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65 lines
1.6 KiB
65 lines
1.6 KiB
7 years ago
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diff --git a/session.c b/session.c
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index 9a75c62..4859245 100644
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--- a/session.c
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+++ b/session.c
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@@ -46,6 +46,7 @@
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#include <arpa/inet.h>
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+#include <ctype.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <grp.h>
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@@ -292,6 +293,21 @@ do_authenticated(Authctxt *authctxt)
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do_cleanup(authctxt);
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}
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+/* Check untrusted xauth strings for metacharacters */
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+static int
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+xauth_valid_string(const char *s)
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+{
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+ size_t i;
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+
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+ for (i = 0; s[i] != '\0'; i++) {
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+ if (!isalnum((u_char)s[i]) &&
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+ s[i] != '.' && s[i] != ':' && s[i] != '/' &&
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+ s[i] != '-' && s[i] != '_')
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+ return 0;
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+ }
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+ return 1;
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+}
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+
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/*
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* Prepares for an interactive session. This is called after the user has
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* been successfully authenticated. During this message exchange, pseudo
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@@ -365,7 +381,13 @@ do_authenticated1(Authctxt *authctxt)
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s->screen = 0;
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}
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packet_check_eom();
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- success = session_setup_x11fwd(s);
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+ if (xauth_valid_string(s->auth_proto) &&
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+ xauth_valid_string(s->auth_data))
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+ success = session_setup_x11fwd(s);
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+ else {
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+ success = 0;
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+ error("Invalid X11 forwarding data");
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+ }
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if (!success) {
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free(s->auth_proto);
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free(s->auth_data);
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@@ -2219,7 +2241,13 @@ session_x11_req(Session *s)
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s->screen = packet_get_int();
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packet_check_eom();
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- success = session_setup_x11fwd(s);
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+ if (xauth_valid_string(s->auth_proto) &&
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+ xauth_valid_string(s->auth_data))
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+ success = session_setup_x11fwd(s);
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+ else {
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+ success = 0;
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+ error("Invalid X11 forwarding data");
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+ }
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if (!success) {
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free(s->auth_proto);
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free(s->auth_data);
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