From 019cefd3fbd256dd04289ce181b0a8330e11b292 Mon Sep 17 00:00:00 2001
From: Maarten Billemont <lhunath@lyndir.com>
Date: Thu, 31 Aug 2017 13:37:28 -0400
Subject: [PATCH] Add support for askpass program for reading answers from the
 user.

---
 platform-independent/cli-c/cli/mpw-cli.c | 109 ++++++++++++++++++++---
 1 file changed, 97 insertions(+), 12 deletions(-)

diff --git a/platform-independent/cli-c/cli/mpw-cli.c b/platform-independent/cli-c/cli/mpw-cli.c
index e3d28998..5d27ce8f 100644
--- a/platform-independent/cli-c/cli/mpw-cli.c
+++ b/platform-independent/cli-c/cli/mpw-cli.c
@@ -117,36 +117,103 @@ static const char *mpw_getenv(const char *variableName) {
     return envBuf? strdup( envBuf ): NULL;
 }
 
+char *mpw_read_fd(int fd);
+char *mpw_read_file(FILE *file);
+
+/** Use the askpass program to prompt the user.
+  * @return A newly allocated string or NULL if askpass is not supported or an error occurred. */
+static char *mpw_askpass(const char *prompt) {
+
+    const char *askpass = mpw_getenv( "MPW_ASKPASS" );
+    if (!askpass)
+        return NULL;
+
+    int pipes[2];
+    if (pipe( pipes ) == ERR) {
+        wrn( "Couldn't pipe: %s\n", strerror( errno ) );
+        return NULL;
+    }
+
+    pid_t pid = fork();
+    if (pid == ERR) {
+        wrn( "Couldn't fork for askpass:\n  %s: %s\n", askpass, strerror( errno ) );
+        return NULL;
+    }
+
+    if (!pid) {
+        // askpass fork
+        close( pipes[0] );
+        if (dup2( pipes[1], STDOUT_FILENO ) == ERR)
+            ftl( "Couldn't connect pipe to process: %s\n", strerror( errno ) );
+
+        else if (execl( askpass, askpass, prompt, NULL ) == ERR)
+            ftl( "Couldn't execute askpass:\n  %s: %s\n", askpass, strerror( errno ) );
+
+        exit( EX_SOFTWARE );
+    }
+
+    close( pipes[1] );
+    char *answer = mpw_read_fd( pipes[0] );
+    close( pipes[0] );
+    int status;
+    if (waitpid( pid, &status, 0 ) == ERR) {
+        wrn( "Couldn't wait for askpass: %s\n", strerror( errno ) );
+        mpw_free_string( &answer );
+        return NULL;
+    }
+
+    if (WIFEXITED( status ) && WEXITSTATUS( status ) == EXIT_SUCCESS && answer && strlen( answer )) {
+        // Remove trailing newline.
+        if (answer[strlen( answer ) - 1] == '\n')
+            answer[strlen( answer ) - 1] = '\0';
+        return answer;
+    }
+
+    mpw_free_string( &answer );
+    return NULL;
+}
+
 /** Ask the user a question.
   * @return A newly allocated string or NULL if an error occurred trying to read from the user. */
 static const char *mpw_getline(const char *prompt) {
 
+    // Get answer from askpass.
+    char *answer = mpw_askpass( prompt );
+    if (answer)
+        return answer;
+
+    // Get password from terminal.
     fprintf( stderr, "%s ", prompt );
 
-    char *buf = NULL;
     size_t bufSize = 0;
-    ssize_t lineSize = getline( &buf, &bufSize, stdin );
+    ssize_t lineSize = getline( &answer, &bufSize, stdin );
     if (lineSize <= 1) {
-        free( buf );
+        mpw_free_string( &answer );
         return NULL;
     }
 
-    // Remove the newline.
-    buf[lineSize - 1] = '\0';
-    return buf;
+    // Remove trailing newline.
+    answer[lineSize - 1] = '\0';
+    return answer;
 }
 
 /** Ask the user for a password.
   * @return A newly allocated string or NULL if an error occurred trying to read from the user. */
 static const char *mpw_getpass(const char *prompt) {
 
-    char *passBuf = getpass( prompt );
-    if (!passBuf)
+    // Get password from askpass.
+    const char *password = mpw_askpass( prompt );
+    if (password)
+        return password;
+
+    // Get password from terminal.
+    char *answer = getpass( prompt );
+    if (!answer)
         return NULL;
 
-    char *buf = strdup( passBuf );
-    bzero( passBuf, strlen( passBuf ) );
-    return buf;
+    password = strdup( answer );
+    bzero( answer, strlen( answer ) );
+    return password;
 }
 
 /** Get the absolute path to the mpw configuration file with the given prefix name and file extension.
@@ -230,9 +297,27 @@ static bool mpw_mkdirs(const char *filePath) {
     return success;
 }
 
+/** Read until EOF from the given file descriptor.
+  * @return A newly allocated string or NULL the read buffer couldn't be allocated. */
+char *mpw_read_fd(int fd) {
+
+    char *buf = NULL;
+    size_t blockSize = 4096, bufSize = 0, bufOffset = 0;
+    ssize_t readSize = 0;
+    while ((mpw_realloc( &buf, &bufSize, blockSize )) &&
+           ((readSize = read( fd, buf + bufOffset, blockSize )) > 0));
+    if (readSize == ERR)
+        dbg( "While reading: %s\n", strerror( errno ) );
+
+    return buf;
+}
+
 /** Read the file contents of a given file.
   * @return A newly allocated string or NULL the read buffer couldn't be allocated. */
-static char *mpw_read_file(FILE *file) {
+char *mpw_read_file(FILE *file) {
+
+    if (!file)
+        return NULL;
 
     char *buf = NULL;
     size_t blockSize = 4096, bufSize = 0, bufOffset = 0, readSize = 0;