openssh/openssh-7.7p1-fips_checks.patch

# HG changeset patch
# Parent  e9b69da9a0f8dca923f8fc2836b38fe6590c791a
#
# Simple implementation of FIPS 140-2 selfchecks. Use OpenSSL to generate and
# verify checksums of binaries. Any hash iused in OpenSSH can be used (MD5 would
# obviously be a poor choice, since OpenSSL would barf and abort immediately in
# FIPS mode). SHA-2 seems to be a reasonable choice.
#
# The logic of the checks is as follows: decide whether FIPS mode is mandated
# (either by checking /proc/sys/crypto/fips_enabled or envoroinment variable
# SSH_FORCE_FIPS. In FIPS mode, checksums are required to match (inability to
# retrieve pre-calculated hash is a fatal error). In non-FIPS mode the checks
# still must be performed, unless the hashes are not installed. Thus if the hash
# file is not found (or the hash matches), proceed in non-FIPS mode and abort
# otherwise.

diff --git a/fips-check.c b/fips-check.c
new file mode 100644
index 0000000..eceb031
--- /dev/null
+++ b/fips-check.c
@@ -0,0 +1,34 @@
+#include "includes.h"
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "digest.h"
+#include "fips.h"
+
+#include <openssl/err.h>
+
+#define PROC_NAME_LEN	64
+
+static const char *argv0;
+
+void
+print_help_exit(int ev)
+{
+	fprintf(stderr, "%s <-c|-w> <file> <checksum_file>\n", argv0);
+	fprintf(stderr, "	-c  verify hash of 'file' against hash in 'checksum_file'\n");
+	fprintf(stderr, "	-w  write hash of 'file' into 'checksum_file'\n");
+	exit(ev);
+}
+
+int
+main(int argc, char **argv)
+{
+    fips_ssh_init();
+	return 0;
+}
diff --git a/fips.c b/fips.c
index 23e3876..297ae99 100644
--- a/fips.c
+++ b/fips.c
@@ -35,30 +35,293 @@
 #include "log.h"
 #include "xmalloc.h"
 
+#include <errno.h>
+#include <fcntl.h>
 #include <string.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
 #include <openssl/crypto.h>
+#include <openssl/err.h>
+#include <openssl/hmac.h>
 
 static int fips_state = -1;
 
+/* calculates HMAC of contents of a file given by filename using the hash
+ * algorithm specified by FIPS_HMAC_EVP in fips.h and placing the result into
+ * newly allacated memory - remember to free it when not needed anymore */
 static int
-fips_check_required_env(void)
+hmac_file(const char *filename, u_char **hmac_out)
+{
+	int check = -1;
+	int fd;
+	struct stat fs;
+	void *hmap;
+	unsigned char *hmac;
+	unsigned char *hmac_rv = NULL;
+
+	hmac = xmalloc(FIPS_HMAC_LEN);
+
+	fd = open(filename, O_RDONLY);
+	if (-1 == fd)
+		goto bail_out;
+
+	if (-1 == fstat(fd, &fs))
+		goto bail_out;
+
+	hmap = mmap(NULL, fs.st_size, PROT_READ, MAP_SHARED, fd, 0);
+
+	if ((void *)(-1) != hmap) {
+		hmac_rv = HMAC(FIPS_HMAC_EVP(), FIPS_HMAC_KEY
+		    , strlen(FIPS_HMAC_KEY), hmap, fs.st_size, hmac, NULL);
+		check = CHECK_OK;
+		munmap(hmap, fs.st_size);
+	}
+	close(fd);
+
+bail_out:
+	if (hmac_rv) {
+		check = CHECK_OK;
+		*hmac_out = hmac;
+	} else {
+		check = CHECK_FAIL;
+		*hmac_out = NULL;
+		free(hmac);
+	}
+	return check;
+}
+
+/* find pathname of binary of process with PID pid. exe is buffer expected to
+ * be capable of holding at least max_pathlen characters
+ */
+static int
+get_executable_path(pid_t pid, char *exe, int max_pathlen)
+{
+	char exe_sl[PROC_EXE_PATH_LEN];
+	int n;
+	int rv = -1;
+
+	n = snprintf(exe_sl, sizeof(exe_sl), "/proc/%u/exe", pid);
+	if ((n <= 10) || (n >= max_pathlen)) {
+		fatal("error compiling filename of link to executable");
+	}
+
+	exe[0] = 0;
+	n = readlink(exe_sl, exe, max_pathlen);
+	/* the file doesn't need to exist - procfs might not be mounted in
+	 * chroot */
+	if (n == -1) {
+		rv = CHECK_MISSING;
+	} else {
+		if (n < max_pathlen) {
+			exe[n] = 0;
+			rv = CHECK_OK;
+		} else {
+			rv = CHECK_FAIL;
+		}
+	}
+	return rv;
+}
+
+/* Read HMAC from file chk, allocating enough memory to hold the HMAC and
+ * return it in *hmac.
+ * Remember to free() it when it's not needed anymore.
+ */
+static int
+read_hmac(const char *chk, u_char **hmac)
+{
+	int check = -1;
+	int fdh, n;
+	u_char *hmac_in;
+
+	*hmac = NULL;
+
+	fdh = open(chk, O_RDONLY);
+	if (-1 == fdh) {
+		switch (errno) {
+			case ENOENT:
+				check = CHECK_MISSING;
+				debug("fips: checksum file %s is missing\n", chk);
+				break;
+			default:
+				check = CHECK_FAIL;
+				debug("fips: ckecksum file %s not accessible\n", chk);
+				break;
+
+		}
+		goto bail_out;
+	}
+
+	hmac_in = xmalloc(FIPS_HMAC_LEN);
+
+	n = read(fdh, (void *)hmac_in, FIPS_HMAC_LEN);
+	if (FIPS_HMAC_LEN != n) {
+		debug("fips: unable to read whole checksum from checksum file\n");
+		free (hmac_in);
+		check = CHECK_FAIL;
+	} else {
+		check = CHECK_OK;
+		*hmac = hmac_in;
+	}
+bail_out:
+	return check;
+}
+
+static int
+fips_hmac_self(void)
+{
+	int check = -1;
+	u_char *hmac = NULL, *hmac_chk = NULL;
+	char *exe, *chk;
+
+	exe = xmalloc(PATH_MAX);
+	chk = xmalloc(PATH_MAX);
+
+	/* we will need to add the suffix and the null terminator */
+	check = get_executable_path(getpid(), exe
+		    , PATH_MAX - strlen(CHECKSUM_SUFFIX) - 1);
+	if (CHECK_OK != check)
+		goto cleanup;
+
+	strncpy(chk, exe, PATH_MAX);
+	strlcat(chk, CHECKSUM_SUFFIX, PATH_MAX);
+
+	check = read_hmac(chk, &hmac_chk);
+	if (CHECK_OK != check)
+		goto cleanup;
+
+	check = hmac_file(exe, &hmac);
+	if (CHECK_OK != check)
+		goto cleanup;
+
+	check = memcmp(hmac, hmac_chk, FIPS_HMAC_LEN);
+	if (0 == check) {
+		check = CHECK_OK;
+		debug("fips: checksum matches\n");
+	} else {
+		check = CHECK_FAIL;
+		debug("fips: checksum mismatch!\n");
+	}
+
+cleanup:
+	free(hmac);
+	free(hmac_chk);
+	free(chk);
+	free(exe);
+
+	return check;
+}
+
+static int
+fips_check_required_proc(void)
 {
 	int fips_required = 0;
-	char *env = getenv(SSH_FORCE_FIPS_ENV);
-
-	if (env) {
-		errno = 0;
-		fips_required = strtol(env, NULL, 10);
-		if (errno) {
-			debug("bogus value in the %s environment variable, ignoring\n"
-			    , SSH_FORCE_FIPS_ENV);
-			fips_required = 0;
-		} else
-			fips_required = 1;
+	int fips_fd;
+	char fips_sys = 0;
+
+	struct stat dummy;
+	if (-1 == stat(FIPS_PROC_PATH, &dummy)) {
+		switch (errno) {
+			case ENOENT:
+			case ENOTDIR:
+				break;
+			default:
+				fatal("Check for system-wide FIPS mode is required and %s cannot"
+				    " be accessed for reason other than non-existence - aborting"
+				    , FIPS_PROC_PATH);
+				break;
+		}
+	} else {
+		if (-1 == (fips_fd = open(FIPS_PROC_PATH, O_RDONLY)))
+			fatal("Check for system-wide FIPS mode is required and %s cannot"
+			    " be opened for reading - aborting"
+			    , FIPS_PROC_PATH);
+		if (1 > read(fips_fd, &fips_sys, 1))
+			fatal("Check for system-wide FIPS mode is required and %s doesn't"
+			    " return at least one character - aborting"
+			    , FIPS_PROC_PATH);
+		close(fips_sys);
+		switch (fips_sys) {
+			case '0':
+			case '1':
+				fips_required = fips_sys - '0';
+				break;
+			default:
+				fatal("Bogus character %c found in %s - aborting"
+				    , fips_sys, FIPS_PROC_PATH);
+		}
 	}
 	return fips_required;
 }
 
+static int
+fips_check_required_env(void)
+{
+	return (NULL != getenv(SSH_FORCE_FIPS_ENV));
+}
+
+static int
+fips_required(void)
+{
+	int fips_requests = 0;
+	fips_requests += fips_check_required_proc();
+	fips_requests += fips_check_required_env();
+	return fips_requests;
+}
+
+/* check whether FIPS mode is required and perform selfchecksum/selftest */
+void
+fips_ssh_init(void)
+{
+	int checksum;
+
+	checksum = fips_hmac_self();
+
+	if (fips_required()) {
+		switch (checksum) {
+			case CHECK_OK:
+				debug("fips: mandatory checksum ok");
+				break;
+			case CHECK_FAIL:
+				fatal("fips: mandatory checksum failed - aborting");
+				break;
+			case CHECK_MISSING:
+				fatal("fips: mandatory checksum data missing - aborting");
+				break;
+			default:
+				fatal("Fatal error: internal error at %s:%u"
+				    , __FILE__, __LINE__);
+				break;
+		}
+		fips_state = FIPS_mode_set(1);
+		if (1 != fips_state) {
+			ERR_load_crypto_strings();
+			u_long err = ERR_get_error();
+			error("fips: OpenSSL error %lx: %s"
+			    , err, ERR_error_string(err, NULL));
+			fatal("fips: unable to set OpenSSL into FIPS mode - aborting");
+		}
+	} else {
+		switch (checksum) {
+			case CHECK_OK:
+				debug("fips: checksum ok");
+				break;
+			case CHECK_FAIL:
+				fatal("fips: checksum failed - aborting");
+				break;
+			case CHECK_MISSING:
+				debug("fips: checksum data missing, but not required - continuing non-FIPS");
+				break;
+			default:
+				fatal("Fatal error: internal error at %s:%u",
+				    __FILE__, __LINE__);
+				break;
+		}
+	}
+	return;
+}
+
 int
 fips_mode(void)
 {
diff --git a/fips.h b/fips.h
index a115a61..3404684 100644
--- a/fips.h
+++ b/fips.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012 Petr Cerny.  All rights reserved.
+ * Copyright (c) 2012-2014 Petr Cerny.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -27,6 +27,15 @@
 #include "sshkey.h"
 
 #define SSH_FORCE_FIPS_ENV	"SSH_FORCE_FIPS"
+#define FIPS_PROC_PATH		"/proc/sys/crypto/fips_enabled"
+
+#define PROC_EXE_PATH_LEN	64
+#define CHECKSUM_SUFFIX		".hmac"
+#define FIPS_HMAC_KEY		"HMAC_KEY:OpenSSH-FIPS@SLE"
+#define FIPS_HMAC_EVP		EVP_sha256
+#define FIPS_HMAC_LEN		32
+
+void	 fips_ssh_init(void);
 
 typedef enum {
 	FIPS_FILTER_CIPHERS,
@@ -34,6 +43,12 @@ typedef enum {
 	FIPS_FILTER_KEX_ALGS
 } fips_filters;
 
+typedef enum {
+	CHECK_OK = 0,
+	CHECK_FAIL,
+	CHECK_MISSING
+} fips_checksum_status;
+
 int	 fips_mode(void);
 int	 fips_correct_dgst(int);
 int	 fips_dgst_min(void);
@@ -41,4 +56,3 @@ enum fp_type	 fips_correct_fp_type(enum fp_type);
 int	 fips_filter_crypto(char **, fips_filters);
 
 #endif
-
diff --git a/sftp-server.c b/sftp-server.c
index b133cbc..c3086b6 100644
--- a/sftp-server.c
+++ b/sftp-server.c
@@ -53,6 +53,8 @@
 
 char *sftp_realpath(const char *, char *); /* sftp-realpath.c */
 
+#include "fips.h"
+
 /* Our verbosity */
 static LogLevel log_level = SYSLOG_LEVEL_ERROR;
 
@@ -1595,6 +1597,9 @@ sftp_server_main(int argc, char **argv, struct passwd *user_pw)
 	extern char *optarg;
 	extern char *__progname;
 
+	/* initialize fips */
+	fips_ssh_init();
+
 	__progname = ssh_get_progname(argv[0]);
 	log_init(__progname, log_level, log_facility, log_stderr);
 
diff --git a/ssh.c b/ssh.c
index ee51823..882d1da 100644
--- a/ssh.c
+++ b/ssh.c
@@ -113,6 +113,8 @@
 #include "ssh-pkcs11.h"
 #endif
 
+#include "fips.h"
+
 extern char *__progname;
 
 /* Saves a copy of argv for setproctitle emulation */
@@ -596,6 +598,10 @@ main(int ac, char **av)
 	struct ssh_digest_ctx *md;
 	u_char conn_hash[SSH_DIGEST_MAX_LENGTH];
 
+	/* initialize fips - can go before ssh_malloc_init(), since that is a
+	 * OpenBSD-only thing (as of OpenSSH 7.6p1) */
+	fips_ssh_init();
+
 	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
 	sanitise_stdfd();
 
diff --git a/sshd.c b/sshd.c
index c8086cd..bb20eec 100644
--- a/sshd.c
+++ b/sshd.c
@@ -1443,6 +1443,10 @@ main(int ac, char **av)
 	Authctxt *authctxt;
 	struct connection_info *connection_info = NULL;
 
+	/* initialize fips - can go before ssh_malloc_init(), since that is a
+	 * OpenBSD-only thing (as of OpenSSH 7.6p1) */
+	fips_ssh_init();
+
 #ifdef HAVE_SECUREWARE
 	(void)set_auth_parameters(ac, av);
 #endif