[wireless-regdb] [PATCH] reglib: Validate all structure and array lengths
Ben Hutchings
ben at decadent.org.uk
Sun Jun 30 19:49:31 EDT 2013
Add checks that:
- Signature length does not exceed the file length (this was already
checked, but did not account for signature lengths greater than 2 GB)
- Database length is long enough for all structures we expect in it
- Array length calculations will not overflow
To keep these checks simple, change the types of array length and index
variables to unsigned int (must be at least 32-bit, matching the file
format) and the types of byte-length variables to size_t.
Alexandre Rebert <alexandre at cmu.edu> reported and provided a test case
for the signature length issue; the others I found by inspection.
Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
---
reglib.c | 58 +++++++++++++++++++++++++++++++++++++++++-----------------
reglib.h | 5 +++--
2 files changed, 44 insertions(+), 19 deletions(-)
diff --git a/reglib.c b/reglib.c
index c4d00f8..224821b 100644
--- a/reglib.c
+++ b/reglib.c
@@ -10,6 +10,7 @@
#include <stdbool.h>
#include <unistd.h>
#include <string.h>
+#include <limits.h>
#include <arpa/inet.h> /* ntohl */
@@ -37,10 +38,16 @@
#include "keys-gcrypt.c"
#endif
-void *reglib_get_file_ptr(uint8_t *db, int dblen, int structlen, uint32_t ptr)
+void *
+reglib_get_file_ptr(uint8_t *db, size_t dblen, size_t structlen, uint32_t ptr)
{
uint32_t p = ntohl(ptr);
+ if (structlen > dblen) {
+ fprintf(stderr, "Invalid database file, too short!\n");
+ exit(3);
+ }
+
if (p > dblen - structlen) {
fprintf(stderr, "Invalid database file, bad pointer!\n");
exit(3);
@@ -49,6 +56,17 @@ void *reglib_get_file_ptr(uint8_t *db, int dblen, int structlen, uint32_t ptr)
return (void *)(db + p);
}
+static size_t
+reglib_array_len(size_t baselen, unsigned int elemcount, size_t elemlen)
+{
+ if (elemcount > (SIZE_MAX - baselen) / elemlen) {
+ fprintf(stderr, "Invalid database file, count too large!\n");
+ exit(3);
+ }
+
+ return baselen + elemcount * elemlen;
+}
+
/*
* reglib_verify_db_signature():
*
@@ -59,7 +77,7 @@ void *reglib_get_file_ptr(uint8_t *db, int dblen, int structlen, uint32_t ptr)
*/
#ifdef USE_OPENSSL
-int reglib_verify_db_signature(uint8_t *db, int dblen, int siglen)
+int reglib_verify_db_signature(uint8_t *db, size_t dblen, size_t siglen)
{
RSA *rsa;
uint8_t hash[SHA_DIGEST_LENGTH];
@@ -118,7 +136,7 @@ out:
#endif /* USE_OPENSSL */
#ifdef USE_GCRYPT
-int reglib_verify_db_signature(uint8_t *db, int dblen, int siglen)
+int reglib_verify_db_signature(uint8_t *db, size_t dblen, size_t siglen)
{
gcry_mpi_t mpi_e, mpi_n;
gcry_sexp_t rsa, signature, data;
@@ -180,7 +198,7 @@ out:
#endif /* USE_GCRYPT */
#if !defined(USE_OPENSSL) && !defined(USE_GCRYPT)
-int reglib_verify_db_signature(uint8_t *db, int dblen, int siglen)
+int reglib_verify_db_signature(uint8_t *db, size_t dblen, size_t siglen)
{
return 1;
}
@@ -220,7 +238,7 @@ const struct reglib_regdb_ctx *reglib_malloc_regdb_ctx(const char *regdb_file)
return NULL;
}
- ctx->header = reglib_get_file_ptr(ctx->db, ctx->dblen,
+ ctx->header = reglib_get_file_ptr(ctx->db, ctx->real_dblen,
sizeof(struct regdb_file_header),
0);
header = ctx->header;
@@ -232,12 +250,13 @@ const struct reglib_regdb_ctx *reglib_malloc_regdb_ctx(const char *regdb_file)
goto err_out;
ctx->siglen = ntohl(header->signature_length);
- /* The actual dblen does not take into account the signature */
- ctx->dblen = ctx->real_dblen - ctx->siglen;
- if (ctx->dblen <= sizeof(*header))
+ if (ctx->siglen > ctx->real_dblen - sizeof(*header))
goto err_out;
+ /* The actual dblen does not take into account the signature */
+ ctx->dblen = ctx->real_dblen - ctx->siglen;
+
/* verify signature */
if (!reglib_verify_db_signature(ctx->db, ctx->dblen, ctx->siglen))
goto err_out;
@@ -272,7 +291,7 @@ void reglib_free_regdb_ctx(const struct reglib_regdb_ctx *regdb_ctx)
free(ctx);
}
-static void reg_rule2rd(uint8_t *db, int dblen,
+static void reg_rule2rd(uint8_t *db, size_t dblen,
uint32_t ruleptr, struct ieee80211_reg_rule *rd_reg_rule)
{
struct regdb_file_reg_rule *rule;
@@ -303,18 +322,21 @@ country2rd(const struct reglib_regdb_ctx *ctx,
{
struct regdb_file_reg_rules_collection *rcoll;
struct ieee80211_regdomain *rd;
- int i, num_rules, size_of_rd;
+ unsigned int i, num_rules;
+ size_t size_of_rd;
rcoll = reglib_get_file_ptr(ctx->db, ctx->dblen, sizeof(*rcoll),
country->reg_collection_ptr);
num_rules = ntohl(rcoll->reg_rule_num);
/* re-get pointer with sanity checking for num_rules */
rcoll = reglib_get_file_ptr(ctx->db, ctx->dblen,
- sizeof(*rcoll) + num_rules * sizeof(uint32_t),
- country->reg_collection_ptr);
+ reglib_array_len(sizeof(*rcoll), num_rules,
+ sizeof(uint32_t)),
+ country->reg_collection_ptr);
- size_of_rd = sizeof(struct ieee80211_regdomain) +
- num_rules * sizeof(struct ieee80211_reg_rule);
+ size_of_rd = reglib_array_len(sizeof(struct ieee80211_regdomain),
+ num_rules,
+ sizeof(struct ieee80211_reg_rule));
rd = malloc(size_of_rd);
if (!rd)
@@ -468,7 +490,8 @@ struct ieee80211_regdomain *
reglib_intersect_rds(const struct ieee80211_regdomain *rd1,
const struct ieee80211_regdomain *rd2)
{
- int r, size_of_regd;
+ int r;
+ size_t size_of_regd;
unsigned int x, y;
unsigned int num_rules = 0, rule_idx = 0;
const struct ieee80211_reg_rule *rule1, *rule2;
@@ -506,8 +529,9 @@ reglib_intersect_rds(const struct ieee80211_regdomain *rd1,
if (!num_rules)
return NULL;
- size_of_regd = sizeof(struct ieee80211_regdomain) +
- ((num_rules + 1) * sizeof(struct ieee80211_reg_rule));
+ size_of_regd = reglib_array_len(sizeof(struct ieee80211_regdomain),
+ num_rules + 1,
+ sizeof(struct ieee80211_reg_rule));
rd = malloc(size_of_regd);
if (!rd)
diff --git a/reglib.h b/reglib.h
index 86087e3..57082fe 100644
--- a/reglib.h
+++ b/reglib.h
@@ -112,8 +112,9 @@ static inline uint32_t reglib_min(uint32_t a, uint32_t b)
return (a > b) ? b : a;
}
-void *reglib_get_file_ptr(uint8_t *db, int dblen, int structlen, uint32_t ptr);
-int reglib_verify_db_signature(uint8_t *db, int dblen, int siglen);
+void *
+reglib_get_file_ptr(uint8_t *db, size_t dblen, size_t structlen, uint32_t ptr);
+int reglib_verify_db_signature(uint8_t *db, size_t dblen, size_t siglen);
/**
* reglib_malloc_regdb_ctx - create a regdb context for usage with reglib
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