Add support for using external signing application and .pem private key files to vbutil_keyblock.

host/lib/host_signature.c

Index: host/lib/host_signature.c
diff --git a/host/lib/host_signature.c b/host/lib/host_signature.c
index c0d0f64f0b80d561eb897bec2d97f1f1d859dada..e00824fef0ab81c2b9c5118d8fa62d877001d60e 100644
--- a/host/lib/host_signature.c
+++ b/host/lib/host_signature.c
@@ -14,6 +14,8 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 #include <unistd.h>
 
 #include "cryptolib.h"
@@ -36,7 +38,7 @@ VbSignature* SignatureAlloc(uint64_t sig_size, uint64_t data_size) {
 
 
 void SignatureInit(VbSignature* sig, uint8_t* sig_data,
-                          uint64_t sig_size, uint64_t data_size) {
+                   uint64_t sig_size, uint64_t data_size) {
   sig->sig_offset = OffsetOf(sig, sig_data);
   sig->sig_size = sig_size;
   sig->data_size = data_size;
@@ -77,7 +79,6 @@ VbSignature* CalculateChecksum(const uint8_t* data, uint64_t size) {
   return sig;
 }
 
-
 VbSignature* CalculateSignature(const uint8_t* data, uint64_t size,
                                 const VbPrivateKey* key) {
 
@@ -133,3 +134,150 @@ VbSignature* CalculateSignature(const uint8_t* data, uint64_t size,
   /* Return the signature */
   return sig;
 }
+
+/* Invoke [external_signer] command with [pem_file] as
+ * an argument, contents of [inbuf] passed redirected to stdin,
+ * and the stdout of the command is put back into [outbuf].
+ * Returns -1 on error, 0 on success.
+ */
+int InvokeExternalSigner(uint64_t size,
+                         const uint8_t* inbuf,
+                         uint8_t* outbuf,
+                         uint64_t outbufsize,
+                         const char* pem_file,
+                         const char* external_signer) {
+
+  int rv = 0, n;
+  int p_to_c[2], c_to_p[2];  /* pipe descriptors */
+  pid_t pid;
+
+  VBDEBUG(("Will invoke \"%s %s\" to perform signing.\n"
+           "Input to the signer will be provided on standard in.\n"
+           "Output of the signer will be read from standard out.\n",
+           external_signer, pem_file));
+
+  /* Need two pipes since we want to invoke the external_signer as
+   * a co-process writing to its stdin and reading from its stdout. */
+  if (pipe(p_to_c) < 0 || pipe(c_to_p) < 0) {
+    VBDEBUG(("pipe() error\n"));
+    return -1;
+  }
+  if ((pid = fork()) < 0) {
+    VBDEBUG(("fork() error"));
+    return -1;
+  }
+  else if (pid > 0) {  /* Parent. */
+    close(p_to_c[STDIN_FILENO]);
+    close(c_to_p[STDOUT_FILENO]);
+
+    /* We provide input to the child process (external signer). */
+    if (write(p_to_c[STDOUT_FILENO], inbuf, size) != size) {
+      VBDEBUG(("write() error while providing input to external signer\n"));
+      rv = -1;
+    } else {
+      close(p_to_c[STDOUT_FILENO]);  /* Send EOF to child (signer process). */
+      do {
+        n = read(c_to_p[STDIN_FILENO], outbuf, outbufsize);
+        outbuf += n;
+        outbufsize -= n;
+      } while (n > 0 && outbufsize);
+
+      if (n < 0) {
+        VBDEBUG(("read() error while reading output from external signer\n"));
+        rv = -1;
+      }
+    }
+    if (waitpid(pid, NULL, 0) < 0) {
+      VBDEBUG(("waitpid() error\n"));
+      rv = -1;
+    }
+  } else {  /* Child. */
+    close (p_to_c[STDOUT_FILENO]);
+    close (c_to_p[STDIN_FILENO]);
+    /* Map the stdin to the first pipe (this pipe gets input
+     * from the parent) */
+    if (STDIN_FILENO != p_to_c[STDIN_FILENO]) {
+      if (dup2(p_to_c[STDIN_FILENO], STDIN_FILENO) != STDIN_FILENO) {
+        VBDEBUG(("stdin dup2() failed (external signer)\n"));
+        close(p_to_c[0]);
+        return -1;
+      }
+    }
+    /* Map the stdout to the second pipe (this pipe sends back
+     * signer output to the parent) */
+    if (STDOUT_FILENO != c_to_p[STDOUT_FILENO]) {
+      if (dup2(c_to_p[STDOUT_FILENO], STDOUT_FILENO) != STDOUT_FILENO) {
+        VBDEBUG(("stdout dup2() failed (external signer)\n"));
+        close(c_to_p[STDOUT_FILENO]);
+        return -1;
+      }
+    }
+    /* External signer is invoked here. */
+    if (execl(external_signer, external_signer, pem_file, (char *) 0) < 0) {
+      VBDEBUG(("execl() of external signer failed\n"));
+    }
+  }
+  return rv;
+}
+
+/* TODO(gauravsh): This could easily be integrated into CalculateSignature()
+ * since the code is almost a mirror - I have kept it as such to avoid changing
+ * the existing interface. */
+VbSignature* CalculateSignature_external(const uint8_t* data, uint64_t size,
+                                         const char* key_file,
+                                         uint64_t key_algorithm,
+                                         const char* external_signer) {
+  uint8_t* digest;
+  uint64_t digest_size = hash_size_map[key_algorithm];
+
+  const uint8_t* digestinfo = hash_digestinfo_map[key_algorithm];
+  uint64_t digestinfo_size = digestinfo_size_map[key_algorithm];
+
+  uint8_t* signature_digest;
+  uint64_t signature_digest_len = digest_size + digestinfo_size;
+
+  VbSignature* sig;
+  int rv;
+
+  /* Calculate the digest */
+  /* TODO: rename param 3 of DigestBuf to hash_type */
+  digest = DigestBuf(data, size, hash_type_map[key_algorithm]);
+  if (!digest)
+    return NULL;
+
+  /* Prepend the digest info to the digest */
+  signature_digest = Malloc(signature_digest_len);
+  if (!signature_digest) {
+    Free(digest);
+    return NULL;
+  }
+  Memcpy(signature_digest, digestinfo, digestinfo_size);
+  Memcpy(signature_digest + digestinfo_size, digest, digest_size);
+  Free(digest);
+
+  /* Allocate output signature */
+  sig = SignatureAlloc(siglen_map[key_algorithm], size);
+  if (!sig) {
+    Free(signature_digest);
+    return NULL;
+  }
+
+  /* Sign the signature_digest into our output buffer */
+  rv = InvokeExternalSigner(signature_digest_len, /* Input length */
+                            signature_digest,     /* Input data */
+                            GetSignatureData(sig), /* Output sig */
+                            (sizeof(VbSignature) + /* Max Output sig size. */
+                             siglen_map[key_algorithm]) ,
+                            key_file,             /* Key file to use */
+                            external_signer);     /* External cmd to invoke */
+  Free(signature_digest);
+
+  if (-1 == rv) {
+    VBDEBUG(("SignatureBuf(): RSA_private_encrypt() failed.\n"));
+    Free(sig);
+    return NULL;
+  }
+
+  /* Return the signature */
+  return sig;
+}