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197 lines
6.7 KiB
197 lines
6.7 KiB
2 years ago
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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
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--- 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
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+++ openssh-7.4p1/pam_ssh_agent_auth-0.10.3/iterate_ssh_agent_keys.c 2017-02-07 14:29:41.626116675 +0100
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@@ -43,12 +43,31 @@
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#include <openssl/evp.h>
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#include "ssh2.h"
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#include "misc.h"
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+#include "ssh.h"
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+#include <sys/types.h>
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+#include <sys/stat.h>
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+#include <sys/socket.h>
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+#include <sys/un.h>
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+#include <unistd.h>
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+#include <stdlib.h>
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+#include <errno.h>
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+#include <fcntl.h>
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#include "userauth_pubkey_from_id.h"
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#include "identity.h"
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#include "get_command_line.h"
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extern char **environ;
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+/*
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+ * Added by Jamie Beverly, ensure socket fd points to a socket owned by the user
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+ * A cursory check is done, but to avoid race conditions, it is necessary
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+ * to drop effective UID when connecting to the socket.
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+ *
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+ * If the cause of error is EACCES, because we verified we would not have that
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+ * problem initially, we can safely assume that somebody is attempting to find a
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+ * race condition; so a more "direct" log message is generated.
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+ */
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+
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static char *
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log_action(char ** action, size_t count)
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{
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@@ -85,7 +104,7 @@ void
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pamsshagentauth_session_id2_gen(Buffer * session_id2, const char * user,
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const char * ruser, const char * servicename)
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{
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- char *cookie = NULL;
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+ u_char *cookie = NULL;
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uint8_t i = 0;
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uint32_t rnd = 0;
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uint8_t cookie_len;
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@@ -112,7 +131,7 @@ pamsshagentauth_session_id2_gen(Buffer *
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if (i % 4 == 0) {
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rnd = pamsshagentauth_arc4random();
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}
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- cookie[i] = (char) rnd;
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+ cookie[i] = (u_char) rnd;
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rnd >>= 8;
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}
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@@ -177,6 +196,86 @@ pamsshagentauth_session_id2_gen(Buffer *
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}
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int
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+ssh_get_authentication_socket_for_uid(uid_t uid)
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+{
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+ const char *authsocket;
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+ int sock;
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+ struct sockaddr_un sunaddr;
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+ struct stat sock_st;
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+
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+ authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
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+ if (!authsocket)
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+ return -1;
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+
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+ /* Advisory only; seteuid ensures no race condition; but will only log if we see EACCES */
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+ if( stat(authsocket,&sock_st) == 0) {
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+ if(uid != 0 && sock_st.st_uid != uid) {
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+ fatal("uid %lu attempted to open an agent socket owned by uid %lu", (unsigned long) uid, (unsigned long) sock_st.st_uid);
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+ return -1;
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+ }
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+ }
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+
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+ /*
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+ * Ensures that the EACCES tested for below can _only_ happen if somebody
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+ * is attempting to race the stat above to bypass authentication.
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+ */
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+ if( (sock_st.st_mode & S_IWUSR) != S_IWUSR || (sock_st.st_mode & S_IRUSR) != S_IRUSR) {
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+ error("ssh-agent socket has incorrect permissions for owner");
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+ return -1;
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+ }
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+
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+ sunaddr.sun_family = AF_UNIX;
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+ strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
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+
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+ sock = socket(AF_UNIX, SOCK_STREAM, 0);
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+ if (sock < 0)
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+ return -1;
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+
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+ /* close on exec */
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+ if (fcntl(sock, F_SETFD, 1) == -1) {
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+ close(sock);
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+ return -1;
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+ }
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+
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+ errno = 0;
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+ seteuid(uid); /* To ensure a race condition is not used to circumvent the stat
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+ above, we will temporarily drop UID to the caller */
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+ if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) {
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+ close(sock);
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+ if(errno == EACCES)
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+ fatal("MAJOR SECURITY WARNING: uid %lu made a deliberate and malicious attempt to open an agent socket owned by another user", (unsigned long) uid);
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+ return -1;
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+ }
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+
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+ seteuid(0); /* we now continue the regularly scheduled programming */
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+
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+ return sock;
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+}
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+
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+AuthenticationConnection *
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+ssh_get_authentication_connection_for_uid(uid_t uid)
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+{
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+ AuthenticationConnection *auth;
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+ int sock;
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+
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+ sock = ssh_get_authentication_socket_for_uid(uid);
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+
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+ /*
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+ * Fail if we couldn't obtain a connection. This happens if we
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+ * exited due to a timeout.
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+ */
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+ if (sock < 0)
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+ return NULL;
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+
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+ auth = xmalloc(sizeof(*auth));
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+ auth->fd = sock;
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+ buffer_init(&auth->identities);
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+ auth->howmany = 0;
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+
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+ return auth;
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+}
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+
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+int
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pamsshagentauth_find_authorized_keys(const char * user, const char * ruser, const char * servicename)
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{
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Buffer session_id2 = { 0 };
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@@ -190,7 +289,7 @@ pamsshagentauth_find_authorized_keys(con
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OpenSSL_add_all_digests();
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pamsshagentauth_session_id2_gen(&session_id2, user, ruser, servicename);
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- if ((ac = ssh_get_authentication_connection(uid))) {
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+ if ((ac = ssh_get_authentication_connection_for_uid(uid))) {
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pamsshagentauth_verbose("Contacted ssh-agent of user %s (%u)", ruser, uid);
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for (key = ssh_get_first_identity(ac, &comment, 2); key != NULL; key = ssh_get_next_identity(ac, &comment, 2))
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{
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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
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--- openssh-7.4p1/pam_ssh_agent_auth-0.10.3/Makefile.in.psaa-build 2016-11-13 04:24:32.000000000 +0100
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+++ openssh-7.4p1/pam_ssh_agent_auth-0.10.3/Makefile.in 2017-02-07 14:40:14.407566921 +0100
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@@ -52,7 +52,7 @@ PATHS=
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CC=@CC@
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LD=@LD@
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CFLAGS=@CFLAGS@
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-CPPFLAGS=-I. -I$(srcdir) @CPPFLAGS@ $(PATHS) @DEFS@
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+CPPFLAGS=-I.. -I$(srcdir) @CPPFLAGS@ $(PATHS) @DEFS@
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LIBS=@LIBS@
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AR=@AR@
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AWK=@AWK@
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@@ -61,7 +61,7 @@ INSTALL=@INSTALL@
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PERL=@PERL@
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SED=@SED@
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ENT=@ENT@
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-LDFLAGS=-L. -Lopenbsd-compat/ @LDFLAGS@
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+LDFLAGS=-L.. -L../openbsd-compat/ @LDFLAGS@
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LDFLAGS_SHARED = @LDFLAGS_SHARED@
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EXEEXT=@EXEEXT@
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@@ -74,7 +74,7 @@ SSHOBJS=xmalloc.o atomicio.o authfd.o bu
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ED25519OBJS=ed25519-donna/ed25519.o
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-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
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+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
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MANPAGES_IN = pam_ssh_agent_auth.pod
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@@ -94,13 +94,13 @@ $(PAM_MODULES): Makefile.in config.h
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.c.o:
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$(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $@
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-LIBCOMPAT=openbsd-compat/libopenbsd-compat.a
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+LIBCOMPAT=../openbsd-compat/libopenbsd-compat.a
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$(LIBCOMPAT): always
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(cd openbsd-compat && $(MAKE))
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always:
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-pam_ssh_agent_auth.so: $(LIBCOMPAT) $(SSHOBJS) $(ED25519OBJS) $(PAM_SSH_AGENT_AUTH_OBJS) pam_ssh_agent_auth.o
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- $(LD) $(LDFLAGS_SHARED) -o $@ $(SSHOBJS) $(ED25519OBJS) $(PAM_SSH_AGENT_AUTH_OBJS) $(LDFLAGS) -lopenbsd-compat pam_ssh_agent_auth.o $(LIBS) -lpam
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+pam_ssh_agent_auth.so: $(PAM_SSH_AGENT_AUTH_OBJS) pam_ssh_agent_auth.o ../uidswap.o
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+ $(LD) $(LDFLAGS_SHARED) -o $@ $(PAM_SSH_AGENT_AUTH_OBJS) $(LDFLAGS) -lssh -lopenbsd-compat pam_ssh_agent_auth.o ../uidswap.o $(LIBS) -lpam
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$(MANPAGES): $(MANPAGES_IN)
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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
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