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authorLukas Fleischer <archlinux@cryptocrack.de>2014-12-20 12:57:15 +0100
committerLukas Fleischer <archlinux@cryptocrack.de>2014-12-27 12:42:12 +0100
commite1aac98bf51982e1bb7cbe61f9af8f0774f4ce6f (patch)
treebb89a7dee40b535904be0ac189defaf70598bb41 /scripts/git-integration/0001-Patch-sshd-for-the-AUR.patch
parent1dcdd3b3ea519681af6b691792a3b81511a7a9d4 (diff)
downloadaur-e1aac98bf51982e1bb7cbe61f9af8f0774f4ce6f.tar.gz
aur-e1aac98bf51982e1bb7cbe61f9af8f0774f4ce6f.tar.xz
Add sshd setup instructions
Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>
Diffstat (limited to 'scripts/git-integration/0001-Patch-sshd-for-the-AUR.patch')
-rw-r--r--scripts/git-integration/0001-Patch-sshd-for-the-AUR.patch152
1 files changed, 152 insertions, 0 deletions
diff --git a/scripts/git-integration/0001-Patch-sshd-for-the-AUR.patch b/scripts/git-integration/0001-Patch-sshd-for-the-AUR.patch
new file mode 100644
index 00000000..6b727123
--- /dev/null
+++ b/scripts/git-integration/0001-Patch-sshd-for-the-AUR.patch
@@ -0,0 +1,152 @@
+From e23745b61a46f034bca3cab9936c24c249afdc7f Mon Sep 17 00:00:00 2001
+From: Lukas Fleischer <archlinux@cryptocrack.de>
+Date: Sun, 21 Dec 2014 22:17:48 +0100
+Subject: [PATCH] Patch sshd for the AUR
+
+* Add SSH_KEY_FINGERPRINT and SSH_KEY variables to the environment of
+ the AuthorizedKeysCommand which allows for efficiently looking up SSH
+ keys in the AUR database.
+
+* Remove the secure path check for the AuthorizedKeysCommand. We are
+ running the sshd under a non-privileged user who has as little
+ permissions as possible. In particular, he does not own the directory
+ that contains the scripts for the Git backend.
+
+* Prevent from running the sshd as root.
+
+Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>
+---
+ auth2-pubkey.c | 48 +++++++++++++++++++++++++++++++++++++++++++-----
+ ssh.h | 12 ++++++++++++
+ sshd.c | 5 +++++
+ sshd_config.5 | 5 +++++
+ 4 files changed, 65 insertions(+), 5 deletions(-)
+
+diff --git a/auth2-pubkey.c b/auth2-pubkey.c
+index 0a3c1de..baf4922 100644
+--- a/auth2-pubkey.c
++++ b/auth2-pubkey.c
+@@ -510,6 +510,8 @@ user_key_command_allowed2(struct passwd *user_pw, Key *key)
+ int status, devnull, p[2], i;
+ pid_t pid;
+ char *username, errmsg[512];
++ struct sshbuf *b = NULL, *bb = NULL;
++ char *keytext, *uu = NULL;
+
+ if (options.authorized_keys_command == NULL ||
+ options.authorized_keys_command[0] != '/')
+@@ -538,11 +540,6 @@ user_key_command_allowed2(struct passwd *user_pw, Key *key)
+ options.authorized_keys_command, strerror(errno));
+ goto out;
+ }
+- if (auth_secure_path(options.authorized_keys_command, &st, NULL, 0,
+- errmsg, sizeof(errmsg)) != 0) {
+- error("Unsafe AuthorizedKeysCommand: %s", errmsg);
+- goto out;
+- }
+
+ if (pipe(p) != 0) {
+ error("%s: pipe: %s", __func__, strerror(errno));
+@@ -568,6 +565,47 @@ user_key_command_allowed2(struct passwd *user_pw, Key *key)
+ for (i = 0; i < NSIG; i++)
+ signal(i, SIG_DFL);
+
++ keytext = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
++ if (setenv(SSH_KEY_FINGERPRINT_ENV_NAME, keytext, 1) == -1) {
++ error("%s: setenv: %s", __func__, strerror(errno));
++ _exit(1);
++ }
++
++ if (!(b = sshbuf_new()) || !(bb = sshbuf_new())) {
++ error("%s: sshbuf_new: %s", __func__, strerror(errno));
++ _exit(1);
++ }
++ if (sshkey_to_blob_buf(key, bb) != 0) {
++ error("%s: sshkey_to_blob_buf: %s", __func__,
++ strerror(errno));
++ _exit(1);
++ }
++ if (!(uu = sshbuf_dtob64(bb))) {
++ error("%s: sshbuf_dtob64: %s", __func__,
++ strerror(errno));
++ _exit(1);
++ }
++ if (sshbuf_putf(b, "%s ", sshkey_ssh_name(key))) {
++ error("%s: sshbuf_putf: %s", __func__,
++ strerror(errno));
++ _exit(1);
++ }
++ if (sshbuf_put(b, uu, strlen(uu) + 1)) {
++ error("%s: sshbuf_put: %s", __func__,
++ strerror(errno));
++ _exit(1);
++ }
++ if (setenv(SSH_KEY_ENV_NAME, sshbuf_ptr(b), 1) == -1) {
++ error("%s: setenv: %s", __func__, strerror(errno));
++ _exit(1);
++ }
++ if (uu)
++ free(uu);
++ if (b)
++ sshbuf_free(b);
++ if (bb)
++ sshbuf_free(bb);
++
+ if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
+ error("%s: open %s: %s", __func__, _PATH_DEVNULL,
+ strerror(errno));
+diff --git a/ssh.h b/ssh.h
+index c94633b..411ea86 100644
+--- a/ssh.h
++++ b/ssh.h
+@@ -97,3 +97,15 @@
+
+ /* Listen backlog for sshd, ssh-agent and forwarding sockets */
+ #define SSH_LISTEN_BACKLOG 128
++
++/*
++ * Name of the environment variable containing the incoming key passed
++ * to AuthorizedKeysCommand.
++ */
++#define SSH_KEY_ENV_NAME "SSH_KEY"
++
++/*
++ * Name of the environment variable containing the incoming key fingerprint
++ * passed to AuthorizedKeysCommand.
++ */
++#define SSH_KEY_FINGERPRINT_ENV_NAME "SSH_KEY_FINGERPRINT"
+diff --git a/sshd.c b/sshd.c
+index 4e01855..60c676f 100644
+--- a/sshd.c
++++ b/sshd.c
+@@ -1424,6 +1424,11 @@ main(int ac, char **av)
+ av = saved_argv;
+ #endif
+
++ if (geteuid() == 0) {
++ fprintf(stderr, "this is a patched version of the sshd that must not be run as root.\n");
++ exit(1);
++ }
++
+ if (geteuid() == 0 && setgroups(0, NULL) == -1)
+ debug("setgroups(): %.200s", strerror(errno));
+
+diff --git a/sshd_config.5 b/sshd_config.5
+index ef36d33..1d7bade 100644
+--- a/sshd_config.5
++++ b/sshd_config.5
+@@ -223,6 +223,11 @@ It will be invoked with a single argument of the username
+ being authenticated, and should produce on standard output zero or
+ more lines of authorized_keys output (see AUTHORIZED_KEYS in
+ .Xr sshd 8 ) .
++The key being used for authentication (the key's type and the key text itself,
++separated by a space) will be available in the
++.Ev SSH_KEY
++environment variable, and the fingerprint of the key will be available in the
++.Ev SSH_KEY_FINGERPRINT environment variable.
+ If a key supplied by AuthorizedKeysCommand does not successfully authenticate
+ and authorize the user then public key authentication continues using the usual
+ .Cm AuthorizedKeysFile
+--
+2.2.1
+