74 lines
2.6 KiB
Diff
74 lines
2.6 KiB
Diff
This fixes an issue where libexpat might read from `/dev/urandom` and
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thus block until the entropy pool is initialized. This hidden
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dependency is very hard to debug. Instead, we require the service
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launcher to delay startup until suitable entropy is available. This
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explicit dependency is much easier to manage, debug, and control.
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Reported-by: Stefan Agner <stefan@agner.ch>
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Signed-off-by: David Rheinsberg <david@readahead.eu>
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---
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src/launch/config.c | 17 +++++++++++++++++
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src/launch/config.h | 1 +
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2 files changed, 18 insertions(+)
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diff --git a/src/launch/config.c b/src/launch/config.c
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index 85521bd..4a6a11e 100644
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--- a/src/launch/config.c
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+++ b/src/launch/config.c
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@@ -6,6 +6,7 @@
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#include <c-stdaux.h>
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#include <expat.h>
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#include <stdlib.h>
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+#include <sys/auxv.h>
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#include "dbus/protocol.h"
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#include "launch/config.h"
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#include "launch/nss-cache.h"
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@@ -1216,9 +1217,24 @@ static void config_parser_blob_fn(void *userdata, const XML_Char *data, int n_da
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* config_parser_init() - XXX
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*/
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void config_parser_init(ConfigParser *parser) {
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+ void *random;
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+
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*parser = (ConfigParser)CONFIG_PARSER_NULL(*parser);
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parser->xml = XML_ParserCreate(NULL);
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+
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+ /*
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+ * The hash-tables of libexpat require a reliable random seed.
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+ * Depending on libexpat compilation flags, this might end up using
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+ * `/dev/urandom` and thus block until random-initialization is
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+ * finished. We avoid this hidden dependency and instead use the
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+ * entropy provided via `AT_RANDOM`. Hence, entropy availability is
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+ * tightly coupled to process startup, and it is the job of the
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+ * service manager to order processes accordingly.
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+ */
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+ random = (void *)getauxval(AT_RANDOM);
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+ assert(random);
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+ memcpy(&parser->salt, random, sizeof(parser->salt));
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}
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/**
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@@ -1262,6 +1278,7 @@ static int config_parser_include(ConfigParser *parser, ConfigRoot *root, ConfigN
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}
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XML_ParserReset(parser->xml, NULL);
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+ XML_SetHashSalt(parser->xml, parser->salt);
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XML_SetUserData(parser->xml, &parser->state);
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XML_SetElementHandler(parser->xml, config_parser_begin_fn, config_parser_end_fn);
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XML_SetCharacterDataHandler(parser->xml, config_parser_blob_fn);
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diff --git a/src/launch/config.h b/src/launch/config.h
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index 4c8df18..8ae9be6 100644
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--- a/src/launch/config.h
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+++ b/src/launch/config.h
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@@ -216,6 +216,7 @@ struct ConfigRoot {
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struct ConfigParser {
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struct XML_ParserStruct *xml;
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+ unsigned long salt;
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struct ConfigState {
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NSSCache *nss;
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--
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2.33.0
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