Retain CAP_NET_RAW capability for transparent proxying.

The capability is retained automatically in unprivileged worker processes after
changing UID if transparent proxying is enabled at least once in nginx
configuration.

The feature is only available in Linux.

6 files changed, 82 insertions, 0 deletions

diff --git a/auto/os/linux b/auto/os/linux
index a0c8795bb..e4aa0e549 100644
--- a/auto/os/linux
+++ b/auto/os/linux
@@ -157,6 +157,37 @@ ngx_feature_test="if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0) == -1) return 1"
 . auto/feature
 
 
+# prctl(PR_SET_KEEPCAPS)
+
+ngx_feature="prctl(PR_SET_KEEPCAPS)"
+ngx_feature_name="NGX_HAVE_PR_SET_KEEPCAPS"
+ngx_feature_run=yes
+ngx_feature_incs="#include <sys/prctl.h>"
+ngx_feature_path=
+ngx_feature_libs=
+ngx_feature_test="if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) == -1) return 1"
+. auto/feature
+
+
+# capabilities
+
+ngx_feature="capabilities"
+ngx_feature_name="NGX_HAVE_CAPABILITIES"
+ngx_feature_run=no
+ngx_feature_incs="#include <sys/capability.h>"
+ngx_feature_path=
+ngx_feature_libs=
+ngx_feature_test="struct __user_cap_data_struct    data;
+                  struct __user_cap_header_struct  header;
+
+                  header.version = _LINUX_CAPABILITY_VERSION_3;
+                  data.effective = CAP_TO_MASK(CAP_NET_RAW);
+                  data.permitted = 0;
+
+                  (void) capset(&header, &data)"
+. auto/feature
+
+
 # crypt_r()
 
 ngx_feature="crypt_r()"
diff --git a/src/core/ngx_cycle.h b/src/core/ngx_cycle.h
index 2b48ccbd6..a825da2f9 100644
--- a/src/core/ngx_cycle.h
+++ b/src/core/ngx_cycle.h
@@ -114,6 +114,8 @@ typedef struct {
 
     ngx_array_t               env;
     char                    **environment;
+
+    ngx_uint_t                transparent;  /* unsigned  transparent:1; */
 } ngx_core_conf_t;
 
 
diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 6d0f4ee52..f8d5707d3 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -6078,6 +6078,12 @@ ngx_http_upstream_bind_set_slot(ngx_conf_t *cf, ngx_command_t *cmd,
     if (cf->args->nelts > 2) {
         if (ngx_strcmp(value[2].data, "transparent") == 0) {
 #if (NGX_HAVE_TRANSPARENT_PROXY)
+            ngx_core_conf_t  *ccf;
+
+            ccf = (ngx_core_conf_t *) ngx_get_conf(cf->cycle->conf_ctx,
+                                                   ngx_core_module);
+
+            ccf->transparent = 1;
             local->transparent = 1;
 #else
             ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
diff --git a/src/os/unix/ngx_linux_config.h b/src/os/unix/ngx_linux_config.h
index 2f6129d88..b22ea4378 100644
--- a/src/os/unix/ngx_linux_config.h
+++ b/src/os/unix/ngx_linux_config.h
@@ -99,6 +99,11 @@ typedef struct iocb  ngx_aiocb_t;
 #endif
 
 
+#if (NGX_HAVE_CAPABILITIES)
+#include <sys/capability.h>
+#endif
+
+
 #define NGX_LISTEN_BACKLOG        511
 
 
diff --git a/src/os/unix/ngx_process_cycle.c b/src/os/unix/ngx_process_cycle.c
index a20a515c7..40654b3a2 100644
--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -839,12 +839,44 @@ ngx_worker_process_init(ngx_cycle_t *cycle, ngx_int_t worker)
                           ccf->username, ccf->group);
         }
 
+#if (NGX_HAVE_PR_SET_KEEPCAPS && NGX_HAVE_CAPABILITIES)
+        if (ccf->transparent && ccf->user) {
+            if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) == -1) {
+                ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
+                              "prctl(PR_SET_KEEPCAPS, 1) failed");
+                /* fatal */
+                exit(2);
+            }
+        }
+#endif
+
         if (setuid(ccf->user) == -1) {
             ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
                           "setuid(%d) failed", ccf->user);
             /* fatal */
             exit(2);
         }
+
+#if (NGX_HAVE_CAPABILITIES)
+        if (ccf->transparent && ccf->user) {
+            struct __user_cap_data_struct    data;
+            struct __user_cap_header_struct  header;
+
+            ngx_memzero(&header, sizeof(struct __user_cap_header_struct));
+            ngx_memzero(&data, sizeof(struct __user_cap_data_struct));
+
+            header.version = _LINUX_CAPABILITY_VERSION_3;
+            data.effective = CAP_TO_MASK(CAP_NET_RAW);
+            data.permitted = data.effective;
+
+            if (capset(&header, &data) == -1) {
+                ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
+                              "capset() failed");
+                /* fatal */
+                exit(2);
+            }
+        }
+#endif
     }
 
     if (worker >= 0) {
diff --git a/src/stream/ngx_stream_proxy_module.c b/src/stream/ngx_stream_proxy_module.c
index ad81cc8b7..818d7329b 100644
--- a/src/stream/ngx_stream_proxy_module.c
+++ b/src/stream/ngx_stream_proxy_module.c
@@ -2155,6 +2155,12 @@ ngx_stream_proxy_bind(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
     if (cf->args->nelts > 2) {
         if (ngx_strcmp(value[2].data, "transparent") == 0) {
 #if (NGX_HAVE_TRANSPARENT_PROXY)
+            ngx_core_conf_t  *ccf;
+
+            ccf = (ngx_core_conf_t *) ngx_get_conf(cf->cycle->conf_ctx,
+                                                   ngx_core_module);
+
+            ccf->transparent = 1;
             local->transparent = 1;
 #else
             ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,