diff -up openssh-7.4p1/pam_ssh_agent_auth-0.10.3/iterate_ssh_agent_keys.c.psaa-build openssh-7.4p1/pam_ssh_agent_auth-0.10.3/iterate_ssh_agent_keys.c
--- openssh-7.4p1/pam_ssh_agent_auth-0.10.3/iterate_ssh_agent_keys.c.psaa-build 2016-11-13 04:24:32.000000000 +0100
+++ openssh-7.4p1/pam_ssh_agent_auth-0.10.3/iterate_ssh_agent_keys.c 2017-02-13 16:06:17.468680048 +0100
@@ -39,6 +39,15 @@
#include "buffer.h"
#include "key.h"
#include "authfd.h"
+#include "ssh.h"
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <fcntl.h>
#include <stdio.h>
#include <openssl/evp.h>
#include "ssh2.h"
@@ -176,6 +185,96 @@ pamsshagentauth_session_id2_gen(Buffer *
return;
}
+/*
+ * Added by Jamie Beverly, ensure socket fd points to a socket owned by the user
+ * A cursory check is done, but to avoid race conditions, it is necessary
+ * to drop effective UID when connecting to the socket.
+ *
+ * If the cause of error is EACCES, because we verified we would not have that
+ * problem initially, we can safely assume that somebody is attempting to find a
+ * race condition; so a more "direct" log message is generated.
+ */
+
+int
+ssh_get_authentication_socket_for_uid(uid_t uid)
+{
+ const char *authsocket;
+ int sock;
+ struct sockaddr_un sunaddr;
+ struct stat sock_st;
+
+ authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
+ if (!authsocket)
+ return -1;
+
+ /* Advisory only; seteuid ensures no race condition; but will only log if we see EACCES */
+ if( stat(authsocket,&sock_st) == 0) {
+ if(uid != 0 && sock_st.st_uid != uid) {
+ fatal("uid %lu attempted to open an agent socket owned by uid %lu", (unsigned long) uid, (unsigned long) sock_st.st_uid);
+ return -1;
+ }
+ }
+
+ /*
+ * Ensures that the EACCES tested for below can _only_ happen if somebody
+ * is attempting to race the stat above to bypass authentication.
+ */
+ if( (sock_st.st_mode & S_IWUSR) != S_IWUSR || (sock_st.st_mode & S_IRUSR) != S_IRUSR) {
+ error("ssh-agent socket has incorrect permissions for owner");
+ return -1;
+ }
+
+ sunaddr.sun_family = AF_UNIX;
+ strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
+
+ sock = socket(AF_UNIX, SOCK_STREAM, 0);
+ if (sock < 0)
+ return -1;
+
+ /* close on exec */
+ if (fcntl(sock, F_SETFD, 1) == -1) {
+ close(sock);
+ return -1;
+ }
+
+ errno = 0;
+ seteuid(uid); /* To ensure a race condition is not used to circumvent the stat
+ above, we will temporarily drop UID to the caller */
+ if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) {
+ close(sock);
+ if(errno == EACCES)
+ fatal("MAJOR SECURITY WARNING: uid %lu made a deliberate and malicious attempt to open an agent socket owned by another user", (unsigned long) uid);
+ return -1;
+ }
+
+ seteuid(0); /* we now continue the regularly scheduled programming */
+
+ return sock;
+}
+
+AuthenticationConnection *
+ssh_get_authentication_connection_for_uid(uid_t uid)
+{
+ AuthenticationConnection *auth;
+ int sock;
+
+ sock = ssh_get_authentication_socket_for_uid(uid);
+
+ /*
+ * Fail if we couldn't obtain a connection. This happens if we
+ * exited due to a timeout.
+ */
+ if (sock < 0)
+ return NULL;
+
+ auth = xmalloc(sizeof(*auth));
+ auth->fd = sock;
+ buffer_init(&auth->identities);
+ auth->howmany = 0;
+
+ return auth;
+}
+
int
pamsshagentauth_find_authorized_keys(const char * user, const char * ruser, const char * servicename)
{
@@ -190,7 +289,7 @@ pamsshagentauth_find_authorized_keys(con
OpenSSL_add_all_digests();
pamsshagentauth_session_id2_gen(&session_id2, user, ruser, servicename);
- if ((ac = ssh_get_authentication_connection(uid))) {
+ if ((ac = ssh_get_authentication_connection_for_uid(uid))) {
pamsshagentauth_verbose("Contacted ssh-agent of user %s (%u)", ruser, uid);
for (key = ssh_get_first_identity(ac, &comment, 2); key != NULL; key = ssh_get_next_identity(ac, &comment, 2))
{
@@ -219,3 +318,4 @@ pamsshagentauth_find_authorized_keys(con
EVP_cleanup();
return retval;
}
+
diff -up openssh-7.4p1/pam_ssh_agent_auth-0.10.3/Makefile.in.psaa-build openssh-7.4p1/pam_ssh_agent_auth-0.10.3/Makefile.in
--- openssh-7.4p1/pam_ssh_agent_auth-0.10.3/Makefile.in.psaa-build 2016-11-13 04:24:32.000000000 +0100
+++ openssh-7.4p1/pam_ssh_agent_auth-0.10.3/Makefile.in 2017-02-13 16:04:58.685753236 +0100
@@ -52,7 +52,7 @@ PATHS=
CC=@CC@
LD=@LD@
CFLAGS=@CFLAGS@
-CPPFLAGS=-I. -I$(srcdir) @CPPFLAGS@ $(PATHS) @DEFS@
+CPPFLAGS=-I.. -I$(srcdir) -I/usr/include/nss3 -I/usr/include/nspr4 @CPPFLAGS@ $(PATHS) @DEFS@
LIBS=@LIBS@
AR=@AR@
AWK=@AWK@
@@ -61,7 +61,7 @@ INSTALL=@INSTALL@
PERL=@PERL@
SED=@SED@
ENT=@ENT@
-LDFLAGS=-L. -Lopenbsd-compat/ @LDFLAGS@
+LDFLAGS=-L.. -L../openbsd-compat/ @LDFLAGS@
LDFLAGS_SHARED = @LDFLAGS_SHARED@
EXEEXT=@EXEEXT@
@@ -74,7 +74,7 @@ SSHOBJS=xmalloc.o atomicio.o authfd.o bu
ED25519OBJS=ed25519-donna/ed25519.o
-PAM_SSH_AGENT_AUTH_OBJS=pam_user_key_allowed2.o iterate_ssh_agent_keys.o userauth_pubkey_from_id.o pam_user_authorized_keys.o get_command_line.o
+PAM_SSH_AGENT_AUTH_OBJS=pam_user_key_allowed2.o iterate_ssh_agent_keys.o userauth_pubkey_from_id.o pam_user_authorized_keys.o get_command_line.o secure_filename.o
MANPAGES_IN = pam_ssh_agent_auth.pod
@@ -94,13 +94,13 @@ $(PAM_MODULES): Makefile.in config.h
.c.o:
$(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $@
-LIBCOMPAT=openbsd-compat/libopenbsd-compat.a
+LIBCOMPAT=../openbsd-compat/libopenbsd-compat.a
$(LIBCOMPAT): always
(cd openbsd-compat && $(MAKE))
always:
-pam_ssh_agent_auth.so: $(LIBCOMPAT) $(SSHOBJS) $(ED25519OBJS) $(PAM_SSH_AGENT_AUTH_OBJS) pam_ssh_agent_auth.o
- $(LD) $(LDFLAGS_SHARED) -o $@ $(SSHOBJS) $(ED25519OBJS) $(PAM_SSH_AGENT_AUTH_OBJS) $(LDFLAGS) -lopenbsd-compat pam_ssh_agent_auth.o $(LIBS) -lpam
+pam_ssh_agent_auth.so: $(PAM_SSH_AGENT_AUTH_OBJS) pam_ssh_agent_auth.o
+ $(LD) $(LDFLAGS_SHARED) -o $@ $(PAM_SSH_AGENT_AUTH_OBJS) $(LDFLAGS) -lssh -lopenbsd-compat pam_ssh_agent_auth.o $(LIBS) -lpam -lnss3
$(MANPAGES): $(MANPAGES_IN)
pod2man --section=8 --release=v0.10.3 --name=pam_ssh_agent_auth --official --center "PAM" pam_ssh_agent_auth.pod > pam_ssh_agent_auth.8