1 files changed, 140 insertions, 0 deletions
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 @@ static int print_bio(const char *str, size_t len, void *bio) {
 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;
+}