = NULL; /* crypt generated from the user's password sent */
+-	char * password;
++	char * password = NULL;
+ 	unsigned int passwordlen;
+-
+ 	unsigned int changepw;
+ 
+-	passwdcrypt = ses.authstate.pw_passwd;
+-
+-#ifdef DEBUG_HACKCRYPT
+-	/* debugging crypt for non-root testing with shadows */
+-	passwdcrypt = DEBUG_HACKCRYPT;
+-#endif
+-
+ 	/* check if client wants to change password */
+ 	changepw = buf_getbool(ses.payload);
+ 	if (changepw) {
+@@ -73,12 +65,21 @@
+ 	}
+ 
+ 	password = buf_getstring(ses.payload, &passwordlen);
+-
+-	/* the first bytes of passwdcrypt are the salt */
+-	testcrypt = crypt(password, passwdcrypt);
++	if (valid_user) {
++		/* the first bytes of passwdcrypt are the salt */
++		passwdcrypt = ses.authstate.pw_passwd;
++		testcrypt = crypt(password, passwdcrypt);
++	}
+ 	m_burn(password, passwordlen);
+ 	m_free(password);
+ 
++	/* After we have got the payload contents we can exit if the username
++	is invalid. Invalid users have already been logged. */
++	if (!valid_user) {
++		send_msg_userauth_failure(0, 1);
++		return;
++	}
++
+ 	if (testcrypt == NULL) {
+ 		/* crypt() with an invalid salt like "!!" */
+ 		dropbear_log(LOG_WARNING, "User account '%s' is locked",
+diff -r cd23631dab5c -r 5d2d1021ca00 svr-authpubkey.c
+--- a/svr-authpubkey.c	Thu Aug 23 22:10:07 2018 +0800
++++ b/svr-authpubkey.c	Thu Aug 23 23:43:12 2018 +0800
+@@ -79,7 +79,7 @@
+ 
+ /* process a pubkey auth request, sending success or failure message as
+  * appropriate */
+-void svr_auth_pubkey() {
++void svr_auth_pubkey(int valid_user) {
+ 
+ 	unsigned char testkey; /* whether we're just checking if a key is usable */
+ 	char* algo = NULL; /* pubkey algo */
+@@ -102,6 +102,15 @@
+ 	keybloblen = buf_getint(ses.payload);
+ 	keyblob = buf_getptr(ses.payload, keybloblen);
+ 
++	if (!valid_user) {
++		/* Return failure once we have read the contents of the packet
++		required to validate a public key. 
++		Avoids blind user enumeration though it isn't possible to prevent
++		testing for user existence if the public key is known */
++		send_msg_userauth_failure(0, 0);
++		goto out;
++	}
++
+ 	/* check if the key is valid */
+ 	if (checkpubkey(algo, algolen, keyblob, keybloblen) == DROPBEAR_FAILURE) {
+ 		send_msg_userauth_failure(0, 0);
+