Add |BIO_read_asn1| to read a single ASN.1 object.
Android needs to be able to read a PKCS#7 blob from a Java InputStream.
This change adds |BIO_read_asn1| which reads a single ASN.1 object from
the start of a BIO without overreading.
(Taken from upstream's https://boringssl-review.googlesource.com/4800)
Change-Id: Id88f34bedfdff4963c72bcd5c84f2915785d1fcd
diff --git a/src/crypto/bio/bio.c b/src/crypto/bio/bio.c
index 48c1466..694a11c 100644
--- a/src/crypto/bio/bio.c
+++ b/src/crypto/bio/bio.c
@@ -56,6 +56,7 @@
#include <openssl/bio.h>
+#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <string.h>
@@ -459,3 +460,142 @@
void BIO_print_errors(BIO *bio) {
ERR_print_errors_cb(print_bio, bio);
}
+
+/* bio_read_all reads everything from |bio| and prepends |prefix| to it. On
+ * success, |*out| is set to an allocated buffer (which should be freed with
+ * |OPENSSL_free|), |*out_len| is set to its length and one is returned. The
+ * buffer will contain |prefix| followed by the contents of |bio|. On failure,
+ * zero is returned.
+ *
+ * The function will fail if the size of the output would equal or exceed
+ * |max_len|. */
+static int bio_read_all(BIO *bio, uint8_t **out, size_t *out_len,
+ const uint8_t *prefix, size_t prefix_len,
+ size_t max_len) {
+ static const size_t kChunkSize = 4096;
+
+ size_t len = prefix_len + kChunkSize;
+ if (len > max_len) {
+ len = max_len;
+ }
+ if (len < prefix_len) {
+ return 0;
+ }
+ *out = OPENSSL_malloc(len);
+ if (*out == NULL) {
+ return 0;
+ }
+ memcpy(*out, prefix, prefix_len);
+ size_t done = prefix_len;
+
+ for (;;) {
+ if (done == len) {
+ OPENSSL_free(*out);
+ return 0;
+ }
+ const size_t todo = len - done;
+ assert(todo < INT_MAX);
+ const int n = BIO_read(bio, *out + done, todo);
+ if (n == 0) {
+ *out_len = done;
+ return 1;
+ } else if (n == -1) {
+ OPENSSL_free(*out);
+ return 0;
+ }
+
+ done += n;
+ if (len < max_len && len - done < kChunkSize / 2) {
+ len += kChunkSize;
+ if (len > max_len) {
+ len = max_len;
+ }
+ uint8_t *new_buf = OPENSSL_realloc(*out, len);
+ if (new_buf == NULL) {
+ OPENSSL_free(*out);
+ return 0;
+ }
+ *out = new_buf;
+ }
+ }
+}
+
+int BIO_read_asn1(BIO *bio, uint8_t **out, size_t *out_len, size_t max_len) {
+ uint8_t header[6];
+
+ static const size_t kInitialHeaderLen = 2;
+ if (BIO_read(bio, header, kInitialHeaderLen) != kInitialHeaderLen) {
+ return 0;
+ }
+
+ const uint8_t tag = header[0];
+ const uint8_t length_byte = header[1];
+
+ if ((tag & 0x1f) == 0x1f) {
+ /* Long form tags are not supported. */
+ return 0;
+ }
+
+ size_t len, header_len;
+ if ((length_byte & 0x80) == 0) {
+ /* Short form length. */
+ len = length_byte;
+ header_len = kInitialHeaderLen;
+ } else {
+ const size_t num_bytes = length_byte & 0x7f;
+
+ if ((tag & 0x20 /* constructed */) != 0 && num_bytes == 0) {
+ /* indefinite length. */
+ return bio_read_all(bio, out, out_len, header, kInitialHeaderLen,
+ max_len);
+ }
+
+ if (num_bytes == 0 || num_bytes > 4) {
+ return 0;
+ }
+
+ if (BIO_read(bio, header + kInitialHeaderLen, num_bytes) != num_bytes) {
+ return 0;
+ }
+ header_len = kInitialHeaderLen + num_bytes;
+
+ uint32_t len32 = 0;
+ unsigned i;
+ for (i = 0; i < num_bytes; i++) {
+ len32 <<= 8;
+ len32 |= header[kInitialHeaderLen + i];
+ }
+
+ if (len32 < 128) {
+ /* Length should have used short-form encoding. */
+ return 0;
+ }
+
+ if ((len32 >> ((num_bytes-1)*8)) == 0) {
+ /* Length should have been at least one byte shorter. */
+ return 0;
+ }
+
+ len = len32;
+ }
+
+ if (len + header_len < len ||
+ len + header_len > max_len) {
+ return 0;
+ }
+ len += header_len;
+ *out_len = len;
+
+ *out = OPENSSL_malloc(len);
+ if (*out == NULL) {
+ return 0;
+ }
+ memcpy(*out, header, header_len);
+ if (BIO_read(bio, (*out) + header_len, len - header_len) !=
+ len - header_len) {
+ OPENSSL_free(*out);
+ return 0;
+ }
+
+ return 1;
+}
diff --git a/src/crypto/bio/bio_test.cc b/src/crypto/bio/bio_test.cc
index 4c88df5..e0193f8 100644
--- a/src/crypto/bio/bio_test.cc
+++ b/src/crypto/bio/bio_test.cc
@@ -329,6 +329,84 @@
return true;
}
+static bool ReadASN1(bool should_succeed, const uint8_t *data, size_t data_len,
+ size_t expected_len, size_t max_len) {
+ ScopedBIO bio(BIO_new_mem_buf(const_cast<uint8_t*>(data), data_len));
+
+ uint8_t *out;
+ size_t out_len;
+ int ok = BIO_read_asn1(bio.get(), &out, &out_len, max_len);
+ if (!ok) {
+ out = nullptr;
+ }
+ ScopedOpenSSLBytes out_storage(out);
+
+ if (should_succeed != (ok == 1)) {
+ return false;
+ }
+
+ if (should_succeed &&
+ (out_len != expected_len || memcmp(data, out, expected_len) != 0)) {
+ return false;
+ }
+
+ return true;
+}
+
+static bool TestASN1() {
+ static const uint8_t kData1[] = {0x30, 2, 1, 2, 0, 0};
+ static const uint8_t kData2[] = {0x30, 3, 1, 2}; /* truncated */
+ static const uint8_t kData3[] = {0x30, 0x81, 1, 1}; /* should be short len */
+ static const uint8_t kData4[] = {0x30, 0x82, 0, 1, 1}; /* zero padded. */
+
+ if (!ReadASN1(true, kData1, sizeof(kData1), 4, 100) ||
+ !ReadASN1(false, kData2, sizeof(kData2), 0, 100) ||
+ !ReadASN1(false, kData3, sizeof(kData3), 0, 100) ||
+ !ReadASN1(false, kData4, sizeof(kData4), 0, 100)) {
+ return false;
+ }
+
+ static const size_t kLargePayloadLen = 8000;
+ static const uint8_t kLargePrefix[] = {0x30, 0x82, kLargePayloadLen >> 8,
+ kLargePayloadLen & 0xff};
+ ScopedOpenSSLBytes large(reinterpret_cast<uint8_t *>(
+ OPENSSL_malloc(sizeof(kLargePrefix) + kLargePayloadLen)));
+ memset(large.get() + sizeof(kLargePrefix), 0, kLargePayloadLen);
+ memcpy(large.get(), kLargePrefix, sizeof(kLargePrefix));
+
+ if (!ReadASN1(true, large.get(), sizeof(kLargePrefix) + kLargePayloadLen,
+ sizeof(kLargePrefix) + kLargePayloadLen,
+ kLargePayloadLen * 2)) {
+ fprintf(stderr, "Large payload test failed.\n");
+ return false;
+ }
+
+ if (!ReadASN1(false, large.get(), sizeof(kLargePrefix) + kLargePayloadLen,
+ sizeof(kLargePrefix) + kLargePayloadLen,
+ kLargePayloadLen - 1)) {
+ fprintf(stderr, "max_len test failed.\n");
+ return false;
+ }
+
+ static const uint8_t kIndefPrefix[] = {0x30, 0x80};
+ memcpy(large.get(), kIndefPrefix, sizeof(kIndefPrefix));
+ if (!ReadASN1(true, large.get(), sizeof(kLargePrefix) + kLargePayloadLen,
+ sizeof(kLargePrefix) + kLargePayloadLen,
+ kLargePayloadLen*2)) {
+ fprintf(stderr, "indefinite length test failed.\n");
+ return false;
+ }
+
+ if (!ReadASN1(false, large.get(), sizeof(kLargePrefix) + kLargePayloadLen,
+ sizeof(kLargePrefix) + kLargePayloadLen,
+ kLargePayloadLen-1)) {
+ fprintf(stderr, "indefinite length, max_len test failed.\n");
+ return false;
+ }
+
+ return true;
+}
+
int main(void) {
CRYPTO_library_init();
ERR_load_crypto_strings();
@@ -350,7 +428,8 @@
if (!TestSocketConnect() ||
!TestPrintf() ||
- !TestZeroCopyBioPairs()) {
+ !TestZeroCopyBioPairs() ||
+ !TestASN1()) {
return 1;
}
diff --git a/src/include/openssl/bio.h b/src/include/openssl/bio.h
index b70b42f..a37077c 100644
--- a/src/include/openssl/bio.h
+++ b/src/include/openssl/bio.h
@@ -338,6 +338,21 @@
* using human readable strings where possible. */
OPENSSL_EXPORT void BIO_print_errors(BIO *bio);
+/* BIO_read_asn1 reads a single ASN.1 object from |bio|. If successful it sets
+ * |*out| to be an allocated buffer (that should be freed with |OPENSSL_free|),
+ * |*out_size| to the length, in bytes, of that buffer and returns one.
+ * Otherwise it returns zero.
+ *
+ * If the length of the object is greater than |max_len| or 2^32 then the
+ * function will fail. Long-form tags are not supported. If the length of the
+ * object is indefinite the full contents of |bio| are read, unless it would be
+ * greater than |max_len|, in which case the function fails.
+ *
+ * If the function fails then some unknown amount of data may have been read
+ * from |bio|. */
+OPENSSL_EXPORT int BIO_read_asn1(BIO *bio, uint8_t **out, size_t *out_len,
+ size_t max_len);
+
/* Memory BIOs.
*
